Home

href="
T874 Multistage Thermostats  
and Q674 Subbases  
PRODUCT DATA  
FEATURES  
T874 Thermostat has silent, dust-free mercury  
switches operated by coiled bimetal elements.  
Heat anticipator(s) are adjustable or fixed cooling  
anticipator(s) are fixed.  
Individual heat and cool levers and scales (most  
models) for temperature setting located on top of  
thermostat case.  
Cover thermometer on most T874 Multistage  
Thermostat models.  
Locking cover and locking lever screws available for  
T874 Multistage Thermostats.  
Versaguard™ Thermostat Guard or custom key lock  
thermostat guards available for T874 Multistage  
Thermostats.  
T874 Thermostat requires a Q674 Subbase.  
Q674 Subbase provides system and fan switching,  
wiring terminals and mounting base for T874  
Multistage Thermostat.  
APPLICATION  
These thermostats and subbases provide low voltage control  
of multistage heating and cooling systems, including heat  
pump systems.  
Adapter plate available for mounting Q674 on wall or  
horizontal outlet box.  
Light-emitting diodes (LEDs) located on subbase for  
easy reference.  
Up to three stages each of heating and cooling control  
possible.  
Models with setpoint restrictions and locking cover  
with no thermometer available for Department of  
Defense (DoD) and other special applications.  
Outdoor reset used on some models to improve  
thermal performance.  
Contents  
Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1  
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1  
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2  
Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2  
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7  
Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11  
Checkout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13  
Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14  
Understanding Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14  
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21  
Cross Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29  
Wiring Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96  
®
U.S. Registered Trademark  
60- 2485- 8  
Copyright © 2001 Honeywell • All Rights Reserved  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Tradeline Models  
T874 THERMOSTAT  
SPECIFICATIONS  
IMPORTANT  
T874 TRADELINE models provide staged heat and/or cool  
operation. See Table 1.  
The specifications given in this publication do not  
include normal manufacturing tolerances. Therefore,  
this unit may not exactly match the listed specifica-  
tions. This product is tested and calibrated under  
closely controlled conditions, and some minor differ-  
ences in performance can be expected if those con-  
ditions are changed.  
Table 1. Heating and Cooling Stages.  
Models  
Heating Stages  
Cooling Stages  
A
1
1
B
1
2
C
2
1
D
2
2
E
2
F
2
T874A-F are standard models.  
Super Tradeline®/Tradeline® Models  
SUPER TRADELINE controls offer features not available on  
TRADELINE or standard models, and are designed to replace  
a wide range of Honeywell and competitive controls.  
TRADELINE FEATURES:  
TRADELINE package with cross reference label and  
special instruction sheet.  
T874A,C model available with factory stops for DoD  
applications.  
TRADELINE models are selected and packaged to provide  
ease of stocking, ease of handling, and maximum  
replacement value. Specifications of SUPER TRADELINE  
and TRADELINE controls are the same as those of standard  
models except as noted below.  
T874A,C model available with adjustable temperature  
locking stops.  
Q674 SUBBASE  
Q674 switching subbases provide system and fan switching.  
See Table 2.  
Super Tradeline Models  
T874 THERMOSTAT  
Table 2. System and Fan Switching.  
T874D Thermostat. Provides two stages of heating and two  
stages of cooling. Use with Q674A-F Subbases.  
Y594D (T874D/Q674E/TG504A) Thermostat/Subbase/key  
lock cover package. Provides two stages of heating and  
two stages of cooling. Includes a key lock cover for setpoint  
protection.  
Q674  
System  
Heat-Auto-Cool  
Heat-Off-Cool  
Fan  
A
B
C
D
E
F
G
J
Auto-On  
Auto-On  
Auto-On  
None  
Auto-On  
Auto-On  
None  
Off-Auto  
None  
Off-Heat-Auto-Cool  
Em. Ht.-Off-Heat-Auto-Cool  
Off-Auto  
Y594G (T874G/Q674F) Thermostat/Subbase package for  
heat pump. Provides two stages of heating and one stage  
of cooling. Automatic changeover in heat or cool mode.  
Available in beige or Premier White® color.  
Y594R (T874R/Q674L) Thermostat/Subbase package for  
heat pump. Provides two stages of heating and one stage  
of cooling. Manual changeover in heat or cool mode. Avail-  
able in beige or Premier White® color.  
Em. Ht.-Auto-Off  
Em. Ht.-Heat-Off-Cool  
Auto-On  
Auto-On  
L
SUPER TRADELINE FEATURES:  
SUPER TRADELINE package with cross reference label  
and special instruction sheet.  
TRADELINE FEATURE:  
SUPER TRADELINE model supplied with locking lever and  
locking cover accessories.  
TRADELINE package with cross reference label and  
special instruction sheet.  
Includes adjustable temperature locking stops.  
T874D replaces T874A-F TRADELINE or standard models.  
Q674A-E,G are standard (non-heat pump) models.  
Q674F,J,L are heat pump models.  
ORDERING INFORMATION  
When purchasing replacement and modernization products from your TRADELINE® wholesaler or distributor, refer to the  
TRADELINE® Catalog or price sheets for complete ordering number.  
If you have additional questions, need further information, or would like to comment on our products or services, please write or  
phone:  
1
.
.
Your local Home and Building Control Sales Office (check white pages of your phone directory).  
Home and Building Control Customer Relations  
2
Honeywell, 1885 Douglas Drive North  
Minneapolis, Minnesota 55422-4386 (800) 328-5111  
In Canada—Honeywell Limited/Honeywell Limitée, 35 Dynamic Drive, Scarborough, Ontario M1V 4Z9.  
International Sales and Service Offices in all principal cities of the world. Manufacturing in Australia, Canada, Finland, France,  
Germany, Japan, Mexico, Netherlands, Spain, Taiwan, United Kingdom, U.S.A.  
60-2485—8  
2
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Thermometer Range: 42° to 88°F (6 to 31°C)  
Standard Models  
Changeover Differential: 4°F (2°C) minimum between heat-  
ing and cooling (5°F [3°C] on T874W). Levers can be set  
apart for greater separation.  
T874 THERMOSTATS  
Models: See Table 3.  
Electrical Rating: 24 to 30 Vac.  
Interstage Differential:  
Standard Models: Mechanical differential is 1°F (0.6°C)  
between heating or cooling stages; operating differential is  
approximately 1.9°F (1°C) between stages in heating or  
cooling.  
Switching: Coiled bimetal elements operate mercury  
switches.  
Special Models: See Table 3.  
Temperature Adjustment: Heating and cooling setting  
levers, with separate scales located on top of thermostat  
base. Common lever for heating and cooling on T874R;  
one cooling lever on T874E,V; and one heating lever on  
T874F,Q.  
Finish: Beige or Premier White® finish.  
Mounting Means: T874 Multistage Thermostat mounts on  
Q674 Subbase. Subbase mounts horizontally on wall or  
outlet box. Mounts on vertical outlet box with optional  
Dimensions: See Fig. 1.  
193121A Adapter Plate Assembly.  
Temperature: Scale Range: 42° to 88°F (6° to 31°C) stan-  
dard; optional ranges available.  
THERMOSTAT MOUNTED  
ON SUBBASE  
SUBBASE  
FRONT  
SIDE  
3/8 (10)  
5-5/8 (143)  
3-9/32 (83)  
HEAT  
50 60 70 80  
COOL  
50 60 70 80  
1-1/2  
(38)  
50 60 70 80  
3
-7/16  
3
(
-1/2  
89)  
(87)  
FAN  
FAN  
AUTO  
ON  
OFF EM. HT. HEAT AUTO COOL  
AUTO  
ON  
OFF EM. HT. HEAT AUTO COOL  
1-7/8 (48)  
5-1/8 (130)  
2-3/16 (56)  
M5849  
Fig. 1. T874 Thermostat and Q674 Subbase dimensions in in. (mm).  
Optional Specifications (T874 Only):  
Thermostat Accessories:  
Locking Cover and Locking Lever Assembly: Part no.  
194559R with thermometer; 194559S without thermome-  
ter. See Fig. 2. Includes cover, screws, and Allen wrench  
for locking cover. The screws must be used to assure  
proper operation.  
Temperature scale ranges are 40° to 75°F (4° to 24°C) heat-  
ing and 75° to 90°F (24° to 32°C) cooling with stop; 44° to  
6
8°F (7° to 20°C) heating, 80° to 86°F (27° to 30°C) cool-  
ing; 6° to 29°C (43° to 85°F) Celsius scale; 3° to 22°C (38°  
to 72°F) and 26° to 32°C (78° to 90°F) cooling with stop.  
Nonadjustable factory-added stop limits heating setpoint to  
Adjustable Lever Stop: Part no. 4074ECK; includes lever stop  
and screws.  
7
2°F (22°C) maximum and cooling setpoint to 78°F (26°C)  
minimum.  
Universal Versaguard™ Thermostat Guard: Includes wall-  
plate, ring base, guard cover, tumbler lock, two keys and  
optional Honeywell logo insert. Double-wall construction  
provides extra measure of tamper-resistance. Tamper-  
resistant lock; key cannot be removed without being in  
locked position. Vents in guard base allow airflow for opti-  
mum thermostat performance. See form 68-0104 for more  
information.  
OEM customer personalization.  
Locking cover and locking lever (see Thermostat Accesso-  
ries).  
Thermostat cover without thermometer.  
Adjustable locking temperature stops.  
Voltage heat anticipation for first or second stage heat or both.  
See Table 3.  
Fast cycling on heating stage(s) for electric heat applications.  
C815A Outdoor Thermistor for improved performance on  
specified models.  
TG511A1000: Clear cover.  
TG511B1008: Opaque cover.  
TG511D1004: Painted steel (off-white) cover. See  
Fig. 2.  
3
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Key Lock Cover: Part no. TG504A replaces existing T874  
cover. Mounts on T874 base and covers thermostat settling  
levers and subbase switches. Includes LED window and  
two keys. Should not be used with 193121A Adapter Plate.  
TG504A1025: Blank face, internal thermometer.  
TG504A1033: External thermometer. See Fig. 2.  
194559R Locking Cover  
with Thermometer  
Allen Wrench  
TG504A1033 Key Lock  
Cover with External  
Thermometer  
TG511D1004 Includes  
Painted Steel Cover,  
Opaque Base and Wallplate  
Fig. 2. T874 Thermostat accessories.  
Table 3. T874 Thermostat Specifications.  
Anticipation  
Heating (Adj) Cooling (Fixed)  
System Stages  
Models and Options  
Replaces Applications Heat Cool Other Stage 1 Stage 2 Stage 1 Stage 2  
T874A—Standard and TRADELINE®.  
T872A  
Standard  
1
1
0.1-1.2A  
0-1.5A  
72°F/78°F (22°C/26°C)setpoint  
stops with locking cover.  
Adjustable anticipator set 0.4A.  
Adjustable locking temperature  
stops (TRADELINE®).  
72°F/78°F (22°C/26°C) setpoint  
stops with locking cover, no  
a
thermometer (for DoD ).  
T874B—Standard and TRADELINE.  
T874C—Standard and TRADELINE.  
T872B  
T872C  
Standard  
Standard  
1
2
2
1
0.1-1.2A  
0.1-1.2A 0.1-1.2A 0-1.5A  
0-1.2A 0-1.0A  
72°F/78°F (22°C/26°C)set stops  
with locking cover, no thermometer  
a
(
for DoD ).  
12°F (7°C) differential between  
H1 and H2 stages (T874C1125).  
Fast cycling.  
0.12-  
.6A  
0.12-  
0.6A  
0
T874D—Standard and SUPER  
TRADELINE®.  
T872D  
Standard  
2
2
0.1-1.2A 0.1-1.2A 0-1.2A 0-1.0A  
Adjustable locking temperature  
stops (SUPER TRADELINE).  
T874E—Standard and TRADELINE.  
T874F—Standard and TRADELINE.  
T872E  
T872F  
2-Stage Cool  
2-Stage Heat  
2
2
0-1.2A 0-1.0A  
0.1-1.2A 0.1-1.2A  
Locking cover.  
a
Department of Defense.  
b
c
d
e
f
Changeover stage operates with heating.  
Fixed voltage type anticipation.  
Changeover stage operates with heating; a secondary changeover is provided in cooling switch.  
Provides night setback used with standard T874 and timer-operated remote switching.  
Manual changeover stage—use Q674B,L subbase.  
g
Changeover stage operates with cooling.Q674 Subbases  
60-2485—8  
4
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Fast cycling.  
Electric Heat  
0.12-  
.6A  
0.12-  
0.6A  
0
T874G—Heat pump, cool  
T872G Heat Pump or  
Standard  
2
1
1
1
1b  
0-1.0Ac  
0.1-1.2A 0-1.0A  
changeover, with fast cycling.  
Fixed anticipator for H2.  
Fast cycling.  
0.1-1.5A  
0.12-  
0.6A  
T874H—Use with Q674C.  
T872H Heat Pump or  
Standard  
1b  
0-1.0Ac  
0-1.0A  
T874J—Heat pump.  
T874K—Heat pump.  
T874L—Heat pump.  
None  
Heat Pump  
2
2
1
1
2d  
1b  
0-1.0Ae  
0.1-1.2A  
0-1.5Ac 0-1.0Ac  
None  
Heat Pump  
0-1.5Ac  
0-1.5A  
None  
T872N  
Heat Pump  
Heat Pump  
2
2
1
1
0.1-1.2A 0.1-1.2A 0-1.5A  
0.1-1.2A 0.1-1.2A 0-1.0A  
T874N—Heat pump, heat  
1b  
changeover.  
T874P—Heat pump.  
T874Q—Night setback heating.  
None  
T872Q  
Heat Pump  
Standard  
Heat Pumpf  
2
1e  
2
1
0.1-1.2A 0.1-1.2A 0-1.5A  
0.1-1.2A  
0-1.5Ac  
0-1.2Ac  
T874R—Heat pump.  
T872R  
None  
1
2
1g  
0.1-1.2A 0-1.5A  
0-1.2Ac  
T874S—Two-speed compressor heat  
Heat Pump  
2
0-1.2A 0-1.0A  
pump.  
T874V—Standard.  
T874W—Heat pump and standard.  
None  
Standard  
3
1
2
0-1.5A  
0-1.2A 0-1.0A  
T872W Heat Pump or  
-1.2Ab 0-1.2Ac,d  
0
Night setback heating.  
Standard  
a
Department of Defense.  
b
c
d
e
f
Changeover stage operates with heating.  
Fixed voltage type anticipation.  
Changeover stage operates with heating; a secondary changeover is provided in cooling switch.  
Provides night setback used with standard T874 and timer-operated remote switching.  
Manual changeover stage—use Q674B,L subbase.  
g
Changeover stage operates with cooling.Q674 Subbases  
Models:  
Mounting: Designed to mount horizontally on an outlet box  
or the wall. Adapter plate assembly available for mounting  
on a vertical outlet box (see Subbase Accessory).  
See Table 4.  
Electrical Ratings:  
Switch Contacts: 2.5A at 30 Vac (7.5A inrush).  
LED Lights (Optional): 30 Vac.  
Finish: Dark brown or gray.  
Dimensions in in. (mm): 3-1/2 (89)height; 5-5/8 (143) width;  
Switches: Two slide switches (one switch on Q674G and K;  
no switches on Q674D) operated by levers. Switch position  
is shown on scaleplate.  
5/16 (8) depth. See Fig. 1.  
Table 4. Q674 Subbase Specifications.  
Switch Positions  
System  
Models and Options  
Replaces Application  
Fan  
Use With  
Q674A—Standard and TRADELINE®.  
Q672A  
Standard  
HEAT-AUTO-COOL  
AUTO-ON  
T874A-D  
Indicator LEDs.  
Q674B—Standard and TRADELINE.  
Q672B  
Standard  
Heat Pump  
HEAT-OFF-COOL  
AUTO-ON  
AUTO-ON  
T874A-D  
T874G,H,L,R  
T874P  
Provision for fan relay operation from  
external fan switch (isolate G terminal).  
Indicator LEDs.  
OVERRIDE-HEAT-  
OFF-COOL  
OFF-AUTO  
OVERRIDE-AUTO-  
OFF  
Q674C—Standard and TRADELINE.  
Indicator LEDs.  
Q672C  
Q672D  
Standard  
Heat Pump  
AUTO-ON  
AUTO-ON  
T874A-H,W  
T874K,L,N  
T874P  
Q674D—Standard and TRADELINE.  
Standard  
5
None  
None  
T874A-F  
For use when subbase switching is not  
required.  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Q674E—Standard and TRADELINE.  
Q674F—Two LED models.  
Q672E  
Q672F  
Standard  
OFF-HEAT-AUTO-  
COOL  
AUTO-ON  
T874A-D  
Heat Pump OFF-EM.HT.-HEAT-  
AUTO-ON T874C,D,G,N,S  
AUTO-ON  
EM.HT. light.  
AUTO-COOL  
OFF-COOL-AUTO-  
HEAT-EM.HT.  
Provision for AUTO fan operation in  
EM.HT.  
Q674G—O and B terminals.  
Q674J—Provision for AUTO fan operation  
in EM.HT.  
Q672G  
Q672J  
Standard  
Heat Pump  
OFF-AUTO  
None  
T874A-F  
T874A,D,G,J  
EM.HT.-AUTO-OFF  
EM.HT.-ON-OFF  
SUPL.HT.-ON-OFF  
AUTO-ON  
AUTO-ON  
AUTO-ON  
None  
Provision for outdoor thermistor.  
Q674K—Standard.  
Q672K  
Q672L  
Standard  
OFF-HEAT-AUTO-  
T874F  
COOL  
OFF-WOOD-WOOD/  
OIL-OIL  
None  
Q674L—Provision for AUTO fan operation in  
EM.HT.  
Heat Pump EM.HT.-HEAT-OFF-  
AUTO-ON  
AUTO-ON  
AUTO-ON  
AUTO-ON  
T874R,W  
COOL  
SUPL.HT.-HEAT-  
OFF-COOL  
Indicator LEDs.  
Q674N—Standard.  
Q674P—Standard.  
Q674Q—Standard.  
Q674R—Standard.  
Q672N  
Q672P  
None  
Evaporative  
Cooler  
Heat Pump  
EVAP-COOL-OFF-  
T874C  
T874G  
T874A  
T874V  
T874C  
HEAT  
SUPL.HT.-HEAT-  
COOL  
HEAT-OFF-COOL LO-MED-HI-  
Fan Coil  
ON  
LO-HI-  
CONT.  
None  
Fan Coil  
OFF-COOL  
International symbols.  
Q674S—Indicator LED.  
None  
Standard  
HEAT-COOL  
None  
Optional Specifications (Q674 Only):  
L terminal is used for system monitoring devices.  
Common R terminal for heating/cooling.  
Changeover in cool or heat mode for heat pumps.  
Auto fan in EM.HT. for heat pumps.  
Models available with up to four LEDs; for example, LEDs can  
show EM. HT, AUX. HT, SERVICE, CHECK, FILTER, and  
LOCKOUT. See Fig. 3.  
System switching marked HEAT-OFF/RESET-COOL for sys-  
tems requiring impedance relay reset. Available on Q674B  
only.  
Subbase Accessory: 193121A Adapter Plate Assembly for  
mounting on vertical outlet box. Assembly includes adapter  
ring and cover plate. Use to cover wall marks from  
replaced thermostat.  
G terminal isolated on heating to provide fan relay operation  
from external low voltage fan switch (Q674B only).  
Auto fan operation on both heat and cool.  
T874 Thermostat with  
T874 Thermostat with  
Q674 Subbase  
with Four LEDs  
One Setpoint Lever  
Separate  
Heating and Cooling Levers  
Fig. 3. Heating, cooling levers and system LED indicators.  
60-2485—8  
6
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
concealed pipes and chimneys.  
unheated (uncooled) areas such as an outside wall behind  
the thermostat.  
MERCURY NOTICE  
This control contains mercury in a sealed tube. Do not  
place control in the trash at the end of its useful life.  
Mount Subbase  
If this control is replacing a control that contains  
mercury in a sealed tube, do not place your old control  
in the trash.  
The subbase can be mounted on a vertical outlet box,  
horizontal outlet box or directly on the wall.  
1. If the subbase is mounted on a vertical outlet box, order  
Honeywell part no. 193121A Adapter Assembly. See  
Fig. 4. The assembly includes an adapter ring, two  
screws and a cover plate to cover marks on the wall.  
Install the ring and cover plate on the vertical outlet box.  
Contact your local waste management authority for  
instructions regarding recycling and the proper  
disposal of this control, or of an old control containing  
mercury in a sealed tube. If you have questions, call  
the Honeywell Customer Response Center at  
NOTE: For a wall installation, hold subbase in position and  
mark holes for anchors. See Fig. 5. Wall anchors  
must be obtained from local hardware store. Be care-  
ful that the wires do not fall back into the wall open-  
ing. Set aside subbase. Drill four  
1-800-468-1502.  
INSTALLATION  
3
/16 in. (4.8 mm) holes and gently tap anchors into  
the holes until flush with the wall.  
When Installing this Product…  
2
.
.
Pull wires through the cover plate (if used) and subbase  
cable opening. See Fig. 6.  
1.  
Read these instructions carefully. Failure to follow them  
could damage the product or cause a hazardous condi-  
tion.  
3
Secure the cover plate (if used) and subbase with the  
screws provided. Do not fully tighten the subbase  
screws.  
2.  
3.  
4.  
Check the ratings given on the product to make sure the  
product is suitable for your application.  
Installer must be a trained, experienced service techni-  
cian.  
Level the subbase using a spirit level, see Fig. 7, and firmly  
tighten subbase mounting screws. The subbase mounting  
holes provide for minor out-of-level adjustments.  
After installation is complete, check out product opera-  
tion as provided in these instructions.  
VERTICAL  
OUTLET  
MOUNTING  
SCREWS (2)  
1
BOX  
COVER  
PLATE  
2
CAUTION  
ADAPTER  
RING  
2
Hazardous Voltage.  
Can damage heating/cooling system.  
1
.
Disconnect power supply before beginning instal-  
lation to prevent electrical shock or equipment  
damage.  
2.  
.
Do not short across coil terminals on relay. This  
can burn out thermostat heat anticipator.  
To prevent interference with the thermostat link-  
age, keep wire length to a minimum and run wires  
as close as possible to the subbase.  
Do not overtighten thermostat captive mounting  
screws because damage to subbase threads can  
result.  
1
HORIZONTAL  
OUTLET  
BOX  
3
4.  
THERMOSTAT  
IMPORTANT  
An incorrectly leveled thermostat will cause the tem-  
THERMOSTAT  
COVER  
COOL  
perature control to deviate from setpoint. It is not a  
calibration problem.  
50  
60 70 80  
SUBBASE  
50  
60 70 80  
HEAT  
SUBBASE  
Location  
MOUNTING SCREWS (2)  
Install the thermostat about 5 ft (1.5m) above the floor in an  
area with good air circulation at average temperature.  
50  
60 70 80  
CAPTIVE  
MOUNTING SCREWS (2)  
Do not mount the thermostat where it can be affected by:  
1
2
NOT INCLUDED WITH UNIT.  
drafts or dead spots behind doors, in corners or under  
cabinets.  
ACCESSORY PART AVAILABLE (193121A).  
M6009  
hot or cold air from ducts.  
Fig. 4. Installing Q674 Subbase on outlet box.  
radiant heat from the sun, fireplace, or appliances.  
7
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
All wiring must comply with local electrical codes and  
ordinances.  
WALL  
IMPORTANT  
Use 18 gauge, solid-conductor wire whenever possi-  
ble. If using 18 gauge stranded wire, no more than  
WIRES THROUGH  
WALL OPENING  
1
0 wires can be used. Do not use larger than  
8 gauge wire.  
1
Follow equipment manufacturer wiring instructions when  
available. To wire subbase, proceed as follows:  
1.  
Connect the system wires to the subbase as shown in  
the applicable diagram. A letter code is located near  
each terminal for identification. Typical terminal desig-  
nation and wiring connections are listed in Table 5. The  
terminal barrier permits straight or wraparound wiring  
connection. See Fig. 7. The subbase can require one or  
more jumpers that may or may not be factory-supplied.  
See Fig. 8 and the wiring diagrams for specific terminals  
to be jumpered.  
WALL  
ANCHORS  
2)  
MOUNTING  
HOLES  
(
MOUNTING  
SCREWS (2)  
M926  
SUBBASE  
Fig. 5. Installing Q674 Subbase on wall.  
FOR STRAIGHT  
INSERTION–  
STRIP 5/16 IN. (8 MM)  
FOR WRAPAROUND–  
STRIP 7/16 IN. (11 MM)  
WIRING  
TERMINAL  
THERMOSTAT  
CABLE OPENING  
SPIRIT LEVEL  
BARRIER  
SUBBASE TERMINAL SCREW  
M928  
Fig. 7. Barrier configuration.  
CAUTION  
Equipment Damage Hazard.  
POST FOR  
MOUNTING  
THERMOSTAT (2)  
MOUNTING  
HOLES (4)  
TO SPRING FINGER  
CONTACTS ON  
THE THERMOSTAT  
Never install more than one wire per terminal unless  
using factory-supplied jumper with spade terminal.  
(UP TO 12)  
M927  
2
.
Firmly tighten each terminal screw.  
Fig. 6. Subbase components and leveling procedure.  
3. Fit wires as close as possible to the subbase. Push  
excess wire back into the hole.  
4.  
Plug hole with nonflammable insulation to prevent drafts  
from affecting the thermostat.  
Wire Subbase  
Disconnect power supply before beginning installation to  
prevent electrical shock or equipment damage.  
60-2485—8  
8
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
JUMPER WIRE  
(SUPPLIED WITH SOME MODELS)  
1
1
1
TWO ADJACENT TERMINALS SHOWN JUMPERED ARE FOR EXAMPLE ONLY. COMPARE WIRING  
DIAGRAM AND SUBBASE TO IDENTIFY TERMINALS TO BE JUMPERED.  
M5899  
Fig. 8. Jumper adjacent terminals for special system hookup using stripped wire 3/4 in. (19 mm).  
For nonadjacent terminals and using jumper wire supplied with subbase.  
Table 5. Terminal Designationsa  
Standard Terminal  
Alternate Designations or  
Customer Specials  
Designation  
Typical Connection  
Heating damper motor; changeover valve  
Emergency heat relay  
Fan relay coil  
System monitor  
B
E
G
L
K
F
O
R
R
V
Cooling damper motor; changeover valve  
Power connection to transformer (internally connected for heating  
and cooling)  
RC  
RH  
W1  
W2  
W3  
Power connection to cooling transformer  
Power connection to heating transformer  
Stage 1 heating control  
Stage 2 heating control  
Stage 3 heating controlb  
H1, R3  
H2, Y, R4  
Y1  
Y2  
Y3  
X
C1, M  
C2  
Stage 1 cooling control  
Stage 2 cooling control  
Stage 3 cooling control  
Clogged filter switch or common connection  
Outdoor thermistor  
X1,X2,C  
T
A
L, C, H  
HSII control panel  
P
Defrost  
O
Momentary circuit, changeover  
LEDs  
A, A1, A2, Z, C, L  
a
b
Other terminal designations can be used that are not listed on this table. Refer to the hookup drawing and internal schematic  
for exact connections.  
W3 controls the auxiliary heat like W2, and allows adding additional stages of auxiliary heat with outdoor thermostats while  
maintaining the proper second stage anticipation.  
9
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 5. Terminal Designationsa  
Standard Terminal  
Designation  
Alternate Designations or  
Customer Specials  
Typical Connection  
External temperature readout, T relay  
LO and HI speed fan relays  
Cooling contactor  
T
R1, R2  
RS  
Y
M
Compressor contactor  
a
b
Other terminal designations can be used that are not listed on this table. Refer to the hookup drawing and internal schematic  
for exact connections.  
W3 controls the auxiliary heat like W2, and allows adding additional stages of auxiliary heat with outdoor thermostats while  
maintaining the proper second stage anticipation.  
mounting screw and two locking screws with insulated heads.  
Outdoor Disconnect  
When installed, the stop brackets limit the movement of the  
T874 HEAT and COOL levers.  
The National Electrical Code requires the installation of a  
disconnect switch within sight of the outdoor unit of an air  
conditioner or heat pump. The switch is for the safety of any  
technician working on the unit. The technician can assure that  
the unit remains unpowered.  
TO INSTALL:  
1
.
Remove the thermostat cover by pulling the bottom  
edge of the cover upward until it snaps free of the  
mounting slots.  
2.  
Turn to the back of the T874 Thermostat. Locate the  
hole for the brass insert in the plastic base below the  
LED window.  
Install and Adjust Stop Brackets  
The stop brackets should be installed only if there is a need to  
restrict the adjustable range of the heating and cooling  
temperature setpoint levers. If adjustable lever stops are  
desired, order 4074ECK Envelope Assembly, which contains  
two adjustable lever stop brackets, one brass insert, one  
3.  
4.  
5.  
Push the brass insert into the hole with finger.  
Turn to the front of the T874 Thermostat.  
Place the two stop brackets in position with the tabs in  
the slot between the HEAT and COOL levers. See  
Fig. 9.  
HOLES FOR INSULATED  
LOCKING LEVER SCREWS  
COOL  
LEVER  
HOLE WITH  
BRASS INSERT  
HEAT  
LEVER  
BRACKET  
TABS  
ADJUSTABLE LOCKING LEVERS  
NONADJUSTABLE STOPS  
WITH LOCKING LEVER SCREWS  
75°F (24°C) MAX. HEAT  
ADJUSTABLE  
LEVER STOP  
BRACKETS  
MOUNTING  
SCREW  
BRACKET  
SLOTS  
75°F (24°C) MIN. COOL  
NONADJUSTABLE D.O.D. STOPS  
ADJUSTABLE STOPS  
72°F (22°C) MAX. HEAT  
8°F (26°C) MIN. COOL  
M7626  
7
Fig. 9. Range limiting and lever locking methods.  
6.  
Insert the mounting screw into the two slots in the stop  
brackets and attach to the brass insert. Tighten the  
screw to pull the brass insert into the back of the ther-  
mostat.  
7. Loosen the mounting screw enough to free the stop  
brackets for adjustment.  
60-2485—8  
10  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
8
.
.
Move the HEAT and COOL levers to the maximum tem-  
perature desired.  
9
Slide the stop brackets until one rests against the HEAT  
lever and the other against the COOL lever.  
1
0. Firmly tighten the mounting screw.  
1. If the HEAT and COOL levers are to be locked in place  
at a specific temperature, use the two insulated head  
screws supplied instead of the two adjustable lever stop  
brackets.  
1
ALLEN  
RETAINING  
SCREWS (2)  
CAUTION  
Equipment Damage Hazard.  
Do not use standard screws that provide metal-to-  
metal contact with the stop brackets. Short circuit and  
potential equipment damage can result.  
M956  
Fig. 10. Installation of locking cover assembly.  
Mount Thermostat  
1.  
Remove the thermostat cover by pulling the bottom  
edge of the cover away from the base until it snaps free  
of the cover clip.  
SETTINGS  
NOTE: The cover is hinged at the top and must be removed  
by pulling up at the bottom.  
CAUTION  
Equipment Damage Hazard.  
2
.
Carefully remove and discard the polystyrene packing  
insert that protects the mercury switches during ship-  
ment.  
On systems using a gas valve, never apply a jumper  
across the valve coil terminals, even temporarily. This  
can burn out thermostat heat anticipator(s).  
3.  
If LED indication (EM.HT., CHECK, etc.) is to be used  
with the Q674 Subbase, install the preprinted insert  
under the thermostat setpoint scale. To install, push  
both thermostat setpoint levers to the far ends of the  
thermostat. Use index finger to gently pull out the plastic  
setpoint scale about 1/4 in. (6 mm). Position the desired  
preprinted insert in the space above the LED lights.  
Reposition setpoint levers.  
Set the Heat Anticipator  
Move the indicator to match the primary control current draw.  
When using a T874 Thermostat with two stages of heating,  
set each heat anticipator to match its respective primary  
control current draw. If you cannot find the current rating on  
the primary control, or if further adjustment is necessary, see  
NOTE and use the following procedure to determine the  
current draw of each stage.  
4.  
Turn over the thermostat base and note the spring fin-  
gers that engage the subbase contacts. Make sure the  
spring fingers are not bent flat, preventing proper elec-  
trical contact with the subbase.  
The current draw of each heating stage must be measured  
with the thermostat removed and power on to the heating  
system.  
5.  
6.  
7.  
8.  
Set the heat anticipator indicator(s) to the respective  
current setting of each stage. See Set The Heat Antici-  
pator section.  
If the thermostat provides optional locking cover assem-  
bly, start the Allen locking screws in the cover with the  
wrench provided. See Fig. 10.  
1
.
Connect an ac ammeter of appropriate range between  
the heating terminals of the subbase:  
a. Stage 1—between W1 and RH or R;  
b. Stage 2—between W2 and RH or R  
c. Stage 3—between W3 and RH or R.  
Move the system switch to HEAT or AUTO.  
After one minute, read the ammeter and record the  
reading:  
Note the two tabs along the top inside edge of the ther-  
mostat base. The tabs fit into corresponding slots on top  
of the subbase. Mount the thermostat on the subbase.  
Align the two captive mounting screws in the thermostat  
base with the posts on the subbase. Tighten both  
screws. Do not overtighten screws or damage to sub-  
base posts can result.  
2.  
.
3
a. Stage 1—__________A;  
b. Stage 2—__________A;  
c. Stage 3—__________A.  
NOTE: If equipment cycles too fast, set the indicator to a  
higher current rating, but not more than one-half divi-  
sion at a time, and recheck the cycle rate. Most con-  
ventional two-stage heating equipment is designed  
to operate at three cycles per hour per stage, and  
one-stage heating equipment at six cycles per hour,  
at 50 percent load conditions. When using the T874  
Thermostat in heat pump systems, set the heat antic-  
ipator at 140 percent of the actual primary control  
current draw to reduce the cycling rate. See Fig. 11.  
11  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Most heat pump systems should cycle 2-1/2 to 3 times per hour.  
HEAT—heating system is automatically controlled by the  
thermostat. Cooling system is off.  
4.  
Hang the upper edge of the thermostat cover on top of  
the thermostat base and swing the cover downward  
until it engages with the cover clip.  
AUTO—thermostat automatically changes between heat-  
ing and cooling system operation, depending on the  
indoor temperature.  
COOL—cooling system is automatically controlled by the  
thermostat. Heating system is off.  
STAGE ONE  
ANTICIPATOR  
HEATING  
EM.HT.—emergency heat relay is automatically controlled  
by the thermostat. Cooling system is off. Compressor is  
de-energized.  
CONTROL  
SUPL.HT.—supplemental heat relay is energized. Cooling  
system is off. Compressor is de-energized.  
WOOD—heating system is operating with only the wood-  
burning stage.  
OIL—heating system is operating with only the oil-burning  
stage.  
WOOD/OIL—wood and oil stages operate sequentially;  
first the WOOD stage operates, then the OIL stage  
operates if the WOOD stage cannot handle the load.  
EVAP—controls cooling system by water evaporation; see  
equipment instructions for further information.  
OVERRIDE—night setback is disabled.  
1
.2.8  
STAGE TWO  
ANTICIPATOR  
HEATING CONTROL  
MOVE INDICATOR TO  
MATCH CURRENT RATING  
OF PRIMARY CONTROL  
M5069  
ON—heating system is controlled by the thermostat. EM.  
HT. or SUPL. HT. relay is not energized.  
Fig. 11. Adjustable heat anticipator scales.  
FAN SWITCH positions control fan operation as follows:  
ON or CONT.—fan operates continuously.  
AUTO—fan operates as controlled by the thermostat in  
heat pump systems or conventional cooling mode; fan  
operates as controlled by the plenum switch in conven-  
tional heating mode.  
Temperature Setting  
Move the heating and cooling levers to the desired comfort  
positions. See Fig. 12. On some models with two stages of  
heating or cooling, the same lever controls both stages. The  
minimum differential between heating and cooling setpoints is  
LO—fan operates constantly at low speed.  
MED—fan operates constantly at medium speed.  
HI—fan operates constantly at high speed.  
4°F (2°C) (5°F [3°C]) on T874W.  
If model has optional screws to lock temperature control  
levers, loosen these screws before making temperature  
adjustment; tighten the screws when levers are set at desired  
position.  
To move the subbase switches to the desired control  
positions, use thumb and index finger to slide the lever. The  
lever must stop over desired function indicator position for  
proper circuit operation.  
STAGE 1  
HEATING  
HEATING  
LEVER  
COOLING  
STAGE 3  
HEATING  
Spring return momentary position switching feature is  
available on selected subbase models. On these models, the  
fan switch is positioned to the right of the system switch. By  
moving the fan switch to the far right and releasing it, the ON  
position circuit makes. The lever springs back on release. This  
position is not marked on the subbase.  
LEVER  
STAGE 1  
COOLING  
Setting the Adjustable Differential  
The adjustable interstage differential feature, on a selected  
T874D model only, can be identified by the scale and tension  
screw near the heating and cooling mercury switches. See  
Fig. 13. On this model, the number of degrees between the  
making of the first and second stage mercury bulbs is  
adjustable. This feature is especially useful if the first stage  
controls the comfort temperature, and the second stage  
controls the energy savings temperature. Timers, such as the  
S6005, for insertion between the first and second stage  
control points must be ordered separately.  
STAGE 2  
HEATING  
CAPTIVE  
MOUNTING  
SCREWS (2)  
STAGE 2  
COOLING  
M7625  
Fig. 12. Internal view of T874W (three stages of  
heating, two stages of cooling).  
Each mark on the scale represents 1°F (0.6°C) The  
differential is factory set at 2°F (1°C) the differential can be set  
as high as 12°F (7°C) To set the adjustable interstage  
differential, loosen the tension screw. See Fig. 13. Slide the  
adjustable scale to align with the number of degrees desired  
between stages. Use the lower edge of the tension screw  
bracket as a guide for alignment. In heating, slide the lever  
wider apart for a larger differential, or closer together for a  
Subbase Setting  
The subbase switching positions control the system operation  
as described below.  
SYSTEM SWITCH (see subbase for positions):  
OFF—both the heating and cooling systems are off. If the  
fan switch is at the AUTO position, the cooling fan is  
also off.  
60-2485—8  
12  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
smaller differential. In cooling, slide the lever closer together  
for a larger differential, or wider apart for a smaller differential.  
While supporting the scale with hand, tighten the tension screw.  
CAUTION  
Equipment Damage Hazard.  
When the thermostat is used to control a two-stage  
heating or cooling system, the second stage mercury  
bulb must never make before the first stage bulb, or  
severe equipment damage could result. To prevent  
this problem, provide at least 2°F (1°C) differential  
between stage-one and stage-two make points.  
Example: in heating, if stage-one makes at 70°F (21°C)  
stage-two should make at 68°F (20°C) or lower.  
IMPORTANT  
Support the scale with hand while tightening tension  
screw. See Fig. 13. Failure to do so can result in  
twisting and damaging bimetal coil.  
HEATING SET-  
POINT LEVER  
TENSION  
SCREW  
HEAT  
50 60 70 80  
FIRST  
STAGE  
SWITCH  
Verify the Adjustment  
Heating  
Start with the heating setpoint lever all the way to the left.  
Slowly move the lever to the right, just until the first stage bulb  
makes (mercury rolls to the right side of the bulb). Note the  
setting on the temperature scale. Slowly move the lever to the  
right until the second stage bulb makes. Note the setting on  
the temperature scale. The difference between the two  
temperatures is the interstage differential, which should match  
the number set on the scale with the tension screw.  
1
.2  
SCALE  
SECOND STAGE  
ADJUSTABLE)  
SWITCH  
(
Cooling  
HEATING  
Start with the cooling setpoint lever all the way to the right.  
Slowly move the lever to the left, just until the first stage bulb  
makes (mercury rolls to the left side of the bulb). Note the  
setting on the temperature scale. Slowly move the lever to the  
left until the second stage bulb makes. Note the setting on the  
temperature scale. The difference between the two  
TENSION  
SCREW  
ALIGN LOWER  
EDGE WITH  
SCALE  
SLIDE LEVER  
temperatures is the interstage differential, which should match  
the number set on the scale with the tension screw.  
NOTCH  
0°F  
WIDER APART  
FOR LARGER  
DIFFERENTIAL  
1
SCALE  
1
CHECKOUT  
COOLING  
Heating  
Move the system switch on the Q674 Subbase to HEAT or  
AUTO. Move the heat lever on the T874 about 10°F (6°C)  
above room temperature. See Fig. 12. Heating system should  
start and the fan should run after a short delay. Move the heat  
lever about 10°F (6°C) below room temperature. The heating  
equipment should shut off, and the fan should run for a short  
time, then shut off.  
TENSION  
SCREW  
ALIGN LOWER  
EDGE WITH  
SCALE  
SLIDE LEVER  
CLOSER TOGETHER  
FOR LARGER  
NOTCH  
4°F  
DIFFERENTIAL  
SCALE  
In heat pump applications, sometimes time delays are  
involved before the compressor and auxiliary heat are  
activated. This is due to a minimum-off timer, which prevents  
the compressor from restarting for five minutes from when the  
thermostat last turned off the compressor, or from when the  
system first received power.  
1
1
EACH MARK ON THE SCALE REPRESENTS 1°F (0.6°C).  
M937  
Fig. 13. Set adjustable interstage differential.  
Cooling  
CAUTION  
Equipment Damage Hazard.  
Do not operate cooling if outdoor temperature is below  
50°F (10°C). Refer to manufacturer recommendations.  
13  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Move the system switch on the Q674 Subbase to COOL or  
AUTO. Move the cool setting lever on the T874 Multistage  
Thermostat about 10°F (6°C) below room temperature. See  
Fig. 12. The cooling equipment and fan should start. If the  
system has two stages of cooling, both stages should start.  
Move the cool lever about 10°F (6°C) above room  
Thermometer  
The thermometer in your thermostat has been accurately  
calibrated at the factory. The thermometer should only need  
adjustment if it has been dropped or shifted due to mishandling.  
If the setpoint lever and the thermometer reading do not  
agree, use the following procedure:  
temperature. The cooling equipment and fan should stop.  
1
.
Remove the thermostat cover by pulling up from the  
bottom edge of the cover away from the base until it  
snaps free of the cover clip.  
Fan  
Move the system switch to COOL, OFF, or AUTO. If  
necessary, position both temperature setting levers so that the  
heating and cooling equipment are off. Move the fan switch to  
ON or CONT. The fan should run continuously. When the fan  
switch is in AUTO, LO, MED, or HI position, fan operation is  
controlled by the heating or cooling system.  
2
.
.
Set the thermostat cover on a table near an accurate  
thermometer.  
3
Allow ten minutes for cover thermometer to sense area  
temperature; compare the readings. Be careful not to  
touch thermometer or breathe on it.  
4.  
If the readings are the same, replace cover and put the  
system into operation.  
Outdoor Reset Thermistor (Where  
Applicable)  
5. If the readings are different, insert a small screwdriver in  
the thermometer slot and turn it until the thermometers  
have the same reading. See Fig. 15.  
If the system is supplied with a thermistor, it must be used; if  
not used, thermostat performance deviates radically from  
proper operation.  
6. Replace thermostat cover and put the system into oper-  
ation.  
The proper thermistor operation must be verified to ensure the  
correct operation of the thermostat. Check thermistor  
operations as follows:  
1
.
.
Disconnect the T wire on the subbase.  
2
Use an ohmmeter to measure resistance between the  
T wire and the A subbase terminal.  
3.  
.
Take outdoor temperature at thermistor location and find  
the correct thermistor resistance on the Fig. 14 chart.  
If the resistance measured in step 2 and the calculated  
resistance in step 3 vary by more than 15 percent, the  
thermistor requires replacement. Contact Honeywell or  
installing dealer for replacement packaged outdoor ther-  
mistor, part no. C815A1005.  
4
4
4
4
4
3
3
3
3
3
2
2
2
2
2
1
1
1
1
1
600  
400  
200  
000  
800  
600  
400  
200  
000  
800  
600  
400  
200  
000  
800  
600  
400  
200  
000  
C815A THERMISTOR RESISTANCE  
R = 400 ohms ± 10% AT 77°F (25°C)  
M5070  
Fig. 15. Thermometer calibration.  
UNDERSTANDING CIRCUITS  
To understand wiring diagrams, it is important to know what all  
the symbols mean and how to trace the path of the circuits  
from the transformer. See Fig. 16 through 25.  
8
6
4
2
00  
00  
00  
00  
0
Circuit descriptions and terminology are defined as follows:  
For standard heating-cooling circuits:  
-20  
0
20  
40  
60  
80  
100  
120 140  
M1590A  
TEMPERATURE OF THERMISTOR (°F)  
Auto changeover—refers to the presence of an AUTO  
position in the system switching (EX: Q674E with OFF-  
HEAT-AUTO-COOL switching). The thermostat auto-  
matically changes between heat and cool modes as  
indoor temperature changes.  
Fig. 14. Thermistor resistance chart.  
CALIBRATION  
Manual changeover—requires a system switch movement  
to change mode (EX: Q674B with HEAT-OFF-COOL  
switching). T874D Multistage Thermostats with 2 heat  
or 2 cool switches are shown on most standard circuits.  
Most standard or TRADELINE® subbases (Q674A-E,G)  
can be used with T874A-F standard or TRADELINE  
Thermostat  
T874 Thermostats are accurately calibrated at the factory.  
They do not have provision for field calibration.  
60-2485—8  
14  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
thermostats. The schematics can be field-modified as  
required (EX: if T874C is being used, eliminate second  
stage of heat).  
perature rise. Fixed anticipation is represented by a zig-  
zag line and adjustable anticipation is a zigzag with an  
arrow. The resistance of the fixed anticipator is so large  
it limits current so that a system relay cannot be pulled  
in from a circuit path going through the fixed anticipator.  
The relay can be pulled in through an adjustable antici-  
pator because its resistance is generally 0 to 5 ohms.  
5. The center portion (the subbase) contains the switches.  
The fan switch is above the system switch. The small  
circles on the switch represent the maximum possible  
contacts available on the Q674 Subbase. The larger cir-  
cles represent the switch positions available on this par-  
ticular Q674, with the solid circle representing where it  
is actually switched on the diagram.  
For heat pump circuits:  
Cool changeover valve—operates on cooling. The revers-  
ing valve or relay is activated either by moving the sys-  
tem switch to COOL (manual changeover) or by a  
mercury switch that makes on a temperature rise (auto  
changeover).  
Heat changeover valve—operates on heating. The revers-  
ing valve or relay is activated either by moving the sys-  
tem switch to HEAT (manual changeover) or by a  
mercury switch that makes on a temperature fall (auto  
changeover).  
System monitor relay—optional equipment on some heat  
pumps includes an R4222P1065 or equivalent. This  
system monitor relay detects a malfunction in the com-  
pressor and indicates the malfunction by activating the  
EMERGENCY HEAT LED on the Q674 Switching Sub-  
base. The system monitor relay is usually wired into the  
L terminal on the Q674.  
NOTE: Solid circles are not interconnected electrically.  
At the right, the relays and contactors are shown, attached to  
the proper terminals. The terminals are represented by large  
circles with terminal designations in capital letters. See Table  
3 for the meaning of each lettered terminal.  
Each mercury switch is identified by function:  
H1—Stage 1 Heating.  
Sometimes power for a fixed anticipator is brought through an  
off system relay like the changeover relay shown in Fig. 20.  
This current is kept low by the high resistance of the fixed  
anticipator so that relay does not pull in.  
H2—Stage 2 Heating.  
H3—Stage 3 Heating.  
C1—Stage 1 Cooling.  
C2—Stage 2 Cooling.  
C3—Stage 3 Cooling.  
C/O—Changeover (heat pumps).  
KEY TO HOOKUP SYMBOLS  
Each anticipator is identified and each switch affected is  
named (EX: H1 anticipator, C1 anticipator).  
RELAY/CONTACTOR CONTACTS  
TRANSFORMER  
All T874 Multistage Thermostats use mercury switches. Each  
schematic indicates switch operation by being drawn in the  
open position with an arrow indicating operation with a  
temperature RISE or FALL.  
(24 VAC SECONDARY)  
B
TERMINAL  
RELAY OR CONTACTOR COIL  
MERCURY SWITCH  
One circuit has been selected that is typical of various models  
used with heat pumps. This circuit has been traced to illustrate  
the functions performed by these control systems.  
LED  
ODT  
OUTDOOR THERMOSTAT  
EHR  
Tracing Method:  
EMERGENCY HEAT RELAY  
1.  
Always begin at the system transformer or R terminal.  
You may want to draw the switch contacts in each  
switch position to aid in tracing. Colored pencils are  
helpful when only one copy of the circuit is available.  
See Fig. 16 for a description of the hookup symbols and  
Fig. 17 through 25 for typical hookups.  
FIXED ANTICIPATOR  
HIGH RESISTANCE  
RTD  
TIME DELAY RELAY  
(TYPICALLY 5 KILOHMS)  
RD  
DEFROST RELAY  
CHP  
PRESSURE SWITCH  
ADJUSTABLE ANTICIPATOR  
LOW RESISTANCE  
TYPICALLY 0 TO 5 OHMS)  
LACO  
2.  
3.  
4.  
Completely trace only one circuit at a time (for example:  
heat or cool).  
(
LOW AMBIENT CUTOFF  
M5848  
Connections are indicated by small dots at the point of  
intersection. If there is no dot, there is no connection.  
The left portion of the circuit (the thermostat) contains  
the mercury switches. The heat switches make on a  
temperature fall, and the cool switches make on a tem-  
Fig. 16. Key to hookup symbols.  
15  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
HOT) L1 L2  
(
1
H1/C1  
ANTICIPATOR  
R
FALL  
2
ODT 1  
EHR 1  
ODT 2  
H1  
RTD 1  
RTD 2  
C1  
W3  
3
4
FAN SWITCH  
AUTO  
ON  
EHR 2  
RTD 3  
RTD 1  
H2  
ANTICIPATOR  
W2  
5
6
AUX. HT.  
LED  
GREEN)  
(
H2  
2
X
FALL  
EM. HT.  
LED (RED)  
SYSTEM  
MONITOR  
SYSTEM  
SWITCH  
RD  
L
FAN RELAY  
G
O
EM. HT.  
HEAT  
OFF  
EM. HT.  
RELAY  
COOL CHANGEOVER  
VALVE  
E
COOL  
LACO  
CHP  
Y
B
COMPRESSOR  
CONTACTOR  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
AUXILIARY HEAT LED AVAILABLE ON SOME MODELS.  
M5072A  
Fig. 17. Internal schematic and typical hookup of a T874R Thermostat and Q674L Subbase in a heat pump application.  
The thermostat provides two-stage heating and one-stage cooling manual changeover operates on cooling.  
60-2485—8  
16  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(HOT)  
H1/C1  
R
ANTICIPATOR  
ODT 1  
EHR 1  
ODT 2  
L2  
FALL  
C1  
2
1
RTD 1  
RTD 2  
H1  
FAN SWITCH  
W3  
W2  
3
4
AUTO  
ON  
EHR 2  
RTD 3  
H2  
ANTICIPATOR  
AUX. HT.  
LED  
GREEN)  
RTD 1  
5
6
(
X
H2  
EM. HT.  
LED (RED)  
SYSTEM  
MONITOR  
FALL  
RD  
SYSTEM  
SWITCH  
L
FAN RELAY  
G
O
EM. HT.  
HEAT  
OFF  
EM. HT.  
RELAY  
CHANGEOVER  
VALVE  
E
COOL  
LACO  
CHP  
1
POWER SUPPLY. PROVIDE  
DISCONNECT MEANS AND  
OVERLOAD PROTECTION  
AS REQUIRED.  
Y
B
COMPRESSOR  
CONTACTOR  
M5840  
Fig. 18. Tracing the changeover relay circuit.  
THERMOSTAT  
H1/ C1  
SUBBASE  
SYSTEM COMPONENTS  
L1  
HOT)  
(
R
ANTICIPATOR  
ODT 1  
EHR 1  
ODT 2  
L2  
2
FALL  
C1  
1
RTD 1  
RTD 2  
H1  
FAN SWITCH  
W3  
3
4
AUTO  
ON  
EHR 2  
RTD 3  
H2  
ANTICIPATOR  
W2  
AUX. HT.  
LED  
GREEN)  
RTD 1  
5
6
(
X
H2  
EM. HT.  
LED (RED)  
SYSTEM  
MONITOR  
FALL  
RD  
SYSTEM  
SWITCH  
L
FAN RELAY  
G
O
EM. HT.  
HEAT  
OFF  
EM. HT.  
RELAY  
CHANGEOVER  
VALVE  
E
1
POWER SUPPLY. PROVIDE  
DISCONNECT MEANS AND  
OVERLOAD PROTECTION  
AS REQUIRED.  
COOL  
LACO  
CHP  
Y
B
COMPRESSOR  
CONTACTOR  
M5841  
Fig. 19. Tracing the heat 1 and anticipation circuit.  
17  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
H1/ C1  
SUBBASE  
SYSTEM COMPONENTS  
L1  
ANTICIPATOR  
(HOT)  
R
FALL  
2
ODT 1  
EHR 1  
L2  
1
H1  
C1  
RTD 1  
RTD 2  
3
4
FAN SWITCH  
W3  
AUTO  
ON  
ODT 2  
EHR 2  
H2  
ANTICIPATOR  
RTD 3  
W2  
5
6
AUX. HT.  
LED  
GREEN)  
RTD 1  
(
H2  
X
FALL  
EM. HT.  
LED (RED)  
SYSTEM  
MONITOR  
RD  
SYSTEM  
SWITCH  
L
FAN RELAY  
G
O
EM. HT.  
HEAT  
OFF  
EM. HT.  
RELAY  
CHANGEOVER  
VALVE  
E
1
POWER SUPPLY. PROVIDE  
DISCONNECT MEANS AND  
OVERLOAD PROTECTION  
AS REQUIRED.  
COOL  
LACO  
CHP  
Y
B
COMPRESSOR  
CONTACTOR  
M5842  
Fig. 20. Tracing the heat 1 anticipation circuit.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
H1/C1  
ANTICIPATOR  
(HOT)  
R
ODT 1  
EHR 1  
L2  
1
FALL  
2
RTD 1  
RTD 2  
FAN SWITCH  
H1  
C1  
W3  
3
4
AUTO  
ON  
ODT 2  
EHR 2  
RTD 3  
H2  
ANTICIPATOR  
W2  
AUX. HT.  
LED  
GREEN)  
RTD 1  
5
6
(
X
H2  
EM. HT.  
LED (RED)  
SYSTEM  
MONITOR  
FALL  
RD  
SYSTEM  
SWITCH  
L
FAN RELAY  
G
O
EM. HT.  
HEAT  
OFF  
EM. HT.  
RELAY  
CHANGEOVER  
VALVE  
E
1
POWER SUPPLY. PROVIDE  
DISCONNECT MEANS AND  
OVERLOAD PROTECTION  
AS REQUIRED.  
COOL  
LACO  
CHP  
Y
B
COMPRESSOR  
CONTACTOR  
M5843  
Fig. 21. Tracing the heat 2, anticipation and AUX. HT. LED circuit.  
60-2485—8  
18  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(
HOT)  
H1/C1  
ANTICIPATOR  
R
ODT 1  
EHR 1  
L2  
FALL  
2
1
RTD 1  
RTD 2  
FAN SWITCH  
H1  
C1  
W3  
3
AUTO  
ON  
ODT 2  
EHR 2  
4
RTD 3  
H2  
ANTICIPATOR  
W2  
AUX. HT.  
LED  
GREEN)  
RTD 1  
5
6
(
X
H2  
EM. HT.  
LED (RED)  
SYSTEM  
MONITOR  
FALL  
RD  
SYSTEM  
SWITCH  
L
FAN RELAY  
G
O
EM. HT.  
HEAT  
OFF  
EM. HT.  
RELAY  
CHANGEOVER  
VALVE  
E
COOL  
1
POWER SUPPLY. PROVIDE  
DISCONNECT MEANS AND  
OVERLOAD PROTECTION  
AS REQUIRED.  
LACO  
CHP  
Y
B
COMPRESSOR  
CONTACTOR  
M5844  
Fig. 22. Tracing the emergency heat and EM. HT. LED circuit.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(HOT)  
R
H1/C1  
ANTICIPATOR  
ODT 1  
EHR 1  
L2  
FALL  
2
1
RTD 1  
RTD 2  
FAN SWITCH  
H1  
W3  
W2  
C1  
H2  
3
4
AUTO  
ON  
ODT 2  
EHR 2  
RTD 3  
ANTICIPATOR  
AUX. HT.  
LED  
GREEN)  
RTD 1  
5
6
(
X
H2  
EM. HT.  
LED (RED)  
SYSTEM  
MONITOR  
FALL  
RD  
SYSTEM  
SWITCH  
L
FAN RELAY  
G
O
EM. HT.  
HEAT  
OFF  
EM. HT.  
RELAY  
CHANGEOVER  
VALVE  
E
1
POWER SUPPLY. PROVIDE  
DISCONNECT MEANS AND  
OVERLOAD PROTECTION  
AS REQUIRED.  
COOL  
LACO  
CHP  
Y
B
COMPRESSOR  
CONTACTOR  
M5845  
Fig. 23. Tracing the cooling circuit.  
19  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
R
W3  
W2  
(HOT)  
H1/C1  
ANTICIPATOR  
ODT 1  
EHR 1  
L2  
FALL  
2
1
RTD 1  
RTD 2  
FAN SWITCH  
H1  
C1  
3
4
AUTO  
ON  
ODT 2  
EHR 2  
RTD 3  
H2  
ANTICIPATOR  
AUX. HT.  
LED  
GREEN)  
RTD 1  
5
6
(
X
H2  
EM. HT.  
LED (RED)  
SYSTEM  
MONITOR  
FALL  
RD  
SYSTEM  
SWITCH  
L
FAN RELAY  
G
O
EM. HT.  
HEAT  
OFF  
EM. HT.  
RELAY  
CHANGEOVER  
VALVE  
1
POWER SUPPLY. PROVIDE  
DISCONNECT MEANS AND  
OVERLOAD PROTECTION  
AS REQUIRED.  
E
COOL  
LACO  
CHP  
Y
B
COMPRESSOR  
CONTACTOR  
M5846  
Fig. 24. Tracing the auto fan circuit.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
H1/C1  
R
(HOT)  
ANTICIPATOR  
ODT 1  
EHR 1  
ODT 2  
L2  
FALL  
2
1
RTD 1  
RTD 2  
FAN SWITCH  
H1  
C1  
W3  
3
4
AUTO  
ON  
EHR 2  
RTD 3  
H2  
W2  
ANTICIPATOR  
AUX. HT.  
LED  
RTD 1  
5
6
(GREEN)  
X
H2  
EM. HT.  
LED (RED)  
SYSTEM  
MONITOR  
FALL  
RD  
SYSTEM  
SWITCH  
L
FAN RELAY  
G
O
EM. HT.  
HEAT  
OFF  
EM. HT.  
RELAY  
CHANGEOVER  
VALVE  
E
1
POWER SUPPLY. PROVIDE  
DISCONNECT MEANS AND  
OVERLOAD PROTECTION  
AS REQUIRED.  
COOL  
LACO  
CHP  
Y
B
COMPRESSOR  
CONTACTOR  
M5847  
Fig. 25. Tracing the fan on circuit.  
60-2485—8  
20  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Heat anticipators add heat during the call for heat. Cooling  
anticipators are activated while the air conditioner is off. See  
Fig. 28. This heater makes the thermostat think it is warmer than  
it really is, and brings it on sooner than the bimetal alone would.  
OPERATION  
Heat Anticipation/Cool Anticipation  
When controlling a heating unit with a thermostat, the  
temperature does not remain exactly at the thermostat  
setpoint, but varies within a certain temperature range. Heat  
anticipation is added to the thermostat to reduce this range.  
L1  
L2  
HOT)  
(
The anticipator is a small resistive heater in the thermostat  
that heats when the system is on (heat mode) or off (cool  
mode). The heat produced by the anticipator raises the  
internal bimetal temperature slightly faster than the  
surrounding room temperature. The thermostat anticipates the  
need to shut off the heating system sooner than it would if  
affected by room temperature only.  
RISE  
STAGE 1  
COOL RELAY  
C1  
C1 ANTICIPATOR  
There are two types of heat anticipation, adjustable and fixed.  
M5825  
Fig. 28. Internal cooling anticipation schematic.  
Adjustable anticipation is also called current anticipation. See  
Fig. 26. The heater is in series with the mercury switch and  
heating primary. The pointer is adjusted to match the current  
draw of the primary control, and the correct amount of heat is  
added for proper cycle rates.  
Interstage Differential  
The mercury switch of each stage of heat makes at a slightly  
different temperature; that is, the mercury makes the contacts  
of the first stage bulb at one temperature, and the second  
stage bulb at another temperature. The difference between  
these two temperatures is the interstage differential.  
L1  
HOT)  
L2  
(
Interstage differential is the difference between the two make  
points when the bulbs are controlled by the heating of the  
bimetal and the action of the heat anticipator. The interstage  
differential is 1.9°F (1°C) between the stages of heating or the  
stages of cooling for most models.  
H1 ANTICIPATOR  
Mechanical differential is the difference between the make  
and break points of each switch. The mechanical differential  
for the T874 is 1°F (0.6°C) between the stages of heating or  
between the stages of cooling for most models.  
H1  
STAGE 1 HEAT RELAY  
FALL  
M5823  
Fig. 26. Adjustable anticipation heater in series with load.  
Fixed anticipation is also called voltage anticipation. See  
Fig. 27. The heater is in parallel with the primary control and is  
not affected by the current draw of the primary. It establishes  
the proper cycle rate for any application.  
Droop  
factor called droop.  
The addition of anticipator heat to the bimetal causes a control  
As the weather grows colder, the heating appliance must  
operate longer and more frequently. More heat must be added  
to the bimetal. The bimetal now thinks it is warmer than it  
really is, and actual room temperature is controlled at a lower  
temperature than the setpoint indicates. At 100 percent heat  
load, this droop can be significant.  
L1  
HOT)  
L2  
(
The C815A Outdoor Reset Thermistor is used in heat pump  
systems to minimize droop. Without some method of  
countering this situation, the occupant could notice the  
temperature offset.  
STAGE 1  
HEAT RELAY  
FALL  
H1 ANTICIPATOR  
H1  
Outdoor Reset  
M5824  
Some T874/Q674 models are intended for use with the  
C815A Outdoor Thermistor. The outdoor thermistor provides  
significantly improved thermostat performance when  
Fig. 27. Fixed anticipation heater in parallel with load.  
compared to conventional multistage thermostats. The C815A  
is usually located in the heat pump condensing unit outdoors.  
21  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
A strip of four inserts is included with TRADELINE T874. Drop  
a strip into the recessed area behind the scaleplate so  
selected LEDs show. Make sure insert is completely seated in  
recessed area. Let scaleplate pop back; then set levers to  
desired position.  
CAUTION  
Equipment Damage Hazard.  
Due to calibration techniques used for T874  
Thermostats with outdoor reset, the C815A Thermistor  
must be wired into the system at all times. Failure to  
do so will result in serious degradation of performance.  
FILTER LED lights when the filter is clogged and needs  
replacement.  
CHECK LED lights when something needs to be checked  
or done to maintain efficient operation of system. See  
heating system instructions for CHECK LED meaning.  
EM. HT. LED lights when the emergency heat is operating.  
SUPL. HT. LED lights when the supplemental heat is  
operating.  
Service and Replacement of C815A Outdoor  
Thermistor  
To check and verify thermistor operation, perform the  
following steps:  
LOCKOUT LED lights when the system is shut down and  
needs maintenance.  
1
.
.
Disconnect wire from T terminal on subbase.  
Measure resistance with ohmmeter across the T sub-  
base wire and X subbase terminal.  
AUXILIARY HEAT LED lights when the auxiliary heat is  
operating.  
2
SERVICE or MALFUNCTION LED can have several  
meanings. Consult heating system instructions.  
3.  
Take outdoor temperature measurement at thermistor  
location and find correct thermistor resistance on the  
chart in Fig. 29.  
LEDs cannot be replaced or added in the field.  
4.  
Compare resistance on the chart with measured resis-  
tance. Replace C815A if resistance varies more than 15  
percent. Contact installing dealer for packaged replace-  
ment outdoor thermistor.  
LEDS  
EM.  
HEAT FILTER SERV. HEAT  
AUX  
4600  
4400  
4200  
4000  
3800  
3600  
3400  
3200  
3000  
2800  
2600  
2400  
2200  
2000  
1800  
1600  
1400  
1200  
1000  
COOL  
80  
50 60 70 80  
C815A THERMISTOR RESISTANCE  
R = 400 ohms ± 10% AT 77°F (25°C)  
M5830  
Fig. 30. T874/Q674 LED location.  
Restricted Setpoint (DoD)  
The Department of Defense (DoD) models are equipped with  
a restricted setpoint feature for fuel efficiency.  
800  
600  
400  
200  
0
Fixed stops are factory-set so setpoint levers cannot be set  
above 72°F (22°C) on heating, or below 78°F (26°C) on cooling.  
-20  
0
20  
40  
60  
80  
100  
120 140  
M1590A  
TEMPERATURE OF THERMISTOR (°F)  
Fig. 29. Thermistor resistance chart.  
Applications  
The T874/Q674 can be applied to standard residential  
systems for automatic or manual changeover, to commercial  
rooftop applications, or to heat pump applications.  
Features  
Two of the features of the T874/Q674 include LED indicators  
and restricted setpoint.  
Changeover on Standard Residential  
Systems  
LED Indicators  
The light-emitting diodes (LED) indicators on the subbase  
light on command when something specific happens in the  
system. See Fig. 30.  
In a standard residential heating-cooling circuit, changeover  
between heating and cooling can be done either automatically  
or manually.  
Up to four different LEDs are available. The thermostat has a  
clear lens window for viewing each LED. On TRADELINE  
models, a small insert is used so the LED function desired can  
be selected. This must be done during installation.  
Automatic changeover is done by an AUTO position on the  
subbase system switch. See Fig. 31. When the switch is in the  
AUTO position, the thermostat automatically changes between  
heat and cool modes, depending on the indoor temperature.  
A blank insert is factory-installed in some T874 models. To  
remove it, push both temperature setting levers to the far ends  
of the thermostat. Use index fingernail to gently pull out the  
scaleplate a fraction of an inch. Turn thermostat upside-down,  
and the blank insert falls out.  
60-2485—8  
22  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
When enthalpy is low enough, the thermostat and a sensor tell  
the economizer damper to open to let in cool air from the  
outside. When enthalpy is high, the thermostat and sensor tell  
the damper to close. No more outside air comes in, so the air  
conditioner is used instead.  
OFF EM. HT. HEAT AUTO COOL  
Heat Pump Application  
M5828  
A heat pump system operates much like an air conditioner.  
However, the heat pump is capable of moving heat in two  
directions; from inside the home to outdoors for cooling, or  
from outdoors to inside for heating.  
Fig. 31. System switching for automatic changeover.  
Automatic changeover is frequently used in areas where there  
are large temperature differences in 24 hours. Some uses for  
the automatic changeover feature are in the southern states  
The heat pump can be controlled by separate relay/contactor  
components, which are energized or de-energized by the T874.  
(
cool in the morning and hot in the afternoon) and in  
commercial applications.  
Changeover between heating and cooling for heat pump  
circuits can be accomplished either manually or automatically.  
Manual changeover requires a system switch movement to  
change the mode. See Fig. 32. Most manual changeover  
switches consist of HEAT-OFF-COOL choices. For heating,  
switch to HEAT. For cooling, switch to COOL. It is not automatic.  
Manual changeover control requires a system switch  
movement to change the mode. The reversing valve is  
activated by moving the system switch to COOL for cooling or  
to HEAT for heating operation.  
Manual changeover is often used in areas where the  
temperature is relatively stable between day and night.  
Automatic changeover is accomplished by one of the mercury  
bulb switches in the thermostat. On a system with automatic  
changeover on cooling, the changeover valve is energized by  
a mercury switch that makes on a temperature rise. On  
heating, the changeover valve is energized by a mercury  
switch that makes on a temperature fall.  
A description of the methods used to control heat pumps  
follows.  
OFF EM. HT. HEAT COOL  
M5829  
Fig. 32. System switching for manual changeover.  
Space Temperature Sensing Low Voltage  
Controls  
Commercial Rooftop Application  
Control systems for heat pumps usually utilize low voltage  
control circuits. The variety of control functions required and  
the relative complexity require a versatile and economical  
method of control. There are several interlocks and indication  
functions that would be more difficult and expensive to wire in  
line voltage circuits. Low voltage controls have the precision  
and flexibility needed.  
The T874 can be used as part of a commercial rooftop  
application to run mechanical cooling.  
An economizer is often used as part of a rooftop application to  
save on air conditioning. See Fig. 33.  
The thermostat used is a low voltage device that has good  
temperature sensitivity and several manual and automatic  
switching capabilities.  
OUTDOOR  
AIR  
Two-Stage Thermostat  
In most installations, the heat pump itself requires auxiliary  
heat, usually in the form of electric strip heaters, to carry the  
building heating load at design conditions. Since the heat  
pump is usually more efficient, the control strategy is to run  
the heat pump whenever possible and the auxiliary heat only  
when necessary—during very cold weather or if the heat  
pump fails. Usually the auxiliary heat is used only below the  
balance point (temperature at which the heat pump cannot  
handle heating load by itself).  
H205 OR H705  
ENTHALPY  
CONTROL  
RETURN  
AIR  
DISCHARGE AIR SENSOR  
DOWNSTREAM FROM THE  
EVAPORATOR COIL  
M5827A  
Fig. 33. Typical commercial rooftop economizer  
application.  
A two-stage thermostat makes this possible. The two stages  
make sequentially as the temperature drops. There is a  
degree or two between stages so that the second stage (the  
Enthalpy is the temperature and humidity of the air. A more  
accurate analysis of the suitability for free cooling can be  
made by monitoring the enthalpy.  
23  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
one controlling the auxiliary heat) makes only when the heat  
pump alone cannot handle the load. That is how the strategy  
of using the most economical heat first is implemented.  
This is particularly important on the 3-stage T874. The  
additional stage means that more droop is introduced when  
the system is in operation. That is the reason the TRADELINE  
T874W is sold in a package with the outdoor sensor and the  
correct subbase.  
Cycling Rate  
Normally, thermostat anticipation is set to cycle a fossil fuel  
furnace about five or six times an hour (at 50 percent load).  
This provides a reasonable balance between comfort, stability  
and economy.  
Outdoor Reset—How it Works  
The heater in the thermostat is connected in series with a  
thermistor sensor that measures outdoor temperature. See  
Fig. 34. In warm weather, the thermistor has very low  
resistance, permitting a large current flow in the heater, which  
generates a relatively large amount of heat in the thermostat.  
A heat pump, being a mechanical refrigeration system, should  
be cycled at a rate of 2-1/2 to 3 times an hour. With a T874,  
this is accomplished by setting the anticipator at the total  
current draw of the controlled device (the contactor and  
possibly the changeover relay or valve). Most likely, the  
compressor operates from the first stage of the thermostat.  
In cold weather, the outdoor sensor has high resistance,  
which results in low current flow and little or no heat being  
added to the thermostat. This raises the control point,  
overcoming the effects of droop and interstage differential.  
The second stage normally controls the auxiliary heaters. This  
heat anticipator can be set for the current draw of the electric  
heat primary, and produces good control.  
L1  
HOT)  
L2  
(
Voltage Anticipation  
Although not a specific requirement for heat pumps, several  
models of the T874 have voltage heat anticipation instead of  
current anticipation.  
C815A  
RESET  
HEATER  
OUTDOOR  
THERMISTOR  
SENSOR  
With voltage anticipation, the amount of heat added to the  
thermostat is constant no matter which load is connected to it.  
The anticipator realizes a constant voltage and produces a  
constant amount of heat during the ON cycle. This allows the  
cycling rate to be designed into the thermostat. The heat  
pump manufacturer is assured of correct performance  
independent of later thermostat adjustments.  
M5826  
Fig. 34. Location of thermistor.  
Changeover  
accomplished either automatically or manually, depending on  
the application. Changeover can occur in heating or cooling.  
Outdoor Reset  
Changeover between heating and cooing can be  
Outdoor reset, which a C815A Outdoor Thermistor makes  
possible, is sometimes applied in heat pump systems to help  
minimize the effect of the differential between stages. It takes  
2
°F (1.1°C) change in temperature to bring on the second  
The changeover valve is energized as long as the subbase  
function switch is in the appropriate position when manual  
changeover is used. If a system manually changes over on  
cooling, the valve energizes whenever the subbase switch is  
in the cooling mode.  
stage and full heating. Added to a certain amount of droop  
under high loads, there can be a large offset between the  
setpoint and room temperature.  
Without some method to counteract this situation, the  
temperature offset from the setpoint could be as much as 6°F  
One of the mercury bulb switches is used for control when the  
thermostat has automatic changeover. When the automatic  
changeover is in cooling, the changeover valve is energized  
when the first stage cooling switch makes. The second stage  
switch turns on the compressor.  
(
3.3°C) under high load conditions. It is not likely that the  
occupants accept this variation without making frequent  
thermostat setting changes.  
Outdoor reset has the effect of raising the setpoint at cold  
outdoor temperatures. Then, even with a few degrees droop,  
the space temperature stays near the desired setting.  
It is more common with new equipment to find that  
changeover occurs with cooling; that is, the changeover valve  
is energized to produce cooling.  
This is done by calibrating the thermostat high by 5°F (3°C)—  
the amount of expected offset. This offset compensates for  
differential and droop at high load factors so the thermostat  
switches at the setpoint. At warm temperatures, heat is added  
to the thermostat to compensate for this offset; at cold  
temperatures, the extra heat is automatically removed. The  
effect is the same as raising the setpoint as the outdoor  
temperature goes down.  
Whether automatic or manual changeover is used and  
whether the reversing valve is energized with cooling or with  
heating, a heat pump system can be controlled by the  
appropriate T874 Multistage Thermostat.  
60-2485—8  
24  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Low Temperature Lockouts  
THERMOSTAT  
HEAT 2  
Some manufacturers of heat pumps have previously controlled  
their units so the compressor was locked out below a specified  
outdoor temperature. This was done because of the stress  
placed on the compressor by the very cold temperatures, and  
the fact that efficiency drops off at low temperatures.  
HEAT 1  
COMP.  
STAGE 1  
Other manufacturers say that although efficiency is low at cold  
temperatures, the problem of starting the cold compressor is  
the most critical point. It is more important to keep the  
compressor running than to shut it off and try to restart it when  
the temperature warms up to +10°F (-12°C). Also the  
crankcase heater, which can run only when the compressor is  
off, compensates for the lower compressor efficiency. So, it is  
equitable to let the heat pump run even with a coefficient of  
performance (COP) slightly less than one, rather than to turn it  
off and have to run the crankcase heater.  
COMP.  
STAGE 2  
OUTDOOR  
THERMOSTAT  
AUXILIARY  
HEAT  
M5838  
Fig. 35. Two-stage heat pump with two-stage thermostat.  
The outdoor thermostat is set at the balance point with both  
heat pump stages running. So if the heat pump can control the  
heating load down to +20°F (-7°C), the auxiliary heat comes  
on with the second stage of the compressor.  
NOTE: To determine the COP of a heat pump, use the fol-  
lowing formula:  
Btu Out/Btu we pay for or Btuh Capacity  
COP =  
Unit Wattage x 3.413 Btu/Watt  
In effect, this control strategy changes the heat input of the  
second stage, depending on the amount of heat needed.  
Additional stages of auxiliary heat can be added with or  
without the control of more outdoor thermostats, See Auxiliary  
Heat section.  
Another factor favoring this control strategy is that newer heat  
pump designs maintain a level of efficiency even at outdoor  
temperatures well below zero. Some brands do not reach  
1.0 COP until -25°F (-32°C).  
Virtually all manufacturers now let the heat pump run  
continuously rather than lock it out at cold temperatures.  
Another way to control a two stage heat pump is with a three-  
stage thermostat. The T874W is designed for this application  
as well as others. See Fig. 36.  
Heat Pumps with Dual Compressors  
Staging residential sized heat pumps is a requirement that  
developed from the need to make heat pumps as efficient as  
possible. One of the methods used to improve overall  
seasonal efficiency is to reduce the amount of time the  
machine is operating in a transitional mode. Transitional mode  
is starting and stopping in addition to recovering from defrost.  
Under light loads, when the heat pump is cycling on and off,  
this can be a significant amount of time and can result in a  
significant efficiency reduction. Capacity control is one way to  
reduce the cycling rate and improve the efficiency.  
The advantage of this system is that no auxiliary heat is used until  
there is an actual demand from the controlled space.  
THERMOSTAT  
HEAT 3 HEAT 2 HEAT 1  
COMP.  
STAGE 1  
COMP.  
STAGE 2  
Additional capacity control methods used on other  
refrigeration systems (unloading, multiple compressors) are  
not as likely to be seen on residential heat pumps.  
AUXILIARY  
HEAT  
With a single-stage heat pump, the compressor is normally  
controlled by the first stage and the auxiliary heat by the  
second stage. The T874G, N and R Thermostats are used for  
this purpose.  
M5837  
Fig. 36. Two-stage heat pump with three-stage thermostat.  
With a two-stage compressor, the two thermostat switches  
control the individual compressor stages. Auxiliary heat is  
controlled along with the compressor stage-two, by the  
thermostat second stage. It comes on with the compressor  
high speed if an outdoor thermostat—wired in series with it—  
is made. See Fig. 35.  
Two speed Heat Pump  
One way to control capacity is to use a two-speed  
compressor. The compressor runs at low speed for stage-one  
heating and cooling. The compressor runs at the low speed  
instead of cycling the heat pump on and off under some light  
load conditions.  
The high speed is stage-two cooling. The compressor runs on  
high speed when loads increase so the low speed can no  
longer handle the cooling load. This reduces cycling rate and  
improves capacity.  
25  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Defrost Control  
L1  
(HOT)  
L2  
In some regions, during half or more of the heating season,  
the outdoor coil operates below 32°F (0°C) Frost or ice builds  
up on the outdoor coil of a heat pump similarly to the frost  
buildup in a household refrigerator. Eventually, this  
TRANSFORMER  
accumulation of ice interferes with efficient heat transfer from  
the outdoor air to the coil and refrigerant. Defrosting is  
occasionally required to remove this ice, and restore the heat  
pump ability to absorb heat from the air.  
THERMOSTAT  
HEAT 2  
DEFROST  
RELAY  
CONTACT  
HEAT 1  
AUXILIARY  
HEAT RELAY  
Defrosting  
A heat pump defrosts its outdoor coil by temporarily switching  
to the cooling mode, which causes hot gas from the  
compressor to be directed to the outdoor coil instead of to the  
indoor coil so the heat pump is taking heat from the home to  
warm up the outdoor coil. Defrosting is the greatest detriment  
to heat pump efficiency.  
M5835  
Fig. 38. Auxiliary heat with defrost control.  
WHEN TO DEFROST  
Timely defrosting is an essential component of effective heat  
pump operation. Failure to defrost often enough permits too  
much ice to accumulate on the coil. At the very least, this hurts  
efficiency; at worst, it results in compressor damage.  
Insufficient defrosting is a condition the heat pump  
manufacturer wants very much to avoid.  
Defrost Control Functions  
Besides changing over to the cooling mode, defrosting  
requires several more control initiated actions that follow.  
OUTDOOR FAN  
A 50 percent reduction in outdoor airflow is the maximum that  
would be tolerated. So the designer of a heat pump would  
select a control point that puts the system into defrost when  
airflow through the outdoor coil approaches half its normal  
level. Restricted airflow causes a greater load on the  
compressor; the outdoor coil runs colder, suction pressure is  
lower and the motor runs hotter.  
When defrosting has begun, it is standard practice to turn off  
the outdoor fan to speed up the melting process. A separate  
defrost relay is required to control that fan. See Fig. 37. Other  
contacts can be needed on the defrost relay to power the  
changeover valve or power part of the auxiliary heat.  
COMPRESSOR  
CONTACTOR  
MOTOR  
At the other end of the scale, defrosting too often hurts the  
overall energy efficiency of the system. Consider that in terms  
of heating the building, defrosting is a big loss. Not only does  
the system stop heating, but it actually moves heat out of the  
building. If electric strip heat is used, it is a further waste  
because its COP is 1.0 and not the 2.0 or more COP realized  
if the heat is provided by the heat pump.  
CONTROLLED BY  
OUTDOOR  
So, concern for equipment safety suggests fairly frequent  
defrosting while economy of operation argues for fewer  
defrost cycles. Since the equipment manufacturer chooses, the  
balance is usually tipped in favor of more frequent defrosting to  
avoid the possibility of damaging the compressor.  
DEFROST RELAY  
FAN MOTOR  
M5839  
Fig. 37. Outdoor fan with defrost control.  
AUXILIARY HEAT DURING DEFROST  
Auxiliary Heat  
Most pump manufacturers bring on some auxiliary heat during  
defrost, although this is not a universal practice. Some rely on  
the second stage of the thermostat to call for auxiliary heat as  
needed. Since the heat pump is operating in the cooling mode  
to defrost, it is delivering cold air to the living space. Auxiliary  
heat is used to offset this cooling. It requires another normally  
open contact on the defrost relay. See Fig. 38.  
Except in warm climates, all air-to-air heat pump installations  
require auxiliary heat capability. Electric resistance heaters  
can provide this auxiliary heat.  
The electric heaters (sometimes called strip heaters) usually  
are supplied in 5 kW units or strips (about 17,000 Btu). The  
indoor unit of the heat pump is designed to accommodate  
various electric heat units so it can be used in variously sized  
buildings in different parts of the country.  
Two-Stage Thermostat  
The most common heat pump control strategy is for the  
thermostat first stage to switch the compressor and the  
second stage to switch the auxiliary heat. See Fig. 39.  
60-2485—8  
26  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
The disadvantage of this system is that it can require several  
outdoor thermostats. Also, since the unit is operating most  
often at nearly full capacity, the thermostat is on longer which  
results in more droop, with a little more offset from the  
thermostat setpoint.  
THERMOSTAT  
HEAT 2 HEAT 1  
In addition, the capacity is tied to theoretical load, based on heat  
loss calculations. Normally this is very close to the actual load,  
but there are times where the second stage is switched on too  
soon (no harm done) or too late (the building gets cold).  
COMPRESSOR  
CONTRACTOR  
CONTROLS  
AT 65°F (18°C)  
AUXILIARY  
HEAT RELAY  
CONTROLS  
AT 63°F (17°C)  
The T874 Thermostat produces time modulated control, which  
is the on time of the thermostat changing during each cycle as  
the load changes. The on time of the heating system is  
directly proportional to the heating load of the building. As an  
example of the quality of time modulated control, consider the  
typical gas furnace. It can have a capacity of 100,000 Btu  
M5836  
Fig. 39. Auxiliary heat in two-stage thermostat.  
This method keeps the auxiliary heat off until the heating load  
is large enough to demand 100 percent heat pump operation.  
That demand is measured by the thermostat and is the actual  
heat requirement of the space. The two-stage thermostat  
requires about a 2°F (1.1°C) room temperature drop to bring  
on the second stage.  
(
293 kW), which is controlled On-Off. The output is 100,000 Btu  
293 kW) or nothing. A quality thermostat controls so closely that  
(
the occupants rarely detect changes in room temperature.  
The same is true with 50,000 or 60,000 Btu (146.5 or  
1
78.8 kW) of heat pump auxiliary electric heat. The T874 can  
provide the same high quality control.  
Stage or Time Modulated Control  
There are two different ways to control auxiliary heat, staged  
or time modulated control.  
This scheme also eliminates the need for outdoor thermostats  
and thus offers the manufacturer an opportunity to reduce unit  
cost. One disadvantage is that a thermostat jiggler can be  
demanding more kW of strip heat when chilly.  
Outdoor thermostats are used to switch additional increments  
of electric heat into the thermostat circuit as the outdoor  
temperature gets lower. All increments of auxiliary heat are  
still controlled by stage-two of the thermostat but only if the  
outdoor temperature requires the additional capacity. See  
Fig. 40.  
The method any particular manufacturer selects depends on  
which arguments it finds persuasive and the opinions of its  
distributors and dealers.  
Three-Stage Thermostat  
THERMOSTAT  
A definite improvement in quality of control and economy can  
be achieved with a three-stage thermostat (T874W), which is  
especially true with heat pumps using dual compressors.  
HEAT 2 HEAT 1  
Three-stage control permits both the heat pump and the  
auxiliary heat to be tied directly to the demand of the  
controlled space. With a two-stage compressor, maximum  
COMPRESSOR  
CONTACTOR  
(
100 percent) heat pump operation is required before auxiliary  
AUXILIARY  
HEAT RELAY 1  
heat is brought on.  
20°F  
(
-7°C)  
Emergency Heat  
OUTDOOR  
THERMOSTATS  
AUXILIARY  
HEAT RELAY 2  
Some provision is generally required to back up the compressor  
in the event of a failure during the heating season. In fact, it is  
quite common to find that local building codes or electric utilities  
require that a specified percent of the building heating  
5
(
°F  
-15°C)  
AUXILIARY  
HEAT RELAY 3  
requirements be available from emergency heat—a source  
other than the heat pump compressor. Almost universally, the  
source is electric resistance heaters. Typically, the requirement  
is for 70 or 80 percent of the building heating needs.  
M5834  
Fig. 40. Outdoor thermostats for auxiliary heat.  
The rationale for this system is that it very closely matches the  
system capacity to the heating load of the building. By  
calculating the heat loss of a building, the installing contractor  
can pick the theoretical outdoor temperature at which to  
permit each additional unit of electric heat to be operated by  
the second stage of the room thermostat.  
Switching to Emergency Heat  
Conventional heat pump control (thermostat logic) usually  
includes a manual subbase switch to bring on the emergency  
heat.  
In one control strategy, the emergency heat relay is turned on  
by the EM.HT. selector switch on the thermostat subbase. The  
compressor is prevented from running. The electric heaters  
are cycled as they normally would be by the second stage of  
27  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
the thermostat. A set of contacts on the emergency heat relay  
is used to bypass each outdoor thermostat so that all electric  
heat is under immediate thermostat stage-two control. So the  
emergency heat relay simply bypasses the outdoor  
thermostats. See Fig. 41.  
Crankcase Heat  
In any mechanical refrigeration system, refrigerant tends to  
migrate to the coldest part of the equipment and condense  
there. In a heat pump, this coldest spot could be the compressor  
because it is usually outdoors. In addition, the oil in the com-  
pressor crankcase is capable of absorbing a high concentration  
of refrigerant. On compressor startup, there are two risks: (1) the  
liquid refrigerant, which is noncompressible, can be drawn into  
the cylinder, and (2) considerable oil can be entrained in the  
refrigerant and swept out of the crankcase through the  
In the second method, the emergency heat relay is cycled  
directly by the thermostat mercury bulb. In this hookup, the  
relay is controlled by the thermostat first stage. The  
emergency heat relay energizes all of the auxiliary heat relays  
on a call for heat. See Fig. 42.  
changeover valve and dispersed in the piping and coils.  
So the emergency heat is controlled by the first stage of the  
thermostat. The emergency heat relay energizes all of the  
electric strip heaters so the heat and the indoor fan come on  
together as soon as the first stage calls for heat.  
So the migration of refrigerant to the crankcase is undesirable  
because it can interfere with system lubrication and because the  
liquid refrigerant must be kept from going through the compressor.  
Adding a crankcase heater creates enough temperature  
differential to prevent this migration because the compressor  
is no longer the coldest part of the system so refrigerant does  
not migrate to it.  
With the first method, the fan remains on (being controlled by  
the first stage of the thermostat) and the electric heaters cycle  
on and off with the second stage.  
In either case, a subbase indicator light is turned on whenever  
the function switch is in the emergency heat (EM.HT.) position.  
Compressor Fault Relay  
Another very simple method of detecting a compressor failure  
has been developed. It uses the voltage developed across the  
capacitor in a permanent split capacitor compressor motor.  
THERMOSTAT  
FUNCTION  
SWITCH  
HEAT 2 HEAT 1  
COMPRESSOR  
The principle involved is that virtually all serious problems  
reduce the voltage across the motor capacitor. By carefully  
selecting the correct coil voltage, the normally closed relay  
does not pull in unless the proper voltage builds up across the  
capacitor, which brings on the SERVICE LED. See Fig. 43.  
AUXILIARY  
HEAT RELAY 1  
OUTDOOR  
THERMOSTAT  
AUXILIARY  
HEAT RELAY 2  
Here is how it works:  
On a call for cooling, the thermostat makes R to Y, the  
contactor coil is powered, and the compressor motor turns on.  
At the same time, the indicator light is energized.  
As the motor gets up to speed—about one second, the  
fault relay sees enough voltage to pull in. Its normally  
closed contact opens and the indicator light goes out.  
Anything that prevents the motor from running prevents the  
fault relay from pulling in.  
EMERGENCY HEAT  
RELAY CONTACT  
EMERGENCY  
HEAT RELAY  
M5833  
Fig. 41. Emergency heat relay that bypasses  
the outdoor thermostats.  
COMPRESSOR MOTOR  
FAULT RELAY  
L1  
L3  
24 V  
RUN  
CAP.  
R
THERMOSTAT  
FUNCTION  
C
HEAT 2 HEAT 1  
SWITCH  
EMERGENCY  
HEAT RELAY  
CONTACT  
START  
S
COMPRESSOR  
Y
R
L
X
L2  
L1  
AUXILIARY  
HEAT RELAY  
(HOT)  
LED  
EMERGENCY  
HEAT RELAY  
RISE  
M5832  
CONTACTOR  
THERMOSTAT-  
SUBBASE  
Fig. 42. Emergency heat relay that energizes all of the  
auxiliary heat relays on a call for heat.  
M5831  
Fig. 43. Compressor fault relay schematic.  
60-2485—8  
28  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
3
4
5
6
.
.
.
.
The Description column identifies certain characteristics  
of the existing device.  
CROSS REFERENCE  
The following section lists the current T874 Trade replace-  
ments for T872 and T874 Multistage Thermostats. It also lists  
the Q674 Trade replacements for Q672 and Q674 Subbases.  
The Trade Replacement column identifies the correct  
replacement device.  
The Remarks column lists any characteristics or adjust-  
ments to be made on the Trade replacement model.  
The Fig. No. column lists the wiring hookup used for the  
specific model number. The wiring diagrams follow the  
Cross Reference section.  
All thermostats listed carry the Honeywell logo unless  
otherwise noted.  
7.  
Refer to the circuit illustration that corresponds with the  
appropriate number. This figure illustrates the internal  
electric circuit for the desired model number.  
When using the Cross Reference Charts, refer to the following  
instructions:  
1
.
.
Locate and identify the existing thermostat and subbase  
model.  
2
Refer to the Model Number column to find the model  
that matches the existing thermostat and subbase.  
Table 6. T872-T874 Thermostat Cross Reference.  
T874 Trade  
a
Model Number  
T872A  
Description  
1-stage heat, 1-stage cool  
Replacement  
Remarks  
A1006  
A1014  
Standard OEM  
T874A1036  
T874A1010  
72-78°F (22-26°C) stop; locking cover; no  
Use T874A1176 for Dept. of  
Defense (DoD) application.  
thermometer  
A1022  
A1030  
A1048  
A1055  
A1063  
A1071  
A1089  
A1097  
A1105  
A1113  
A1121  
A1139  
A1147  
A1154  
A1162  
A1170  
A1188  
A1196  
A1204  
A1212  
Heat anticipator set at 0.45A  
0.4A heat anticipator setting  
TRADELINE  
AAF logo; locking cover  
Climatrol logo  
Lennox logo; 0.5A heat anticipator setting  
Melco logo  
Westinghouse logo  
Amana logo; 1.2A heat anticipator setting  
Trane logo  
Airtemp (Chrysler) logo  
Singer logo; no. 02005384  
American Standard logo  
Carrier logo and color; no. HH07AT074  
General Electric logo; no. AY28X097  
Sears logo; no. 4291441  
Command-Aire logo  
T874A1036  
T874A1036  
T874A1036  
T874A1036  
T874A1036  
T874A1036  
T874A1036  
T874A1036  
T874A1036  
T874A1036  
T874A1036  
T874A1036  
T874A1036  
T874A1036  
T874A1036  
T874A1036  
T874A1036  
T874A1036  
T874A1036  
T874A1010  
Singer logo; Celsius scale; no. 02005521  
Carteret logo  
General Electric; no. AY28X114; 72-78°F  
Use T874A1176 for Dept. of  
Defense (DoD) application.  
(
22-26°C) stop  
A1220  
A1238  
A1246  
Singer logo; no. 050240-01  
Celsius scale  
T874A1036  
T874A1036  
TRADELINE; locking cover and adjustable locking T874A1150  
lever stops  
A1253  
A1261  
Trane Comfort Corp  
T874A1036  
T874A1176  
TRADELINE; 72-78°F (22-26°C) stop; locking  
cover; no thermometer; meets DoD specs  
a
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.  
29  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 6. T872-T874 Thermostat Cross Reference.  
T874 Trade  
a
Model Number  
Description  
Replacement  
Remarks  
A1279  
General Electric logo; no. AY28X114A; 75°F stop; T874A1010  
Use T874A1176 for Dept. of  
locking cover; no thermometer.  
Defense (DoD) application.  
A1287  
General Electric; no. AY28X097A; fan current  
shunt for auto fan in heating; heat anticipator set at Q674B1018  
.4A.  
T874A1036/  
Set thermostat stage 1 heat  
anticipator for total of fan and stage  
1 primary control current draw.  
0
A1295  
A1303  
A1311  
A1329  
A1337  
A1345  
A1352  
A1360  
A1378  
Lennox; Celsius scale  
Lennox logo; no. 64A0601; meets DoD specs  
Envirotron special; Celsius scale  
Carrier logo; Celsius scale; no. HH07AT074C  
Square D; no. HCD-3; heat anticipator set at 0.2A T874A1036  
TRADELINE; Celsius scale  
Heat anticipator set 1.2A  
Friedrich logo; heat anticipator set at 0.2A  
Wesco logo; heat anticipator set at 0.8A  
1-stage heat, 2-stage cool  
Standard OEM  
0.4A heat anticipator setting  
TRADELINE  
Westinghouse logo  
American Standard logo  
Climatrol logo  
Carrier logo  
Trane logo  
Fedders logo  
Climatrol logo  
Carteret logo  
Singer logo; no. 050240-03  
Celsius scale  
T874A1036  
T874A1176  
T874A1010  
T874A1036  
T874A1010  
T874A1036  
T874A1036  
T874A1036  
T872B  
B1005  
B1013  
B1021  
B1039  
B1047  
B1054  
B1062  
B1070  
B1088  
B1096  
B1104  
B1112  
B1120  
B1138  
T874B1019  
T874B1019  
T874B1019  
T874B1019  
T874B1019  
T874B1019  
T874B1019  
T874B1019  
T874B1019  
T874B1019  
T874B1019  
T874B1019  
T874B1019  
T874B1019  
Singer logo; no. 02005711; locking cover and  
lever.  
B1146  
B1153  
T872C  
Lennox logo; no. P-8-8895  
Lennox logo; Celsius scale  
2-stage heat, 1-stage cool  
Standard OEM  
T874B1019  
T874B1019  
C1004  
C1012  
C1020  
T874C1018  
T874C1018  
T874C1141  
Heat anticipator set at 0.4A  
72-78°F (22-26°C) stop; locking cover; no  
Use T874C1141 for Dept. of  
Defense (DoD) application.  
thermometer; 42-88°F (6-31°C) setpoint range.  
C1038  
C1046  
C1053  
C1061  
C1079  
TRADELINE  
American Standard logo  
Friedrich logo  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
Lennox logo; no. P-8-8896  
Westinghouse logo; stage 1 heat anticipator set at T874C1018  
0.75A; stage 2 anticipator set at 1.2A  
C1087  
C1095  
Fast cycle performance on both heat stages;  
T874C1018  
T874C1018  
Adjust anticipator faster for correct  
anticipator range 0.12-0.6A  
performance.  
Payne logo; no. 0.1-0.175  
a
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.  
60-2485—8  
30  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 6. T872-T874 Thermostat Cross Reference.  
T874 Trade  
a
Model Number  
C1103  
C1111  
C1129  
C1137  
Description  
Amana logo; anticipator set at 1.2A  
Airtemp (Chrysler) logo  
Replacement  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
Remarks  
Day and Night logo; no. 0.1-0.174  
Fast cycle performance on both heat stages  
Adjust anticipator faster for correct  
performance.  
C1145  
C1152  
C1160  
C1178  
C1186  
C1194  
C1202  
C1210  
C1228  
C1236  
C1244  
C1251  
C1269  
C1277  
C1285  
C1293  
C1301  
C1319  
C1327  
C1335  
C1343  
C1350  
C1368  
Rheem logo  
Ruud logo  
Climatrol logo  
Wesco logo  
Sears logo  
First Co. logo  
Carrier logo  
Carrier logo; Celsius scale  
0.4A heat anticipator setting  
Carrier logo; no. HH07AT070  
Fraser-Johnson logo  
Trane logo  
Fedders logo  
Climatrol special  
Autogas logo  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
T874C1125  
Fedders logo  
Climatrol logo  
Command-Aire logo  
Melco logo; lock cover and levers  
Singer logo (Carteret)  
Singer logo; no. 050240-04  
Celsius scale  
12°F (67°C) differential between heat 1 and  
heat 2  
C1376  
C1384  
C1392  
AAF logo; locking cover; 72-78°F (22-26°C) stop T874C1018  
Servel logo T874C1018  
TRADELINE; fast cycle performance on both heat T874C1018  
Adjust anticipator faster for correct  
stages.  
performance.  
C1400  
72-78°F (22-26°C) stop; locking cover; no  
thermometer; meets DoD specs  
T874C1141  
C1418  
C1426  
C1434  
C1442  
C1459  
C1467  
C1475  
C1483  
C1491  
Solaron logo  
T874C1018  
None  
T874C1018  
T874C1018  
None  
T874C1018  
T874C1018  
T874C1018  
T874C1141  
Lennox logo; no. 42C04; four LEDs  
Carrier logo; no. HH07AT070C; Celsius scale  
Goettl logo  
Goettl logo; used with Q672N1001, N1019  
Lennox logo; Celsius scale  
Tappan logo; no. 080-13708-37  
Fasco logo; no. 1230-8161  
Lennox logo; no. 64A0501; locking cover; no  
thermometer; meets DoD specs  
a
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.  
31  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 6. T872-T874 Thermostat Cross Reference.  
T874 Trade  
a
Model Number  
Description  
Replacement  
Remarks  
C1509  
Fedders logo; used with Q672L1102  
Y594R1425  
Wiring differences (old=new): C=X,  
K=E; remove Y-W1 jumper.  
C1517  
Climatrol logo; used with Q672L1102  
Y594R1425  
Wiring differences (old=new): C=X,  
K=E; remove Y-W1 jumper.  
C1525  
C1533  
C1541  
Square D logo; no. HCD-2  
Airtemp logo  
Airtemp logo; used with Q672L1102  
T874C1018  
T874C1018  
Y594R1425  
Wiring differences (old=new): C=X,  
K=E; remove Y-W1 jumper.  
C1566  
C1574  
C1582  
C1590  
TRADELINE; Celsius scale  
Whalen special; used with Q672B1269  
Lennox; meets DoD  
T874C1018  
None  
None  
Replacement has °F scaleplate.  
Singer; 8°F (4.4°C) differential between stage  
T874C1125  
Replacement has 2°F (1° C)  
1
and stage 2  
differential between H1 and H2.  
C1608  
Singer logo; no. 02005784 8°F (4.4°C) differential T874C1125  
Replacement has 2°F (1°C)  
between stage 1 and stage 2  
differential between H1 and H2.  
C1616  
C1624  
C1632  
C1640  
C1665  
C1673  
Celsius scale; stop set at 23°C  
Heat Wave logo; no. 0360-116  
York logo; heat anticipator set at 0.2A  
Heat anticipator set at 0.4A  
Wesco logo; heat anticipator set at 0.8A  
Wards logo; used with Q672B1285, B1293  
None  
Add 4074ECK adjustable stop.  
T874C1018  
T874C1018  
T874C1018  
T874C1018  
Gas systems:  
T874C1018/  
Q674B1034  
Electric systems: Adjust anticipator faster for correct  
T874C1018/  
Q674B1075  
performance.  
C1681  
C1699  
Lechauffage Urbain logo; Celsius scale  
T874C1018  
T874C1018  
Duotherm logo; used with Q672E1068 or  
See subbase description for  
replacement information.  
Q672F1000  
C1707  
C1715  
T872D  
Sigler logo; used with Q672N1027  
Westinghouse logo  
2-stage heat, 2-stage cool  
Standard OEM  
TRADELINE  
Westinghouse logo  
Climatrol logo  
Lennox logo; no. P-8-8897; used with Q672E1191. T874D1165  
York logo  
Singer logo; no. 02005385  
Rheem logo  
Rudd logo  
None  
T874C1018  
D1003  
D1011  
D1029  
D1037  
D1045  
D1052  
D1060  
D1078  
D1086  
D1094  
D1102  
D1110  
D1128  
D1136  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
York logo; locking cover  
American Standard logo  
ITT logo  
Carrier logo  
No anticipator on stage 1 cool; used with  
Q672C1029  
a
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.  
60-2485—8  
32  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 6. T872-T874 Thermostat Cross Reference.  
T874 Trade  
a
Model Number  
D1144  
Description  
Carrier logo; no. HH07AT072  
Replacement  
T874D1165  
Remarks  
D1151  
General Electric logo; no. AY28X098; 0.4 heat  
T874D1165  
anticipator setting  
D1169  
Airtemp (Chrysler) logo; used with Q672E1118  
T874D1165/  
Q674E1049  
Wiring differences (old=new):  
A=W1; set H1 anticipator to 1.2A.  
D1177  
D1185  
D1193  
D1201  
D1219  
D1227  
D1235  
D1243  
D1250  
D1268  
D1276  
D1284  
D1292  
Trane logo  
Dunham-Bush logo  
Fedders logo  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
Climatrol logo  
Command-Aire logo  
Singer logo; no. 02005522; Celsius scale  
Singer logo; (Carteret)  
Friedrich logo  
Singer logo; no. 050240-02  
Airtemp logo  
Celsius scale  
Solaron  
Tokyo Carrier logo; no. HH07AT072C; Celsius  
scale  
D1300  
D1318  
SUPER TRADELINE  
T874D1165  
General Electric logo; no. AY28X098A; fan current T874D1165/  
shunt for auto fan in heating.  
Q674B1075  
T874D1165  
D1326  
General Electric logo; locking cover 72-78°F  
(
22-26°C) stop; fan current shunt for auto fan in  
heating.  
D1334  
D1342  
D1359  
Lennox logo; Celsius scale  
Tappan logo; no. 080-13708-32  
T874D1165  
T874D1165  
T874D1165  
Singer logo; no. 02005740; Celsius scale; 6.6°C  
Only 2°F (1°C) differential between  
H1 and H2.  
differential between H1 and H2.  
D1367  
D1375  
Friedrich logo; no. 600-580-23  
T874D1165  
Singer logo; no. 02005713; Celsius scale; controls None  
2
separate heat/cool circuits; used with  
Q674G1017  
D1383  
D1391  
TRADELINE; Celsius scale  
T874D1165  
Singer logo; no. 02005712; controls two separate None  
heat/cool circuits; used with Q674G1017  
D1409  
D1417  
D1425  
D1433  
12°F (7°C) differential between H1 and H2  
Fedders logo  
Climatrol logo  
T874D1165  
T874D1165  
T874D1165  
Singer logo; no. 02005785; 8°F (4.4°C) differential T874D1165  
between H1 and H2  
D1441  
D1474  
T872E  
American Air Filter  
Carrier; no. HH07AT072-03; Celsius scale  
2-stage cool  
T874D1165  
T874D1165  
E1002  
E1010  
E1028  
Standard OEM  
TRADELINE  
Westinghouse logo  
T874E1016  
T874E1016  
T874E1016  
a
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.  
33  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 6. T872-T874 Thermostat Cross Reference.  
T874 Trade  
a
Model Number  
E1036  
E1044  
E1051  
E1069  
E1077  
E1085  
E1093  
E1101  
E1119  
E1127  
E1135  
E1143  
E1150  
E1168  
T872F  
F1001  
F1019  
F1027  
F1035  
Description  
American Standard logo  
Replacement  
T874E1016  
T874E1016  
T874E1016  
T874E1016  
T874E1016  
T874E1016  
T874E1016  
T874E1016  
T874E1016  
T874E1016  
T874E1016  
T874E1016  
T874E1016  
T874E1016  
Remarks  
York logo; locking cover  
ITT logo  
Climatrol logo  
Airtemp (Chrysler) logo  
Lennox logo  
Trane logo  
Dunham-Bush logo  
Fedders logo  
Climatrol logo  
General Electric logo; no. AY28X108  
Lennox logo; Celsius scale  
Celsius scale  
Airtemp logo  
2-stage heat  
Standard OEM  
TRADELINE  
T874F1015  
T874F1015  
T874C1018  
Lennox logo; fast cycle heat anticipator  
Luxaire logo; fast cycle performance on both heat T874C1018  
M839 draws 0.72A; set adjustable  
heat anticipator to setting of 0.9A  
for proper cycle rate.  
stages.  
F1043  
F1050  
F1068  
F1076  
F1084  
F1092  
F1100  
F1118  
F1126  
York logo; locking cover; used with M839.  
Raehco logo  
Fast cycle performance on both heat stages.  
Wesco logo  
Lennox logo  
Auto Gas logo  
T874C1018  
T874F1015  
T874C1018  
T874F1015  
T874F1015  
T874F1015  
T874F1015  
T874F1015  
Celsius scale  
Lennox logo; Celsius scale  
Stages 1 and 2 heat electrically isolated; used with None  
Q672D1002  
F1134  
F1159  
F1167  
F1175  
Square D logo; HCD-4  
Wesco logo; heat anticipator set at 0.8A  
York logo  
T874F1015  
T874F1015  
T874F1015  
Oneida Heater logo; no. 30A0287-01; used with  
T874F1015/  
Q672K1012.  
Q674K1026  
T872G  
Heat pump models; 2-stage heat,  
1
-stage cool, 1-stage changeover.  
G1000  
Fast cycle performance stage 2 heat; fixed  
anticipator stage 1 heat and cool; changeover with  
cooling; used with Q672F1018.  
Adjustable anticipator stage 2 heat; fixed  
anticipator stage 1 heat and cool; changeover with  
cooling; used with Q672E1027.  
Y594G1252  
Y594G1393  
Wiring differences (old=new):  
W=W2, X1=X.  
G1018  
Wiring differences (old=new):  
Y1=O, Y2=Y.  
a
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.  
60-2485—8  
34  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 6. T872-T874 Thermostat Cross Reference.  
T874 Trade  
a
Model Number  
Description  
Replacement  
Remarks  
G1026  
Lennox logo; fast cycle performance; stage 2 heat; None  
fixed anticipator stage 1 heat and cool;  
changeover with cooling; used with Q672E1019,  
F1067.  
See subbase description for  
replacement information.  
G1034  
Westinghouse logo; adjustable anticipator stage 2 Y594G1252  
heat; fixed anticipator stage 1 heat and cool;  
changeover with cooling; used with Q672F1091,  
F1141, F1257 or Q672J1013, J1062.  
Wiring differences (old=new):  
W=W2.  
G1042  
G1059  
G1067  
York logo; fixed anticipator on all stages heat and Y594G1567  
cool; changeover with cooling; used with  
Q672J1021.  
TRADELINE; no anticipator stage 2 heat; fixed  
anticipator stage 1 heat and cool; changeover with  
cooling; used with Q672J1039 outdoor reset.  
Y594G1161  
Designed for use on General  
Electric heat pumps.  
Lennox logo; no. P-8-11222; fast cycle  
See subbase description for  
replacement information.  
performance; stage 2 heat; fixed anticipator stage  
1
heat and cool; changeover with cooling; used  
with Q672E1142, F1083.  
G1075  
G1083  
Carrier logo; adjustable anticipator stage 2 heat;  
fixed anticipator stage 1 heat and cool;  
changeover with cooling; used with Q672J1054,  
L1052.  
Adjustable anticipator stage 2 heat; fixed  
anticipator stage 1 heat and cool; changeover with  
cooling; includes shunt to bypass stage 2  
anticipator with auxiliary heat relays; used with  
Q672F1158.  
See subbase description for  
replacement information.  
Y594G1252  
G1091  
G1109  
Lennox logo; same as T872G1026 except meets  
See subbase description for  
replacement information.  
Wiring differences (old=new): C=X.  
DoD specs.  
Tappan logo; no. 080-13708-52; adjustable  
anticipator stage 1 heat and cool; changeover with  
cooling; used with Q672F1117.  
Changeover; used with Q672F1125.  
Lennox logo; no. 63A0401; Celsius scale; isolated None  
auxiliary heat power circuit; fast cycle anticipator  
stage 2 heat.  
Y594G1252  
Y594G1252  
G1117  
G1125  
Wiring differences (old=new): C=X.  
G1133  
G1141  
G1158  
Rheem logo; no. RXMT-B71; adjustable  
Y594G1252  
anticipator stage 2 heat; fixed anticipator stage 1  
heat and cool; changeover with cooling; includes  
shunt to bypass stage 2 anticipator with auxiliary  
heat relays; used with Q672F1158, F1232.  
Ruud logo; adjustable anticipator stage 2 heat;  
fixed anticipator stage 1 heat and cool;  
changeover with cooling; includes shunt to bypass  
stage 2 anticipator with auxiliary heat relays; used  
with Q672F1158.  
Y594G1252  
Carrier logo; same as T872G1075. Except DoD  
See subbase description for  
replacement information.  
styling.  
G1166  
G1174  
G1182  
BDP used with Q672F1125.  
BDP used with Q672F1125.  
Y594G1252  
Y594G1252  
Wiring differences (old=new): C=X.  
Wiring differences (old=new): C=X.  
Carrier; no. HH07AT071C; Celsius scale; used  
See subbase description for  
with Q672L1052, J1054.  
replacement information.  
G1190  
Tappan; no. B13708-57; used with Q672L1078 for None  
and 10 ton heat pumps with 2 compressors.  
8
a
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.  
35  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 6. T872-T874 Thermostat Cross Reference.  
T874 Trade  
a
Model Number  
Description  
Replacement  
Remarks  
G1208  
Marvair logo; special for Crispaire; used with  
Y594G1393  
Q672F1166, F1323.  
G1216  
G1224  
Janitrol logo; no. 26G05; stage 2 heat anticipator Y594G1252  
set at 1.2A; used with Q672F1117.  
Wiring differences (old=new): C=X.  
TRADELINE; adjustable anticipator stage 2 heat; Y594G1419  
fixed anticipator stage 1 heat and cool;  
changeover in cool; used with Q672F1208.  
G1232  
G1240  
G1257  
Heat Wave (Southwest Mfg.) logo; stage 2 heat  
anticipator set at 1.2A; used with Q672F1224.  
Lennox; fast cycle anticipator stage 2 heat; used None  
with Q672F1240.  
Carrier logo; no. HH07AT073; used with  
None  
Q672L1169 (HH93AZ071).  
G1265  
G1273  
Addison logo; used with Q672F1265.  
Carrier logo; (DoD model); 68°F (20°C) maximum  
heating; 78°F (26°C) minimum cooling; used with  
Q672L1052, J1054  
Y594G1252  
Wiring differences (old=new): C=X.  
See subbase description for  
replacement information.  
G1281  
G1299  
Wesco logo; used with Q672F1265.  
Y594G1252  
Y594G1567  
Wiring differences (old=new): C=X.  
York logo; meets DoD specs; used with  
Q672L1177.  
G1307  
G1315  
G1323  
G1331  
Carrier; no. 38EQ1900; Celsius; used with  
Q672J1054, L1052.  
See subbase description for  
replacement information.  
Luxaire special; stage 2 heat anticipator set to  
Y594G1252  
None  
1.2A; used with Q672F1281.  
Lennox special; used with Q672L1201 and  
C815A1013.  
York; used with Q672J1021.  
Y594G1567  
Wiring differences (old=new):  
X=X1, L=X2, W=E; Y1-W1 and Y2-  
W2 jumpers required.  
G1356  
Westinghouse; used with Q672L1219.  
T874D1165/  
Q674F1022  
Wiring differences (old=new):  
X=X1, L=X2, W=E; Y1-W1 and Y2-  
W2 jumpers required.  
G1364  
G1372  
York; used with Q672D1077.  
Tappan/Janitrol logo; no. B-13708-521;  
used with Q672F1117.  
None  
Y594G1252  
Wiring differences (old=new): C=X.  
G1398  
T872H  
York logo; no. 025-21454C; used with Q672J1021. Y594G1567  
Heat pump model; 1 stage heat,  
1
stage cool, 1 stage changeover.  
H1009  
Command-Aire logo; fixed anticipator stage 1 heat Y594H1012  
and cool; changeover with cooling; used with  
Q672C1086.  
H1017  
H1025  
T872M  
Friedrich logo.  
Friedrich logo; Celsius.  
Y594H1012  
Y594H1012  
1 stage heat, 1 stage cool with stage 2 heat factory  
set at 60°F (16°C).  
M1003  
Standard OEM; used with Q672D and external  
switching means.  
T874C1125  
T874C1125 has 12°F (6.7°C)  
differential between stage 1 and  
stage 2 heat.  
T872N  
N1002  
Heat pump model; 2-stage heat, 1-stage cool plus  
changeover, changeover in heat mode.  
None  
a
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.  
60-2485—8  
36  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 6. T872-T874 Thermostat Cross Reference.  
T874 Trade  
a
Model Number  
Description  
Replacement  
Remarks  
N1010  
Williamson logo; adjustable anticipator stage 1 and T874N1016/  
heat; fixed anticipator stage 1 cool; used with Q674F1220  
T874N1016  
2
Q672F1133 or F1315.  
N1028  
N1036  
N1044  
TRADELINE heat mode changeover; used with  
Q672F1216.  
Bard; used with Q672F1299.  
T874N1016/  
Q674F1220  
Thermotron logo; 1st stage changeover heat  
mode; used with Q672F1299.  
T874N1016/  
Q674F1220  
T872Q  
1-stage heat; used with another T872 for heating  
setback.  
Q1009  
Q1017  
Standard OEM  
York logo  
T874C1125  
T874C1125  
Replacement only good for  
1
-stage heat and 1-stage cool  
applications.  
Q1025  
Q1033  
Q1041  
ITT logo  
Lennox logo; no. P-8-8899.  
Lennox logo; no. 63A6401.  
None  
None  
None  
T872R  
Heat pump model; 2-stage heat, 1-stage cool,  
manual changeover.  
R1008  
Fixed anticipator stage 1 heat and cool; no  
anticipator stage 2 heat; changeover with cooling;  
used with Q672B1046.  
Y594R1425  
Y594R1425  
Wiring differences (old=new):  
W=W2; W1-Y1 jumper required.  
R1016  
R1024  
Addison same as T872R1008; used with  
Wiring differences (old=new):  
W=W2; W1-Y1 jumper required.  
Q672B1103.  
Lennox logo; fast cycle stage 2 heat; fixed  
See subbase description for  
anticipator stage 1 heat and cool; changeover with  
replacement information.  
cooling; used with Q672B1160 and Q672L1003.  
R1032  
R1040  
York logo; fixed anticipator stage 1 and 2 heat and Y594R1664  
stage 1 cool; changeover with cooling; used with  
Q672L1011.  
Lennox logo; fast cycle stage 2 heat; fixed  
anticipator stage 1 heat and cool; isolated stage 2  
heat switch; changeover with cooling; used with  
Q672B1202 no. P-8-11221, Q672L1029  
See subbase description for  
replacement information.  
R1057  
R1065  
R1073  
TRADELINE; fixed anticipator stage 1 heat and  
cool; no anticipator stage 2 heat; changeover on  
cooling; used with Q672L1037; outdoor reset.  
Adjustable anticipator stage 2 heat; fixed  
anticipator stage 1 heat and cool; changeover on  
cooling; used with Q672L1045.  
Lennox logo; no. 63A0301; Celsius scale;  
separate auxiliary heat power circuit; fast cycle  
stage 2 heat antic.  
Y594R1763  
Y594R1243  
None  
Designed for use on General  
Electric heat pumps. Wiring  
differences (old=new): A=T.  
R1081  
R1099  
R1107  
R1115  
Ruud logo; same circuit as T872R1065; used with Y594R1243  
Q672L1045, L1136.  
Dunham Bush special; used with Q672L1060,  
L1383.  
Y594R1243  
Y594R1243  
Rheem; no. RXMT-B70; used with Q672L1045,  
L1136.  
Friedrich logo; fixed anticipator; used with  
Q672B1244, L1086.  
See subbase description for  
replacement information.  
a
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.  
37  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 6. T872-T874 Thermostat Cross Reference.  
T874 Trade  
a
Model Number  
R1123  
Description  
York logo; no. 025-21453C; Celsius scale.  
Replacement  
Remarks  
Y594R1664  
R1131  
Lennox logo; separate auxiliary heat power circuit; None  
fast cycle stage 2 heat anticipator; outdoor reset;  
used with Q672L1144, C815A1013.  
R1149  
Westinghouse logo; adjustable stage 2 heat  
anticipator; cooling changeover; fixed anticipator  
stage 1 heat and cool; used with Q672L1110,  
L1128, L1151.  
Y594R1243  
Wiring differences (old=new):  
W=W2.  
R1156  
Marvair logo; used with Q672L1094, L1250.  
Y594R1243  
Replacement has auto fan in  
Emergency Heat mode.  
R1164  
R1172  
Bard; used with Q672L1185.  
Heil Quaker; used with Q672L1193.  
Y594R1243  
Y594R1243  
Wiring differences (old=new): B=X,  
W=W2.  
R1180  
R1198  
R1206  
R1214  
York; Celsius; used with Q672L1011.  
TRADELINE; used with Q672L1227  
For use with W89; used with Q672L1235.  
Intertherm logo; used with Q672L1276.  
Y594R1664  
Y594R1243  
None  
Y594R1300  
Wiring differences (old=new):  
W1=B, Z=L, K=E.  
R1222  
R1230  
York logo; used with C815A1039; adjustable  
anticipator stage-2 heat; used with Q672L1284  
Y594R1672  
None  
Amana logo; no. C62397-1; used with  
Q672L1300, W89.  
R1255  
R1271  
Singer logo; used with Q672L1326 and W89.  
None  
Y594R1664  
Westinghouse logo; used with Q672L1375 and  
W89.  
R1297  
R1305  
R1321  
R1339  
York; Celsius scale; used with Q672L1011.  
Used with Q672L1235 and W89.  
Duotherm logo; used with Q672L1409, and W89. None  
None  
None  
Williamson; used with Q672L1391.  
Y594R1243  
T872S  
Heat pump model; 2-stage heat plus changeover,  
1
-stage cool.  
S1005  
Westinghouse logo; adjustable anticipator stage 1 T874C1018/  
Wiring differences (old=new):  
V=RC-RH, F=G, C=Y1, Z=B,  
H2=W2; W1-Y1 jumper required.  
and 2 heat; fixed anticipator stage 1 heat;  
Q674C1058  
changeover with heating: used with Q672C1045  
T872T  
T1004  
T872W  
1-heat stage, 1-vent and 2-cool stages.  
Trane logo; used with Q672B1129.  
3-heat stages, 2-cool stages, manual changeover  
None  
W1019  
W1027  
W1035  
Lennox logo; no. 52C7501; used with Q672L1342 None  
and C815A1013.  
Westinghouse logo; used with Q672L1268 and  
C815A1021.  
None  
TRADELINE; used with C815A1043 and  
Y594W1014  
Q672B1251.  
a
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and the subbase.  
60-2485—8  
38  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 7. Q672-Q674 Subbase Cross Reference.  
Q674 Trade  
a
Model Number  
Q672A  
Description  
System: HEAT-AUTO-COOL, Fan: AUTO-ON  
Standard OEM  
TRADELINE  
RC-RH jumper  
RC-RH jumper; Chek Lite  
System: HEAT-OFF-COOL, Fan: AUTO-ON  
Standard OEM  
Isolated G terminal.  
System: HEAT-OFF-RESET-COOL  
TRADELINE  
Replacement  
Remarks  
A1005  
A1013  
A1021  
A1039  
Q674A1019  
Q674A1019  
Q674A1019  
Q674A1019  
RC-RH jumper required.  
RC-RH jumper required.  
Q672B  
B1004  
B1012  
B1020  
B1038  
B1046  
Q674B1034  
Q674B1018  
Q674B1034  
Q674B1034  
Y594R1425  
Used system off as reset position.  
Heat pump circuit; used with T872R1008.  
Wiring differences (old=new):  
W1=Y1, W=W2.  
B1053  
B1061  
B1079  
B1087  
B1095  
B1103  
RC-RH jumper  
Chek Lite  
Auto fan operation in heat and cool.  
Carrier no. HH93AZ078; RC-RH jumper.  
Carrier no. HH93AZ084; RC-RH jumper.  
Q674B1034  
Q674B1034  
Q674B1075  
Q674B1075  
Q674B1034  
Y594R1425  
RC-RH jumper required.  
Addison; heat pump circuit; used with  
Wiring differences (old=new):  
W=W2; W1-Y1 jumper required.  
T872R1016.  
B1111  
B1129  
B1137  
B1145  
B1152  
Carrier no. HH93AZ080; isolated G terminal.  
Trane special circuit; used with T872T1004.  
RC-RH jumper; isolated G terminal.  
Fedders special  
Q674B1018  
None  
Q674B1018  
Q674B1034  
Q674B1075  
RC-RH jumper required.  
RC-RH jumper required.  
Fedders special; auto fan operation in heat  
and cool.  
B1160  
B1178  
Lennox; heat pump circuit; used with  
T872R1024; includes compressor lockout in  
EM. HT.  
Y594R1243  
Q674B1075  
Wiring differences (old=new):  
V-VR=R, M=Y, Y=W2, F=G, R=O.  
General Electric no. AY28X107; auto fan  
operation in heat and cool.  
B1186  
B1194  
Trane; isolated G terminal; Filter LED.  
Q674B1018  
Q674B1075  
General Electric no. AY28X124; auto fan  
Set T874 stage-1 anticipator for  
combined load of heat relay and fan  
relay.  
operation in heat and cool.  
B1202  
Lennox no. P-8-11223; heat pump circuit; used Y594R1243  
with T872R1040.  
Wiring differences (old=new):  
V-VR=R, M=Y, Y=W2, F=G, R=O.  
B1210  
B1228  
None  
Q674B1018  
General Electric no. BAY28X137; isolated  
G terminal.  
B1236  
B1244  
B1251  
Carrier no. HH-93AZ079; RC-RH jumper;  
LOCKOUT LED indicates compressor lockout  
switch activated.  
Q674B1034  
RC-RH jumper; LED cannot be  
provided in TRADELINE model.  
Friedrich; heat mode changeover; used with  
T874C1018/  
Q674B1034  
Wiring differences (old=new): C=no  
connection; RC-RH and W1-Y1  
jumpers required.  
T872R1115.  
Used with T872W1035 and C815A1043.  
Y594W1014  
a
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.  
39  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 7. Q672-Q674 Subbase Cross Reference.  
Q674 Trade  
a
Model Number  
Description  
Replacement  
Remarks  
B1269  
Whalen; Hi-Lo fan switch; constant fan in heat None  
and cool system switch positions; used with  
T872C1574.  
B1277  
B1285  
Square D no. HCB-5.  
Q674B1034  
Gas Furnace:  
T874C1018/  
Q674B1034  
Wards; RC-RH and F-W3 jumpers; used with  
T872C1673.  
Electric Furnace:  
Adjust anticipator faster for correct  
T874C1018/  
performance.  
Q674B1075  
B1293  
Lennox no. 41C96; used with T872C1673.  
Same as  
Q672B1285  
Q672C  
System: OFF-AUTO, Fan: AUTO-ON  
Standard OEM  
Westinghouse; RC-RH jumper.  
C1003  
C1011  
C1029  
Q674C1058  
Q674C1058  
Q674E1049  
RC-RH jumper required.  
W1-Y2 jumper; for heat pump; used with  
Replacement has heat/cool system  
T872D1136.  
switching.  
C1037  
C1045  
Chrysler Airtemp; System: COOL-OFF-AUTO. Q674C1058  
Westinghouse; heat pump; used with  
T874C1018/  
Wiring differences (old=new):  
V=RC-RH, F=G, C=Y1, Z=B,  
H2=W2; W1-Y1 jumper required.  
T872S1005.  
Q674C1058  
C1052  
Isolated stage 2 heat circuit for dc electric heat Recontrol  
relay.  
Use T874G1246/Q674F1212 which  
adds HEAT-COOL-EM.HT. system  
switch.  
C1060  
C1078  
C1086  
Fedders special.  
General Electric no. AY28X109.  
Q674C1058  
Q674C1058  
Y594H1012  
Command-Aire; heat pump; used with  
T872H1009.  
C1102  
TRADELINE  
Q674C1058  
Q672D  
System: None. Fan: None.  
Standard OEM; used with T872F1126.  
Lennox special.  
Carrier; RC-RH jumper.  
Carrier no. HH93AZ070; RC-RH jumper.  
General Electric no. AY-28X100.  
Square D no. HCB-4.  
D1002  
D1010  
D1028  
D1036  
D1044  
D1069  
D1077  
D1085  
Q674D1040  
None  
None  
Q674D1040  
None  
RC-RH jumper required.  
None  
None  
Q674D1040  
York; used with T872G1364.  
TRADELINE  
Q672E  
System: OFF-HEAT-AUTO-COOL  
Fan: AUTO-ON  
E1001  
E1019  
Standard OEM  
Q674E1049  
Lennox no. P-8-8892; heat pump; cool mode  
T874D1165/  
changeover; used with T872G1026.  
Q674B1075  
E1027  
E1035  
E1043  
Heat pump circuit; W1-Y2 jumper; cool mode  
changeover; used with T872G1018.  
Y594G1393  
Y594G1393  
Q674E1049  
Wiring differences (old=new): Y1=O,  
Y2=Y.  
Heat pump circuit; W1-Y2 jumper; cool mode  
Wiring differences (old=new): Y1=O,  
changeover.  
Y2=Y.  
Heat pump circuit; heat mode changeover.  
Wiring differences (old=new):  
W1=B, W2=W1; W1-Y1 jumper.  
a
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.  
60-2485—8  
40  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 7. Q672-Q674 Subbase Cross Reference.  
Q674 Trade  
a
Model Number  
E1050  
E1068  
E1076  
E1084  
Description  
Replacement  
Q674E1049  
Q674E1049  
Q674E1049  
Q674E1049  
Q674E1049  
Remarks  
TRADELINE  
RC-RH jumper; used with T872C1699.  
RC-RH internal jumper; EM. HT. LED.  
Carrier no. HH93AZ076; RC-RH jumper.  
RC-RH jumper required.  
RC-RH jumper required.  
RC-RH jumper required.  
E1092  
Carrier no. HH93AZ082; RC-RH jumper; B  
terminal; isolated G terminal.  
E1100  
E1118  
General Electric no. AY28X099.  
Airtemp; heat pump; used with T872D1169.  
Q674E1049  
T874D1165/  
Wiring differences (old=new):  
Q674E1049  
A=W1; set H1 anticipator to 1.2A.  
E1126  
E1134  
Common R terminal.  
Q674E1049  
RC-RH jumper required.  
ITT Nesbitt; RC-RH jumper; O and B terminals; Q674E1049  
isolated G terminal.  
E1142  
E1159  
Lennox no. P-8-11224; heat pump;  
V-VR jumper; cool mode changeover; used with  
T872G1067.  
Carrier no. HH93AZ077; RC-RH jumper;  
LOCKOUT LED indicates activation of  
compressor lockout switch.  
Y594G1252  
Q674E1049  
Wiring differences (old=new):  
V-VR=R, Y=W2, R=O, M=Y, F=G.  
RC-RH jumper required; no LED in  
TRADELINE model.  
E1167  
E1183  
E1191  
Square D no. HCB-2; Chek Lite.  
Square D no. HCB-3.  
Q674E1049  
Q674E1049  
Q674E1049  
Lennox; HIGH and LOW LEDs; used with  
No LEDs on replacement.  
T872D1045.  
Q672F  
System: EM. HT.-HEAT-AUTO-COOL-OFF  
Fan: AUTO-ON.  
F1000  
F1018  
With EM. HT. LED; used with T872C1699.  
Q674F1022  
Remove W3-X2 jumper to E-X2.  
Heat pump; heat mode changeover; Chek Lite; Y594G1252  
Wiring differences (old=new):  
used with T872G1000.  
W=W2, X1=X.  
F1026  
F1034  
Chek Lite; W2-X2 jumper.  
Q674F1022  
Q674F1022  
Airtemp; EM. HT. LED; RC-RH and X2-E  
If RC-RH jumper removed on  
Q672F1034, Q674F1022 does not  
replace.  
jumpers.  
F1042  
F1059  
W2-X2 jumper; Chek Lite.  
Carrier no. HH93AZ074; EM. HT. LED.  
Q674F1022  
Q674F1022  
Remove W2-X2 jumper to E-X2; X  
terminal same as C.  
F1067  
F1075  
F1083  
Lennox; heat pump; cool mode changeover;  
EM. HT. LED; used with T872G1026.  
None  
Heat pump circuit; EM. HT. LED; 2 terminal; RC- None  
RH jumper.  
Lennox no. P-8-11225; heat pump;  
V-VR jumper; cool mode changeover; EM. HT.  
LED; used with T872G1067.  
None  
F1091  
Westinghouse; heat pump; EM. HT. LED; cool Y594G1252  
mode changeover; compressor lockout in  
EM. HT.; used with T872G1034.  
Wiring differences (old=new):  
W=W2.  
F1109  
F1117  
Airtemp no. 3778567ACC; R-X2 jumper;  
Q674F1022  
R-X2 jumper required.  
EM. HT. LED.  
Tappan no. 080-13708-53; heat pump; EM. HT. Y594G1252  
LED; cool mode changeover; compressor  
lockout and auto fan in EM. HT.; used with  
T872G1109, G1216, G1372.  
Wiring differences (old=new): C=X.  
a
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.  
41  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 7. Q672-Q674 Subbase Cross Reference.  
Q674 Trade  
a
Model Number  
Description  
Replacement  
Remarks  
F1125  
BDP no. 3442DP90; used with T872G1117,  
Y594G1252  
Wiring differences (old=new): C=X.  
G1166, G1174.  
F1133  
Williamson; heat pump; EM. HT. LED; heat  
mode changeover; compressor lockout in  
EM. HT.; used with T872N1010.  
T874N1016/  
Q674F1220  
F1141  
F1158  
Westinghouse; EM. HT. LED; auto fan in  
Y594G1252  
Y594G1252  
Wiring differences (old=new):  
W=W2.  
EM. HT.; used with T872G1034.  
Rheem Ruud; heat pump; EM. HT. LED; cool  
mode changeover; compressor lockout in  
EM. HT.; used with T872G1083, G1133, G1141;  
auto fan in EM. HT.  
F1166  
F1174  
F1182  
Crispaire; EM. HT. LED; used with T872G1208. Y594G1252  
Carrier no. HH93AZ081; EM. HT. LED. Q674F1022  
Square D no. HCB-1; Chek Lite; R-X2 jumper; Q674F1022  
R-X2 jumper; add monitor switch  
between X1 and low side of power.  
System: Aux. Heat replaces EM. HT.  
F1190  
F1208  
EM. HT. LED; X2-E and RC-RH jumpers.  
None  
TRADELINE; cool mode changeover; EM. HT. Y594G1419  
LED; used with T872G1224.  
F1216  
F1224  
TRADELINE; heat mode changeover; EM. HT. T874N1016/  
LED; used with T872N1028.  
Q674F1220  
Y594G1252  
Heatwave (Southwest Mfg.); compressor  
lockout in EM. HT.; EM. HT. LED; used with  
T872G1232.  
F1232  
Rheem; cool mode changeover; EM. HT. and  
AUX. HEAT LEDs; compressor lockout in  
EM. HT.; used with T872G1133.  
Y594G1252  
F1240  
F1257  
Lennox; cool mode changeover; EM. HT. and  
None  
SERVICE LEDs; used with T872G1240.  
Westinghouse; cool mode changeover;  
EM. HT. and AUX. HEAT LEDs; auto fan in  
EM. HT; used with T872G1034.  
Y594G1252  
Wiring differences (old=new):  
W=W2.  
F1265  
F1273  
Wesco Addison; Chek and EM. HT. LEDs; used Y594G1252  
Wiring differences (old=new): C=X.  
with T872G1281, G1265.  
Southwest special; no. 0361-136; W2-X2  
jumper.  
None  
F1281  
F1299  
Luxaire special; used with T872G1315.  
Bard special; used with T872N1036, N1044.  
Y594G1252  
T874N1016/  
Q674F1220  
F1315  
F1323  
Williamson special; used with T872N1010.  
T874N1016/  
Q674F1220  
Y594G1252  
Crispaire special; used with T872G1208.  
System: OFF-AUTO. Fan: None.  
Standard OEM  
Singer; O-B jumper; used with T872D1375.  
Includes O and B terminals.  
Q672G  
G1009  
G1017  
G1025  
G1033  
G1041  
Q674G1070  
Q674G1070  
Q674G1070  
Q674G1070  
Q674G1070  
General Electric no. AY28X102.  
Singer no. 02005649; French wording; O-B  
Less French wording.  
jumper.  
G1066  
SLI-Mammoth; heat pump; heat mode  
changeover.  
Q674G1070  
Connect fan (G) wire to Y1 terminal;  
B-O and RC-RH jumpers.  
a
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.  
60-2485—8  
42  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 7. Q672-Q674 Subbase Cross Reference.  
Q674 Trade  
a
Model Number  
G1074  
Description  
Singer no. 02005754; X1 and X2 terminals for  
field-added indicator lights; used with  
T872D1375.  
Replacement  
None  
Remarks  
G1082  
Singer no. 02005792; X1 and X2 terminals for  
field-added indicator lights; used with  
T872D1375.  
None  
G1090  
TRADELINE; B and O terminals.  
Q674G1070  
Q672H  
System: OFF-ON  
Fan: NIGHT INT.-DAY CONT.  
H1008  
Q672J  
Used with T872.  
None  
None  
System: EM. HT.-AUTO-OFF  
Fan: AUTO-ON.  
J1005  
J1013  
With EM. HT. LED; used with T872C or D.  
Westinghouse; heat pump; EM. HT. LED; cool Y594G1252  
mode changeover; compressor lockout in  
EM. HT.; used with T872G1034.  
J1021  
J1039  
York; heat pump; EM. HT. LED; cool mode  
changeover; compressor lockout and auto fan in  
EM. HT.; E-W jumper; used with T872G1042,  
G1331, G1398.  
Heat pump; EM. HT. and AUX. HEAT LEDs;  
cool mode changeover; compressor lockout and  
auto fan in EM. HT.; used with T872G1059.  
Y594G1567  
Y594G1161  
Designed for use on General  
Electric heat pumps.  
J1047  
J1054  
Singer no. 02005699; heat pump; EM. HT. LED; Q674F1022  
heat mode changeover.  
Carrier no. HH93AZ073A; heat pump; EM. HT. Y594G1252  
LED; cool mode changeover; compressor  
lockout in EM. HT.; used with T872G1075,  
G1182, G1307.  
Wiring differences (old=new): C=X.  
J1062  
Westinghouse; EM. HT. and AUX. HEAT LEDs; Y594G1252  
Wiring differences (old=new):  
W=W2.  
used with T872G1034.  
Q672K  
System: OFF-HEAT-AUTO-COOL. Fan: None.  
K1004  
Carrier no. HH93AZ072.  
Q674E1049  
Fan switch does not function.  
K1012  
Oneida Heater no. 30A0288-01; System: OFF- T874F1155/  
WOOD-WOOD/OIL-OIL; used with T872F1175. Q674K1026  
Q672L  
System: EM. HT.-HEAT-OFF-COOL.  
Fan: ON-AUTO.  
L1003  
L1011  
Lennox; heat pump; EM. HT. LED; cool mode  
Y594R1425  
Y594R1664  
changeover; used with T872R1024.  
York; heat pump; EM. HT. LED; cool mode  
changeover; compressor lockout and auto fan in  
EM. HT.; used with T872R1032, R1180, R1297.  
L1029  
Lennox no. P-8-11226; heat pump; EM. HT.  
LED; V-VR jumper; cool mode changeover;  
compressor lockout in EM. HT.; used with  
T872R1040.  
Y594R1425  
Wiring differences (old=new):  
V-VR=R, M=Y, Y=W2, F=G, R=O.  
L1037  
L1045  
Heat pump; EM. HT. and AUX. HT. LEDs; cool Y594R1763  
mode changeover; compressor lockout and auto  
fan in EM. HT.; used with T872R1057.  
Wiring differences (old=new): A=T;  
designed for used on General  
Electric heat pumps.  
Rheem; heat pump; EM. HT. LED; cool mode  
changeover; compressor lockout in EM. HT.;  
auto fan in EM. HT; used with T872R1065,  
R1081, R1107.  
Y594R1243  
a
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.  
43  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 7. Q672-Q674 Subbase Cross Reference.  
Q674 Trade  
a
Model Number  
Description  
Replacement  
Remarks  
L1052  
Carrier no. HH93AZ075; heat pump; EM. HT.  
LED; cool mode changeover; compressor  
lockout in EM. HT.; used with T872G1075,  
G1182, G1273, G1307.  
Y594R1615  
Wiring differences (old=new): C=X.  
L1060  
L1078  
Dunham Bush; EM. HT. LED; used with  
Y594R1243  
None  
T872R1099.  
Tappan no. B13708-58; heat pump; EM. HT.  
LED; cool mode changeover; compressor  
lockout in EM. HT.; EM. HT. relay provides fan  
operation in EM. HT.; used with T872G1190.  
L1086  
L1094  
L1102  
L1110  
L1128  
L1136  
Friedrich; heat mode changeover; EM. HT. LED; Y594R1243  
Wiring differences (old=new): X2=E,  
C=X.  
used T872R1115 with L terminal.  
Crispaire; W2-H jumper; EM. HT. LED; used  
with T872R1065, R1156.  
Y594R1243  
Replacement has auto fan in  
Emergency Heat mode.  
Fedders; heat mode changeover; EM. HT. LED; Y594R1425  
Wiring differences (old=new): K=E,  
C=X; remove Y-W1 jumper.  
used with T872C1509, C1517, C1541.  
Westinghouse; EM. HT. LED; used with  
T872R1149.  
Y594R1243  
Y594R1243  
Y594R1243  
Wiring differences (old=new):  
W=W2.  
Westinghouse; EM. HT. LED; used with  
Wiring differences (old=new):  
W=W2.  
T872R1149.  
Rheem no. 41-20796-07; cool mode  
changeover; EM. HT. and AUX. HT. LEDs; used  
with T872R1081, T872R1107.  
L1144  
Lennox; V-VR jumper; EM. HT. and SERVICE  
LEDs; isolated stage 2 heat; used with  
T872R1131, C815A1013.  
None  
L1151  
L1169  
Westinghouse; AUX. HT. and EM. HT. LEDs;  
Y594R1243  
None  
Wiring differences (old=new):  
W=W2.  
used with T872R1149.  
Carrier no. HH93AZ071; EM. HT. LED; used  
with T872G1257 (HH07AT073).  
L1177  
L1185  
L1193  
York; DoD; EM. HT. LED; used with T872G1299. Y594G1567  
Bard; used with T872R1164.  
Y594R1243  
Y594R1243  
Heil Quaker no. NAXA001TS01; used with  
Wiring differences (old=new): B=X,  
W=W2.  
T872R1172.  
L1201  
L1219  
Lennox special; no. 1485701; used with  
T872G1323.  
Westinghouse special; used with T872G1356. T874D1165/  
None  
Wiring differences (old=new): X=X1,  
L=X2, W=E; Y1-W1 and  
Q674F1022  
Y2-W2 jumpers required.  
L1227  
L1235  
L1250  
Heat pump; used with T872R1198.  
Intertherm; used with T872R1206, R1305.  
Y594R1243  
None  
Y594R1243  
Crispaire special; used with T872R1156 and  
C815A1021.  
L1268  
L1276  
Westinghouse special; used with T872W1027  
and C815A1021.  
Intertherm special; used with T872R1214.  
None  
Y594R1300  
Wiring differences (old=new):  
W1=B, Z=L, K=E.  
L1284  
L1300  
York special; used with T872R1222.  
Amana special; no. C62345-1; used with  
T872R1230.  
Y594R1672  
None  
L1326  
Singer; used with T872R1255.  
None  
a
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.  
60-2485—8  
44  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 7. Q672-Q674 Subbase Cross Reference.  
Q674 Trade  
a
Model Number  
L1342  
Description  
Lennox no. 52C7601; used with T872W1019  
Replacement  
None  
Remarks  
and C815A1013.  
L1375  
L1383  
L1391  
L1409  
Westinghouse; used with T872R1271, W89.  
Dunham Bush; used with T872R1099.  
Williamson; used with T872R1339.  
Duotherm special; used with T872R1321, W89. None  
System: OFF-HEAT-COOL-EVAP.  
None  
Y594R1243  
Y594R1243  
Q672N  
N1001  
N1019  
N1027  
Goettl; heat pump; heat mode changeover;  
evaporative cooler circuit; Fan: AUTO-ON;  
System: AUTO; used with T872C1459.  
Goettl; heat pump; heat mode changeover;  
evaporative cooler circuit; W1-Y1 jumper; used  
with T872C1459.  
Siegler special; used with T872C1707.  
System: EM. HT.-HEAT-COOL.  
None  
None  
None  
Q672P  
P1009  
Carrier special; no. HH93AZ069; used with  
Y594R1243  
Replacement has OFF system  
switch position  
T872G1075 (HH07AT071).  
a
When replacing a T872 Thermostat and Q672 Subbase, always replace both the thermostat and subbase.  
45  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Description  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Number  
Remarks  
T874A  
A1002  
A1010  
1-stage heat, 1-stage cool.  
44, 65 Honeywell logo; Standard OEM; used with Q674B1331.  
T874A1036  
T874A1010  
44  
Honeywell logo; includes Allen wrench and screws to  
lock cover; non-adjustable range stops set at 72°F (max.  
heat) and 78°F (min. cool) (22-26°C); field adjustable  
locking levers.  
A1028  
A1036  
44  
44  
Honeywell logo; heat anticipator factory set at 0.4A.  
Honeywell logo; TRADELINE® model; includes Allen  
wrench and screws to lock cover; field adjustable locking  
levers.  
T874A1036  
T874A1036  
A1044  
A1051  
44  
44  
44  
Obsolete. AAF/Snyder General logo; part no. 4ELN-  
T874A1036 Replacement has °F  
scaleplate.  
3
006C; °F/°C scaleplate.  
Lennox logo; part no. 12F9901; °F/°C scaleplate; heat  
T874A1036 Replacement has °F  
anticipator set at 0.45A.  
scaleplate.  
A1069  
A1077  
Obsolete. Westinghouse logo; used with Q674A-E,G.  
T874A1036  
T874A1036  
46, 82 Obsolete. Amana Air Conditioning logo; part no.  
D68535-1; heat anticipator factory set at 1.2A; used with  
Q674B1075, E1056; used in Y594A1001, A1019.  
A1085  
A1093  
A1101  
44, 46, Obsolete. Trane logo; part no. 13510451; used with  
T874A1036  
5
5, 66 Q674B1018, B1075, D1008.  
44  
Obsolete. McQuay logo; part no. 02005935; °F/°C  
T874A1036 Replacement has °F/°C  
scaleplate.  
scaleplate.  
51, 53 Carrier logo; part no. HH07AT174; used with Q674B.  
Y594C1421 or When using the T874C1036,  
a
T874A1036  
set stage 1 heat anticipator for  
total current draw of fan and  
stage 1 heat primary.  
A1119  
82  
Obsolete. Sears logo; part no. 541. 91441/49. 9144; °F/  
T874A1036 Replacement has °F  
°
C scaleplate; used with Q674E1007; used in  
scaleplate.  
Y594A1068.  
A1127  
A1135  
A1143  
A1150  
44  
44  
44  
44  
Obsolete. Climate Control logo; part no. 02005936; °C  
T874A1036 Replacement has °F  
scaleplate.  
T874A1036  
scaleplate.  
Fedders multi-logo; part no. THTX-110-WCHA,  
88-58-00500-001.  
Honeywell logo; °C scaleplate.  
T874A1036 Replacement has °F  
scaleplate.  
T874A1150  
Honeywell logo; TRADELINE model; includes Allen  
wrench and screws to lock cover; field adjustable locking  
levers (68°F max. heat, 78°F min. cool).  
A1168  
A1176  
44  
44  
Obsolete. Trane Comfort Corps logo.  
T874A1036  
T874A1176  
Honeywell logo; meets DoD specs; includes Allen  
wrench and screws to lock cover; no thermometer; non-  
adjustable range stops set at 72°F (max. heat) and 78°F  
(min. cool) (22-26°C); field adjustable locking levers.  
A1184  
51, 53 Trane logo; part no. BAY28X182; °F/°C scaleplate;  
automatic fan in heating and cooling modes; heat  
anticipator set at 0.4A; used with Q674B1141, E1080.  
T874A1036a When used with Q674E1080,  
set stage 1 heat anticipator for  
total current draw of fan and  
stage 1 heat primary;  
replacement has °F  
scaleplate.  
A1192  
44  
Obsolete. Lennox logo; part no. 13F0001; °C scaleplate;  
heat anticipator factory set at .458A.  
T874A1036 Replacement has °F  
scaleplate.  
aBoth the thermostat and subbase must be replaced.  
60-2485—8  
46  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Model  
Fig.  
No.  
Trade Model  
Replacement  
T874A1036  
Number  
Description  
Remarks  
a
A1200  
51, 53 Obsolete. Carrier logo; part no. HH07AT164; °C  
scaleplate; includes Allen wrench and screws to lock  
cover; used with Q674B.  
Set stage 1 heat anticipator for  
total current draw of fan and  
stage 1 heat primary;  
replacement has °F  
scaleplate.  
A1226  
A1234  
44  
44  
Honeywell logo; Honeywell Canada TRADELINE model;  
T874A1036 Replacement has °F  
°
C scaleplate; includes Allen wrench and screws to lock  
scaleplate.  
cover.  
Obsolete. Friedrich Climate Master logo; heat anticipator  
T874A1036  
factory set 1.2A.  
A1242  
A1259  
A1267  
A1275  
44  
44  
59  
44  
Obsolete. Friedrich Climate Master logo.  
Obsolete. Wesco logo; heat anticipator set at 0.8A.  
Obsolete. McQuay logo; used with Q674Q1004.  
T874A1036  
T874A1036  
T874A1036  
T874A1176  
Obsolete. Lennox logo; part no. 13F0101; meets DoD  
specifications.  
A1283  
75  
McQuay Air Conditioning logo; part no. 03005047; used  
with Q674C1132 and thermistor to display outdoor  
temperature.  
T874A1036 Replacement does not have  
ability to display external  
temperature or momentary  
system switch position.  
A1291  
A1309  
64  
44  
No logo; three-speed fan; one setpoint lever for heat and  
cool setpoints; used with Q674Q1012; used in  
Y594A1126.  
Obsolete. Arcoaire Air Conditioning and Heating logo;  
part no. AO2076; includes Allen wrench and screws to  
lock cover.  
T874A1036/ Replacement has two levers  
a
Q674B1075  
and 1 speed fan.  
T874A1036  
A1317  
A1325  
44  
75  
Obsolete. McQuay logo; part no. 60685301; no  
T874A1036  
scaleplate; used with Q674A-E,G.  
Obsolete. McQuay logo; part no. 60685401; no  
scaleplate; used with Q674C1306 and outdoor  
thermistor to display outdoor temperature.  
T874A1036 Replacement does not have  
ability to display external  
temperature or momentary  
system switch position.  
A1341  
44  
44  
Obsolete. Trane logo; part no. THT-0577; meets DoD  
specifications.  
York-Miraco logo.  
T874A1176  
A1358  
A1366  
T874A1036  
a
51, 53 Obsolete. BDP Multi-logo; part no. HH07AT182.  
T874A1036  
Set stage 1 heat anticipator for  
total current draw of fan and  
stage 1 heat primary.  
T874A1036a  
A1374  
A1390  
A1416  
A1424  
A1440  
44  
44  
44  
American Standard logo; part no. ASYSTAT610; heat  
anticipator factory set at 0.4A.  
Obsolete. Climate Control logo; part no. 654958804; °F/  
T874A1036 Replacement has °F  
scaleplate.  
°C scaleplate.  
Obsolete. Reznor logo; part no. 654758803; °F/°C  
T874A1036 Replacement has °F  
scaleplate.  
scaleplate.  
214 Obsolete. Carrier Olympia Series Split System logo; part See OEM for  
no. HH07AT194; used with Q674B1455 (HH93AZ208).  
Obsolete. Simplex System 2000 logo; heat anticipator  
factory set at 1.2A; used with Q674G1005; used in  
Y594A.  
replacement.  
T874A1036  
91  
A1465  
212 Honeywell Trol-A-Temp™ logo; Premier White® color;  
heat anticipator factory set at 0.10A; used with  
Q674E1379.  
None  
See Trol-A-Temp for  
replacement.  
aBoth the thermostat and subbase must be replaced.  
47  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Description  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Number  
Remarks  
A1481  
A1507  
A1523  
44  
Obsolete. Honeywell logo; Carrier part no. HH621602;  
includes locking cover and non-adjustable range stops  
set at 72°F (max. heat) and 78°F (min. cool).  
Obsolete. Climate-Tel logo; includes Allen wrench and  
screws to lock cover and non-adjustable range stops set  
at 72°F (max. heat) and 78°F (min. cool).  
T874A1036  
44  
T874A1176  
224, Obsolete. AAF/Snyder General logo; part no.  
See OEM for  
replacement.  
225 066804404; °F/°C scaleplate; no cooling anticipation;  
used with Q674E1312, C1298.  
A1549  
A1556  
224, Obsolete. McQuay logo; part no. 066816601; no cooling See OEM for  
2
25 anticipation; used with Q674E1312, C1298.  
replacement.  
a
51, 53 Carrier logo; part no. HH07AT164-W; °C scaleplate;  
Premier White® color; includes Allen wrench and  
screws to lock cover; used with Q674B.  
T874A1036  
Replacement has °F  
scaleplate; replacement is  
beige.  
A1572  
A1580  
A1598  
224, Obsolete. McQuay logo; part no. 066816611; Premier  
See OEM for  
replacement.  
T874A1036  
2
25 White® color; °F/°C scaleplate; no cooling anticipation.  
91  
California Economizer logo; Premier White® color; heat  
anticipator factory set at 1.2A.  
224, McQuay logo; part no. 073319001; Premier White®  
See OEM for  
2
25 color; °F/°C scaleplate; includes Allen wrench, screws to replacement.  
lock cover and AAF insert.  
A1614  
A1622  
44  
Honeywell logo; TRADELINE® model; °C scaleplate;  
Premier White® color; includes Allen wrench and  
screws to lock cover; used with Q674B.  
T874A1036 Replacement has °F  
scaleplate; replacement is  
beige.  
T874A1010  
44  
Obsolete. York logo; part no. 2TH04703224A; includes  
Allen wrench and screws to lock cover and non-  
adjustable range stops set at 72°F (max. heat) and 78°F  
(min. cool).  
T874B  
B1001  
B1019  
1-stage heat, 2-stage cool.  
Obsolete. Honeywell logo.  
44  
44  
T874B1019  
T874B1019  
Honeywell logo; TRADELINE model; includes Allen  
wrench and screws to lock cover.  
B1027  
B1035  
44  
Obsolete. Westinghouse logo.  
T874B1019  
T874B1019  
44, 46 Obsolete. Trane logo; used with Q674B1018, B1075;  
used in Y594B1026, B1034.  
B1043  
B1050  
B1068  
44  
44  
44  
Obsolete. Honeywell logo; °C scaleplate.  
T874B1019 Replacement has °F  
scaleplate.  
Lennox logo; part no. 13F0201; °F/°C scaleplate.  
T874B1019 Replacement has °F  
scaleplate.  
Honeywell logo; Honeywell Canada TRADELINE model;  
T874B1019 Replacement has °F  
scaleplate.  
°
C scaleplate; includes Allen wrench and screws to lock  
cover.  
B1076  
B1084  
B1092  
B1100  
B1118  
88  
44  
44  
88  
44  
Obsolete. Lennox Power Saver Two-Speed logo; part  
T874B1019 Replacement has °F  
scaleplate.  
no. 91C7401; °F/°C scaleplate; used with Q674E1155.  
Obsolete. Lennox Two-Speed logo; part no. 13F0301;  
T874B1019 Replacement has °F  
°C scaleplate.  
scaleplate.  
Obsolete. Honeywell logo; Heil Quaker part no.  
T874B1019  
HQ521389HW.  
Obsolete. Janitrol logo; part no. CHTS36-60; °F/°C  
scaleplate; used with Q674E1338; used in Y594B1042.  
T874B1019 Replacement has °F  
scaleplate.  
Honeywell logo; °C scaleplate; used with  
T874B1019 Replacement has °F  
Q674A-E, G.  
scaleplate.  
aBoth the thermostat and subbase must be replaced.  
60-2485—8  
48  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Number  
Description  
Remarks  
B1134  
222 Obsolete. Carrier Synergy 2000 logo; part no.  
T874B1019/ Wiring differences (old=new):  
a
HH07AT199; °C scaleplate; used with Q674E1395  
Q674E1049  
W1=W; RC-RH jumper  
required; replacement has no  
LEDs.  
(HH93AZ209).  
T874C  
2-stage heat, 1-stage cool.  
C1000  
44, 76 Honeywell logo; used with Q674B1075, C1181; used in  
T874C1018  
T874C1018  
Y594C1058.  
C1018  
C1026  
60, 61, Honeywell logo; TRADELINE model; includes Allen  
8
1, 92 wrench and screws to lock cover; used with  
Q674C1074.  
44  
Obsolete. AAF logo; °C scaleplate; includes Allen  
wrench and screws to lock cover; non-adjustable range  
stops set at 23°C (max. heat and min. cool) (73°F).  
T874C1018 Replacement has °F  
scaleplate.  
C1034  
C1042  
44  
44  
Lennox logo; part no. 13F0401; °F/°C scaleplate.  
T874C1018 Replacement has °F  
scaleplate.  
T874C1018  
Obsolete. Westinghouse logo; H1 anticipator factory set  
at.75A; H2 anticipator factory set at 1.2A; used with  
Q674A-E,G.  
C1059  
44, 142 Obsolete. Amana Air Conditioning logo; part no.  
D68535-2; H1 anticipator factory set at 1.2A; used with  
Q674E1056, Q674B1059, Q674F1022; used in  
T874C1018  
Y594C1009, Y594C1017, Y594C1256, Y594C1330.  
C1067  
C1075  
44  
Obsolete. Sears logo; part no. 42. 9297; °F/°C  
T874C1018 Replacement has °F  
scaleplate.  
scaleplate.  
51, 53 Carrier logo; part no. HH07AT170; used with  
Q674B1166.  
Y594C1421 or When using the T874C1018,  
a
T874C1018  
set stage 1 heat anticipator for  
total current draw of fan and  
stage 1 heat primary.  
C1083  
C1117  
C1125  
44  
44  
Obsolete. Trane logo; used with Q674E1007; used in  
Y594C1082.  
Honeywell logo; °C scaleplate.  
T874C1018  
T874C1018 Replacement has °F  
scaleplate.  
T8611M2025  
60, 61, Obsolete. Honeywell logo; 12°F (6.7°C) differential  
9
2
between stage 1 heat and stage 2 heat; used with  
Q674G1047.  
C1133  
C1141  
96  
44  
Obsolete. AAF/Snyder General logo; part no.  
T874C1018 Must have H1 anticipator set  
to maximum value.  
4
ELN7546; no H1 heat anticipation; used with Q674A-  
G,N and Q674C1173.  
Obsolete. Honeywell logo; meets DoD specs; includes  
Allen wrench and screws to lock cover; no thermometer;  
non-adjustable range stops set at 72°F (max. heat) and  
T874C1141  
7
8°F (min. cool) (22-26°C); field adjustable locking  
levers.  
C1158  
C1166  
44  
Obsolete. Solaron special.  
T874C1018  
T874C1018  
a
51, 53 Obsolete. Carrier logo; part no. HH07AT160; °C  
scaleplate; includes Allen wrench and screws to lock  
cover; used with Q674B.  
Replacement has °F  
scaleplate; set stage 1 heat  
anticipator for total current  
draw of fan and stage 1 heat  
primary.  
C1174  
C1182  
44  
60  
Obsolete. Goettl logo.  
T874C1018  
T874C1018  
Obsolete. Goettl logo; H1 anticipator factory set at 0.8A;  
used with Q674N1015.  
C1190  
44  
Obsolete. Lennox logo; part no. 13F0501; °C scaleplate.  
T874C1018 Replacement has °F  
scaleplate.  
aBoth the thermostat and subbase must be replaced.  
49  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Description  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Number  
Remarks  
C1216  
C1224  
C1240  
44  
Obsolete. Fasco part no. 1230-8197.  
T874C1018  
T874C1018  
T874C1018 Replacement has °F  
scaleplate.  
105 Obsolete. Square D logo.  
44  
44  
44  
Honeywell logo; Honeywell Canada TRADELINE model;  
°
C scaleplate; includes Allen wrench and screws to lock  
cover.  
C1257  
C1265  
Obsolete. Singer part no. 0200-5931; 8°F (4.4°C)  
T874C1125 Replacement has 12°F  
differential between H1 and  
H2 heat.  
T874C1125 Replacement has 12°F  
differential between H1 and  
H2 heat; replacement has °F  
scaleplate.  
differential between H1 and H2 heat.  
Obsolete. Singer special; °C scaleplate; 5°C (8°F)  
differential between H1 and H2 heat.  
C1273  
44  
Honeywell logo; °C scaleplate; includes Allen wrench  
and screws to lock cover; non-adjustable range stops  
factory set at 23°C (max. heat and min. cool) (73°F).  
T874C1018 Replacement has °F  
scaleplate.  
C1281  
C1307  
C1315  
44  
44  
44  
Obsolete. Heat Wave special.  
T874C1018  
T874C1018  
T874C1018  
Obsolete. Friedrich Climate Master logo.  
Obsolete. Wesco logo; heat anticipator factory set at  
0.8A.  
C1323  
44  
Obsolete. Le Chauffage Urbain special; °C scaleplate.  
T874C1018 Replacement has °F  
scaleplate.  
C1331  
C1349  
C1372  
82, 141 Obsolete. Duotherm logo; used with Q674E or Q674F.  
T874C1018  
T874C1018  
T874C1018/ For systems requiring  
Q674B1034 automatic fan in cooling mode  
only.  
61  
52  
Obsolete. Sigler logo; used with Q674N1023.  
Obsolete. Honeywell logo; used with Q674B1190.  
T874C1018/ For systems requiring  
Q674B1075 automatic fan in heating and  
cooling.  
C1398  
C1406  
C1414  
105 Obsolete. Fedders logo; °F/°C scaleplate; used with  
Q674L1090.  
Y594R1425a Wiring differences (old=new):  
K=E, C=X; replacement has °F  
scaleplate.  
Y594R1425a Wiring differences (old=new):  
K=E, C=X; replacement has °F  
scaleplate.  
Y594R1425a Wiring differences (old=new):  
K=E, C=X; replacement has °F  
scaleplate.  
105 Obsolete. Climatrol logo; °F/°C scaleplate; used with  
Q674L1090.  
105 Obsolete. Airtemp logo; °F/°C scaleplate; used with  
Q674L1090.  
C1422  
C1430  
187 Obsolete. Honeywell logo; used with Q674B1208.  
None  
T874C1018  
49  
Obsolete. Lennox Zone Master Two-Speed logo; part  
no. 25F7201; used with Q674B1224.  
C1448  
110, Obsolete. Lennox logo; part no. 24F5101; meets DoD  
Y594R1763a Wiring differences (new=old):  
R=V-VR, Y=M, G=F, B-X,  
1
90 specifications; requires outdoor reset; used with  
Q674L1165, L1355.  
W=Y, T=A, O=R, X2=E;  
Emergency Heat becomes  
stage 1 heat source.  
Y594R1243a  
C1455  
C1463  
127 Obsolete. Williamson logo; used with Q674L1322.  
82  
Obsolete. AAF logo; °C scaleplate.  
T874C1018 Replacement has °F  
scaleplate.  
C1471  
56  
Obsolete. Mammoth logo; part no. 71120102; used with  
Q674B1257; used in Y594C1314.  
T874C1018  
aBoth the thermostat and subbase must be replaced.  
60-2485—8  
50  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Y594C1322  
Number  
Description  
Remarks  
a
C1489  
121 Obsolete. Honeywell logo; non-adjustable range stops  
set at 75°F (max. heat and min. cool) (24°C); used with  
Q674L1157.  
Y594C1322a  
T874C1018  
T874C1018  
T874C1018  
Y594C1322a  
C1497  
C1513  
C1562  
C1570  
C1638  
121 Obsolete. Honeywell logo; meets DoD specifications;  
used with Q674L1157.  
44  
44  
45  
Obsolete. Borg-Warner multi-logo; part no.  
TH11703124A.  
6
Obsolete. Honeywell logo; Heil Quaker part no.  
HQ712001HW.  
Obsolete. Williamson logo; used with Q674B1000; used  
in Y594C1280.  
121 Obsolete. Honeywell logo; meets DoD specifications;  
includes Allen wrench and screws to lock cover; no  
thermometer; non-adjustable range stops set at 72°F  
(
max. heat) and 78°F (min. cool) (22-26°C); field  
adjustable locking levers; used with Q674L1561; used in  
Y594C1322.  
C1653  
C1661  
70  
99  
Obsolete. Fiberglas Canada; °C scaleplate; no H1, H2,  
or C1 anticipation; used with Q674S1000; used in  
Y594C1348.  
Obsolete. McQuay logo; part no. 61202401; °F/°C  
scaleplate; includes momentary system switch position  
with spring release; used with Q674C1363.  
See OEM for  
replacement.  
T874C1125/ Replacement has HEAT-OFF-  
a
Q674B1075  
COOL system switching; no  
momentary system switch  
position; no LEDs.  
C1695  
C1703  
45  
45  
Obsolete. Miller logo; used with Q674B1000; used in  
Y594C1355.  
T874C1018  
T874C1018  
Obsolete. Intertherm logo; used with Q674B1000; used  
in Y594C1363.  
C1737  
C1745  
44  
44  
Obsolete. Honeywell logo; Carrier part no. HH621603.  
Obsolete. AAF/Snyder General logo; part no.  
T874C1018  
T874C1018  
4ELN7919.  
C1752  
219 Obsolete. McQuay/Snyder General logo; part no.  
T8611M2025  
0
61202402; 12°F offset between H1 and H2; °F/°C  
scaleplate; no C1 anticipation; used with Q674C1363.  
Bard logo.  
C1760  
C1778  
44  
T874C1018  
See OEM for  
replacement.  
219 Obsolete. AAF/Snyder General logo; part no.  
0
66804405; 12°F offset between H1 and H2; °F/°C  
scaleplate; no C1 anticipation; used with Q674C1363.  
C1794  
53  
Obsolete. Carrier logo; Canada; part no. HH07AT160-W;  
Premier White® color; °C scaleplate; includes locking  
cover.  
T874C1018 Set stage 1 heat anticipator for  
total current draw of fan and  
stage 1 heat primary.  
C1802  
C1810  
246 Obsolete. California Economizer logo; °F/°C scaleplate;  
T874C1018  
Y594C1389  
used with Q674G1005; used in Y594C1371.  
237 Obsolete. Honeywell logo; TRADELINE model; Premier  
White® color; used with Q674B1547; used in  
Y594C1389.  
C1844  
238 Energy Night logo; used with Q674F1592; used in  
Y594R1425 Jumper E-W2; system switch:  
EM.HT.-HEAT-OFF-COOL.  
Y594C1413.  
C1851  
C1869  
60  
Obsolete. Whalen logo.  
T874C1018  
219 McQuay logo; part no. 0073318801 Premier White®  
See OEM for  
color; °F/°C scaleplate.  
replacement.  
aBoth the thermostat and subbase must be replaced.  
51  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Description  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Number  
Remarks  
C1877  
53  
Obsolete. Honeywell logo; TRADELINE model; used  
Y594D1347 Jumper RC-RH; system  
switch: OFF-HEAT-AUTO-  
COOL  
with Q674B1554; used in Y594C1421.  
T874D  
2-stage heat, 2-stage cool.  
D1009  
166, 82 Obsolete. Honeywell logo; used with Q674F1337,  
T874D1165  
T874D1165  
E1007; used in Y594D1222, D1339.  
D1017  
44, 88 Obsolete. Honeywell logo; TRADELINE model; includes  
Allen wrench and screws to lock cover; used with  
Q674A-G and Q674E1155.  
D1025  
D1033  
D1041  
44  
44  
53  
Obsolete. Westinghouse logo; H1 anticipator factory set  
T874D1165  
at 0.75A; H2 anticipator factory set at 1.2A.  
Lennox logo; part no. 13F0601; °F/°C scaleplate.  
T874D1165 Replacement has °F  
scaleplate.  
T874D1165  
York logo; part no. 2TH04701524A; used with  
Q674B1125.  
D1058  
D1066  
D1074  
44  
44  
Obsolete. Shiger special.  
Obsolete. ITT logo.  
T874D1165  
T874D1165  
a
51, 53, Carrier logo; part no. HH07AT172; used with  
T874D1165  
Set H1 anticipator for current  
draw of fan and stage 1 heat  
primary.  
146 Q674F1030 (HH93AZ174), F1063 (HH93AZ181) or  
Q674B.  
D1082  
44, 46, Trane logo; used with Q674B1018, C1009, B1075,  
8, 72 B1133; used in Y594D1024, D1040.  
T874D1165  
4
D1090  
D1108  
D1116  
44  
44  
Obsolete. Dunham-Bush logo.  
Obsolete. Westinghouse logo.  
T874D1165  
T874D1165  
T874D1165 Replacement has °F  
76, 89, Obsolete. Comfortmaker logo; part no. 1505-682; °F/°C  
9
4
scaleplate; used with Q674C1116, E1197, G1104.  
Obsolete. Airtemp special.  
Honeywell logo; °C scaleplate.  
scaleplate.  
D1124  
D1132  
44  
44  
T874D1165  
T874D1165 Replacement has °F  
scaleplate.  
D1140  
D1157  
44  
Obsolete. Solaron special.  
T874D1165 Replacement has °F  
scaleplate.  
51, 53, Carrier logo; part no. HH07AT172; °C scaleplate; used  
46 with Q674B or Q674F1030, F1063.  
T874D1165a Replacement has °F  
1
scaleplate; set H1 anticipator  
for current draw of fan and  
stage 1 heat primary.  
D1165  
D1173  
D1181  
82  
Honeywell logo; SUPER TRADELINE® model; includes  
Allen wrench and screws to lock cover, field-adjustable  
range stops, field-adjustable locking levers.  
T874D1165  
51, 53 Trane logo; part no. BAY28X183; heat anticipator factory  
T874D1165a Set H1 anticipator for current  
draw of fan and stage 1 heat  
primary.  
T874D1165a Set H1 anticipator for current  
draw of fan and stage 1 heat  
primary.  
set at 0.4A.  
51, 53 Obsolete. General Electric logo; locking cover includes  
Allen wrench and screws to lock cover and range stops  
set at 72°F (max. heat) and 78°F (min. cool).  
D1199  
D1207  
44  
Obsolete. Lennox logo; part no. 13F0701; °C scaleplate.  
T874D1165 Replacement has °F  
scaleplate.  
114 Obsolete. Lennox logo; part no. 24F5201; used with  
Q674L1199 and C815A1013 or Q674L1389.  
T8611M2025 Wiring differences (old=new):  
(programmable) V-VR=R, Y=W3, X=C, R=O,  
M=Y, M2=Y2-W2, F=G;  
jumper Y2-W2; no outdoor  
reset needed; use only one  
system transformer.  
aBoth the thermostat and subbase must be replaced.  
60-2485—8  
52  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Number  
Description  
Remarks  
D1215  
D1223  
D1231  
44  
44  
44  
Obsolete. Friedrich Climate Master logo; part no.  
T874D1165 Replacement has °F  
AT5415; °F/°C scaleplate.  
scaleplate.  
Honeywell logo; Honeywell Canada TRADELINE model;  
Celsius scale.  
T874D1165 Replacement has °F  
scaleplate.  
T874D1165 Replacement has 2°F  
differential between H1 and  
H2.  
Obsolete. Honeywell logo; 12°F (7°C) differential  
between H1 and H2.  
D1249  
D1256  
D1264  
44  
44  
Obsolete. Fedders special.  
Obsolete. Climatrol special.  
T874D1165  
T874D1165  
107 Obsolete. Carrier Heat Pump System Control logo; part  
See OEM for  
no. HH07AT173; used with Q674L1116 (HH93AZ171).  
replacement.  
a
D1272  
51, 53 Obsolete. Carrier logo; part no. HH07AT162-03; °C  
scaleplate; used with Q674B.  
T874D1165  
Replacement thermostat has  
°F scaleplate; set H1  
anticipator for current draw of  
fan and stage 1 heat primary.  
D1280  
D1298  
44  
Obsolete. Command-Aire logo.  
T874D1165  
See OEM for  
replacement.  
90, 232 Obsolete. Singer special; °C scaleplate; controls two  
separate heat/cool circuits; used with Q674D or  
Q674G1054, G1062.  
D1306  
D1314  
90, 186 Obsolete. Trane special; part no. 02005949; controls  
See OEM for  
replacement.  
T874D1165 Replacement has °F  
scaleplate; 2°F differential  
between H1 and H2.  
two separate heat/cool circuits; used with Q674G1013.  
44  
Obsolete. McQuay logo; part no. 02005941; 12°F  
6.6°C) differential between H1 and H2.  
(
D1322  
D1330  
D1355  
46  
44  
44  
Obsolete. Amana logo; part no. D68535-03; used with  
Q674B1075; used in Y594D1149.  
Obsolete. Trane logo; part no. 13080242; °C scaleplate.  
T874D1165  
T874D1165 Replacement has °F  
scaleplate.  
T874D1165 Replacement has 2°F  
differential between H1 and  
H2.  
Obsolete. Climate Control special; part no. 02005942;  
°
C scaleplate; 6°C (11°F) differential between H1 and  
H2.  
D1363  
D1405  
D1413  
44  
44  
44  
Obsolete. McQuay logo; part no. 02005943; 12°F  
T874D1165 Replacement has 2°F  
differential between H1 and  
H2; 2°F differential between  
C1 and C2.  
T874D1165 Replacement has 2°F  
differential between H1 and  
H2; 2°F differential between  
C1 and C2.  
(
6.6°C) differential between H1 and H2; 6°F (3.3°C)  
differential between C1 and C2.  
Obsolete. Trane logo; part no. 02005952; 12°F (6.6°C)  
differential between H1 and H2; 6°F (3.3°C) differential  
between C1 and C2.  
Obsolete. Trane logo; part no. 02005956; 12°F (6.6°C)  
differential between H1 and H2.  
T874D1165 Replacement has 2°F  
differential between H1 and  
H2.  
D1421  
D1439  
D1447  
D1454  
44  
90  
90  
Obsolete. Climate Control special; part no. 02005938;  
T874D1165 Replacement has °F  
°
C scaleplate.  
scaleplate.  
McQuay logo; part no. 02005935; used with  
T874D1165  
Q674G1096.  
Obsolete. Climate Control special; part no. 02005940;  
T874D1165 Replacement has °F  
scaleplate.  
T874D1165a Set H1 anticipator for current  
draw of fan and stage 1 heat  
primary.  
°C scaleplate; used with Q674G1096.  
51, 53 Obsolete. Carrier logo.  
D1462  
80  
Obsolete. Fedders multi-logo; part no. THTX-220-A0HB,  
8-58-00550-001; used with Q674E1205.  
T874D1165  
8
aBoth the thermostat and subbase must be replaced.  
53  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Description  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Number  
Remarks  
D1470  
44  
Obsolete. York logo; part no. 2TH04701624A; includes  
T874D1165 Replacement has °F  
Allen wrench and screws to lock cover; °C scaleplate.  
scaleplate.  
D1488  
D1496  
44  
44  
Obsolete. Risco special.  
T874D1165  
T874D1165  
Obsolete. Borg Warner multi-logo; part no.  
6
TH04701524A; includes Allen wrench and screws to  
lock cover.  
D1504  
82  
York logo; part no. 025-23321-000; °C scaleplate; used  
T874D1165 Replacement has °F  
scaleplate.  
with Q674E1007; used in Y594D1180.  
D1512  
D1520  
44  
44  
Honeywell logo; Heil Quaker part no. HQ712002HW.  
Obsolete. Bard logo; adjustable lever stops set 68°F  
T874D1165  
T874D1165  
(
max. heat) and 78°F (min. cool).  
D1538  
D1553  
44  
44  
Obsolete. McQuay logo; part no. 02005937.  
T874D1165  
T874D1165 Replacement has 2°F  
Obsolete. Climate Control special; part no. 02005944;  
°
C scaleplate; 6°C differential between H1 and H2; 3°C  
differential between H1 and  
differential between C1 and C2.  
H2; 2°F differential between  
C1 and C2; replacement has  
°F scaleplate.  
D1561  
D1587  
D1595  
44  
44  
Obsolete. General Electric logo; used with Q674 A-G.  
Obsolete. Stiles Four Seasons logo.  
T874D1165  
T874D1165  
139 Obsolete. Nepco logo; used with Q674F1394.  
T874D1165/ Replacement has HEAT-OFF-  
a
Q674B1018  
COOL system switching; no  
LEDs.  
D1603  
D1611  
44  
44  
Obsolete. Arcoaire logo.  
T874D1165  
T874D1165 Replacement has °F  
scaleplate.  
Obsolete. No logo; Friedrich part no. AT5411; °F/°C  
scaleplate.  
D1629  
D1678  
82  
44  
Obsolete. Reznor logo; °F/°C scaleplate; used with  
Q674E1007; used in Y594D1248.  
T874D1165 Replacement has °F  
scaleplate.  
Obsolete. Honeywell logo; Saudi Oger special; °C  
T874D1165 Replacement has °F  
scaleplate; one setpoint lever; used with Q674A-K.  
scaleplate; separate heating  
and cooling setpoint levers.  
D1686  
98  
Obsolete. McQuay logo; part no. 60685501; 8°F (4.4°C)  
differential between H1 and H2; 6°F (3.3°C) differential  
between C1 and C2; used with Q674E1312.  
T874D1165 Replacement has 2°F  
differential between H1 and  
H2; 2°F differential between  
C1 and C2.  
D1694  
202 Obsolete. McQuay logo; part no. 60685201; used with  
Q674G1120.  
See OEM for  
replacement.  
D1702  
D1710  
D1728  
D1744  
44  
44  
44  
44  
Obsolete. McQuay logo; part no. 60685101.  
Trane logo.  
York-Miraco logo.  
T874D1165  
T874D1165  
T874D1165  
T874D1165  
American Standard logo; heat anticipator factory set at  
0.4A.  
D1751  
D1769  
D1777  
D1785  
D1793  
44  
82  
44  
82  
44  
Obsolete. Goettl logo; part no. 372080; range stops set  
T874D1165  
at 68°F (max. heating) and 78°F (min. cooling).  
Obsolete. Arcoaire logo; part no. 1506753; °F/°C  
T874D1165 Replacement has °F  
scaleplate.  
T874D1165 Replacement has °F  
scaleplate; used with Q674E1346; used in Y594D1297.  
Obsolete. Climate Control logo; part no. 65495806; °F/  
°C scaleplate.  
scaleplate.  
Obsolete. Comfortmaker logo; part no. 1505753; °F/°C  
T874D1165 Replacement has °F  
scaleplate.  
T874D1165 Replacement has °F  
scaleplate; used with Q674E1346; used in Y594D1305.  
Obsolete. McQuay logo; part no. 65495805; °F/°C  
scaleplate.  
scaleplate.  
aBoth the thermostat and subbase must be replaced.  
60-2485—8  
54  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Number  
Description  
Remarks  
D1801  
45, 208 Trol-A-Temp by Honeywell logo; H1 and H2 anticipators  
None  
See Trol-A-Temp for  
set at 0.10A; used with Q674B1463, D1115.  
replacement.  
D1819  
44  
Marv Air Com Stat logo; part no. 50059; adjustable  
interstage between H1 and H2 and between C1 and C2;  
includes Allen wrench and screws to lock cover; field  
adjustable range stops; °F/°C scaleplate.  
T874D1165 Replacement has a 2°F fixed  
interstage differential between  
H1 and H2 and between C1  
and C2; replacement has °F  
scaleplate.  
D1827  
D1843  
45, 208 Trol-A-Temp by Honeywell logo; Premier White® color;  
H1 and H2 heat anticipators set at 0.10A; used with  
Q674B1471, D1123.  
None  
See Trol-A-Temp.  
45  
Obsolete. Janitrol logo; Goodman part no. CHT 90-120;  
T874D1165  
T874D1165  
T874D1165 Replacement has 2°F fixed  
interstage differential between  
H1 and H2 and between C1  
and C2.  
used with Q674B1000; used in Y594D1321.  
D1850  
D1868  
44  
44  
Honeywell logo; Carrier part no. HH621606.  
Bard logo; part no. 8405-031; H1 and H2 heat  
anticipators factory set at 0.25A; 5°F interstage  
differential between H1 and H2 and between C1 and C2;  
includes Allen wrench and screws to lock cover; field  
adjustable range stops.  
D1876  
44  
44  
Obsolete. AAF/Snyder General logo; part no.  
T874D1165 Replacement has °F  
scaleplate.  
T874D1165  
4
ELN6981A; °F/°C scaleplate.  
D1892  
D1918  
Obsolete. Climate-Tel logo.  
224, Obsolete. AAF/Snyder General logo; °F/°C scaleplate;  
25 no cooling anticipation; used with Q674E1312, C1298;  
6804407.  
See OEM for  
2
replacement.  
6
D1926  
226 Obsolete. AAF/Snyder General logo; °F/°C scaleplate;  
See OEM for  
replacement.  
no cooling anticipation; used with Q674G1120;  
66804406.  
D1934  
D1942  
44  
82  
Bard logo.  
T874D1165  
Y594D1347  
a
Honeywell logo; TRADELINE model; used with  
Q674E1403; used in Y594D1347; designed to replace  
York part no. 2TH04701024.  
D1959  
D1967  
D1975  
44  
44  
Rheem part no. 41-21444-01.  
Obsolete. Desert Aire logo.  
T874D1165  
T874D1165  
224, Obsolete. McQuay part no. 066816603; °F/°C  
See OEM for  
225 scaleplate; no cooling anticipation.  
replacement.  
D1983  
D1991  
226 Obsolete. McQuay part no. 066816602; °F/°C  
scaleplate; no cooling anticipation; used with  
Q674G1120.  
51, 53 Carrier logo; Premier White® color; °C scaleplate.  
See OEM for  
replacement.  
T874D1165a Set H1 anticipator for total  
current draw of fan and stage  
1
primary; replacement has °F  
scaleplate.  
D2007  
D2023  
44  
44  
Ultra-Zone logo.  
Honeywell logo; TRADELINE model; Premier White®  
color; °C scaleplate; includes locking cover; used with  
Q674A-K.  
T874D1165  
T874D1165 Replacement has °F  
scaleplate and is beige.  
D2031  
D2049  
82  
Obsolete. Honeywell logo; no cover; used with  
T874D1165 or  
Y594D1354  
T874D1165 Replacement has °F  
Q674E1049 and TG504A1025; used in Y594D1354.  
45, 72, Obsolete. Carrier Heat Pump System Control logo; part  
5, 66, no. HH07AT236; °F/°C scaleplate; used with Q674B-D,  
84 Q674G; used in Y594D.  
5
scaleplate.  
1
aBoth the thermostat and subbase must be replaced.  
55  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Description  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Number  
Remarks  
D2056  
D2064  
D2072  
44  
53  
53  
Obsolete. ComStat logo; part no. 50056; °F/°C  
T874D1165 Replacement has °F  
scaleplate and 2°F fixed  
differential in heating and  
cooling.  
scaleplate; adjustable interstage on both heating and  
cooling; includes locking cover and field-adjustable  
locking levers.  
Obsolete. Carrier Weathermaker; part no. HH07AT209;  
stage 1 and 2 heat anticipator factory set 0.1A; taupe  
color; used with Q674E1445; used in Y594D1412.  
T874D1165 Set stage 1 heat anticipator for  
total current draw of fan and  
stage 1 heat primary.  
Replacement is beige.  
Obsolete. Carrier Zone Perfect; part no. HH07AT208;  
taupe color; used with Q674E1445; used in Y594D1420.  
T874D1165 Set stage 1 heat anticipator for  
total current draw of fan and  
stage 1 heat primary.  
Replacement is beige.  
D2080  
D2098  
139 Obsolete. Hydroheat logo.  
T874D1165/ Replacement system switch:  
a
Q674B1018  
HEAT-OFF-COOL; no LEDs.  
44  
44  
44  
Obsolete. Honeywell logo; °F scaleplate; one setpoint  
lever; used with Q674D1008; used in Y594D1438.  
T874D1165 Replacement has °F  
scaleplate and two setpoint  
levers  
T874D1165 Replacement has °F  
scaleplate and two setpoint  
levers.  
D2106  
Obsolete. Honeywell logo; °C scaleplate; one setpoint  
lever; used with Q674D1008; used in Y594D1446.  
D2114  
D2122  
Obsolete. Bard logo; °C scaleplate.  
T874D1165 Replacement has °F  
scaleplate.  
224, Obsolete. McQuay  
25  
T874D2023 Replacement has °C  
scaleplate.  
2
T874D1165 Replacement has °F  
scaleplate.  
D2130  
226 Obsolete. McQuay  
See OEM for  
replacement.  
D2148  
D2155  
44  
Obsolete. Dry Aire Systems logo; °F/°C scaleplate.  
T874D1165  
139 Hydroheat logo; Premier White® color; °F/°C scaleplate;  
T874D1165/ Replacement system switch:  
a
used with Q674F1634.  
Q674B1018  
T874D1165  
HEAT-OFF-COOL; no LEDs.  
D2163  
D2171  
D2189  
D2197  
208 Obsolete. Amana logo; part no. P1217501F; °F/°C  
scaleplate.  
44  
44  
44  
Obsolete. Amana logo; part no. P1217701F; °F/°C  
T874D1942  
T874D1165  
T874D1165  
scaleplate.  
Armstrong logo; part no. 01142A024; °F/°C scaleplate;  
includes Air Ease insert.  
Liebert logo; part no. 138968P3; °F/°C scaleplate;  
interstage differential between H1 and H2 and between  
C1 and C2; includes Allen wrench and screws to lock  
cover; field-adjustable locking levers.  
D2205  
T874E  
44  
Aaon logo; Premier White® color; °F/°C scaleplate.  
0-stage heat, 2-stage cool.  
T874D1165  
E1008  
E1016  
44  
44  
Obsolete. Honeywell logo.  
Honeywell logo; TRADELINE model; includes Allen  
wrench and screws to lock cover; field-adjustable  
locking levers.  
T874E1016  
T874E1016  
E1024  
E1032  
44  
44  
Obsolete. Westinghouse logo.  
Lennox logo; part no. 13F0901; °F/°C scaleplate.  
T874E1016  
T874E1016 Replacement has °F  
scaleplate.  
E1040  
72  
Obsolete. Trane logo; used with Q674C1009; used in  
Y594E1015.  
T874E1016  
aBoth the thermostat and subbase must be replaced.  
60-2485—8  
56  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Number  
Description  
Remarks  
E1081  
E1099  
E1107  
44  
44  
44  
Trane logo; part no. BAY28X186; °F/°C scaleplate.  
T874E1016 Replacement has °F  
scaleplate.  
Obsolete. Lennox logo; part no. 13F1001; °C scaleplate.  
Honeywell logo; °C scaleplate.  
T874E1016 Replacement has °F  
scaleplate.  
T874E1016 Replacement has °F  
scaleplate.  
E1123  
E1149  
E1156  
44  
44  
44  
Obsolete. Amana logo; part no. D68535-4.  
Obsolete. York logo; part no. 2TH04701724A.  
Obsolete. Borg Warner multi-logo; part no.  
T874E1016  
T874E1016  
T874E1016  
6TH04701724A.  
E1164  
E1206  
E1230  
44  
44  
44  
Obsolete. E. A. Juffali & Bros. logo.  
Obsolete. Trane logo.  
Obsolete. Climar logo.  
2-stage heat, 0-stage cool.  
Honeywell logo.  
Honeywell logo; TRADELINE model; includes Allen  
wrench and screws to lock cover; field-adjustable  
locking levers.  
T874E1016  
T874E1016  
T874E1016  
T874F  
F1007  
F1015  
44  
44  
T874F1015  
T874F1015  
F1023  
F1031  
44  
44  
Obsolete. Lennox logo; part no. 13F1101.  
T874F1015  
Obsolete. Honeywell logo; °C scaleplate; used with  
T874F1015  
T874F1015  
None  
Replacement has °F  
scaleplate.  
40003440-001 wallplate; used in Y594F1022.  
F1049  
F1056  
F1072  
F1098  
F1106  
F1114  
44  
Obsolete. Lennox logo; °C scaleplate.  
Replacement has °F  
scaleplate.  
55,  
Obsolete. Honeywell logo; stages 1 and 2 heat  
electrically isolated; used with Q674D1008.  
6
6
44  
Obsolete. Wesco logo; heat anticipator factory set at  
T874F1015  
T874F1015  
T874F1155  
T874F1015  
0.8A.  
189 Obsolete. Lennox logo; used with Q674D1008 to control  
Set H1 and H2 anticipators to  
lowest settings.  
an M839.  
95  
44  
Obsolete. Oneida logo; part no. 30A0287-02; used with  
Q674K1018 on combination wood and oil applications.  
Honeywell logo; Honeywell Canada TRADELINE model;  
Replacement has °F  
scaleplate.  
°
C scaleplate; includes Allen wrench and screws to lock  
cover; field-adjustable locking levers.  
F1122  
F1130  
62  
Obsolete. Honeywell logo; two heat setpoint levers;  
T874F1015/ Replacement has no LED.  
Q674D1040  
used with Q674B1307.  
72, 91 Obsolete. Reznor logo; °F/°C scaleplate; used with  
Q674C, D, or G; used with Q674C1009, G1005; used in  
Y594F1048.  
T874F1015  
Replacement has °F  
scaleplate.  
F1148  
F1155  
44  
95  
Obsolete. Trane logo; part no. THT 0584.  
T874F1015  
T874F1155  
Honeywell logo; used with Q674K1026 on combination  
wood and oil applications.  
T874G  
Heat pump models; 2-stage heat, 1-stage cool;  
1
–stage changeover.  
G1006 84, 155 Obsolete. Honeywell logo; used with Q674E1015.  
Y594G1252a Wiring differences (old=new):  
R=O, M=Y, F=G, V=R, Y=W2;  
E-W2 jumper required.  
aBoth the thermostat and subbase must be replaced.  
57  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Description  
G1014 86, 150 Obsolete. Lennox logo; part no. 24F5801; °F/°C  
scaleplate; H2 anticipator factory set at 0.25A for fast  
cycle performance; changeover in cooling mode;  
independent heating and cooling circuits; used with  
Q674E1148, F1113.  
G1022 86, 150 Obsolete. Lennox logo; part no. 24F5701; °F/°C  
scaleplate; H2 anticipator factory set at 0.25A for fast  
cycle performance; changeover in cooling mode;  
independent heating and cooling circuits; used with  
Q674E1148, F1113.  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Y594G1252  
Number  
Remarks  
a
Wiring differences (old=new):  
R=O, M=Y, F=G, Y=W2,  
V-VR=R (must use single  
transformer).  
Y594G1252a Wiring differences (old=new):  
R=O, M=Y, F=G, Y=W2,  
V-VR=R (must use single  
transformer).  
G1048  
153, Obsolete. Westinghouse logo; H2 anticipator factory set  
Y594G1252a Wiring differences when  
replacing T874G/Q674J1019  
1
59 at 1.2A; used with Q674F1121, J1019.  
(
old=new): W=W2.  
G1055  
161 Carrier Heat Pump System Control logo; part no.  
HH07AT171; H2 anticipator factory set at 0.8A;  
changeover in cooling mode; used with Q674J1035  
None  
See subbase description for  
replacement information.  
(HH93AZ173).  
G1071 50,103, Obsolete. Carrier Heat Pump System Control logo;  
26, meets DoD specifications; H2 anticipator factory set at  
83 0.8A; used with Q674P1005 (HH93AZ169), L1041  
HH93AZ175), B1158, or J1050.  
Y594G1419 Wiring differences (old=new):  
C=X; jumper Y1-W1.  
1
1
(
G1089  
154 Obsolete. Marvair logo; special for Crispaire; H2  
anticipator factory set at 1.2A; used with Q674F1204;  
used in Y594G1153.  
Y594G1393a Wiring differences (old=new):  
A=L.  
Y594G1252a  
Y594G1252a  
G1097  
G1105  
G1113  
155 Obsolete. Honeywell logo; Rheem part no. ZXMT-B79;  
used with Q674F1238 (41-20797-14).  
153 Obsolete. Heat Wave (Southwest Mfg.) logo; H2  
anticipator factory set at 1.2A; used with Q674F1170.  
103 Obsolete. Carrier Heat Pump System Control logo;  
Y594G1419a Wiring differences (old=new):  
C=X; jumper Y1 -W1.  
meets DoD specifications; H2 anticipator factory set at  
0.8A; used with Q674L1041.  
G1121  
103 Obsolete. Carrier Heat Pump System Control logo; part  
no. HH07AT161; °C scaleplate; H2 anticipator factory  
set at 0.8A; includes Allen wrench and screws to lock  
cover.  
Y594G1419a Wiring differences (old=new):  
C=X; jumper Y1-W1.  
G1139  
G1147  
G1154  
G1162  
G1170  
143, Obsolete. Honeywell logo; used with Q674B1240,  
None  
See subbase description for  
replacement information.  
234 C1108.  
148 Obsolete. Honeywell logo; changeover in cooling mode; Y594G1252a Wiring differences (old=new):  
used with Q674F1139.  
C=X.  
84, 139 Obsolete. Lennox logo; used with Q674E1015, F1105.  
Y594G1252a See subbase description for  
replacement information.  
155 Obsolete. Lennox logo; meets DoD specifications; used  
with Q674F.  
160 Obsolete. York logo; part no. 2TH11702424A; H2  
anticipator is fixed; used with Q674J1027; used in  
Y594G1013.  
147 Obsolete. Honeywell logo; Keeprite/Westinghouse  
special; H2 anticipator factory set 1.2A; °C scaleplate;  
changeover in cooling mode; used with Q674F1295.  
160 Obsolete. York logo; °C scaleplate; changeover in  
cooling mode; used with Q674J1027; used in  
Y594G1138.  
Y594G1419a W1-Y1 jumper required.  
Y594G1567a  
G1188  
G1196  
Y594G1252a Wiring differences (old=new):  
S=L.  
Y594G1567a  
aBoth the thermostat and subbase must be replaced.  
60-2485—8  
58  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Y594G1161  
Number  
Description  
Remarks  
a
G1204  
162 Honeywell logo; designed for use on Trane heat pumps;  
no H2 anticipation; changeover in cooling mode; used  
with Q674J1043 and C815A1005; used in Y594G1161.  
155 Obsolete. Honeywell logo; H2 anticipator factory set at  
Designed for use on Trane  
heat pumps.  
Y594G1252a  
G1212  
0
.2A; changeover in cooling mode; includes shunt to  
bypass H2 anticipator with W3 heat relays; used with  
Q674F1238.  
G1220  
G1238  
G1246  
235 Obsolete. Rheem logo; part no. RXMT-C71; changeover Y594G1252a  
in cooling mode; used with Q674F1238.  
155 Obsolete. Ruud logo; part no. UXMT-C71; changeover  
Y594G1252a  
in cooling mode; used with Q674F1238.  
Obsolete. Honeywell logo; changeover in cooling mode.  
Y594G1252a  
155 Used with Q674F1212; used in Y594G1195, G1252,  
G1369.  
Y594G1393a  
None  
170 Used with Q674F1410; used in Y594G1393.  
G1261 58, 157 Obsolete. Borg-Warner; used with Q674D1032, F1253.  
G1279 58, 157 Obsolete. Bryant logo; used with Q674D1032, F1253.  
G1287 58, 157 Obsolete. Wesco logo; used with Q674D1032, F1253.  
See subbase description for  
replacement information.  
None  
None  
See subbase description for  
replacement information.  
See subbase description for  
replacement information.  
G1295  
58  
Obsolete. York logo; part no. 2TH11702724A; used with  
Q674D1032.  
T874D1165/ Wiring differences (old=new):  
Q674D1040 Y=Y2, O=Y1, W=W2; jumper  
W1-Y2.  
Y594G1575a  
G1345  
G1352  
160 Obsolete. York logo; part no. 2TH11702624A; °C  
scaleplate; used with Q674J1027.  
73  
79  
Obsolete. Command-Aire logo; 12°F differential  
between H1 and H2 for night setback; used with  
Q674C1066.  
Y594H1012a Wiring differences (old=new):  
Y1=O, Y2=Y, L=R, R=none; R-  
L jumper required; no night  
setback.  
T8600D1004 Wiring differences (old=new):  
programmable) Y1=O, Y2=Y, L=RH; RC-RH  
jumper required; includes  
(
night setback.  
G1378  
G1402  
Obsolete. Mammoth logo; H2 anticipator factory set at  
Y594H1012a Wiring differences (old=new):  
0
.8A; 12°F differential between H1 and H2 for night  
R1=none, R2=L; R-L jumper  
setback; °F/°C scaleplate; used with Q674C1124; used  
in Y594G1294.  
required; no night setback.  
T8090A1007/ Includes night setback; W-Y  
a
Q682A1038  
jumper required.  
(
programmable)  
a
129 Obsolete. York part no. 2TH11702824A; meets DoD  
specifications; used with Q674L1363.  
Y594R1425  
Wiring differences (old=new):  
W=W2, X=E, B=X; jumper  
Y-W1.  
a
G1410  
G1428  
155 Obsolete. Borg-Warner multi-logo; part  
no. 6TH11703024A; used with Q674F1311.  
160 Obsolete. Borg-Warner multi-logo; part no.  
T874G1246 or  
a
Y594G1252  
Y594G1567a  
6
TH11702424A; used with Q674J1027; used in  
Y594G1229.  
G1436  
58  
Obsolete. Borg-Warner multi-logo; part no.  
T874D1165/ Wiring differences (old=new):  
Q674D1040 Y=Y2, O=Y1, W=W2; jumper  
W1-Y2.  
6
TH11702724A.  
aBoth the thermostat and subbase must be replaced.  
59  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Description  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Y594G1567a  
Number  
Remarks  
G1444  
G1451  
G1469  
G1485  
160 Obsolete. ROCA logo; °C scaleplate; used with  
Replacement has °F  
Q674J1027.  
scaleplate.  
a
155 Obsolete. BDP multi-logo; part no. HH641502; used with T874G1246 or  
a
Q674F1212; used in Y594G1245.  
V594G1252  
Y594G1252  
a
194 Obsolete. No logo; Addison special; used with  
Wiring differences (old=new):  
Y1=O, C=X, W1=Y1, X=L.  
Q674F1345; used in Y594G1344.  
163 Obsolete. AAF logo; part no. 4ELN-7839; °F/°C  
scaleplate; 10°F differential between H1 and H2 for night  
setback and momentary RESET system switch position;  
used with Q674C1199.  
Y594G1393a No night setback or  
momentary reset switch.  
T8611G1004 Includes night setback; no  
programmable) momentary reset switch.  
(
a
G1493  
G1501  
167 Obsolete. Honeywell logo; Rheem part no. 41-20797-18; Y594G1526  
used with Q674F1360.  
195 Obsolete. Coleman logo; part no. 3600-375; changeover Y594G1252a Wiring differences (old=new):  
in cooling mode; used with Q674F1378.  
L1=L; changeover in cooling  
only.  
Y594G1393a No night setback or  
momentary reset switch.  
G1535  
163 Obsolete. AAF/Snyder General logo; 4ELN7839 °F/°C  
scaleplate; 10°F differential between H1 and H2 for night  
setback and momentary RESET system switch position;  
used with Q674C1199.  
T8611G1004 Includes night setback.  
(programmable)  
a
G1543  
G1568  
G1576  
194 Obsolete. Addison logo; Weather King part no. 8403-  
Y594G1252  
Wiring differences (old=new):  
Y1=O, C=X, W1=Y, X=L.  
1
97; used with Q674F1345; used in Y594G1328.  
160 Obsolete. Luxaire logo; part no. 026-00068-000; °C  
Y594G1367a Replacement has °F  
scaleplate; used with Q674J1126; used in Y594G1351.  
scaleplate.  
169 Obsolete. Coleman logo; part no. 3600-373; changeover Y594G1633a  
in heating and cooling mode; used with Q674F1402;  
used in Y594G1377.  
G1584  
73  
Obsolete. No logo; Friedrich part no. AT5784; 8°F  
4.4°C) differential between H1 and H2; used with  
Q674C1223.  
Y594H1012a Wiring differences (old=new):  
Y1=O, Y2=Y, L=R, R=none;  
L-R jumper required; no night  
setback.  
(
T8611G1004 Includes night setback.  
(programmable)  
a
G1592  
G1600  
G1618  
155 Obsolete. Arcoaire logo; used with Q674F1212; used in T874G1246 or  
a
Y594G1385.  
Y594G1252  
Y594G1419  
a
199 Obsolete. Honeywell logo; meets DoD specifications;  
Wiring differences (old=new):  
jumper W1-Y1.  
used with Q674F1428; used in Y594G1401.  
73  
Obsolete. Honeywell logo; 12°F differential between H1  
and H2 for night setback; used with Q674C1256.  
Y594H1012a Wiring differences (old=new):  
Y1=O, Y2=Y, L=R, R=none;  
L-R jumper required; no night  
setback.  
T8600C1162 Wiring differences (old=new):  
programmable) L=R, W=O; W-Y jumper  
required; includes night  
(
setback.  
G1626  
G1642  
167 Honeywell logo; used with Q674F1436; used in  
Y594G1526.  
227 Honeywell logo; TRADELINE model; meets DoD  
specifications; used with Q674F1444; used in  
Y594G1419.  
None  
Y594G1419a  
aBoth the thermostat and subbase must be replaced.  
60-2485—8  
60  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Y594H1012  
Number  
Description  
Remarks  
Wiring differences (old=new):  
R2=L, R1=none; L-R jumper  
required; no night setback.  
a
G1659  
177 Obsolete. Mammoth logo; 0.8A maximum current  
through B or O terminal; 12°F differential between H1  
and H2 for night setback; used with Q674C1330; used in  
Y594G1427.  
T8611G1004 Includes night setback.  
(
programmable)  
a
G1675  
G1691  
174 Obsolete. American Standard logo; part no.  
ASYSTAT650; used with Q674J1142; used in  
Y594G1443.  
176 Obsolete. Command Aire logo; part no. P1013-0060;  
Y594G1161  
Y594H1012a Wiring differences (old=new):  
Y1=O, Y2=Y, R=none; L-R  
jumper required; no night  
setback.  
1
2°F (6.6°C) differential between H1 and H2 for night  
setback; used with Q674C1389, C1397.  
T8611G1004 Includes night setback.  
(programmable)  
a
G1717  
G1741  
G1758  
175 Obsolete. Carrier Heat Pump System Control logo; part  
no. HH07AT102N; used with Q674J1167; used in  
Y507J1201.  
Y594G1252  
Y594G1476a  
None  
Wiring differences (old=new):  
C=X, D=L; replacement has  
AUX. HEAT and EM. HEAT  
LEDs.  
227 Honeywell logo; TRADELINE model; includes factory  
set range stops at 68°F (max. heat) and 78°F (min.  
cool); Premier White® color; used with Q674F1477;  
used in Y594G1476.  
211 Trol-A-Temp by Honeywell logo; Premier White® color;  
changeover is provided by Trol-A-Temp zone panel;  
used with Q674F1485; used in Y594G1492.  
See Trol-A-Temp for  
replacement.  
G1774  
G1782  
G1790  
216 Obsolete. Comfortmaker logo; part no. 1505756; used  
Y594G1252a Wiring differences (old=new):  
E=W2, W1=W3, X=E, C=X.  
with Q674J1175; used in Y594G1500.  
216 Obsolete. Arcoaire logo; part no. 1506756; used with  
Q674J1175; used in Y594G1518.  
161 Obsolete. Carrier logo; Premier White® color; °C  
scaleplate; includes Allen wrench and screws to lock  
cover; used with Q674J1191.  
Y594G1252a Wiring differences (old=new):  
E=W2, W1=W3, X=E, C=X.  
Y594G1252a Wiring differences (old=new):  
C=X; replacement has °F  
scaleplate.  
G1816  
G1824  
G1832  
G1840  
163 Climate Master logo; part no. AT5716; °F/°C scaleplate;  
Y594G1393a No momentary reset switch.  
1
0°F differential between H1 and H2 and momentary  
RESET system switch position.  
227 Honeywell logo; Australian TRADELINE model; Premier Y594G1476a  
White® color; °C scaleplate; used with Q674F1477;  
used in Y594G1534.  
231 Obsolete. Intertherm logo; used with Q674F1519; used  
Y594G1252a Replacement has auto  
changeover in cooling mode  
only.  
in Y594G1542.  
231 Obsolete. Miller logo; used with Q674F1519; used in  
Y594G1559.  
Y594G1252a Replacement has auto  
changeover in cooling mode  
only.  
G1857  
G1865  
229 Obsolete. Lennox logo; °C scaleplate; Premier White®  
color; used with Q674F1535; used in Y594G1583.  
160 Honeywell logo; TRADELINE model; designed to  
replace Y594G1013 (York part no. 2TH11702424),  
Y594G1229 (York part no. 6TH11702424), and York part  
no. 2TH117704124); used with Q674J1209; used in  
Y594G1567.  
Y594G1161a Wiring differences (old=new):  
E=X2, C=B, L=F.  
Y594G1567a  
aBoth the thermostat and subbase must be replaced.  
61  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Description  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Y594G1567  
Number  
Remarks  
Replacement is beige.  
a
G1873  
160 Obsolete. Honeywell logo; TRADELINE model; Premier  
White® color; designed to replace Y594G1013 (York  
part no. 2TH11702424), Y594G1229 (York part no.  
6
TH11702424), and York part no. 2TH117704124); used  
with Q674J1225; used in Y594G1575.  
167 Rheem; part no. 41-20797-18.  
a
G1881  
G1899  
Y594G1526  
Y594G1633  
a
169 Obsolete. Amana; part no. 10574101; used with  
Q674F1550; used in Y594G1591.  
Y594G1252a  
G1915  
155 Econar logo; used with Q674F1212; used in  
Y594G1609.  
70 Used with Q674F1410.  
a
1
Y594G1393  
G1923  
176 Trane logo; part no. X13510599010; H2 make 12°F  
Y594H1012a Wiring differences (old=new):  
Y1=O, Y2=Y, R=none; L-R  
jumper required; no night  
setback.  
below H1 make.  
T8611G1004 Includes night setback.  
(
(
programmable)  
G1931  
G1949  
155, Obsolete. Honeywell logo; Premier White® color; °C  
None  
See subbase description for  
replacement information.  
1
70 scaleplate; used with Q674F1568.  
73  
Obsolete. Carrier Heat Pump System Control logo; part  
no. HH07AT204; °F/°C scaleplate; H2 make 8°F below  
H1 make; used in Y594.  
Y594H1012a Wiring differences (old=new):  
Y1=O, Y2=Y, L=R, R=none; R-  
L jumper required; no night  
setback.  
T8600D1004 Wiring differences (old=new):  
programmable) Y1=O, Y2=Y, L=RH; RC-RH  
jumper required; includes  
night setback.  
G1956 30, 103, Obsolete. Carrier logo; Canada; Premier White® color;  
26, °C scaleplate; includes locking cover.  
83  
Y594G1476 Replacement has °F  
1
scaleplate.  
1
160 York logo; Canada; Premier White® color; °C scaleplate; Y594G1575a Replacement has °F  
used in Y594G1625. scaleplate.  
G1964  
G1972  
G1980  
G1998  
G2004  
Y594G1633a  
169 Honeywell logo; TRADELINE model; used with  
Q674F1584; used in Y594G1633.  
169 Obsolete. Amana logo; part no. 10574103; used with  
Q674F1600; used in Y594G1641.  
Y594G1633a Wiring differences (old=new):  
W3=W2.  
Y594G1252a  
155 Obsolete. Tempstar logo (Inter-City Products); used in  
Y594G1658; used with Q674F1212.  
103 Honeywell logo; TRADELINE model; used with Q674L;  
used in Y594G.  
Y594G1666  
1
61 Used with Q674J1274; used in Y594G1674.  
Y594G1674  
Y594G1716  
G2046  
155, WaterFurnace logo; part no. TA21H03; Premier White®  
170 color; °F/°C scaleplate; used with Q674F1667; used in  
Y594G1716.  
T874H  
Heat pump model; 1-stage heat, 1-stage cool,  
1
-stage changeover in cool.  
H1005  
74  
Obsolete. Command Aire logo; used with Q674C1041.  
Y594H1012a Wiring differences (old=new):  
Y1=O, Y2=Y; L-R jumper  
required.  
Obsolete. Friedrich part no. AT5813; °C scaleplate; used Y594H1012a Wiring differences (old=new):  
with Q674C1041. Y1=O, Y2=Y; L-R jumper  
required; replacement has °F  
scaleplate.  
H1013  
74  
aBoth the thermostat and subbase must be replaced.  
60-2485—8  
62  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Model  
Fig.  
No.  
74  
Trade Model  
Replacement  
Y594H1012  
Number  
Description  
Remarks  
a
H1021  
Obsolete. Friedrich Climate Master logo; part no.  
Wiring differences (old=new):  
Y1=O, Y2=Y; L-R jumper  
required; replacement has °F  
scaleplate.  
AT5821; °F/°C scaleplate; used with Q674C1041.  
H1039  
H1054  
79  
74  
Obsolete. Mammoth logo; °F/°C scaleplate; used with  
Q674C1124; used in Y594H1004.  
Obsolete. No logo; Friedrich part no. AT5854; used with  
Y594H1012a Wiring differences (old=new):  
R1=R, R2=L.  
Y594H1012a Wiring differences (old=new):  
Y1=O, Y2=Y; L-R jumper  
required.  
Y594H1012a  
Q674C1041.  
H1062  
H1070  
164 Honeywell logo; used with Q674C1249; used in  
Y594H1012.  
172, Obsolete. Carrier Heat Pump System Control logo; part  
None  
See subbase description for  
replacement information.  
173 no. HH07AT166; °C scaleplate; used with Q674B1406  
(HH93AZ200) or Q674C1322 (HH93AZ199).  
H1088  
H1096  
H1112  
172, Obsolete. Carrier Heat Pump System Control logo; part  
None  
See subbase description for  
replacement information.  
173 no. HH07AT167; used with Q674B1406 (HH93AZ200)  
or Q674C1322 (HH93AZ199).  
177 Obsolete. Mammoth Water Source Heat Pump logo; °F/ Y594H1012a Wiring differences (old=new):  
°
C scaleplate; changeover stage 0.8A maximum; used B  
R1=R, R2=L; L-R jumper  
required.  
or O terminal; used with Q674C1330.  
74  
No logo; Friedrich part no. AT5812; used with  
Y594H1012a Wiring differences (old=new):  
Y1=O, Y2=Y; L-R jumper  
required.  
Y594H1012a Wiring differences (old=new):  
Q674C1355.  
H1120  
H1138  
205 Obsolete. Command Aire logo; part no. P1013-0055;  
used with Q674C1389, C1397.  
Y1=O, Y2=Y.  
221 Obsolete. Climate Master logo; part no. AT5838; used  
Y594H1012a Wiring differences (old=new):  
Y1=O, Y2=Y; replacement has  
with Q674C1470.  
MALFUNCTION LED only.  
H1146  
H1153  
205 Trane logo; part no. X13510598010.  
Y594H1012a Wiring differences (old=new):  
Y1=O, Y2=Y.  
See subbase description for  
replacement information.  
173 Obsolete. Carrier Heat Pump System Control logo; part  
no. HH07AT167; °F/°C scaleplate; used with  
Q674C1322; used in Y594H1053.  
None  
H1161  
74  
Obsolete. Carrier Heat Pump System Control logo; part  
no. HH07AT203; °F/°C scaleplate; used with  
Q674C1496; used in Y594H1038.  
Y594H1012a Wiring differences (old=new):  
Y1=O, Y2=Y; L-R jumper  
required.  
T874J  
Heat pump model. 2-stage heat, 1-stage cool.  
J1002  
124, Obsolete. Carrier Heat Pump System Control logo; part  
None  
See subbase description for  
replacement information.  
1
44, no. HH07AT175; used with Q674J1068 (HH93AZ183),  
06, Q674J1159 (HH93AZ196), Q674L1074 (HH93AZ186),  
2
2
07 Q674L1637 (HH93AZ195).  
J1010  
J1028  
124, Obsolete. BDP multi logo; part no. 34427DP124/P272-  
None  
None  
See subbase description for  
replacement information.  
1
71 2471; used with Q674J1084, L1371.  
124, Obsolete. Carrier Heat Pump System Control logo; part  
See subbase description for  
1
44, no. HH07AT165; °C scaleplate; used with Q674J1068  
06, (HH93AZ183), Q674J1159 (HH93AZ196), Q674L1074  
replacement information.  
2
2
07 (HH93AZ186), Q674L1637 (HH93AZ195).  
J1036  
J1044  
J1051  
124, Obsolete. Miller logo; part no. 9132230; used with  
T8511G1021  
T8511G1021  
None  
1
71 Q674J1217.  
124, Obsolete. Intertherm logo; part no. 9132240; used with  
171 Q674J1217.  
124, Obsolete. Carrier logo; part no. HH07AT165-W; Premier  
See subbase description for  
replacement information.  
144 White® color; °C scaleplate.  
aBoth the thermostat and subbase must be replaced.  
63  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Description  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Number  
Remarks  
J1069  
124, Obsolete. Honeywell logo; TRADELINE model; used  
T8511G1021  
1
44, with Q674J1282; used in Y594J1019.  
06,  
2
2
07  
J1077  
T874K  
124, Obsolete. Nordyne logo; part no. 9148300; °F/°C  
T8511G1021  
1
71 scaleplate.  
Heat pump model; 2-stage heat, 1-stage cool, automatic  
changeover in heat.  
K1001  
77  
Obsolete. LSI Mammoth logo; used with Q674C1090.  
Y594G1419a Wiring differences (old=new):  
RH-RC=R, W1=B, W3=W2,  
W2=W1; remove Y1-W1  
jumper.  
K1019  
K1027  
181 Obsolete. McQuay/Snyder General logo; part no.  
Y594G1252a Wiring differences (old=new):  
6
0687301; °F/°C scaleplate; H1 anticipator set at 0.83A;  
°F interstage differential between H1 and H2 for night  
C=X, W=B, A=L; jumper  
8
E-W2; no night setback.  
setback; used with Q674C1280.  
T8611G1004 Wiring differences (old=new):  
programmable) C=X, W=B, A=X2; jumper X2-  
R; remove external time clock;  
(
includes night setback.  
181 Obsolete. AAF/Snyder General logo; part no.  
Y594G1252a Wiring differences (old=new):  
0
66804403; °F/°C scaleplate; H1 anticipator set at  
C=X, W=B, A=L; jumper  
0
.83A; 8°F interstage differential between H1 and H2 for  
E-W2; no night setback.  
night setback; used with Q674C1280.  
T8611G1004 Wiring differences (old=new):  
programmable) C=X, W=B, A=X2; jumper  
X2-R; remove external time  
(
clock; includes night setback.  
T874L  
L1000  
L1018  
Heat pump model; 2-stage heat, 1-stage cool,  
changeover in cool.  
198 Obsolete. Carrier logo; part no. HH07AT176; used with  
Y594G1419a E-W2 jumper required.  
Q674E1270 (HH93AZ189).  
138, Obsolete. Carrier Multiplex System logo; part no.  
See OEM for  
replacement.  
1
65 HH07AT178; used with Q674B1356 (HH93AZ192) or  
Q674C1264 (HH93AZ193).  
L1026  
L1034  
198 Obsolete. Honeywell logo; BDP part no. P272-2786;  
used with Q674E1304.  
203 Obsolete. McQuay logo; part no. 60687201; °F/°C  
scaleplate; H1 anticipator factory set at 0.83A; used with  
Q674C1280.  
Y594G1419a E-W2 jumper required.  
Y594G1419a Wiring differences (old=new):  
Y=Y1, W=B, A=X1; remove  
Y1-W1 jumper.  
L1059  
L1067  
215, Obsolete. Carrier logo; part no. HH07AT192; used with  
See OEM for  
2
13 Q674B1448 (HH93A2202) or Q674C1413  
replacement.  
(
HH93AZ204).  
203 Obsolete. AAF/Snyder General logo; part no.  
Y594G1419a Wiring differences (old=new):  
Y=Y1, W=B, A=X1; remove  
Y1-W1 jumper.  
0
66804402; H1 anticipator factory set at 0.83A; used  
with Q674C1280.  
L1075  
T874N  
N1008  
N1016  
N1024  
203 Obsolete. McQuay logo; part no. 073318601; Premier  
See OEM for  
White® color; °F/°C scaleplate; includes AAF insert.  
replacement.  
Heat pump model; 2-stage heat; 1-stage cool plus  
changeover; changeover in heat mode.  
178 Obsolete. Williamson logo; used with Q674F1196; used  
T874N1016  
T874N1016  
in Y594N1007.  
178 Honeywell Heat Pump Thermostat logo; used with  
Q674F1220.  
179, Bard logo; H1 and C1 anticipation fixed; used with  
None  
See subbase description for  
replacement information.  
217 Q674F1261.  
aBoth the thermostat and subbase must be replaced.  
60-2485—8  
64  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Number  
Description  
Remarks  
N1040  
N1057  
N1065  
T874P  
P1006  
179 Obsolete. Honeywell logo; H1 and C1 anticipation fixed;  
None  
used with Q674F1261; used in Y594N1015.  
178 Obsolete. Intertherm logo; part no. 9111882; used with  
Q674F1220; used in Y594N1023.  
T874N1016  
T874N1016  
178 Obsolete. Miller logo; Nordyne part no. 9122240; used  
with Q674F1220; used in Y594N1031.  
Heat pump model; 2-stage heat, 1-stage cool, automatic  
changeover in cool.  
57, 78 Obsolete. McQuay logo; part no. 860-442725B-00; 8°F  
None  
See subbase description for  
replacement information.  
(
4.4°C) interstage differential between H1 and H2; used  
with Q674B1273, C1140.  
P1014  
P1022  
78  
97  
97  
Obsolete. Friedrich/Climate Master logo; °F/°C  
T8600D2028 Wiring differences (old=new):  
scaleplate; 8°F (4.4°C) differential between H1 and H2 (programmable) L=R, W=O; W-Y jumper  
for night setback; used with Q674C1207.  
required; includes night  
setback.  
Obsolete. Friedrich/Climate Master logo; part no.  
AT5922; °F/°C scaleplate; 8°F (4.4°C) differential  
between H1 and H2 for night setback; used with  
Q674C1215.  
None  
See subbase description for  
replacement information.  
P1030  
P1055  
Obsolete. No logo; Friedrich part no. AT5930; 8°F  
None  
None  
See subbase description for  
replacement information.  
(
4.4°C) differential between H1 and H2 for night setback;  
used with Q674C1215.  
68, 97 Obsolete. Carrier Heat Pump System Control logo; part  
no. HH07AT205; °F/°C scaleplate; heat interstage  
differential 8°F (4.4°C).  
See subbase description for  
replacement information.  
T874Q  
Q1005  
Q1013  
1-stage heat; used with another T874 for night setback.  
Honeywell logo.  
44  
44  
T874A1036  
T874A1036 Replacement has °F  
Obsolete. Lennox logo; part no. 13F1201; °F/°C  
scaleplate.  
scaleplate.  
Q1021  
T874R  
R1004  
R1012  
R1020  
44  
Obsolete. Lennox logo; part no. 13F1301; °C scaleplate.  
T874A1036 Replacement has °F  
scaleplate.  
Heat pump model; 2-stage heat, 1-stage cool, manual  
changeover.  
47  
47  
Obsolete. Honeywell logo; used with Q674B1042; used  
Y594R1243a Wiring differences (old=new):  
W1=W2.  
in Y594R1029.  
Obsolete. Honeywell logo; Addison heat pump; used  
with Q674B1109.  
Y594R1243a Wiring differences (old=new):  
W1=W2.  
102 Obsolete. Lennox logo; part no. 24F5401; °F/°C  
scaleplate; H1 and C1 anticipators are fixed; auxiliary  
heat circuit powered by separate transformer; used with  
Q674L1025.  
Y594R1243a Wiring differences (old=new):  
M=Y, F=G, V-VR=R, Y=W2,  
R=O; replacement has °F  
scaleplate.  
R1038  
R1046  
102 Obsolete. Lennox logo; °C scaleplate; H1 and C1  
anticipators are fixed; auxiliary heat circuit powered by  
separate transformer; used with Q674L1025.  
Y594R1243a Wiring differences (old=new):  
M=Y, F=G, V-VR=R, Y=W2,  
R=O; replacement has °F  
scaleplate.  
Y594R1664a  
120, Obsolete. York logo; part no. 2TH11702224A; H2  
1
01 anticipator is fixed; used with Q674L1272 in Y594R1011  
or with Q674L1094.  
R1053  
R1061  
109 Obsolete. Honeywell logo; H2 anticipator is fixed; used  
with Q674L1140; used in Y594R1136.  
104 Obsolete. Honeywell logo; H2 anticipator is field  
adjustable; changeover in cooling; used with  
Q674L1082.  
Y594R1763a Designed for use on Trane  
heat pumps.  
Y594R1243a Replacement has auto fan in  
Emergency Heat mode.  
aBoth the thermostat and subbase must be replaced.  
65  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Description  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Y594R1243  
Number  
Remarks  
a
R1079  
R1087  
R1095  
123 Obsolete. Ruud logo; part no. UXMT-C70; used with  
Q674L1157.  
Y594R1664a  
120 Obsolete. Honeywell logo; Special for Dunham Bush;  
use with Q674L.  
123 Obsolete. Rheem logo; part no. RXMT-C70; used with  
T874R1152/  
a
Q674L1157.  
Y594R1243  
a
R1103  
R1111  
104 Obsolete. Westinghouse logo; used with Q674L.  
116, Obsolete. Marvair logo; H2 anticipator factory set at  
Y594R1243  
a
Y594R1243  
Replacement has auto fan in  
Emergency Heat mode.  
1
04 1.2A; used with Q674L1215, L1082; used in  
Y594R1128.  
R1129  
R1137  
113 Bard logo; used with Q674L1181.  
Y594R1243a Wiring differences (old=new):  
X1=X.  
Y594R1292a  
108, Obsolete. Honeywell logo; Heil Quaker part no.  
1
25 HQ711597HW; used with Q674L1132; used in  
Y594R1110.  
Y594R1664a  
Y594R1243a  
None  
R1145  
R1152  
R1160  
R1178  
120 Obsolete. York logo; °C scaleplate; H2 anticipator is  
fixed; used with Q674L1272; used in Y594R1102.  
115 Honeywell logo; used with Q674L1207, L1033; used in  
Y594R1243.  
182 Obsolete. Honeywell Advanced Heat Pump System  
logo; used with Q674L1298 and W89.  
110, Obsolete. Lennox logo; part no. 24F5601; °F/°C  
Y594R1763a Wiring differences (old=new):  
V-VR=R, M=Y, F=G, X=B,  
1
11 scaleplate; auxiliary heat circuit powered by separate  
transformer; fast cycle stage H2 anticipator; requires  
outdoor reset and independent circuits; used with  
Q674L1165, L1355.  
Y=W, A=T, R=O, E=X2.  
R1186  
182 Obsolete. Honeywell Advanced Heat Pump System  
None  
logo; used with Q674L1231 and W89.  
R1194  
R1202  
115 Obsolete. Amana logo; used with Q674L1249 and W89. Y594R1243a  
Y594R1672a Wiring differences (old=new):  
201 Obsolete. Intertherm logo; part no. 9111871; used with  
Q674L1264 or Q674L1595; used in Y594R1185.  
W2=W, Z=no connection,  
K=X, W=G, W1=H, X=B.  
R1210  
R1228  
101 Obsolete. Roca logo; °C scaleplate; used with  
Q674L1017.  
Y594R1243a Wiring differences (old=new):  
W=W2, X=L, B=X.  
Y594R1672a  
120 Obsolete. York logo; part no. 2TH11702524A; °C  
scaleplate; used with Q674L1272 and C815A1005;  
used in Y594R1144.  
R1236  
R1244  
R1251  
115 Obsolete. Williamson logo; includes Allen wrench and  
T874R1152  
T874R1152/  
screws to lock cover; used with Q674L1348.  
115 Obsolete. Westinghouse logo; used with Q674L1314  
and W89.  
120 Obsolete. York logo; part no. 2TH11702324A; H2  
anticipator is fixed; used with Q674L1272 and  
C815A1039.  
a
Y594R1243  
a
Y594R1672  
R1269  
122 Obsolete. Fedders multi logo; part no.  
THTX-120-HEHB 88-58-00540-001; used with  
Q674L1066; used in Y594R1037.  
Y594R1615a Wiring differences (old=new):  
K=E, C=X, W1=B, Z=L.  
R1285  
R1301  
123 Obsolete. Honeywell logo; Rheem part no. 41-20796-15; Y594R1243a  
used with Q674L1157.  
113 Obsolete. Comfortmaker logo; part no. 1505-714; used  
with Q674L1181; used in Y594R1417.  
Y594R1243a Wiring differences (old=new):  
X1=X.  
aBoth the thermostat and subbase must be replaced.  
60-2485—8  
66  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Number  
Description  
Remarks  
R1319  
191 Obsolete. Carrier part no. 42QH400083; used with  
See OEM for  
Q674B1281 on two speed fan applications.  
replacement.  
a
R1327  
120 Obsolete. Borg-Warner multi-logo; part no.  
Y594R1672  
6
TH11702224A; used with Q674L1272; used in  
Y594R1193.  
Y594R1243a  
R1335  
R1343  
106 Obsolete. BDP multi-logo; part no. HH641501; H2  
anticipator factory set 1.2A; used with Q674L1405; used  
in Y594R1201.  
133 Obsolete. Fedders multi-logo; part no.  
THTX-120-HEHC 88-58-0056-001; used with  
Q674L1413; used in Y594R1219.  
Y594R1425a Wiring differences (old=new):  
K=E, C=X1, Z=L; remove  
Y1-W1 jumper.  
R1350  
R1368  
113 Obsolete. Honeywell logo; used with Q674L1181.  
Y594R1243a Wiring differences (old=new):  
X1=X.  
Y594R1797a  
125 Obsolete. Coleman logo; part no. 3600-368; used with  
Q674L1421; used in Y594R1235.  
R1376  
R1384  
115 Honeywell logo; °C scaleplate; used with Q674L1207.  
131, Obsolete. Carrier Heat Pump System Control logo; part  
T874R1152  
Y594G1243  
a
Wiring differences (old=new):  
C=X.  
135 no. HH07AQ170; used with Q674L (HH93AZ187),  
Q674L (HH93AZ197), or Q674L (HH93AZ198).  
128 Obsolete. Williamson logo; used with Q674L1447; used  
in Y594R1250.  
R1392  
R1400  
R1426  
Y594R1425a Wiring differences (old=new):  
A=L.  
113 Obsolete. LSI part no. 104710001; used with  
See subbase description for  
Q674L1181, L1462.  
replacement information.  
Y594R1763a  
136 Obsolete. Trane Weathertron Heat Pump logo; part no.  
BAYSTAT339 (WY28X0112); °F/°C scaleplate; used  
with Q674L1496; used in Y594R1284.  
R1434  
R1442  
R1459  
R1467  
R1475  
R1483  
R1491  
R1509  
R1517  
R1525  
R1541  
R1558  
R1566  
134 Ruud logo; part no. 41-20796-32; used with Q674L1504; Y594R1300a  
used in Y594R1649.  
Y594R1300a  
134 Rheem logo; part no. 41-20796-28; used with  
Q674L1504; used in Y594R1631.  
134 Obsolete. Honeywell logo; Rheem part no. 41-20796-25; Y594R1300a  
used with Q674L1504.  
Y594R1292a  
Y594R1300a  
108 Honeywell logo; used with Q674L1512; used in  
Y594R1292.  
123 Honeywell logo; scale range 42°F to 88°F; used with  
Q674L1520; used in Y594R1300.  
130 Obsolete. Comfortmaker logo; °F/°C scaleplate; used  
with Q674L1538 and C815A1005; used in Y594R1318.  
Y594R1763a Wiring differences (old=new):  
W1=W, E=X2, X=F, C=B.  
Y594R1615a  
137 Obsolete. Honeywell logo; TRADELINE model; used  
with Q674L1553; used in Y594R1326.  
47  
Obsolete. Slant/Fin logo; used with Q674B1042; used in  
Y594R1334.  
Y594R1243a Wiring differences (old=new):  
W1=W2.  
Y594R1763a Wiring differences (old=new):  
130 Obsolete. Arcoaire logo; part no. 150671; used with  
Q674L1538 and C815A1005; used in Y594R1342.  
W1=W, E=X2, X=F, C=B.  
113 Obsolete. Arcoaire logo; used with Q674L1181; used in  
Y594R1359.  
Y594R1243a Wiring differences (old=new):  
X1=X.  
Y594R1300a  
67  
Obsolete. Goettl logo; part no. 372071; used with  
Q674B1349.  
Y594R1300a  
134 Obsolete. Universal Parts logo; part no. 41-20796-45;  
used with Q674L1504; used in Y594R1623.  
130 Obsolete. Honeywell logo; used with Q674L1538 and  
Y594R1763a Wiring differences (old=new):  
W1=W, E=X2, X=F, C=B.  
C815A1005; used in Y594R1375.  
aBoth the thermostat and subbase must be replaced.  
67  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Description  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Y594R1243  
Number  
Remarks  
a
R1574  
R1582  
R1590  
R1608  
132 Obsolete. Comfortmaker logo; part no. 1505739; used  
Wiring differences (old=new):  
with Q674L1538; used in Y594R1383.  
C=X, X=L, W=W2.  
132 Obsolete. Arcoaire logo; part no. 150739; used with  
Q674L1538; used in Y594R1391.  
115 Obsolete. Refac logo; used with Q674L1207.  
Y594R1243a Wiring differences (old=new):  
C=X, X=L, W=W2.  
T874R1152/ Replacement has °F  
a
Y594R1243  
Y594R1763  
scaleplate.  
Wiring differences (old=new):  
W2=W, X=B, Z=F, K=X2,  
W1=O.  
a
119 Obsolete. Honeywell logo; Intertherm heat pump; used  
with Q674L1264; used in Y594R1409.  
Y594R1425a  
R1616  
R1624  
168 Honeywell logo; SUPER TRADELINE® model; used  
with Q674L1587; used in Y594R1425.  
200 Obsolete. Honeywell logo; used with Q674L1595; used  
Y594R1243a Wiring differences (old=new):  
X=B, Z=F, W2=W, K=X2,  
W1=O.  
in Y594R1433.  
a
R1632  
R1640  
134 Obsolete. Honeywell logo; used with Q674L1603.  
Y594R1243  
a
115 Obsolete. Hitecsa logo; °C scaleplate; H2 anticipator  
Y594R1243  
Replacement has °F  
scaleplate.  
factory set at 1.2A; used with Q674L1207.  
Y594R1763a  
R1657  
136 Obsolete. American Standard logo; part no.  
ASYSTAT651; requires outdoor reset; used with  
Q674L1611; used in Y594R1441.  
Y594R1292a  
R1673  
R1699  
108 Heil logo; part no. 1060321, HAXB004TW01; used with  
Q674L1132; used in Y594R1466.  
119 Obsolete. Miller logo; used with Q674L1264; used in  
Y594R1482.  
Y594R1763a Wiring differences (old=new):  
W2=W, X=B, Z=F, K=X2,  
W1=O.  
R1707  
R1715  
R1723  
209 Trol-A-Temp by Honeywell logo; Premier White® color;  
used with Q674L1678; used in Y594R1490.  
None  
See Trol-A-Temp for  
replacement.  
209 Trol-A-Temp by Honeywell logo; used with Q674L1186;  
None  
See Trol-A-Temp for  
replacement.  
used in Y594R1508.  
218 Obsolete. No logo; Snyder General part no. 654958B07; Y594R1672a Wiring differences (old=new):  
°
F/°C scaleplate; used with Q674L1702 and  
W1=W, X=X2, C=B.  
C815A1005; used in Y594R1516.  
Y594R1292a  
Y594R1292a  
R1731  
108 Obsolete. Inter-City Products logo; part no.  
HQ11477909HW; used with Q674L1132; used in  
Y594R1524.  
R1749  
R1814  
R1822  
R1830  
R1855  
108 Tempstar logo; part no. 1060322, TAXB004TW01; used  
with Q674L1132; used in Y594R1532.  
108 Obsolete. Honeywell logo; Keeprite part no. THPC; °C  
scaleplate; used with Q674L1132; used in Y594R1607.  
Y594R1292a Replacement has °F  
scaleplate.  
Y594R1615a  
230 Honeywell logo; TRADELINE model; used with  
Q674L1710; used in Y594R1615.  
Y594R1300a  
134 Obsolete. Addison logo; WeatherKing part no. 41-  
20796-61; used with Q674L1504; used in Y594R1656.  
228 Obsolete. Lennox logo; Premier White® color; °C  
scaleplate; outdoor reset required (use C815A1005);  
used with Q674L1728; used in Y594R1714.  
Y594R1763a Wiring differences (old=new):  
Y1=Y, L=F, W1=W, E=X2,  
C=B; replacement has °F  
scaleplate.  
Y594R1664a  
R1871  
120 Honeywell logo; designed to replace Y594R1011 (York  
part no. 2TH11702224); used with Q674L1736; used in  
Y594R1664.  
aBoth the thermostat and subbase must be replaced.  
60-2485—8  
68  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Y594R1672  
Number  
Description  
Remarks  
a
R1889  
120 Honeywell logo; designed to replace Y594R1151 (York  
part no. 2TH11702324), Y594R1193 (York part no.  
6
TH11702224), and York part no. 2TH11704024; used  
with Q674L1736 and C815A1054; used in Y594R1672.  
Y594R1680a  
R1897  
R1905  
230 Honeywell logo; Premier White® color; used with  
Q674L1751; used in Y594R1680.  
120 Obsolete. Honeywell logo; Premier White® color;  
designed to replace Y594R1151 (York part no.  
Y594R1672a Replacement is beige.  
2
TH11702324), Y594R1193 (York part no.  
6
TH11702224), and York part no. 2TH11704024; used  
with Q674L1777 and C815A1054; used in Y594R1698.  
R1913  
120 Obsolete. Honeywell logo; Premier White® color;  
Y594R1664a Replacement is beige.  
designed to replace Y594R1011 (York part no.  
2
TH11702224); used with Q674L1777; used in  
Y594R1706.  
Y594R1243a  
Y594R1763a  
R1921  
R1939  
115 Obsolete. Econar logo; used with Q674L1207; used in  
Y594R1722.  
197 American Standard logo (Trane); part no.  
ASYSTAT651A; includes outdoor reset; used with  
Q7674L1801; used in Y594R1748.  
168 Obsolete. Inter-City Products logo; part no.  
HQ1149406HW; used with Q674L1819; used in  
Y594R1755.  
Y594R1425a  
R1947  
R1954  
197 Honeywell logo; TRADELINE model; includes outdoor  
Y594R1763a Direct replacement for  
Y594R1748 (T874R1939/  
Q674L1801) American  
reset; used with Q674L1827; used in Y594R1763.  
Standard logo (ASYSTAT  
6
51A) and Y594R1136  
(T874R1053/Q674L1140).  
R1962  
115 Obsolete. Consolidated Industries logo; part no.  
Y594R1680a Includes CHECK LED.  
9036100; Premier White® color; used with Q674L1843;  
used in Y594R1771.  
120 York logo; Canada; Premier White® color; °C scaleplate; Y594R1672a Replacement has °F  
used in Y594R1789; used with C815A1039. scaleplate.  
R1970  
R1988  
125 Honeywell logo; TRADELINE model; used with  
Y594R1797 Direct replacement for  
Y594R1235 (T874R1368/  
Q674L1421) Evcon/Coleman  
part no. 3600-368.  
Q674L1868; used in Y594R1797.  
R2002  
R2010  
R2028  
R2036  
245 Obsolete. Amana Air Conditioning logo; part no.  
Y594R1797 Wiring differences (old=new):  
1
0574102; used in Y594R1805.  
C/X=X.  
245 Obsolete. Amana Air Conditioning logo; part no.  
Y594R1797 Wiring differences (old=new):  
C/X=X, W3=W2.  
Y594R1797  
10574104.  
209 Obsolete. York logo; part no. 2TH11703424A; used with  
Q674L1918 in Y594R1821.  
134 Ruud logo; °C scaleplate; used with Q674L1504.  
2-stage heat, 3-stage cool.  
See OEM for  
replacement.  
T874S  
S1001  
223 Obsolete. Carrier Synergy 2000 Heat Pump System  
T8611M2025 Includes night setback.  
(programmable)  
Control logo; used with Q674F1501.  
or see OEM for  
direct  
replacement.  
T874V  
1-stage cool.  
V1008  
69  
Obsolete. No logo; Carrier part no. HH07AT177; used  
T874A1036  
with Q674R1003.  
aBoth the thermostat and subbase must be replaced.  
69  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 8. T874 Cross Reference.  
Description  
Model  
Fig.  
No.  
Trade Model  
Replacement  
Number  
Remarks  
T874W  
3-stage heat, 2-stage cool, manual changeover.  
W1007  
118 Obsolete. Honeywell logo; Westinghouse special; used  
T8611M2025 Includes night setback.  
(programmable)  
with Q674L1256.  
W1015  
W1023  
W1031  
W1049  
54  
Honeywell logo; used with Q674B1216 and C815A1005;  
used in Y594W1014.  
T874W1015  
233 Obsolete. Lennox Advanced Heat Pump System logo;  
T874W1015  
used with Q674L1280 and W89.  
140 Obsolete. No logo; Rheem part no. 41-20797-20; used  
T8611M2025 Includes night setback.  
with Q674L1546 and C815A1005; used in Y594W1022. (programmable)  
100 Obsolete. McQuay logo; part no. 61202501; 12°F  
interstage differential between H2 and H3 for night  
setback; used with Q674C1363.  
T8611M2025 Includes night setback.  
(programmable)  
W1056  
W1064  
220 Obsolete. McQuay/Snyder General logo; part no.  
See OEM for  
replacement.  
1
202501; 12°F differential between H2 and H3 for night  
setback; used with Q674C1363 (61202502).  
220 Obsolete. AAF/Snyder General logo; part no.  
See OEM for  
replacement.  
0
66804408; 12°F differential between H2 and H3 for  
night setback; used with Q674C1363 (66804408).  
W1072  
W1080  
140 Obsolete. Honeywell logo (Inter-City Products); used in  
T8611M2025 Includes night setback.  
(programmable)  
Y594W1030.  
220 McQuay logo; part no. 073318901; Premier White®  
color; 12°F differential between H2 and H3 for night  
setback.  
None  
W1106  
T874Y  
247 Obsolete. Addison logo; part no. 843-277; °F/°C  
T8611M2025  
scaleplate; used with Q674L1934 in Y594W1055.  
Heat pump model; 2-stage heat, 2-stage cool, heat or  
cool auto changeover.  
Y1005  
210 Obsolete. Mammoth Water Source Heat Pump logo;  
See OEM for  
replacement.  
used with Q674E1353; used in Y594Y1004.  
Y1013  
248 Obsolete. WaterFurnace logo; part no. TA21H03;  
Premier White® color; °F/°C scaleplate; used with  
Q674F1675 (32003081).  
See OEM for  
replacement.  
aBoth the thermostat and subbase must be replaced.  
60-2485—8  
70  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 9. Q674 Subbase Cross Reference.  
Model  
Fig.  
No.  
Q674 Trade  
Number  
Description  
Replacement  
Remarks  
Q674A  
System: HEAT-AUTO-COOL; Fan: AUTO-ON  
A1001  
A1019  
A1035  
A1043  
A1050  
71 Standard OEM.  
Q674A1019  
Q674A1019  
Q674A1019  
Q674A1019  
Q674A1043  
71 TRADELINE® model; used with T874A-D.  
71 Obsolete. Trane part no. BAS-0435; used with T874A-D.  
71 Honeywell logo; TRADELINE model;  
71 Obsolete. Standard OEM.  
Q674B  
System: HEAT-OFF-COOL; Fan: AUTO-ON  
B1000  
45 Standard OEM; used with T874C1570, C1695, C1703,  
Q674B1034  
Q674B1018  
D1843; used in Y594C1363.  
B1018  
44 Standard OEM; used with T874B1035, D1082; used in  
Y594B1026, D1016.  
B1026  
B1034  
B1042  
45 Obsolete. System: HEAT-OFF-RESET-COOL.  
45 TRADELINE  
Q674B1034  
Q674B1034  
Y594R1243  
a
47 Obsolete. Used with T874R1004, R1509; used in  
Wiring differences (old=new):  
W1=W2.  
Y594R1029, R1334.  
B1059  
B1075  
B1083  
B1091  
B1109  
B1117  
B1125  
B1133  
B1141  
45 Obsolete. Factory installed RC-RH jumper; used with  
T874C1059; used in Y594C1256.  
Q674B1034  
Q674B1075  
Field wire RC-RH.  
46 Auto fan in heating and cooling mode; used with  
T874B1035, C1000, D1082; used in Y594D1040.  
51 Obsolete. Carrier part no. HH93AZ178; factory  
installed RC-RH jumper.  
Q674B1075a One system transformer only.  
Q674B1034  
45 Obsolete. Carrier part no. HH93AZ184; factory  
installed RC-RH jumper.  
47 Obsolete. Addison heat pump; used with T874R1012.  
Y594R1243a Wiring differences (old=new):  
W1=W2.  
Q674B1018a  
44 Obsolete. Carrier part no. HH93AZ180; factory  
installed RC-RH jumper.  
53 Obsolete. York part no. 2TB04700324A; used with  
Q674B1075a Jumper RC-RH; replacement  
has no LOCKOUT LED.  
Q674B1018  
T874D1041.  
48 Obsolete. Includes FILTER LED; used with  
T874D1082; used in Y594D1156.  
51 Trane part no. BAY28X185; automatic fan operation in  
Q674B1075  
Set T874 H1 anticipator for  
combined load of heat relay  
and fan relay.  
heat and cool mode.  
B1158  
B1166  
50 Obsolete. Used with T874G1071.  
T874C1018/ W1-Y1 and RH-RC jumpers  
a
Q674B1018  
required.  
249 Carrier part no. HH93AZ179; factory installed RC-RH  
jumper; LOCKOUT LED; used with T874C1075  
Y594C1421 or Replacement only requires  
a
Q674B1075  
one transformer and has no  
LOCKOUT LED.  
(HH07AT170).  
B1190  
52 Obsolete. Wards special; factory installed RH-RC and  
Gas Furnace:  
Q674B1034  
F-W3 jumpers; used with T874C1372.  
ElectricFurnace:  
Q674B1075  
B1208  
B1216  
187 Obsolete. Used with T874C1422.  
None  
Q674B1216  
54 Used with T874W1015 and C815A1005; used in  
Y594W1014.  
B1224  
49 Obsolete. Lennox part no. 25F7301; four LEDs; used  
with T874C1430.  
Q674B1034  
Replacement has no LEDs.  
a
Both the thermostat and subbase must be replaced.  
71  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 9. Q674 Subbase Cross Reference.  
Model  
Fig.  
No.  
Q674 Trade  
Number  
Description  
Replacement  
Remarks  
a
B1240  
234 Obsolete. Northrup heat pump; AUX HEAT LED; used  
Y594G1252  
Wiring differences (old=new):  
Y1=Y2, W1=W2; EM HT  
system switch position is not  
operational.  
with T874G1139.  
B1257  
B1273  
56 Obsolete. LSI-Mammoth; RESET LED; automatic fan  
operation in heat and cool modes; used with  
T874C1471; used in Y594C1314.  
Q674B1075  
T874A1036/  
Replacement has no LED.  
57 Obsolete. McQuay part no. 860-442727B-00; System:  
Wiring differences (old=new):  
Y=Y1, L=R, W=O; jumper Y1-  
W1; no night setback.  
a
OVERRIDE-HEAT-OFF-COOL; used with T874P1006.  
Q674B1075  
T8600D2028 Wiring differences (old=new):  
programmable) L=R, W=O; W-Y jumper  
required; night setback.  
(
B1281  
191 Obsolete. Carrier no. 42QH400103; System: HEAT-  
OFF-COOL; Fan: LOW-HI-CONT; international  
symbols on switches; used with T874R1319.  
See OEM for  
replacement.  
B1299  
B1307  
46 Obsolete. Heil Quaker part no. HQ521714HW.  
62 Obsolete. Includes two LEDs; used with T874F1122.  
Q674B1075  
T874F1015/  
Replacement has no LEDs.  
a
Q674D1040  
B1315  
68 Obsolete. Friedrich part no. AQ5215; OVERRIDE and  
SERVICE LEDs; used with T874P1022, P1030.  
T8600D2028 Wiring differences (old=new):  
(programmable) L=R, W=O; W-Y jumper  
required; set dual fuel switch  
to electric heat; night setback.  
B1331  
B1349  
65 Obsolete. Includes two LEDs; used with T874A1002.  
Q674B1034  
Y594R1300  
Replacement has no LEDs.  
a
67 Obsolete. Goettl part no. 372072; used with  
T874R1541.  
B1356  
138 Obsolete. Carrier part no. HH93AZ192; used with  
T874L1018 (HH07AT178).  
See OEM for  
replacement.  
B1372  
B1380  
B1398  
44 Obsolete. Trane part no. BAS-0427; used with T874A-D.  
46 Obsolete. Trane part no. BAS-0426; used with T874A-D.  
Q674B1018  
Q674B1075  
Q674B1034  
48 Obsolete. Trane part no. BAS-0431; FILTER LED; used  
Replacement has no LEDs.  
with T874A-D.  
B1406  
172 Obsolete. Carrier part no. HH93AZ200; FAULT and  
CHECK FILTER LEDs; used with T874H1070  
T874A1150/  
Wiring differences (old=new):  
Y=Y1; jumper W1-Y1;  
a
Q674B1075  
(
HH07AT166), T874H1088 (HH07AT167) or  
replacement has no LEDs.  
T874H1153 (HH07AT167); used in Y594H1046.  
B1414  
B1448  
51 American Standard (Trane) part no. ASYSTAT1617.  
Q674B1075  
215 Obsolete. Carrier part no. HH93A2202; Fan: Lo-Med-  
See OEM for  
High-On; used with T874L1059.  
replacement.  
B1455  
214 Obsolete. Carrier part no. HH93AZ208; Fan: Lo-Med-  
High-On; used with T874A1424 (HH07AT194).  
See OEM for  
replacement.  
B1463  
B1471  
B1513  
45 Trol-A-Temp; used with T874D1801.  
45 Trol-A-Temp; used with T874D1827.  
None  
None  
Q674B1075  
See Trol-A-Temp.  
See Trol-A-Temp.  
53 Obsolete. TRADELINE; exact replacement for  
Jumper RC-RH; replacement  
Q674B1125 (York part no. 2TB04700324).  
has no LOCKOUT LED.  
B1521  
53 Obsolete. Carrier Canada part no. HH93AZ179-W;  
gray color; includes LOCKOUT LED and removable  
jumpers between RC and RH terminals.  
Q674B1075  
Jumper RC-RH; replacement  
has no LOCKOUT LED; beige  
color.  
B1539  
B1547  
45 Obsolete. Carrier part no. HH93AZ139; used with  
Q674B1034  
Y594C1389  
T874D2049; used in Y594D1370.  
237 Obsolete. TRADELINE; gray color; used with  
T874C1810; used in Y594C1389.  
a
Both the thermostat and subbase must be replaced.  
60-2485—8  
72  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 9. Q674 Subbase Cross Reference.  
Model  
Fig.  
No.  
Q674 Trade  
Number  
Description  
Replacement  
Remarks  
B1554  
82 Obsolete. TRADELINE; includes LOCKOUT LED and  
removable jumpers between RC and RH terminals;  
used with T874C1877; used in Y594C1421.  
Y594D1347  
Jumper RH-RC; system  
switch: Off-HEAT-AUTO-  
COOL.  
B1562  
45 Obsolete. Amana logo; part no. P1217701F;  
Q674B1034  
removable jumpers between RC and RH terminals.  
B1570  
B1588  
45 Obsolete. Armstrong logo; part no. 03299A18.  
45 Obsolete. Standard OEM.  
Q674B1034  
Q674B1034  
Replacement is beige.  
Replacement is beige.  
Q674C  
System: OFF-AUTO; Fan: AUTO-ON  
C1009  
72 Standard OEM; used with T874D1082; used in  
Q674C1058  
Q674C1058  
Q674C1058  
Y594D1024.  
C1017  
Obsolete. Includes factory-installed RC-RH jumper;  
used with T874A,F,Q.  
72 Trane part no. BAY28X187.  
C1033  
C1041  
a
74 Obsolete. Command Aire heat pump; used with  
Y594H1012  
Wiring differences (old=new):  
Y1=O, Y2=Y; W-Y jumper  
required.  
T874H1005, H1054.  
C1058  
C1066  
72 TRADELINE  
Q674C1058  
Y594H1012  
a
73 Obsolete. Command Aire heat pump; used with  
Wiring differences (old=new):  
Y1=O, Y2=Y, L=R, R=none; R-  
L jumper required; no night  
setback.  
T874G1352.  
T8600D2028 Wiring differences (old=new):  
programmable) Y1=O, Y2=Y, L=R; W-Y  
jumper required; night  
(
setback.  
C1074  
C1090  
81 Obsolete. Used with T874C1018.  
Q674C1058  
Y594R1419  
Jumper W2-Y1 and RH-RC.  
a
77 Obsolete. LSI-Mammoth heat pump; used with  
Wiring differences (old=new):  
RH-RC=R, W1=B, W3=W2,  
W2=W1; remove Y1-W1  
jumper.  
T874K1001.  
C1108  
C1116  
C1124  
C1132  
143 Obsolete. Northrup special; AUX HEAT LED; used with  
T874G1139.  
Y594R1243a Wiring differences (old=new):  
Y1=Y, W1=W2, C=X.  
Replacement has no LEDs.  
76 Obsolete. McQuay part no. 02005959; two LEDs; used  
Q674C1058  
with T874D1116.  
79 Obsolete. LSI-Mammoth heat pump; RESET LED;  
used with T874G-H; used in Y594G-H.  
75 Obsolete. McQuay part no. 03005049; spring return  
momentary system switch position; used with  
T874A1283.  
Y594G1294  
T8600D2028  
See OEM for  
replacement.  
C1140  
78 Obsolete. McQuay no. 860-442728B-00; System:  
T8600D2028 Wiring differences (old=new):  
(programmable) L=R, W=O; W-Y jumper  
required; night setback.  
OVERRIDE-AUTO-OFF; used with T874P1006.  
C1157  
C1165  
72 Obsolete. York part no. 2TB04700124A.  
Q674C1058  
192 Obsolete. McQuay part no. 03005050; spring return  
See OEM for  
momentary system switch position.  
replacement.  
C1173  
96 Obsolete. American Air Filter part no. 4ELN-8787; used  
with T874C1133.  
76 Obsolete. California heat pump; used with T874C1000.  
163 Obsolete. American Air Filter part no. 4ELN-8788; two  
LEDs; spring return momentary system switch position;  
used with T874G1485, G1535.  
Q674C1058  
Q674C1058  
Replacement has no LEDs.  
C1181  
C1199  
T8600D2028 No momentary reset switch.  
a
Both the thermostat and subbase must be replaced.  
73  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 9. Q674 Subbase Cross Reference.  
Q674 Trade  
Model  
Fig.  
No.  
Number  
Description  
Replacement  
Remarks  
C1207  
C1215  
C1223  
78 Obsolete. Friedrich; System: OVERRIDE-AUTO-OFF;  
T8600D2028 Wiring differences (old=new):  
(programmable) L=R, W=O; W-Y jumper  
required; night setback.  
T8600D2028 Wiring differences (old=new):  
(programmable) L=R, W=O; W-Y jumper  
required; night setback.  
Y594H1012a Wiring differences (old=new):  
Y1=O, Y2=Y, L=R, R=none; R-  
L jumper required; no night  
setback.  
used with T874P1014.  
97 Obsolete. Friedrich part no. AQ5315; System:  
OVERRIDE-AUTO-OFF; OVERRIDE and SERVICE  
LEDs; used with T874P1022, P1030.  
73 Obsolete. Friedrich part no. AQ5323; used on systems  
requiring night setback contacts; used with  
T874G1584.  
T8600D2028 Wiring differences (old=new):  
(
programmable) L=R, W=O; W-Y jumper  
required; night setback.  
Y594H1012a  
C1249  
C1256  
164 Includes MALFUNCTION LED; used with T874H1062;  
used in Y594H1012.  
73 Obsolete. Used with T874G1618.  
Y594H1012a Wiring differences (old=new):  
Y1=O, Y2=Y, L=R, R=none; R-  
L jumper required; no night  
setback.  
T8600D2028 Wiring differences (old=new):  
programmable) L=R, W=O; W-Y jumper  
required; night setback.  
(
C1264  
C1280  
C1298  
C1306  
165 Obsolete. Carrier part no. HH93AZ193; used with  
T874L1018 (HH07AT178).  
See OEM for  
replacement.  
181, Obsolete. McQuay heat pump; part no. 60687401;  
T8600D2028 See thermostat description for  
replacement information.  
203 COMP FAULT LED; used with T874K1019, L1034.  
76, Obsolete. McQuay part no. 60684801; SERVICE LED;  
See OEM for  
225 used with T874A1523, A1549, D1918.  
replacement.  
75 Obsolete. McQuay part no. 60685001; SERVICE LED;  
spring return momentary system switch position; used  
with T874A1325.  
See OEM for  
replacement.  
C1314  
C1322  
72 Obsolete. Trane part no. BAS-0429; used with T874A-F.  
Q674C1058  
Y594H1012  
a
173 Obsolete. Carrier part no. HH93AZ199; FAULT and CK  
FILTER LEDs; used with T874H1070 (HH07AT166),  
T874H1088 (HH07AT167) or T874H1153  
Wiring differences (old=new):  
2=X.  
(HH07AT167); used in Y594H1053.  
C1330  
177 Obsolete. LSI-Mammoth part no. 71115201; RESET  
LED; used on systems with night setback contacts;  
used with T874G1659, H1096; used in Y594G1427,  
H1020.  
Y594H1012a Wiring differences (old=new):  
R1=R; R2=L.  
C1355  
C1363  
74 Friedrich part no. AQ355; SERVICE LED; used with  
Y594H1012a Wiring differences (old=new):  
Y1=O, Y2=Y; L-R jumper  
required.  
T874H1112.  
99 Obsolete. McQuay part no. 61202601; SERVICE LED;  
auto fan in heat and cool mode; used with T874C.  
T874C1125/  
Replacement has HEAT-OFF-  
a
Q674B1075  
COOL.  
219 Obsolete. Used with T874C.  
220 Obsolete. Used with T874W.  
100 Obsolete. Used with T874W.  
See OEM for  
replacement.  
See OEM for  
replacement.  
T8611M2025 Includes night setback.  
(
programmable)  
C1371  
72 American Standard part no. ASYSTAT616.  
Q674C1058  
a
Both the thermostat and subbase must be replaced.  
60-2485—8  
74  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 9. Q674 Subbase Cross Reference.  
Model  
Fig.  
No.  
Q674 Trade  
Number  
Description  
Replacement  
Remarks  
C1389  
C1397  
C1413  
C1439  
C1454  
205, Obsolete. Command Aire part no. P1099-0021; two  
None  
See thermostat description for  
176 LEDs; used with T874G-H.  
replacement information.  
205, Obsolete. Command Aire part no. P1099-0023; used  
None  
See thermostat description for  
replacement information.  
171 with T874G-H.  
213 Obsolete. Carrier part no. HH93AZ204; Fan: Lo-Med-  
See OEM for  
replacement.  
High-On; used with T874L1059.  
217 Obsolete. Bard part no. 8404-016; used with  
T874N1024.  
See OEM for  
replacement.  
a
163 Obsolete. Climate Master part no. AQ5354; two LEDs;  
Y594G1393  
No momentary reset switch.  
Replacement has no LEDs.  
Wiring differences (old=new):  
Y1=O, Y2=Y; replacement has  
MALFUNCTION LED only.  
spring return momentary system switch position.  
C1462  
C1470  
25 Climate Master Special.  
Q674C1058  
Y594H1012  
a
221 Obsolete. Climate Master part no. RQ5370; used with  
T874H1138.  
C1496  
C1504  
74 Obsolete. Carrier part no. HH93AZ213; includes  
SERVICE LED; used with T874H1161; used in  
Y594H1038.  
83 Obsolete. Carrier part no. HH93AZ214; used in Y594.  
Y594H1012a Wiring differences (old=new):  
Y1=O, Y2=Y; L-R jumper  
required.  
Y594H1012a Wiring differences (old=new):  
Y1=O, Y2=Y, L=R, R=none; R-  
L jumper required; no night  
setback.  
T8600D2028 Wiring differences (old=new):  
programmable) Y1=O, Y2=Y, L=R; W-Y  
jumper required; night  
(
setback.  
C1512  
97 Obsolete. Carrier part no. HH93AZ216; System:  
Override-Auto-Off; includes two LEDs; used in Y594.  
T8600D2028 Wiring differences (old=new):  
(programmable) L=R, W=O; W-Y jumper  
required; night setback.  
C1520  
C1538  
72 Obsolete. Carrier part no. HH93AZ210; used with  
T874D2049; used in Y594D1388.  
163 Climate Master part no. AQ5354; System: Off-Auto-  
Override; includes two LEDs and momentary spring  
position.  
Q674C1058  
Y594G1393  
No momentary reset switch.  
C1546  
C1553  
C1561  
C1579  
C1595  
76, Obsolete. McQuay part no. 060684802; gray color;  
Q674C1058  
Q674C1058  
Replacement has no LEDs;  
beige color  
Replacement is beige.  
225 includes one LED.  
181, Obsolete. McQuay logo; part no. 073319901; includes  
203 one LED.  
76 McQuay logo; part no. 073319701; includes one LED.  
See OEM for  
replacement.  
99, McQuay logo; part no. 073320001; includes one LED.  
See OEM for  
100  
replacement.  
72 Obsolete. Standard OEM.  
System: None; Fan: None  
Q674C1058  
Q674D1040  
Q674D  
D1008  
55, 66 Obsolete. Used with T874D1082, F1056; used in  
Y594D1057.  
D1016  
D1032  
55 Obsolete. Carrier part no. HH93AZ170; RC-RH jumper.  
58 Obsolete. Borg-Warner; used with T874G.  
Q674D1040  
T874D1165/  
RC-RH jumper required.  
Wiring differences (old=new):  
Y=Y2, O=Y1, W=W2; jumper  
W1-Y2 required.  
a
Q674D1040  
D1040  
D1057  
55 TRADELINE  
55, 66 Obsolete. York part no. 2TB04700424A.  
Q674D1040  
Q674D1040  
a
Both the thermostat and subbase must be replaced.  
75  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 9. Q674 Subbase Cross Reference.  
Model  
Fig.  
No.  
Q674 Trade  
Number  
Description  
Replacement  
Remarks  
D1065  
63 Obsolete. Includes two LEDs; used with T874F1122.  
T874F1015/  
Replacement has no LEDs.  
a
Q674D1040  
D1099  
D1107  
55, 66 Obsolete. Trane part no. BAS-0430; used with T874A-F.  
55, 66 Obsolete. Snyder General part nos. 654958801/  
Q674D1040  
Q674F1040.  
1520503/ 4ELN30070.  
D1115  
D1123  
D1156  
208 Trol-A-Temp; used with T874D1801.  
208 Trol-A-Temp; gray color; used with T874D1827.  
None  
None  
Q674D1040  
See Trol-A-Temp.  
See Trol-A-Temp.  
Replacement is beige color.  
55 Obsolete. Gray color; includes removable jumper  
between RC and RH terminals.  
D1164  
D1172  
66 Obsolete. Carrier part no. HH93AZ211; used in  
Y594D1440.  
Q674D1040  
Q674D1040  
Q674D1040  
208 Obsolete. Amana logo; part no. P121501F; removable  
jumpers between RC and RH terminals.  
D1180  
D1198  
55 Obsolete. York logo; part no. 2TH04703224A.  
55, 66 Obsolete. Standard OEM.  
T874D1165/  
Replacement is beige color.  
Q674D1040  
Q674E  
System: OFF-HEAT-AUTO-COOL; Fan: AUTO-ON  
82 Used with T874D1504; used in Y594D1180.  
E1007  
Q674E1049  
a
E1015  
84 Obsolete. Lennox heat pump; used with T874G1006,  
Y594G1252  
Wiring differences (old=new):  
R=O, M=Y, F=G, V=R, Y=W2;  
E-W2 jumper required.  
G1154.  
E1049  
E1056  
193 TRADELINE; used with T874D2031 and TG504A1025;  
used in Y594D1354.  
Q674E1049  
Q674E1049  
82 Obsolete. Amana part no. D68535-7; used with  
RC-RH jumper required.  
RC-RH jumper required.  
RC-RH jumper required.  
T874C1059, C1331; used in Y594C1009.  
E1064  
E1072  
83 Obsolete. RC-RH jumpered internally; EM HEAT LED.  
Q674E1049  
Q674E1049  
82 Carrier part no. HH93AZ176; RC-RH jumpered  
internally.  
E1080  
E1098  
E1106  
82 Trane part no. BAY28X184.  
85 Obsolete. Used with T874A-D.  
185 Obsolete. ITT Nesbitt.  
Q674E1049  
Q674E1049  
See OEM for  
replacement.  
E1114  
87 Carrier part no. HH93AZ177; RC-RH jumper;  
LOCKOUT LED to indicate compressor lockout; used  
with HH07AT series thermostats.  
Q674E1049  
Q674E1049  
RC-RH jumper required;  
replacement has no LED.  
E1122  
E1148  
83 Obsolete. Square D part no. 63600-002-10; CHECK  
Replacement has no LED.  
LED.  
86 Obsolete. Lennox heat pump; used with T874G1014,  
G1022.  
Y594G1252a Wiring differences (old=new):  
R=O, M=Y, F=G, Y=W2,  
V-VR=R; must use single  
transformer.  
E1155  
E1197  
88 Obsolete. Lennox part no. 91C7501; HIGH and LOW  
LEDs; used with T874B1076, D1017.  
Q674E1049  
Q674E1049  
Replacement has no LEDs.  
89 Obsolete. McQuay part no. 02005961; two LEDs; used  
Wiring differences (old=new):  
D=O; replacement has no  
LEDs.  
with T874D1116.  
E1205  
80 Obsolete. Fedders special; SERVICE LED; used with  
T874D1462.  
Q674E1049  
Replacement has no LEDs.  
E1213  
E1221  
82 York part no. 2TB04700224A.  
82 Heil Quaker part no. HQ712003HW.  
Q674E1403  
Q674E1049  
a
Both the thermostat and subbase must be replaced.  
60-2485—8  
76  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 9. Q674 Subbase Cross Reference.  
Model  
Fig.  
No.  
Q674 Trade  
Number  
Description  
Replacement  
Remarks  
E1262  
E1270  
82 Lennox part no. 13F1701.  
Q674E1049  
Y594G1419  
a
198 Obsolete. Carrier part no. HH93AZ189; used with  
E-W2 jumper required.  
T874L1000 (HH07AT176).  
E1304  
E1312  
82 Obsolete. BDP part no. P272-1887; used with  
T874L1026.  
Y594G1419a E-W2 jumper required.  
224 Obsolete. McQuay part no. 60684901; one LED; used  
Q674E1049  
Replacement has no LEDs.  
with T874A1523, A1549, D1686, D1918.  
E1320  
E1338  
82 Obsolete. Trane part no. BAS-0434.  
88 Obsolete. Goodman part no. CHTS36-60; HIGH and  
LOW LEDs; used with T874B1100; used in  
Y594B1042.  
Q674E1049  
Q674E1049  
Replacement has no LEDs.  
E1346  
E1353  
82 Obsolete. Snyder General part nos. 1505753/1506753/  
Q674E1049  
T8611M2025  
6
54958B02; used with T874D1769; used in  
Y594D1297.  
210 Obsolete. Mammoth; used with T874Y1005; used in  
Y594Y1004.  
E1379  
E1395  
212 Trol-A-Temp by Honeywell; used with T874A1465.  
None  
See Trol-A-Temp.  
222 Obsolete. Carrier part no. HH93AZ209; used with  
T874B1019/  
Wiring differences (old=new):  
W1 =W; RC-RH jumper  
required; replacement has no  
LEDs.  
a
T874B1134 (HH07AT199).  
Q674E1049  
Y594D1347a  
Q674E1049  
E1403  
E1411  
82 TRADELINE; designed to replace York 2TH04701024;  
used with T874D1942; used in Y594D1347.  
82 Obsolete. Carrier Canada part no. HH93AZ176-W;  
gray color; removable jumper between RC and RH  
terminals.  
RC-RH jumper required.  
Replacement is beige color.  
E1429  
E1445  
87 Carrier Canada part no. HH93AZ177-W; gray color;  
includes LOCKOUT LED; removable jumper between  
RC and RH terminals.  
Q674E1049  
Q674E1049  
RC-RH jumper required.  
Replacement has no LOCK-  
OUT LED and is beige color.  
82 Obsolete. Carrier part no. HH93AZ217-W; gray color;  
RC-RH jumper required.  
removable jumper between RC and RH terminals.  
Replacement is beige color.  
E1460  
E1478  
224 McQuay logo; part no. 073319801; includes one LED.  
82 Obsolete. Armstrong logo; part no. 03299A19.  
Q674E1049  
Q674E1049  
RC-R jumper required.  
Replacement is beige color.  
E1486  
82 Obsolete. Standard OEM.  
RC-R jumper required.  
Replacement is beige color.  
Q674F  
System: EM.HT.-HEAT-AUTO-COOL-OFF;  
Fan: AUTO-ON  
F1006  
F1022  
F1030  
F1048  
141 Obsolete. Includes EM HEAT LED; used with  
Q674F1022  
Q674F1022  
Q674F1022  
Q674F1022  
Jumper E-X2.  
T874C1331.  
142 Includes LED and field selectable inserts; used with  
T874C1059; used in Y594C1017, C1330.  
146 Carrier part no. HH93AZ174; SUPL HEAT LED; used  
Wiring differences (old=new):  
C=X1, X=X2.  
Replacement does not include  
Z terminal and only requires  
one transformer.  
with T874D1074 (HH07AT172).  
149 Obsolete. Includes EM HEAT LED and auxiliary power  
terminal Z.  
F1063  
F1071  
146 Obsolete. Carrier part no. HH93AZ181; SUPL HEAT  
LED; used with T874D1074 (HH07AT172).  
Q674F1022  
Q674F1022  
Wiring differences (old=new):  
C=X1, X=X2.  
142 Obsolete. Square D part no. 63600-002-11; CHECK  
LED.  
a
Both the thermostat and subbase must be replaced.  
77  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 9. Q674 Subbase Cross Reference.  
Model  
Fig.  
No.  
Q674 Trade  
Number  
Description  
Replacement  
Remarks  
F1089  
152 Obsolete. Includes EM HEAT LED; X2-E and RC-RH  
Q674F1022  
jumpers.  
F1097  
F1105  
142 Obsolete. Southwest special; W2-X2 jumper.  
Q674F1022  
Y594G1252  
a
145 Obsolete. Lennox heat pump; EM HEAT LED; used  
Wiring differences (old=new):  
V=R, Y=W2, F=G, X2=X, R=O,  
M=Y; L-E jumper required.  
with T874G1154.  
F1113  
150 Obsolete. Lennox heat pump; part no. 24F6201; V-VR  
jumper; EM HEAT LED; changeover in cooling; used  
with T874G1014, G1022.  
Y59461252a Wiring differences (old=new):  
R=O, M=Y, F=G, Y=WC,  
V=VR=R; must use single  
transformer.  
Y594G1252a  
F1121  
F1139  
F1162  
F1170  
153 Obsolete. Westinghouse heat pump; EM HEAT LED;  
used with T874G1048.  
148 Obsolete. Tappan heat pump; EM HEAT LED; auto fan  
Y594G1252a Wiring differences (old=new):  
C=X.  
Y594G1393a  
in emergency heat mode; used with T874G1147.  
151 Obsolete. Crispaire heat pump; EM HEAT LED; used  
with T874G.  
Y594G1252a  
153 Obsolete. Heatwave (Southwest Mfg.) heat pump; EM  
HT LED; used with T874G1105.  
Y594G1252a  
Q674F1220  
F1188  
F1196  
153 Obsolete. Luxaire heat pump.  
178 Obsolete. Williamson; EM HEAT and SERVICE LEDs;  
used with T874N1008; used in Y594N1007.  
F1204  
F1212  
154 Obsolete. Special for Crispaire; EM HEAT and COMP  
FAULT LEDs; used with T874G1089; used in  
Y594G1153.  
155 Includes AUX HEAT and EM HEAT LEDs; used with  
T874G1246, G1451, G1592, G1915; used in  
Y594G1252.  
Y594G1393a Wiring differences (old=new):  
A=L.  
Q674F1212 or  
a
Y594G1252  
F1220  
F1238  
178 Used with T874N1016; used in Y594N.  
155 Obsolete. Rheem part no. 41-20797-14; AUX HEAT  
and EM HEAT LEDs; used with T874G1097, G1212,  
G1220, G1238.  
156 Obsolete. Westinghouse heat pump; EM HEAT and  
AUX HEAT LEDs; auto fan in emergency heat mode;  
changeover in cooling mode.  
Q674F1220  
Y594G1252  
a
Y594G1252a  
F1246  
F1253  
F1261  
F1279  
F1295  
157 Obsolete. Wesco/Addison heat pump; used with  
Y594G1252a Wiring differences (old=new):  
Y1=O, C=X, W1=Y, X=L.  
T874G1261, G1279, G1287.  
179 Includes two LEDs; used with T874N1024; used in  
Y594N.  
Y594G1419a Wiring differences (old=new):  
L=X2, Y=Y1.  
158 Obsolete. Westinghouse heat pump; two LEDs; used  
Y594G1252a Wiring differences (old=new):  
L1=L.  
with T874G.  
147 Obsolete. Keeprite/Westinghouse heat pump;  
SERVICE, AUX HEAT and EM HEAT LEDs; used with  
T874G1188.  
Y594G1252a Wiring differences (old=new):  
S=L; replacement does not  
include A or T terminals.  
Y594G1252a  
Q674F1022  
F1311  
F1329  
F1337  
155 York heat pump; AUX HEAT and EM HEAT LEDs; used  
with T874G1410.  
142 Obsolete. Heil Quaker part no. HQ712005HW; one  
LED and field selectable inserts.  
166 Obsolete. WeatherKing heat pump; two LEDs and field  
selectable inserts; used with T874D1009; used in  
Y594D1222.  
Q674F1022  
Wiring differences (old=new):  
R=RC-RH; replacement has  
no LEDs.  
F1345  
194 Obsolete. Addison heat pump; EM HEAT and CHECK  
Y594G1252a Wiring differences (old=new):  
LEDs; used with T874G; used in Y594G.  
Y1=O, C=X, W1=Y, X=L.  
a
Both the thermostat and subbase must be replaced.  
60-2485—8  
78  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 9. Q674 Subbase Cross Reference.  
Model  
Fig.  
No.  
Q674 Trade  
Number  
Description  
Replacement  
Remarks  
a
F1360  
167 Obsolete. Rheem part no. 41-20797-17; AUX HEAT  
Y594G1526  
and EM HEAT LEDs; used with T874G1493.  
F1378  
195 Obsolete. Includes EM HEAT and AUX HEAT LEDs;  
used with T874G1501.  
Y594G1252a Wiring differences (old=new):  
L1=L; changeover in cooling  
only.  
F1394  
F1402  
139 Obsolete. Nepco heat pump; HEAT PUMP and AUX  
HEAT LEDs; System: AUX HEAT-HEAT PUMP-2  
STAGE HEAT-OFF-COOL; used with T874D1595.  
T874D1165/  
Replacement has HEAT-OFF-  
COOL system switching and  
no LEDs.  
a
Q674B1018  
Y594G1633a  
169 Obsolete. Coleman heat pump; two LEDs; used with  
T874G1576; used in Y594G1377.  
a
F1410  
F1428  
170 Used with T874G1246, G1915; used in Y594G1393.  
199 Obsolete. Used with T874G1600; used in Y594G1401.  
Y594G1393  
a
Y594G1419  
Wiring differences (old=new):  
jumper W1-Y1.  
F1436  
167 Includes AUX HEAT and EM HEAT LEDs; changeover  
in heating mode; used with T874G1626; used in  
Y594G1526.  
None  
Y594G1419a  
Q674F1012  
Y594G1476a  
None  
F1444  
F1451  
F1477  
F1485  
227 Includes AUX HEAT, EM HEAT and CHECK LEDs;  
used with T874G1642; used in Y594G1419.  
204 Obsolete. York part no. 2TB047700524A; one LED and  
field selectable inserts.  
Wiring differences (old=new):  
X2=X; X1=B.  
227 TRADELINE; gray color; used with T874G1741,  
G1824; used in Y594G1476, G1534.  
211 Trol-A-Temp by Honeywell; changeover is provided by  
Trol-A-Temp zone panel; used with T874G1758; used  
in Y594G1492.  
See Trol-A-Temp.  
F1501  
F1519  
223 Obsolete. Carrier two-speed compressor heat pump;  
T8611M2025 Includes night setback.  
(programmable)  
used with T874S1001.  
a
231 Obsolete. Nordyne; used with T874G1832, G1840;  
used in Y594G1542, G1559.  
Y594G1252  
Replacement has auto  
changeover in cooling mode  
only.  
F1535  
F1543  
F1550  
F1568  
F1584  
229 Obsolete. Lennox heat pump; gray color; used with  
T874G1857; used in Y594G1583.  
204 Obsolete. TRADELINE  
Y594G1161a Wiring differences (old=new):  
E=X2, C=B, L=F.  
Q674F1022  
Y594G1633  
Y594G1476  
Y594G1633a  
Wiring differences (old=new):  
X2=X, X1=B.  
243 Obsolete. Amana part no. 10573901; includes two  
LEDs; used with T874G1899; used in Y594G1591.  
155 Obsolete. Gray color; includes two LEDs; used with  
Y1-W1 jumper required.  
only T874G1931.  
169 TRADELINE; includes two LEDs; used with  
T874G1972; used in Y594G1633. Direct replacement  
for Coleman/Evcon Y594G1377 (T874G1576/  
Q674D1402); Coleman part no. 3600-373.  
F1592  
238 Heat Controller; Fan: AUTO-ON; System: AUX HEAT-  
HEAT PUMP- 2 STAGE HEAT-OFF-COOL; includes  
two LEDs; used with T874C1844; used in Y594C1413.  
Y594R1425  
E-W2 jumper required; system  
switch: EM.HT.-HEAT-OFF-  
COOL.  
F1600  
F1634  
169 Obsolete. Amana part no. 10573903; includes two  
Y594G1633  
Y594G1716  
Wiring differences (old=new);  
LEDs; used with T874G1980; used in Y594G1641.  
W3=W2.  
139 Standard OEM; System: AUX HEAT-HEAT PUMP-  
2
STG HEAT-OFF-COOL; includes two LEDs; used  
with T874D2155.  
F1667  
155 WaterFurnace logo; part no. TA21H03; System: OFF-  
AUTO-HEAT-EM HT; includes two LEDs; used with  
T874G2046.  
Y594G1716  
a
Both the thermostat and subbase must be replaced.  
79  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 9. Q674 Subbase Cross Reference.  
Model  
Fig.  
No.  
Q674 Trade  
Number  
Description  
Replacement  
Remarks  
F1675  
248 Obsolete. WaterFurnace logo; part no. TA21H03;  
See OEM for  
includes four LEDs.  
replacement.  
Q674G  
System: OFF-AUTO; Fan: None  
G1005  
184 Obsolete. Used in Y594F1063.  
Q674G1070  
G1013  
186 Obsolete. Climate Control; used with T874D1298.  
See OEM for  
replacement.  
G1021  
91 Obsolete. Includes O and B terminals; used with  
T874A-F,Q or T874D1082; used in Y594D1032.  
92 Obsolete. Used with T874C1018, C1125.  
Q674G1070  
T8611  
G1047  
G1054  
188 Obsolete. Singer part no. 0200-5963; used with  
See OEM for  
T874D1298.  
replacement.  
G1062  
232 Obsolete. Singer; used with T874D1298.  
91 TRADELINE  
See OEM for  
replacement.  
Q674G1070  
G1070  
G1088  
92 Obsolete. LSI-Mammoth part no. 71120201; used with  
See OEM for  
T874C.  
replacement.  
G1096  
G1104  
G1120  
90 Obsolete. Climate Control part no. 02005958; used  
with T874D1439, D1447.  
See OEM for  
replacement.  
94 Obsolete. McQuay part no. 0200-5963; two LEDs;  
See OEM for  
used with T874D1116.  
replacement.  
202, Obsolete. McQuay part no. 60684701; two SERVICE  
See OEM for  
replacement.  
226 LEDs; no fan switching; used with T874D1694, G1926.  
G1138  
G1153  
91 Obsolete. Trane part no. BAS-0433; used with T874A-F.  
Q674G1070  
Q674G1070  
184 Obsolete. Carrier part no. HH93AZ212; used in  
Y594D1396.  
G1161  
G1179  
184 Gray color.  
Q674G1070 Replacement is beige color.  
202 Obsolete. McQuay logo; part no. 073319601; includes  
Q674G1161  
Replacement has no LEDs.  
two LEDs.  
Q674J  
System: EM.HT.-AUTO-OFF; Fan: AUTO-ON  
J1001  
J1019  
J1027  
180 Obsolete. Singer heat pump part no. 02005964; EM  
See OEM for  
replacement.  
Y594G1252  
HEAT LED; changeover heat mode.  
a
159 Obsolete. Westinghouse heat pump; EM HT LED;  
System: EM.HT.-ON-OFF; used with T874G1048.  
160 Obsolete. York part no. 025-22291; EM HEAT LED;  
auto fan in emergency heat mode; changeover in cool  
mode; used with T874G1170, G1196, G1428, G1345,  
G1444; used in Y594G1013, G1138, G1229.  
161 Carrier heat pump; part no. HH93AZ173; System:  
SUPL.HT.-ON-OFF; SUPL HEAT LED; used with  
T874G1055 (HH07AT171).  
162 TRADELINE heat pump model; designed for use on  
Trane heat pumps; AUX HT and EM HT LEDs; auto fan  
in emergency heat; changeover in cooling mode; used  
with T874G1204 and C815A1008; used in Y594G1161.  
Wiring differences (old=new):  
W=W2.  
Y594G1567a  
Y594G1674a  
J1035  
J1043  
Q674J1043 or Designed for use on Trane  
a
Y594G1161  
heat pumps.  
Y594G1674a  
Y594J1019  
J1050  
J1068  
183 Obsolete. Westinghouse heat pump; EM HEAT and  
AUX HEAT LEDs; used with T874G1071.  
144 Obsolete. Carrier heat pump; part no. HH93AZ183;  
used with T874J1002 (HH07AT175) or T874J1028  
(HH07AT165).  
J1076  
180 Obsolete. McQuay part no. 02005964; two LEDs; used  
Q674F1022  
Replacement has no LEDs.  
with T874A,D.  
a
Both the thermostat and subbase must be replaced.  
60-2485—8  
80  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 9. Q674 Subbase Cross Reference.  
Model  
Fig.  
No.  
Q674 Trade  
Number  
Description  
Replacement  
Remarks  
J1084  
171 Obsolete. BDP heat pump; part no. 34427DP126,  
Y594J1019  
Wiring differences (old=new):  
P272-1879; EM HEAT LED; used with T874J1010.  
W1=W2, F=L.  
J1118  
196 Obsolete. Carrier heat pump; part no. HH93AZ188;  
SUPL HEAT LED; System: SUPL.HT.-ON-OFF; used  
with T874G1055 (HH07AT171).  
Y594G1674  
Wiring differences (old=new):  
C=X;Y1=W1; jumper required;  
no auto fan in emergency  
heat.  
Y594G1567a  
Y594G1161a  
J1126  
J1142  
160 Obsolete. Luxaire no. 026-00068-000; EM HEAT LED;  
used with T874G1568; used in Y594G1351.  
174 Obsolete. American Standard part no. WY28X0250;  
AUX HEAT and EM HEAT LEDs; used with  
T874G1675; used in Y594G1443.  
J1159  
J1167  
206 Obsolete. Carrier heat pump; part no. HH93AZ196;  
Y594J1019  
used with T874J1002 (HH07AT175) or T874J1028  
(HH07AT165).  
175 Obsolete. Carrier heat pump; MANUAL, AUTO, HEAT  
PUMP and DEFROST LEDs; System: SUPL HEAT-  
ON-OFF; used with T874G1717; used in Y507J1201.  
Y594G1252a Wiring differences (old=new):  
C=X, D=L; replacement has  
AUX HEAT and EM HEAT  
LEDs.  
J1175  
216 Obsolete. Snyder General part nos. 1505756,  
Y594G1252a Wiring differences (old=new):  
1
506756; CHECK, AUX HEAT and SYSTEM LEDs;  
E=W2, W1=W3, X=E, C=X.  
used with T874G1774, G1782; used in Y594G1500,  
G1518.  
J1191  
J1209  
161 Obsolete. Carrier heat pump; gray color; used with  
Y594G1252a Wiring differences (old=new):  
C=X; replacement has °F  
scaleplate.  
Y594G1567a  
T874G1790.  
160 TRADELINE; designed to replace Y594G1013 (York  
part no. 2TH11702424), Y594G1229 (York part no.  
6
TH11702424) and York part no. 2TH11704124; used  
with T874G1865; used in Y594G1567.  
J1217  
J1225  
171 Obsolete. Nordyne part no. 9132250; used with  
Y594J1019  
Wiring differences (old=new):  
F=L.  
T874J1036, J1044.  
160 Obsolete. TRADELINE; gray color; designed to replace  
Y594G1013 (York part no. 2TH11702424), Y594G1229  
Y594G1567a Replacement is beige.  
(
York part no. 6TH11702424) and York part no.  
2
TH11704124; used with T874G1873; used in  
Y594G1575.  
J1241  
J1258  
144 Obsolete. Carrier Canada part no. HH93AZ183-W;  
gray color; System: SUPL HT-ON-OFF; includes one  
LED.  
161 Obsolete. Carrier Canada part no. HH93AZ173-W;  
gray color; System: SUPL HT-ON-OFF; includes one  
LED.  
See OEM for  
replacement.  
Y594G1674a Replacement is beige color.  
Y594G1567a  
Y594G1674  
J1266  
J1274  
J1282  
160 York Canada; gray color; includes EM HT LED; used in  
Y594G1625.  
161 TRADELINE; System: SUPL HT-ON-OFF; includes  
one LED; used with T874G2004; used in Y594G1674.  
244 Obsolete. TRADELINE; System: SUPL HT-ON-OFF;  
includes SUPL HT LED; used with T874J1069; used in  
Y594J1019.  
(Recontrol)  
T8511G1021  
Q674K  
System: OFF-HEAT-AUTO-COOL; Fan: None  
K1000  
K1018  
93 Obsolete. Carrier part no. HH93AZ172; RC-RH jumper.  
95 Obsolete. Oneida Heater part no. 3040284-02;  
System: OFF-WOOD-WOOD/OIL-OIL; used with  
T874F1106.  
Q674E1049  
Q674K1026  
Fan switch is not operational.  
a
Both the thermostat and subbase must be replaced.  
81  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 9. Q674 Subbase Cross Reference.  
Model  
Fig.  
No.  
Q674 Trade  
Number  
Description  
Replacement  
Remarks  
K1026  
95 System: OFF-WOOD-WOOD/ OIL-OIL; used with  
Q674K1026  
T874F1155.  
K1034  
K1042  
93 Obsolete. Snyder General part no. 4ELN-7920.  
93 Obsolete. Carrier part no. HH93AZ172-W; gray color;  
includes removable jumper between RC and RH  
terminals.  
Q674E1049  
Q674E1049  
Fan switch is not operational.  
Fan switch is not operational.  
Q674L  
System: EM.HT.-HEAT-OFF-COOL; Fan: ON-AUTO  
101 Obsolete. York heat pump; EM HEAT LED; cooling  
mode changeover; compressor lockout; auto fan in  
EM.HT; used with T874R1046.  
L1017  
Y594R1243a Wiring differences (old=new):  
W=W2, X=L, B=X.  
L1025  
102 Obsolete. Lennox heat pump; part no. 24F6101; EM.  
HEAT LED; V-VR jumper; used with T874R1020,  
J1038.  
Y594R1243a Wiring differences (old=new):  
M=Y, F=G, V-VR=VR, Y=W2,  
R=O.  
Y594R1243a  
L1033  
L1041  
115 Obsolete. Rheem heat pump; EM HEAT LED; used  
with T874R1152.  
103 Obsolete. Carrier heat pump; part no. HH93AZ175;  
SUPL HEAT LED; used with T874G1055  
Y594G1419  
Wiring differences (old=new):  
C=X, jumper Y1=W1.  
(HH07AT171), G1071 (HH93AZ175), G1113.  
L1066  
L1074  
122 Obsolete. Fedders heat pump; used with T874R1269;  
Y594R1615a Wiring differences (old=new):  
K=E, C=X, W1=B, Z=L.  
Y594J1001  
used in Y594R1037.  
124 Obsolete. Carrier heat pump; part no. HH93AZ186;  
SUPL HT LED; used with T874J1002 (HH07AT175) or  
T874J1028 (HH07AT165).  
L1082  
L1090  
104 Obsolete. Crispaire heat pump; W2-H jumper; EM  
Y594R1243a Replacement has auto fan in  
emergency heat mode.  
HEAT LED; used with T874R1061, R1111.  
105 Obsolete. Fedders heat pump; EM HEAT LED;  
changeover in heat mode; used with T874C1398,  
C1406, C1414.  
106 Obsolete. Westinghouse; EM HEAT LED.  
Y594R1425a Wiring differences (old=new):  
K=E, C=X.  
Y594R1243a  
L1108  
L1116  
107 Obsolete. Carrier part no. HH93AZ171; SUPL HEAT  
See OEM for  
LED; used with T874D1264 (HH07AT173).  
replacement.  
a
L1132  
108 Heil Quaker part no. HQ711598; used with T874R1137,  
R1673, R1731, R1749, R1814; used in Y594R1110,  
R1466, R1524, R1532, R1607.  
Y594R1292  
L1140  
L1157  
109 Obsolete. Includes EM HEAT and AUX HEAT LEDs;  
Y594R1763a Designed for use on Trane  
heat pumps.  
Q674L1207a  
used with T874R1053; used in Y594G1136.  
115 Obsolete. Rheem part no. 41-20796-14; EM HEAT and  
AUX HEAT LEDs; used with T874R.  
a
1
1
21 Obsolete. Used with T874C.  
23 Obsolete. Used with T874R.  
Y594C1322  
Y594R1243  
Y594R1763  
a
a
L1165  
110 Obsolete. Lennox no. 24F5901; factory installed V-VR  
jumper; EM HEAT and SERVICE LEDs; stage 2 heat is  
isolated; used with T874C1448, R1178 and  
C815A1013.  
Wiring differences (old=new):  
V-VR=R, M=Y, F=G, X=B,  
Y=W, A=T, R=O, E=X2.  
Y594R1243a  
L1173  
L1181  
112 Obsolete. Westinghouse; AUX HEAT and EM HEAT  
LEDs.  
113 Used with T874R1129; used in Y594R.  
Y594R1243a Wiring differences (old=new):  
X1=X.  
a
Both the thermostat and subbase must be replaced.  
60-2485—8  
82  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 9. Q674 Subbase Cross Reference.  
Model  
Fig.  
No.  
Q674 Trade  
Number  
Description  
Replacement  
Remarks  
L1199  
114 Obsolete. Lennox no. 24F6001; used with T874D1207  
T8611M2025 Wiring differences (old=new):  
(programmable) V-VR=R, Y=W3, X=C, R=O,  
M=Y, M2=Y2-W2, F=G;  
and C815A1013.  
jumper Y2-W2; no outdoor  
reset needed; use only one  
system transformer.  
L1207  
L1215  
115 Used with T874R1152, R1590, R1640, R1921; used in Q674L1207 or  
a
Y594R1243, R1706.  
Y594R1243  
Y594R1243  
a
116 Obsolete. Crispaire heat pump; used with T874R1111;  
Replacement has auto fan in  
emergency heat mode. Wiring  
differences (old=new): A=L;  
set anticipator to 1.2.  
used in Y594R1128.  
L1223  
117 Obsolete. Westinghouse special.  
See OEM for  
replacement.  
L1231  
L1249  
L1256  
182 Obsolete. Used with T874R1186 and W89.  
115 Obsolete. Used with T874R1194 and W89.  
None  
Y594R1243  
a
118 Obsolete. Westinghouse special; used with  
T8611M2025 Includes night setback.  
T874W1007.  
(programmable)  
a
L1264  
L1272  
119 Obsolete. Intertherm heat pump; EM HEAT and SERV Y594R1672 or Wiring differences (old=new):  
a
LEDs; used with T874R1202, R1608, R1699; used in  
Y594R1185, R1409, R1482.  
Y594R1763  
Y594R1672a  
W2=W, X=B, Z=no  
connection, K=X, W1=H.  
120 Obsolete. York part no. 025-22290; used with  
T874R1046, R1145; used in Y594R1011, R1102; used  
with T874R1228, R1251 R1327 and C815A1039; used  
in Y594R1144, R1151, R1193.  
Y594W1014a  
L1280  
L1298  
L1314  
L1322  
L1330  
L1348  
L1355  
233 Obsolete. Lennox no. 52C7601; used with T874W1023  
and W89.  
182 Obsolete. Singer heat pump; used with T874R1160  
and W89.  
See OEM for  
replacement.  
115 Obsolete. Westinghouse heat pump; used with  
Q674L1207 or  
a
T874R1244 and W89.  
Y594R1243  
a
127 Obsolete. EM HEAT and AUX HEAT LEDs; used with  
T874C1455.  
120 Obsolete. York heat pump; used with T874R.  
Y594R1243  
Y594R1664a Wiring differences (old=new):  
L=X, X=B.  
Q674L1207  
115 Obsolete. Williamson heat pump; used with  
T874R1236.  
111, Obsolete. Lennox part no. 31F3201; V-VR jumper;  
Y594R1763a Wiring differences (old=new):  
V-VR=R, M=Y, F=G, X=B,  
190 used with T874C1448, R1178 and C815A1015.  
Y=W, A=T, R=O, E=X2.  
L1363  
129 Obsolete. York heat pump; EM HEAT LED; used with  
T874G1402.  
Y594R1425a Wiring differences (old=new):  
W=W2, X=E, B=X; jumper Y-  
W1.  
L1371  
L1389  
124 Obsolete. BDP heat pump; part no. 34427DP125,  
P272-1878; EM HEAT LED; used with T874J1010.  
Y594J1001  
Wiring differences (old=new):  
W1=W2, F=L.  
114 Obsolete. Lennox part no. 41F6501; V-VR jumper;  
T8611M2025 Wiring differences (old=new):  
(programmable) V-VR=R, Y=W3, X=C, R=O,  
M=Y, M2=Y2-W2, F=G;  
used with T874D1207.  
jumper Y2-W2; no outdoor  
reset needed; use only one  
system transformer.  
L1397  
103 Obsolete. Carrier part no. HH93AZ185A; SUPL HEAT  
LED.  
Y594G1393a Wiring differences (old=new):  
C=X.  
a
Both the thermostat and subbase must be replaced.  
83  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 9. Q674 Subbase Cross Reference.  
Model  
Fig.  
No.  
Q674 Trade  
Number  
Description  
Replacement  
Remarks  
a
L1405  
106 Obsolete. BDP heat pump; part no. HH641501; used  
Y594R1243  
with T874R1335; used in Y594R1201.  
L1413  
133 Obsolete. Fedders heat pump; used with T874R1343;  
used in Y594R1219.  
Y594R1425a Wiring differences (old=new):  
K=E, C=X, Z=L; remove  
W1-Y jumper.  
Y594R1797a  
L1421  
L1439  
125 Obsolete. Coleman heat pump; used with T874R1368;  
used in Y594R1235.  
131 Obsolete. Carrier part no. HH93AZ187; SUPL HEAT  
LED; System: SUPL HT-HEAT- COOL; used with  
T874R1384 (HH07AQ170).  
Q674L1207 or Wiring differences (old=new):  
a
Y594G1393  
C=X.  
L1447  
L1454  
L1462  
L1496  
L1504  
L1512  
L1520  
L1538  
128 Obsolete. Williamson heat pump; three LEDs; used  
Y594R1425a Wiring differences (old=new):  
A=L.  
Y594R1393a Wiring differences (old=new):  
with T874R1392; used in Y594R1250.  
131 Obsolete. Carrier part no. HH93AZ197; SUPL HEAT  
LED; used with T874R1384 (HH07AQ170).  
113 Obsolete. LSI heat pump; part no. 104710002; used  
C=X.  
Y594R1243a Wiring differences (old=new):  
X1=X.  
with T874R1400.  
Y594R1763a  
Y594R1300a  
Y594R1292a  
Y594R1300a  
136 Obsolete. Trane heat pump; used with T874R1426;  
used in Y594R1284.  
134 Rheem part no. 41-20796-24; used with T874R1442,  
R1434, R1459; used in Y594R1631, R1649, R1854.  
108 Includes two LEDs; used with T874R1467; used in  
Y594R1292.  
123 Includes EM HEAT and AUX HEAT LEDs; used with  
T874R1475; used in Y594R1300.  
130 Obsolete. Snyder General heat pump; used with  
T874R1483, R1517, R1566 and C815A1005; used in  
Y594R1318, R1342, R1375.  
Y594R1763a Wiring differences (old=new):  
C=B, W1=W, E=X2, X=F.  
132 Obsolete. Used with T874R1574, R1582; used in  
Y594R1243a Wiring differences (old=new):  
C=X, X=L, W=W2.  
Y594R1383, R1391.  
L1546  
140 Obsolete. Rheem part no. 41-20797-21; three LEDs;  
used with T874W1031 and C815A1005; used in  
Y594W1022.  
T8611M2025 Includes night setback.  
(programmable)  
Y594R1615a  
L1553  
L1561  
137 Obsolete. Includes three LEDs; used with T874R1491;  
used in Y594R1326.  
121 Obsolete. Used with T874C1638; used in Y594C1322.  
Y594C1322a Use Y594C1322 when T874C  
is used.  
123 Obsolete. Used with T874R.  
Y594R1243a Use Y594R1243 when T874R  
is used.  
L1579  
135 Obsolete. Carrier heat pump; part no. HH93AZ198;  
SUPL HEAT LED; used with T874R1384  
Y594R1243a Wiring differences (old=new):  
C=X.  
(HH07AQ170).  
a
L1587  
L1595  
168 Used with T874R1616; used in Y594R1425.  
Y594R1425  
a
200, Obsolete. Miller heat pump; used with T874R1624 or  
Y594R1243 or  
a
201 T874R1202; used in Y594R1433.  
Y594R1763  
Y594R1243  
Y594R1763  
a
L1603  
L1611  
134 Obsolete. Used with T874R1632.  
136 Obsolete. American Standard heat pump; part no.  
WY28X235; used with T874R1657; used in  
Y594R1441.  
a
Y594J1001a  
L1637  
207 Obsolete. Carrier heat pump; part no. HH93AZ195;  
used with T874J1002 (HH07AT175) or T874J1010  
(HH07AT165).  
a
Both the thermostat and subbase must be replaced.  
60-2485—8  
84  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 9. Q674 Subbase Cross Reference.  
Model  
Fig.  
No.  
Q674 Trade  
Number  
Description  
Replacement  
Remarks  
See Trol-A-Temp.  
L1678  
L1686  
L1702  
209 Trol-A-Temp by Honeywell; gray color; used with  
None  
T874R1707; used in Y594R1490.  
209 Trol-A-Temp by Honeywell; used with T874R1715;  
used in Y594R1508.  
132 Obsolete. Snyder General heat pump; part no.  
None  
See Trol-A-Temp.  
Y594R1672a Wiring differences (old=new):  
C=B, W1=W, X=X2.  
6
54958B07; used with T874R1723 and C815A1005;  
used in Y594R1516.  
a
L1710  
L1728  
230 Used with T874R1822; used in Y594R1615.  
228 Obsolete. Lennox; gray color; used with T874R1855;  
Y594R1615  
Y594R1763  
a
Wiring differences (old=new):  
Y1=Y, L=F, W1=W, E=X2, C=B.  
used in Y594R1714.  
Y594R1664a  
L1736  
120 Designed to replace Y594R1011 (York part no.  
2
TH11702224); used with T874R1871; used in  
Y594R1664.  
Y594R1672a  
Y594R1680a  
Designed to replace Y594R1151 (York part no.  
2
TH11702324), Y594R1193 (York part no.  
6
TH11702224) and York part no. 2TH11704024; used  
with T874R1889 and C815A1054; used in Y594R1672.  
L1751  
L1769  
L1777  
230 Gray color; used with T874R1897, used in  
Y594R1680.  
124 Obsolete. Nordyne part no. 9132260; used with T874J. See OEM for  
replacement.  
a
120 Obsolete. Gray color; designed to replace Y594R1151  
Y594R1672  
Replacement is beige.  
(
York part no. 2TH11702324), Y594R1193 (York part  
no. 6TH11702224) and York part no. 2TH11704024;  
used with T874R1905 and C815A1059; used in  
Y594R1698.  
Designed to replace Y594R1011 (York part no.  
Y594R1664a Replacement is beige.  
2
TH11702224); used with T874R1913; used in  
Y594R1706.  
L1785  
L1793  
103 Obsolete. Carrier part no. HH93AZ175-W; Canada;  
gray color; System: Supl Ht-Heat-Off-Cool; includes  
one LED.  
124 Obsolete. Carrier Canada part no. HH93AZ186-W;  
gray color; Fan: Auto-On; System: Supl Ht-Heat-Off-  
Cool; includes one LED.  
Y594G1476a Wiring differences (old=new):  
C=X; Y1-W1 jumper required.  
Y594J1019a  
Y594R1763a  
Y594R1425a  
L1801  
L1819  
197 American Standard (Trane) part no. THT1225; includes  
two LEDs; used with T874R1939; used in Y594R1748.  
168 Obsolete. Inter-City Products part no. HQ1149407HW;  
includes three LEDs; used with T874R1947; used in  
Y594R1755.  
Y594R1763a  
L1827  
197 TRADELINE; includes two LEDs; used with  
T874R1954; used in Y594R1763; direct replacement  
for Trane/American Standard Y594R1748  
(
T874R1939/Q674L1801) Trane part no. ASYSTAT  
6
31A, Y594R1136 (T874R1053/Q674L1140).  
a
L1835  
L1843  
140 Obsolete. Inter-City Products; includes three LEDs;  
T8611M2025 Includes night setback.  
used in Y594W1030.  
(programmable)  
a
115 Obsolete. Consolidated Industries part no. 9036100;  
gray color; includes two LEDs; used with T874R1962;  
used in Y594R1771.  
Y594R1680  
Includes CHECK LED.  
Y594R1672a  
L1850  
120 York Canada; gray color; includes one LED; used with  
T874R1970; used in Y594R1789.  
a
Both the thermostat and subbase must be replaced.  
85  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 9. Q674 Subbase Cross Reference.  
Model  
Fig.  
No.  
Q674 Trade  
Number  
Description  
Replacement  
Remarks  
a
L1868  
125 TRADELINE; includes two LEDs; used with  
T874R1988; used in Y594R1797; direct replacement  
for Evcon/Coleman Y594R1235 (T874R1368/  
Q674L1421) Coleman part no. 3600-368.  
Y594R1797  
L1876  
L1884  
L1892  
245 Obsolete. Amana part no. 10573902; includes two  
Y594R1797  
Y594R1797  
Y594G1674  
Wiring differences (old=new):  
C/X=X.  
LEDs; used with T874R2002; used in Y594R1805.  
245 Obsolete. Amana part no. 10573904; includes two  
LEDs; used with T874R2010; used in Y594R1813.  
103 Obsolete. TRADELINE; System: SUPL HT-HEAT-  
OFF-COOL; includes one LED; used with T874G2004;  
used in Y594G1666; direct replacement for Carrier  
Y507J1011 (T874G1055/Q674L1041) Carrier part no.  
HH07AT171/HH93AZ175.  
Wiring differences (old=new):  
C/X=X, W3=W2.  
Replacement has auto  
changeover.  
L1900  
241 Obsolete. TRADELINE; System: SUPL HT-HEAT-  
OFF-COOL; includes SUPL HT LED; used with  
T874J1069; used in Y594J1001; direct replacement for  
Carrier T874J1028/Q674J1068 (Carrier part no.  
HH07AT165/HH93AZ183), Carrier T874J1002/  
Q674J1068 (Carrier part no. HH07AT175/  
HH93AZ183).  
Y594J1019  
Replacement has auto  
changeover.  
Y594R1797a  
T8611M2025  
L1918  
L1934  
125 Obsolete. York logo; part no. 2TH11703424A; includes  
two LEDs; used with T874R2028 in Y594R1821.  
123 Obsolete. Addison logo; part no. 843-277; includes  
three LEDs; used with T874W1106 in Y594W1055.  
Q674N  
System: OFF-HEAT-COOL-EVAP; Fan: AUTO-ON  
N1015  
60 Obsolete. Goettl heat pump; changeover in heat mode;  
See OEM for  
replacement.  
evaporative cooler circuit; used with T874C1182.  
N1023  
61 Obsolete. Sigler heat pump; evaporative cooler circuit;  
used with T874C1349.  
See OEM for  
replacement.  
Q674P  
P1005  
System: SUPL HT-HEAT-COOL; Fan: AUTO-ON  
126 Obsolete. Carrier heat pump; part no. HH93AZ169;  
Y594G1419a Wiring differences (old=new):  
C=X; jumper Y1-W1;  
used with T874G1071 (HH07AT171).  
replacement has OFF-EM HT-  
HEAT-AUTO-COOL system  
switching.  
Q674Q  
System: HEAT-OFF-COOL; Fan: LOW-MED-HI-ON  
59 Obsolete. McQuay special; used with T874A1267.  
Q1004  
See OEM for  
replacement.  
Q1012  
64 Used with T874A1291.  
None  
Q674R  
R1003  
System: OFF-COOL; Fan: LO-HI-CONT  
69 Obsolete. Carrier part no. HH93AZ190; international  
See OEM for  
replacement.  
symbols on fan and switches; used with T874V1008  
(HH07AT177).  
Q674S  
S1000  
System: HEAT-COOL; Fan: None  
70 Obsolete. Fiberglas; Canada; SERVICE LED; used  
See OEM for  
replacement.  
with T874C1653; used in Y594C1348.  
Q674W  
W1006  
System: OFF-ON; Fan: LO-MED-HI  
240 Obsolete. Snyder General part no. 044271801.  
See OEM for  
replacement.  
a
Both the thermostat and subbase must be replaced.  
60-2485—8  
86  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 10. Y594 Cross Reference.  
Model  
Fig.  
No.  
Trade Model  
a
Number  
Description  
Replacement  
Remarks  
Y594A  
A1001  
A1019  
A1035  
A1043  
A1050  
A1068  
46  
82  
44  
46  
Obsolete. Amana part no. D68535-11; contains  
T874A1077, Q674B1075.  
T874A1036/  
Q674B1075  
Obsolete. Amana part no. P68535-12; contains  
T874A1036/  
T874A1077, Q674E1056.  
Q674E1049  
Obsolete. Trane part no. 268-0187-1; contains  
T874A1085, Q674B1018.  
T874A1036/  
Q674B1018  
Obsolete. Trane part no. 268-0201-5; contains  
T874A1036/  
T874A1085, Q674B1075.  
Q674B1075  
55, 66 Obsolete. Trane part no. 268-0201-3; contains  
T874A1085, Q674D1008.  
82  
T874A1036/  
Q674D1040  
Obsolete. Sears part no. 42-9144; contains  
T874A1036/  
T874A1119, Q674E1007.  
Q674E1049  
A1126  
A1159  
64  
91  
Contains T874A1291, Q674Q1012.  
Obsolete. Contains T874A1440, Q674G1005.  
None  
T874A1150/  
Q674G1070  
A1167  
A1175  
A1191  
184 California Economizer; Premier White® color;  
contains T874A1580 and Q674G1161.  
T874A1036/  
Q674G1070  
Replacement is beige color.  
55  
Obsolete. York logo; part no. 2TH04703224;  
T874A1010/  
contains T874A1622, Q674D1180.  
Q674D1040  
46  
Obsolete. Amana logo: part no. P6853524R;  
contains T874A1002, Q674B1075.  
T874A1036/  
Q674B1075  
Y594B  
B1026  
B1034  
B1042  
44  
46  
88  
Trane part no. BAYSTAT012; contains T874B1035,  
Q674B1018.  
T874B1019/  
Q674B1018  
Obsolete. Trane part no. 163-552-1; contains  
T874B1019/  
T874B1035, Q674B1075.  
Q674B1075  
Obsolete. Goodman part no. CHTS36-60; contains  
T874B1100, Q674E1338.  
T874B1019/  
Q674E1049  
No LEDs on replacement.  
Jumper RC-RH.  
Y594C  
C1009  
C1017  
C1058  
C1082  
C1256  
C1280  
C1314  
82  
Obsolete. Amana part no. D68535-9; contains  
T874C1059, Q674E1056.  
T874C1018/  
Q674E1049  
142 Obsolete. Amana part no. D68535-10; contains  
T874C1018/  
T874C1059, Q674F1022.  
Obsolete. Contains T874C1000, Q674B1075.  
Q674F1022  
46  
82  
45  
45  
56  
T874C1018/  
Q674B1075  
Obsolete. Trane part no. 166-162-1; contains  
T874C1083, Q674E1007.  
T874C1018/  
Q674E1049  
Obsolete. Amana part no. D68535-16; contains  
T874C1018/  
Q674B1034  
Jumper RC-RH.  
T874C1059, Q674B1059.  
Obsolete. Williamson; contains T874C1570,  
Q674B1000.  
Obsolete. LSI; contains T874C1471, Q674B1257.  
T874C1018/  
Q674B1034  
T874C1018/  
Q674B1018  
Jumper RC-RH; no RESET  
LED on replacement.  
C1322  
C1330  
121 Obsolete. Contains T874C1638, Q674L1561.  
Y594C1322  
142 Obsolete. Amana part no. D68535-21; contains  
T874C1018/  
T874C1059, Q674F1022.  
Q674F1022  
a
Both the thermostat and subbase must be replaced.  
87  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 10. Y594 Cross Reference.  
Model  
Fig.  
No.  
Trade Model  
a
Number  
Description  
Replacement  
Remarks  
C1348  
70  
Obsolete. Fiberglas; contains T874C1653,  
T874C1000/  
Wiring differences (old=new):  
Y=Y1; jumper RC-RH and Y1-  
W1; replacement has no  
Q674S1000.  
Q674B1075  
SERVICE LED; replacement  
has fan switching and HEAT-  
OFF-COOL system switching.  
C1355  
C1363  
45  
45  
Obsolete. Nordyne “Miller” part no. 9122250;  
contains T874C1695, Q674B1000.  
T874C1018/  
Q674B1034  
Obsolete. Nordyne “Intertherm” part no. 911100001;  
T874C1018/  
Wiring differences (old=new):  
Y=Y1; jumper RC-RH; Y1-W;  
replacement has no SERVICE  
LED.  
contains T874C1703, Q674B1000.  
Q674B1075  
C1371  
C1389  
C1413  
C1421  
C1439  
184 Obsolete. California Economizer; contains  
T874C1802 and Q674G1005.  
T874C1018/  
Q674G1070  
237 Obsolete. TRADELINE; Premier White® color;  
Y594C1389  
Y594R1425  
Y594D1347  
None  
contains T874C1810 and Q674B1547.  
238 Heat Controller “Energy Night” logo; contains  
T874C1844 and Q674F1592.  
E-W2 jumper required; system:  
EM.HT.-Heat-Off-Cool.  
249 Obsolete. TRADELINE; contains T874C1877 and  
Replacement has auto  
Q674B1554.  
changeover; jumper RH-RC.  
T874C1869 and Q674C1579.  
Y594D  
D1016  
D1024  
D1032  
D1040  
D1057  
D1149  
D1156  
D1180  
D1222  
44  
72  
91  
46  
Obsolete. Trane part no. 268-0201-2; contains  
T874D1082, Q674B1018.  
T874D1165/  
Q674B1018  
Trane part no. BAYSTAT010; contains T874D1082,  
T874D1165/  
Q674C1009.  
Q674C1058  
Obsolete. Trane part no. BAYSTAT011; contains  
T874D1082, Q674G1021.  
T874D1165/  
Q674G1070  
Amana part no. P68535-19R; contains T874D1082,  
T874D1165/  
Q674B1075.  
Q674B1075  
55, 66 Obsolete. Trane part no. BAYSTAT007; contains  
T874D1082, Q674D1008.  
T874D1165/  
Q674D1040  
46  
48  
82  
Obsolete. Amana part no. P68535-20C; contains  
T874D1165/  
T874D1322, Q674B1075.  
Q674B1075  
Obsolete. Trane part no. BAYSTAT013; contains  
T874D1082, Q674B1133.  
T874D1165/  
Q674B1018  
Replacement has no FILTER  
LED.  
York part no. 025-23321-000; contains T874D1504,  
T874D1165/  
Q674E1007.  
Q674E1049  
166 Obsolete. WeatherKing; contains T874D1009,  
Q674F1337.  
T874D1165/  
Q674F1022  
Wiring differences (old=new):  
R=RH; jumper RC-RH;  
replacement has no EM.HT. or  
AUX. HT. LEDs.  
D1248  
D1297  
D1305  
D1321  
D1339  
82  
82  
82  
45  
82  
Obsolete. Reznor part no. 93437; contains  
T874D1629, Q674E1007.  
T874D1165/  
Q674E1049  
Obsolete. ArcoAire part no. 1506753; contains  
T874D1165/  
T874D1769, Q674E1346.  
Q674E1049  
Obsolete. Comfortmaker part no. 1505753; contains  
T874D1785, Q674E1346.  
T874D1165/  
Q674E1049  
Obsolete. Goodman part no. CHT 90-120; contains  
T874D1165/  
T874D1843, Q674B1000.  
Q674B1034  
Obsolete. Nordyne part no. 5471180; contains  
T874D1009, Q674E1007.  
T874D1165/  
Q674E1049  
a
Both the thermostat and subbase must be replaced.  
60-2485—8  
88  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 10. Y594 Cross Reference.  
Model  
Fig.  
No.  
82  
Trade Model  
a
Number  
Description  
Replacement  
Y594D1347  
Y594D1354  
Remarks  
D1347  
D1354  
TRADELINE® contains T874D1942, Q674E1403.  
82  
SUPER TRADELINE® contains T874D2031 (no  
cover), Q674E1049, and TG504A with two keys.  
D1370  
D1388  
D1396  
D1404  
D1412  
45  
72  
Obsolete. Carrier part no. 50QE90022101; contains  
T874D2049 and Q674B1539.  
T874D1165/  
Q674B1034  
Replacement has °F  
scaleplate.  
Obsolete. Carrier part no. 50QE90023101; contains  
T874D1165/  
Replacement has °F  
T874D2049 and Q674C1520.  
Q674C1058  
scaleplate.  
184 Obsolete. Carrier part no. 50QE90025101; contains  
T874D2049 and Q674G1153.  
55, 66 Obsolete. Carrier part no. 50QE90024101; contains  
T874D1165/  
Q674G1070  
Replacement has °F  
scaleplate.  
T874D1165/  
Replacement has °F  
T874D2049 and Q674D1164.  
Obsolete. Carrier “Weathermaker” part no.  
HH07AT209; taupe color; contains T874D2064 and  
Q674E1445.  
Obsolete. Carrier “Zone Perfect” part no.  
HH07AT208; taupe color; contains T874D2072 and  
Q674E1445.  
Q674D1040  
scaleplate.  
82  
82  
T874D1165/  
Q674E1049  
Replacement is beige color.  
Replacement is beige color.  
D1420  
T874D1165/  
Q674E1049  
D1438  
D1446  
55, 66 Obsolete. Contains T874D2098 and Q674D1008.  
T874D1165/  
Q674D1040  
Replacement has 2 setpoint  
levers.  
Replacement has °F  
scaleplate and 2 setpoint  
levers.  
55, 66 Obsolete. Contains T874D2106 and Q674D1008.  
T874D1165/  
Q674D1040  
D1453  
D1461  
208 Obsolete. Amana logo; part no. P1217501F;  
contains T874D2163 and Q674D1172.  
T874D1165/  
Q674D1040  
45  
Obsolete. Amana logo; part no. P1217701F;  
T874D1942/  
contains T874D2171 and Q674B1562.  
Q674B1034  
Y594E  
E1015  
72  
Obsolete. Trane part no. BAYSTAT015; contains  
T874E1040, Q674C1009.  
T874B1019/  
Q674C1058  
Y594F  
F1022  
F1048  
F1063  
44  
72  
91  
Obsolete. Contains T874F1031 and 40003440-001  
wallplate with installed diode.  
T874F1015  
Obsolete. Reznor part no. 93436; contains  
T874F1015/  
Q674C1058  
T874F1130, Q674C1009.  
Obsolete. Reznor part no. 93435; contains  
T874F1130, Q674G1005.  
T874F1015/  
Q674G1070  
Y594G  
G1013  
G1138  
G1153  
160 Obsolete. York part no. 2TH11702424; contains  
T874G1170, Q674J1027.  
Y594G1567  
Y594G1567  
Y594G1252  
160 Obsolete. York part no. 025-22286; contains  
T874G1196, Q674J1027.  
154 Obsolete. Crispaire part no. HP10-51; contains  
T874G1089, Q674F1204.  
Wiring differences (old=new):  
A=L.  
G1161  
G1195  
162 Contains T874G1204, Q674J1043.  
Y594G1161  
Y594G1252  
155 Obsolete. Heil Quaker part no. HQ521387HW;  
contains T874G1246, Q674F1212.  
G1229  
G1245  
G1252  
160 Obsolete. York part no. 6TH11702424; contains  
T874G1428, Q674J1027.  
Y594G1567  
Y594G1252  
Y594G1252  
155 Obsolete. BDP part no. HH641502; contains  
T874G1451, Q674F1212.  
155 TRADELINE; contains T874G1246, Q674F1212.  
a
Both the thermostat and subbase must be replaced.  
89  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 10. Y594 Cross Reference.  
Model  
Fig.  
No.  
Trade Model  
a
Number  
Description  
Replacement  
Remarks  
G1294  
G1328  
G1344  
G1351  
79  
Obsolete. LSI; contains T874G1378, Q674C1124.  
See OEM for  
H2 is night setback.  
replacement.  
194 Obsolete. Addison part no. 8403-197; contains  
T874G1543, Q674F1345.  
194 Obsolete. Heat Controller part no. 7601-110B;  
Y594G1252  
Y594G1252  
Y594G1567  
Wiring differences (old=new):  
Y1=O, X=L, C=X.  
Wiring differences (old=new):  
contains T874G1469, Q674F1345.  
Y1=O, X=L, C=X; W1=Y.  
160 Obsolete. Luxaire part no. 026-00068-000; contains  
T874G1568, Q674J1126.  
G1369  
G1377  
155 Obsolete. Contains T874G1246, Q674F1212.  
Y594G1252  
Y594G1633  
169 Obsolete. Coleman part no. 3600-373; contains  
T874G1576, Q674F1402.  
G1385  
155 Obsolete. ArcoAire; contains T874G1592,  
Q674F1212.  
Y594G1252  
G1393  
G1419  
G1427  
170 Obsolete. Contains T874R1393, Q674L1454.  
227 TRADELINE; contains T874G1642, Q674F1444.  
Y594G1393  
Y594G1419  
177 Obsolete. Mammoth part no. 73034101; contains  
See OEM for  
H2 is night setback.  
T874G1659, Q674C1330.  
replacement.  
G1443  
G1476  
G1492  
G1500  
G1518  
174 Obsolete. American Standard (Trane) part no.  
ASYSTAT650; contains T874G1675, Q674J1142.  
Y594G1161  
Y594G1476  
None  
227 TRADELINE; same as Y594G1419 except Premier  
White® color; contains T874G1741, Q674F1477.  
211 Trol-A-Temp; contains T874G1758, Q674F1485.  
See Trol-A-Temp for  
replacement.  
216 Obsolete. Comfortmaker part no. 1505756; contains  
T874G1774, Q674J1175.  
See OEM for  
replacement.  
216 Obsolete. ArcoAire part no. 1506756; contains  
See OEM for  
T874G1782, Q674J1175.  
replacement.  
G1526  
G1534  
167 TRADELINE; contains T874G1626, Q674F1436.  
None  
None  
227 TRADELINE; °C; white; Australia; contains  
T874G1824, Q674F1477.  
G1542  
G1559  
231 Obsolete. Intertherm part no. 9129290; contains  
T874G1832, Q674F1519.  
Y594G1252  
Y594G1252  
Cooling changeover only.  
Cooling changeover only.  
231 Obsolete. Miller part no. 9129310; contains  
T874G1840, Q674F1519.  
G1567  
G1575  
160 TRADELINE; contains T874G1865, Q674J1209.  
Y594G1567  
Y594G1567  
160 Obsolete. TRADELINE; same as Y594G1567  
except Premier White® color; contains T874G1873,  
Q674J1225; direct replacement for York  
Replacement is beige.  
2
TH11702424 (Y594G1013 contains T874G1170/  
Q674J1027) and 6TH11702424 (Y594G1229  
contains T874G1428/Q674J1027).  
G1583  
G1591  
G1609  
229 Obsolete. Lennox Canada part no. 97E78; contains  
Y594G1161  
Y594G1633  
Y594G1252  
Wiring differences (old=new):  
E=X2, C=B, L=F.  
T874G1857, Q674F1535.  
243 Obsolete. Amana part no. 10636701; contains  
T874G1899 and Q674F1550.  
155 Obsolete. Econar; contains T874G1915 and  
Q674F1212.  
a
Both the thermostat and subbase must be replaced.  
60-2485—8  
90  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 10. Y594 Cross Reference.  
Model  
Fig.  
No.  
73  
Trade Model  
a
Number  
Description  
Replacement  
Remarks  
a
G1617  
Obsolete. Carrier part no. 50QE90020101; contains  
Y594H1012  
Wiring differences (old=new):  
Y1=O, Y2=Y, L=R, R=none;  
R-L jumper required; no night  
setback.  
T874G1949 and Q674C1504.  
T8600D2028  
Wiring differences (old=new):  
(
programmable) Y1=O, Y2=Y, L=R; W-Y jumper  
required; night setback.  
Y594G1567a  
Y594G1633a  
G1625  
G1633  
160 York Canada part no. 2TH11702524; contains  
T874G1964 and Q674J1266.  
Replacement has °F  
scaleplate.  
169 TRADELINE; contains T874G1972 and  
Q674F1584; direct replacement for Y594G1377  
(
T874G1576/Q674F1402) Evcon/Coleman part no.  
3
600-373.  
G1641  
G1658  
G1666  
169 Obsolete. Amana part no. 10636703; contains  
Y594G1633  
Y594G1252  
Y594G1674  
Wiring differences (old=new):  
W3=W2.  
T874G1980 and Q674F1600.  
155 Obsolete. Tempstar “Inter-City Products” part no.  
1149910; contains T874G1998 and Q674F1212.  
103 Obsolete. TRADELINE; manual changeover;  
contains T874G2004 and Q674L1892; direct  
replacement for Y507J1011 (T874G1055/  
Q674L1041) Carrier part no. 99TZ90041106  
Replacement has auto  
changeover.  
(HH07AT171/HH93AZ1750).  
G1674  
G1716  
161 TRADELINE; automatic changeover; contains  
T874G2004 and Q674J1274; direct replacement  
Y507J1003 (T874G1055/Q674J1035) Carrier part  
no. 99TZ90040106 (HH07AT171/HH93AZ173).  
Y594G1674  
Y594G1716  
155 WaterFurnace logo; part no. TA21H03; contains  
T874G2046 and Q674F1667.  
Y594H  
H1004  
H1012  
H1020  
79  
Obsolete. LSI part no. 73033901; contains  
T874H1039 and Q674C1124.  
T8600D2028  
Y594H1012  
Y594H1012  
H2 is night setback.  
164 Contains T874H1062 and Q674C1249; replaces  
T874H1005/Q674C1041.  
177 Obsolete. Mammoth part no. 71117101; contains  
T874H1096 and Q674C1330.  
Wiring differences (old=new):  
R1=R, R2=L; use jumper  
provided.  
Wiring differences (old=new):  
X1=O, Y2=Y; L-R jumper  
required.  
Wiring differences (old=new):  
Y=Y1; W1-Y1 jumper required;  
replacement has no LEDs.  
Y594H1012a  
H1038  
H1046  
H1053  
74  
Obsolete. Carrier part no. 50QE90019101; contains  
T874H1161 and Q674C1496.  
172 Obsolete. Carrier part no. 50QE90026101; contains  
T874H1153 and Q674B1406.  
T874A1130/  
a
Q674B1075  
Y594H1012a  
173 Obsolete. Carrier part no. 50QE90027101; contains  
T874H1153 and Q674C1322.  
Wiring differences (old=new):  
Z=X.  
Y594J  
J1001  
241 Obsolete. TRADELINE; manual changeover;  
contains T874J1069 and Q674L1900; direct  
replacement for T874J1002 or T874A1028 used  
with Q674L1074 or Q674L1637 (HH07AT175 or  
HH07AT165 used with HH93AZ186 or  
HH93AZ195).  
(Recontrol)  
T8511G1021  
a
Both the thermostat and subbase must be replaced.  
91  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 10. Y594 Cross Reference.  
Trade Model  
Model  
Fig.  
No.  
a
Number  
Description  
Replacement  
Remarks  
J1019  
244 Obsolete. TRADELINE; automatic changeover;  
contains T874J1069 and Q674J1282; direct  
replacement for T874J1002 or T874J1028 used  
with Q674J1068 or Q674J1159 (HH07AT175 or  
HH07AT165 used with HH93AZ183 or  
HH93AZ196).  
(Recontrol)  
T8511G1021  
Y594N  
N1007  
N1015  
N1023  
N1031  
178 Obsolete. Williamson part no. 75-189; contains  
T874N1008 and Q674F1196.  
179 Obsolete. Contains T874N1040 and Q674F1261.  
T874N1016/  
Q674F1196  
Y594G1419  
a
Wiring differences (old=new):  
L=X2, Y=Y1.  
178 Obsolete. Intertherm part no. 9111882; contains  
T874N1057 and Q674F1220.  
T874N1016/  
Q674F1220  
178 Obsolete. Nordyne “Miller” part no. 9122240;  
T874N1016/  
contains T874N1065 and Q674F1220.  
Q674F1220  
Y594P  
P1005  
97  
Obsolete. Carrier part no. 50QE90021101; contains  
T874P1055 and Q674C1512.  
T8600D2028  
Wiring differences (old=new):  
Y=Y1, W=O; Y1-W1 jumper  
required.  
Y594R  
R1011  
R1029  
R1037  
R1102  
R1110  
R1128  
120 Obsolete. York part no. 2TH11702224; contains  
T874R1046 and Q674L1272.  
Y594R1664  
Y594R1243  
Y594R1615  
Y594R1664  
Y594R1292  
Y594R1243  
47  
Obsolete. Bryant; contains T874R1004 and  
Wiring differences (old=new):  
W1=W2.  
Q674B1042.  
122 Obsolete. Fedders part no. 88-58-00540-001;  
contains T874R1269 and Q674L1066.  
Wiring differences (old=new):  
K=E, C=X, W1=B, Z=L.  
120 Obsolete. York part no. 025-22285-000; contains  
T874R1145 and Q674L1272.  
108 Obsolete. Heil Quaker part no. HQ712004HW;  
contains T874R1137 and Q674L1132.  
116 Obsolete. Crispaire part no. HP9-51; contains  
Wiring differences (old=new):  
A=L.  
T874R1111 and Q674L1215.  
R1136  
R1151  
109 Obsolete. Contains T874R1053 and Q674L1140.  
Y594R1763  
Y594R1672  
120 Obsolete. York part no. 2TH11702324; contains  
T874R1251, Q674L1272 and C815A1039.  
R1185  
201 Obsolete. Intertherm part no. 9111871; contains  
T874R1202 and Q674L1264.  
Y594R1672  
Wiring differences (old=new):  
W2=W, X=B, Z=no  
connection, K=X, W1=H.  
R1193  
R1201  
R1219  
120 Obsolete. York part no. 6TH11702224; contains  
T874R1327 and Q674L1272.  
Y594R1664  
Y594R1243  
Y594R1425  
106 Obsolete. BDP part no. HH641501; contains  
T874R1335 and Q674L1405.  
133 Obsolete. Fedders part no. 88-58-00560-001;  
contains T874R1343 and Q674L1413.  
Wiring differences (old=new):  
K=E, C=X, Z=L; remove  
factory installed jumper.  
R1235  
125 Obsolete. Coleman part no. 3600-368; contains  
T874R1368 and Q674L1421.  
Y594R1797  
R1243  
R1250  
115 TRADELINE; contains T874R1152 and Q674L1207.  
Y594R1243  
Y594R1425  
128 Obsolete. Williamson part no. 75-191; contains  
Wiring differences (old=new):  
A=L.  
T874R1392 and Q674L1447.  
R1284  
136 Obsolete. Trane part no. BAYSTAT339; contains  
T874R1426 and Q674L1496.  
Y594R1763  
a
Both the thermostat and subbase must be replaced.  
60-2485—8  
92  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 10. Y594 Cross Reference.  
Model  
Fig.  
No.  
Trade Model  
a
Number  
Description  
Replacement  
Remarks  
R1292  
108 Contains T874R1467 and Q674L1512; replaces  
Y594R1292  
Y594R1110 (T874R1137/Q674L1132).  
R1300  
R1318  
123 Contains T874R1475 and Q674L1520.  
Y594R1300  
Y594R1763  
130 Obsolete. Comfortmaker part no. 1505721; contains  
Wiring differences (old=new):  
W1=W, E=X2, X=F, C=B.  
T874R1483, Q674L1538 and C815A1005.  
R1326  
R1334  
R1342  
R1359  
R1375  
R1383  
R1391  
R1409  
137 Obsolete. SUPER TRADELINE; contains  
T874R1491 and Q674L1553.  
Y594R1615  
Y594R1243  
Y594R1763  
Y594R1243  
Y594R1763  
Y594R1243  
Y594R1243  
Y594R1763  
47  
Obsolete. Slant Fin; contains T874R1509 and  
Wiring differences (old=new):  
W1=W2.  
Q674B1042.  
130 Obsolete. ArcoAire part no. 1506721; contains  
T874R1517, Q674L1538 and C815A1005.  
Wiring differences (old=new):  
W1=W, E=X2, X=F, C=B.  
113 Obsolete. ArcoAire part no. A02074; contains  
Wiring differences (old=new):  
X1=X.  
T874R1525 and Q674L1181.  
130 Obsolete. Contains T874R1566, Q674L1538 and  
C815A1005.  
Wiring differences (old=new):  
W1=W, E=X2, X=F, C=B.  
132 Obsolete. Comfortmaker part no. 1505739; contains  
Wiring differences (old=new):  
W=W2, C=X, X=L.  
T874R1574 and Q674L1538.  
132 Obsolete. ArcoAire part no. 1506739; contains  
T874R1582 and Q674L1538.  
Wiring differences (old=new):  
W=W2, C=X, X=L.  
119 Obsolete. Intertherm part no. 6244630; contains  
Wiring differences (old=new):  
W2=W, X=B, Z=F, K=X2,  
W1=O.  
T874R1608 and Q674L1264.  
R1417  
R1425  
R1433  
113 Obsolete. Comfortmaker part no. 1505-735;  
contains T874R1301 and Q674L1181.  
Y594R1243  
Y594R1425  
Y594R1243  
Wiring differences (old=new):  
X1=X.  
168 SUPER TRADELINE; contains T874R1616 and  
Q674L1587.  
200 Obsolete. Miller part no. 9115900; contains  
T874R1624 and Q674L1595.  
Wiring differences (old=new):  
W2=W, X=B, Z=F, K=X2,  
W1=O.  
R1441  
R1466  
R1482  
136 Obsolete. American Standard (Trane) part no.  
ASYSTAT651; contains T874R1657 and  
Q674L1611.  
108 Heil Quaker part no. 1060321; model no.  
HAXB004TW01; contains T874R1673 and  
Q674L1132.  
Y594R1763  
Y594R1292  
Y594R1763  
119 Obsolete. Nordyne “Miller” part no. 9122230;  
Wiring differences (old=new):  
W2=W, X=B, Z=F, K=X2,  
W1=O.  
contains T874R1699 and Q674L1264.  
R1490  
R1508  
R1516  
R1524  
209 Trol-A-Temp; contains T874R1707 and Q674L1678.  
209 Trol-A-Temp; contains T874R1715 and Q674L1686.  
None  
None  
See Trol-A-Temp for  
replacement.  
See Trol-A-Temp for  
replacement.  
132 Obsolete. Snyder General part no. 654958B07;  
contains T874R1723, Q674L1702 and C815A1005.  
108 Obsolete. Inter-City Products part no.  
HQ1147925HW; contains T874R1731 and  
Q674L1132.  
Y594R1763  
Y594R1292  
Wiring differences (old=new):  
W1=W, C=B, X=X2.  
R1532  
R1607  
108 Heil Quaker part no. 1060322; model no.  
TAXB004TW01; contains T874R1749 and  
Q674L1132.  
Y594R1292  
Y594R1292  
108 Obsolete. Keeprite THPC; contains T874R1814 and  
Q674L1132.  
a
Both the thermostat and subbase must be replaced.  
93  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 10. Y594 Cross Reference.  
Trade Model  
Model  
Fig.  
No.  
a
Number  
Description  
Replacement  
Remarks  
R1615  
230 TRADELINE; contains T874R1822 and  
Q674L1710; replaces Y594R1326 (T874R1491/  
Q674L1553).  
Y594R1615  
R1623  
R1631  
R1649  
R1656  
R1664  
134 Obsolete. Rheem Universal Parts part no. 41-  
Y594R1300  
Y594R1300  
Y594R1300  
Y594R1300  
Y594R1664  
2
0796-46; contains T874R1558 and Q674L1504.  
134 Rheem part no. 41-20796-29; contains T874R1442  
and Q674L1504.  
134 Ruud part no. 41-20796-33; contains T874R1434  
and Q674L1504.  
134 Obsolete. WeatherKing part no. 41-20796-64;  
contains T874R1830 and Q674L1504.  
120 TRADELINE; contains T874R1871 and  
Q674L1736; direct replacement for York  
2
TH11702224 (Y594R1011 contains T874R1046/  
Q674L1272).  
R1672  
R1680  
120 TRADELINE; contains T874R1889, Q674L1736  
Y594R1672  
Y594R1680  
and C815A1054; direct replacement for York  
2
TH11702324 (Y594R1151 contains T874R1251/  
Q674L1272/C815A1039) and 6TH11702224  
(Y594R1193 contains T874R1327/Q674L1272).  
230 TRADELINE; same as Y594R1615 except Premier  
White® color; contains T874R1897 and  
Q674L1751; direct replacement for Y594R1326  
(T874R1491/Q674L1553).  
R1698  
R1706  
120 Obsolete. TRADELINE; Premier White® color;  
Y594R1672  
Y594R1664  
Replacement is beige.  
Replacement is beige.  
contains T874R1905, Q674L1777 and C815A1054.  
120 Obsolete. TRADELINE; same as Y594R1664  
except Premier White® color; contains T874R1913  
and Q674L1777; direct replacement for Y594R1011  
(
T874R1046/Q674L1272) York part no.  
2
TH11702224.  
R1714  
228 Obsolete. Lennox part no. 97E79; Canada; Premier  
White® color; contains T874R1855 and  
Q674L1728.  
Y594R1763  
Wiring differences (old=new):  
Y1=Y, L=F, W1=W, E=W2,  
C=B.  
Y594R1243a  
Y594R1763a  
Y594R1425a  
R1722  
R1748  
R1755  
115 Obsolete. Econar; contains T874R1921 and  
Q674L1207.  
197 American Standard (Trane) part no. ASYSTAT651A;  
contains T874R1939 and Q674L1801.  
168 Obsolete. Inter-City Products part no.  
HQ1149376HW; contains T874R1947 and  
Q674L1819.  
R1763  
197 TRADELINE: contains T874R1954 and  
Y594R1763  
Q674L1827; direct replacement for Y594R1136  
(T874R1053/Q674L1140), Y594R1748  
T874R1939/Q674L1801) Trane part no.  
(
ASYSTAT651A, Y594R1441 (T874R1657/  
Q674L1611) Trane part no. ASYSTAT651.  
Y594R1680a  
Y594R1672a  
R1771  
R1789  
115 Obsolete. Consolidated Industries part no.  
Includes CHECK LED.  
9
036100; contains T874R1962 and Q674L1843.  
120 York Canada part no. 2TH11701524; contains  
Replacement has °F  
scaleplate.  
T874R1970 and Q674L1850.  
a
Both the thermostat and subbase must be replaced.  
60-2485—8  
94  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
Table 10. Y594 Cross Reference.  
Model  
Fig.  
No.  
Trade Model  
a
Number  
Description  
Replacement  
Remarks  
a
R1797  
125 TRADELINE; contains T874R1988 and  
Y594R1797  
Q674L1868; direct replacement for Y594R1235  
(
T874R1368/Q674L1421) Evcon/Coleman part no.  
3
600-368).  
R1805  
R1813  
R1821  
R1839  
R1854  
245 Obsolete. Amana part no. 10636702; contains  
Y594R1797  
Y594R1797  
Y594R1797  
Wiring differences (old=new):  
C/X=X.  
T874R2002 and Q674L1876.  
245 Obsolete. Amana part no. 10636704; contains  
T874R2010 and Q674L1884.  
Wiring differences (old=new):  
C/X=X, W3=W2.  
125 Obsolete. York logo; part no. 2TH11703424A;  
contains T874R2028 and Q674L1918.  
134 Rudd logo; part no. 41-20796-48; contains  
T874R2036 and Q674L1504.  
See OEM for  
replacement.  
Y594R1300  
123 Obsolete. Rheem logo; part no. 41-20796-47;  
contains T874R1996 and Q674L1504.  
Y594W  
W1014  
W1022  
W1030  
54  
Contains T874W1015, Q674B1216 and  
C815A1005.  
Y594W1014  
T8611M2025.  
T8611M2025  
140 Obsolete. Rheem part no. 41-20797-19; contains  
T874W1031, Q674L1546 and C815A1005.  
68  
Obsolete. Inter-City Products part no. 1072350;  
Includes night setback.  
contains T874W1072, Q674L1835 and C815A1005 (programmable)  
Outdoor Thermistor.  
W1055  
247 Obsolete. Addison logo; part no. 843-277; contains  
T8611M2025  
T874W1106, Q674L1934 and C815A1005.  
Y594Y  
Y1004  
210 Obsolete. Mammoth part no. 71117301; contains  
T874Y1005 and Q674E1353.  
See OEM for  
replacement.  
Y1012  
248 Obsolete. WaterFurnace logo; part no. TA21H03;  
contains T874Y1013 and Q674F1675.  
a
Both the thermostat and subbase must be replaced.  
95  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
WIRING DIAGRAMS  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
HOT)  
RH  
W1  
(
HEAT RELAY 1  
HEAT RELAY 2  
L2  
1
1
H1  
FAN  
SWITCH  
FALL  
AUTO  
W2  
H1 ANTICIPATOR  
ON  
HEAT CHANGEOVER  
VALVE  
NOTE:  
Model  
ing  
Heating Cool-  
4
B
No.  
Bulbs  
H1  
Bulbs  
C1  
COOL CHANGEOVER  
VALVE  
H2  
2
T874A  
T874B  
T874C  
T874D  
T874E  
T874D  
6
8
H1  
C1,C2  
C1  
FALL  
H2 ANTICIPATOR  
SYSTEM  
SWITCH  
O
H1,H2  
H1,H2  
C1,C2  
C1,C2  
FAN RELAY  
HEAT  
OFF  
G
H1,H2  
C1  
RISE  
COMPRESSOR  
CONTACTOR 2  
9
COOL  
Y2  
1
0
COMPRESSOR  
CONTACTOR 1  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
Y1  
L2  
L1  
1
1
RC  
C2  
RISE  
(HOT)  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
1
JUMPER RH, RC FOR SINGLE TRANSFORMER.  
M2903  
Fig. 44. Schematic and hookup of T874A,B,C,D,E,F with Q674B. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
HOT)  
L2  
RH  
W1  
(
HEAT RELAY 1  
HEAT RELAY 2  
3
1
1
FAN  
SWITCH  
H1  
FALL  
AUTO  
W2  
H1 ANTICIPATOR  
ON  
HEAT CHANGEOVER  
VALVE  
4
B
H2  
X1  
6
8
FALL  
H2 ANTICIPATOR  
SYSTEM  
SWITCH  
O
COOL CHANGEOVER  
VALVE  
HEAT  
OFF  
C1  
RISE  
G
FAN RELAY  
9
2
COOL  
Y2  
COMPRESSOR  
CONTACTOR 2  
1
0
C1 ANTICIPATOR  
C2 ANTICIPATOR  
Y1  
1
1
COMPRESSOR  
CONTACTOR 1  
L2  
L1  
C2  
RC  
RISE  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
(HOT)  
1
M933C  
JUMPER RH, RC FOR SINGLE TRANSFORMER.  
3
OPTIONAL LED ON SOME MODELS.  
Fig. 45. Schematic and hookup of T874C,D with Q674B. Used in standard applications.  
60-2485—8  
96  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
HEAT RELAY 1  
1
W1  
W2  
FAN  
SWITCH  
H1  
HEAT RELAY 2  
FALL  
AUTO  
ON  
H1 ANTICIPATOR  
HEAT CHANGEOVER  
VALVE  
4
B
R
O
L1  
H2  
(HOT)  
6
8
L2  
FALL  
H2 ANTICIPATOR  
SYSTEM  
SWITCH  
1
COOL  
CHANGEOVER  
VALVE  
HEAT  
OFF  
C1  
RISE  
G
9
COOL  
FAN RELAY  
Y2  
10  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
C2  
COMPRESSOR  
CONTACTOR 2  
11  
Y1  
COMPRESSOR  
CONTACTOR 1  
RISE  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M2904  
Fig. 46. Schematic and hookup of T874A,B,D with Q674B. Used in standard applications.  
.
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
O
FAN  
SWITCH  
COOL CHANGEOVER  
VALVE  
1
2
H1/C1  
ANTICIPATOR  
AUTO  
ON  
G
H1  
C1  
FAN RELAY  
FALL  
3
4
L1  
HOT)  
R
(
L2  
SYSTEM  
SWITCH  
1
HEAT  
OFF  
5
6
W1  
AUX. HT.  
RELAY  
COOL  
H2  
FALL  
Y
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
COMPRESSOR  
CONTACTOR  
M2906  
Fig. 47. Schematic and hookup of T874R with Q674B. Used in heat pump applications.  
97  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(
HOT)  
HEAT RELAY 1  
L2  
1
W1  
G
1
H1  
FAN  
SWITCH  
FAN RELAY  
FALL  
AUTO  
ON  
H1 ANTICIPATOR  
EXTERNAL  
FAN SWITCH  
4
RC  
W2  
H2  
H2  
HEAT RELAY 2  
6
8
FALL  
ANTICIPATOR  
HEAT CHANGEOVER  
VALVE  
C1  
RISE  
B
SYSTEM  
SWITCH  
L2  
9
RH  
L1  
HEAT  
OFF  
(HOT)  
2
1
X1  
10  
FILTER  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
LED (RED)  
COOL  
O
COOL CHANGEOVER  
VALVE  
11  
C2  
RISE  
Y1  
COMPRESSOR  
CONTACTOR 1  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
Y2  
COMPRESSOR  
CONTACTOR 2  
CLOGGED FILTER, SERVICE SWITCH.  
M2905  
Fig. 48. Schematic and hookup of T874D with Q674B. Used in standard applications.  
60-2485—8  
98  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
H1  
SUBBASE  
SYSTEM COMPONENTS  
HEAT RELAY 1  
ANTICIPATOR  
1
W1  
H2  
FALL  
FAN SWITCH  
HEAT  
LED (RED)  
BLOWER RELAY  
AUTO  
ON  
G
R
4
H2 ANTICIPATOR  
L1  
(HOT)  
6
L2  
HEAT RELAY 2  
1
FALL  
H1  
W2  
T
SYSTEM  
SWITCH  
8
C1 ANTICIPATOR  
HEAT  
OFF  
9
COOL LED  
YELLOW)  
COMPRESSOR  
CONTACTOR  
(
COOL  
C1  
10  
Y1  
L
RISE  
1
HSII  
CONTROL  
PANEL  
LO SPEED  
LED (GREEN)  
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
C
HI SPEED  
LED (GREEN  
L1  
(HOT)  
L2  
H
M5945  
Fig. 49. Schematic and hookup of T874C with Q674B. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
O
H1  
COOL CHANGEOVER  
VALVE  
ANTICIPATOR  
FALL  
2
4
H1  
FAN  
SWITCH  
Y
AUTO  
COMPRESSOR  
CONTRACTOR  
ON  
FALL  
G
H2 ANTICIPATOR  
H2  
AUX. HT. RELAY  
W2  
FAN RELAY  
6
8
SYSTEM  
SWITCH  
CO  
L2  
L1  
RISE  
HEAT  
OFF  
R
9
(HOT)  
1
C1 ANTICIPATOR  
C1 RISE  
COOL  
10  
M8000  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
Fig. 50. Schematic and hookup of T874G with Q674B. Used in heat pump applications.  
99  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
FALL  
SUBBASE  
SYSTEM COMPONENTS  
HEAT RELAY 1  
W1  
H1  
1
3
FAN  
SWITCH  
FAN RELAY  
H1 ANTICIPATOR  
G
AUTO  
ON  
L1  
(HOT)  
1
L2  
RC  
4
6
2
HEAT RELAY 2  
W2  
B
FALL  
HEAT CHANGEOVER VALVE  
COOL CHANGEOVER VALVE  
H2 ANTICIPATOR  
H2  
3
SYSTEM  
SWITCH  
8
9
RH  
O
C1  
HEAT  
OFF  
RISE  
3
COOL  
C1 ANTICIPATOR  
COMPRESSOR CONTACTOR 1  
COMPRESSOR CONTACTOR 2  
1
0
Y1  
Y2  
C2 ANTICIPATOR  
RISE  
1
1
C2  
1
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.  
B, O TERMINALS ON SOME MODELS.  
L1 L2  
(HOT)  
3
M5944  
Fig. 51. Schematic and hookup of T874D with Q674B. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
W1  
H1 ANTICIPATOR  
1
FAN SWITCH  
HEAT RELAY 1  
FAN RELAY  
H1  
AUTO  
ON  
G
FALL  
L1  
RC  
(HOT)  
3
L2  
1
4
2
W3  
5
6
W2  
F
H2  
HEAT RELAY 2  
FALL  
H2 ANTICIPATOR  
SYSTEM  
SWITCH  
RH  
B
HEAT  
OFF  
8
9
COOL  
C1 RISE  
COMPRESSOR  
CONTACTOR  
O
C1 ANTICIPATOR  
Y1  
10  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
2
3
OPTIONAL FIELD WIRE JUMPER. W3 AND F TO BE JUMPERED EXCEPT FOR TWO STAGE GAS APPLICATION.  
FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.  
M5999  
Fig. 52. Schematic and hookup of T874C with Q674B. Used in standard applications.  
60-2485—8  
100  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
HEAT RELAY 1  
1
4
H1  
FAN SWITCH  
AUTO  
ANTICIPATOR  
W1  
W2  
HEAT RELAY 2  
H1  
FALL  
FALL  
RISE  
ON  
H2  
6
8
H2 ANTICIPATOR  
L1  
(HOT)  
SYSTEM  
SWITCH  
R
L2  
HEAT  
OFF  
1
C1  
9
G
COOL  
FAN RELAY  
10  
Y2  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
COMPRESSOR  
CONTACTOR 2  
11  
Y1  
C2  
RISE  
COMPRESSOR  
CONTACTOR 1  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M3202A  
Fig. 53. Schematic and hookup of T874D with Q674B. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
L1 (HOT)  
1
2
H1 ANTICIPATOR  
R
FALL  
H1  
C815A THERMISTOR  
L2  
H2 ANTICIPATOR  
H3 ANTICIPATOR  
T
FAN SWITCH  
AUTO  
FALL  
3
4
W1  
W2  
H3  
HEAT RELAY 1  
HEAT RELAY 3  
ON  
HEAT RELAY 2  
5
6
W3  
B
FALL  
H2  
SYSTEM  
SWITCH  
RESET HEATER  
HEAT CHANGEOVER VALVE  
FAN RELAY  
HEAT  
OFF  
RISE  
8
G
O
C1  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
COOL  
10  
COOL CHANGEOVER VALVE  
COMPRESSOR CONTACTOR 2  
RISE  
11  
Y2  
Y1  
C2  
1
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD PROTECTION  
AS REQUIRED.  
COMPRESSOR CONTACTOR 1  
M3674  
Fig. 54. Schematic and hookup of T874W with Q674B. Used in standard applications.  
101  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(HOT)  
RH  
B
FALL  
H1  
3
L2  
1
H1 ANTICIPATOR  
HEAT RELAY 1  
1
W1  
4
NO  
FAN  
SWITCH  
3
H2 ANTICIPATOR  
5
6
HEAT RELAY 2  
W2  
FALL  
H2  
2
8
9
COMPRESSOR  
CONTACTOR 2  
NO  
SYSTEM  
SWITCH  
C1  
Y2  
RISE  
COMPRESSOR  
CONTACTOR 1  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
Y1  
10  
L2  
C2  
RC  
L1  
RISE  
(HOT)  
11  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
JUMPER RC, RH FOR SINGLE TRANSFORMER.  
3
B AND 5 TERMINALS AVAILABLE ON SOME MODELS.  
M3667A  
Fig. 55. Schematic and hookup of T874A,D,F with Q674D. Used in standard applications.  
SUBBASE  
SYSTEM COMPONENTS  
RESET  
1
FALL  
X
FAN  
RESET  
SWITCH  
AUTO  
ON  
LED (RED)  
H1  
FAN RELAY  
G
R
H1 ANTICIPATOR  
L1  
(HOT)  
4
L2  
1
AUX. HT. RELAY  
H2 ANTICIPATOR  
6
W2  
B
SYSTEM  
SWITCH  
H2  
FALL  
8
HEAT  
OFF  
B RELAY  
O RELAY  
O
9
COOL  
C1 ANTICIPATOR  
RISE  
Y2  
C1  
10  
COMPRESSOR  
CONTACTOR 1  
11  
Y1  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M5975  
Fig. 56. Schematic and hookup of T874C with Q674B. Used in standard applications.  
60-2485—8  
102  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
Y
FALL  
H2  
FAN SWITCH  
COMPRESSOR  
CONTACTOR  
FAN RELAY  
AUTO  
ON  
1
2
G
R
L1  
(HOT)  
L2  
H1 ANTICIPATOR  
3
CLOSED-DAY  
OPEN-NITE  
B RELAY  
1
B
L
4
5
6
SYSTEM  
SWITCH  
OVERRIDE  
HEAT  
S
P
JUMPER  
2
CO  
OFF  
RISE  
H1  
COOL  
8
9
COOL CHANGEOVER  
VALVE  
W
T
RISE  
C1 ANTICIPATOR  
10  
C1  
1
2
POWERSUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED.  
M8004  
Fig. 57. Schematic and hookup of T874P with Q674B. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
2
3
4
Y
H1 ANTICIPATOR  
H1  
NO FAN  
SWITCH  
ECONOMIZER  
PACKAGE  
FALL  
FALL  
RH  
Y
O
O
H2 ANTICIPATOR  
C1 ANTICIPATOR  
6
W
W2  
H2  
8
9
NO SYSTEM  
SWITCH  
RISE  
B
CO  
10  
RC  
O
CONTROL  
PANEL  
C1  
M3722  
RISE  
Fig. 58. Schematic and hookup of T874G with Q674D. Used in standard applications.  
103  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
H1  
SUBBASE  
SYSTEM COMPONENTS  
1
W1  
B
ANTICIPATOR  
SYSTEM  
SWITCH  
HEAT  
RELAY 1  
HEAT  
OFF  
4
COOL  
1
FALL  
L1  
(HOT)  
R
H1  
FAN  
SWITCH  
L2  
8
RISE  
C1  
G1  
L2  
L1  
C1  
LO  
9
K1 RELAY  
MED  
HIGH  
ON  
G2  
O
K1  
K2  
K1  
K2  
ANTICIPATOR  
10  
K2 RELAY  
K2  
HI  
MED  
LO  
Y1  
3
SPEED FAN  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
COMPRESSOR  
CONTACTOR  
SCHEMATIC  
M3729  
Fig. 59. Schematic and hookup of T874A with Q674Q. Used in fan coil applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(HOT) L2  
1
H1 ANTICIPATOR  
1
W1  
G
FAN  
SWITCH  
COOL RELAY  
CONTACT  
FAN RELAY  
AUTO  
FALL  
H1  
ON  
4
R
6
ELEC. HT. RELAY  
FALL  
SYSTEM  
SWITCH  
H2 ANTICIPATOR  
W2  
H2  
EVAP  
COOL  
CHANGEOVER  
VALVE  
8
9
B
OFF  
RISE  
COMPRESSOR  
CONTACTOR  
HEAT  
C1  
Y1  
Y2  
C1 ANTICIPATOR  
EVAPORATOR  
RELAY  
10  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M2863  
Fig. 60. Schematic and hookup of T874C with Q674N. Used in evaporative cooler applications.  
60-2485—8  
104  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
FALL  
SUBBASE  
SYSTEM COMPONENTS  
COMPRESSOR  
CONTACTOR  
Y1  
H1  
1
FAN RELAY  
G
H1 ANTICIPATOR  
FAN  
SWITCH  
4
AUTO  
ON  
1
L1  
HOT)  
L2  
FALL H2  
ANTICIPATOR  
R
(
6
H2  
ELEC. HT. RELAY  
W2  
Y2  
O
RISE  
8
EVAPORATOR  
RELAY  
SYSTEM  
SWITCH  
C1  
EVAP.  
9
COOL  
OFF  
CHANGEOVER  
RELAY  
10  
HEAT  
C1  
ANTICIPATOR  
M2862  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
Fig. 61. Schematic and hookup of T874C with Q674N. Used in evaporative cooler applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
FAN RELAY  
FAN SWITCH  
AUTO  
G
FALL  
H2  
ON  
1
4
W2  
H2 ANTICIPATOR  
AUX. HT. RELAY  
R
C
YELLOW  
GREEN  
WOOD/COAL  
RELAY  
FALL  
H1  
SYSTEM  
SWITCH  
8
9
W1  
X2  
HEAT  
OFF  
COMPRESSOR  
CONTACTOR  
COOL  
H1 ANTICIPATOR  
EXTERNAL COOLING  
THERMOSTAT  
(SUCH AS T87 F)  
L2  
L1  
10  
(HOT)  
1
X1  
Y
R
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
M3723A  
Fig. 62. Schematic and hookup of T874F with Q674B. Used in wood/coal applications.  
105  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
NO FAN  
SWITCH  
AUX. HT. RELAY  
FALL  
H2  
1
4
W2  
R
1
H2 ANTICIPATOR  
L1  
(HOT)  
YELLOW  
NO  
SYSTEM  
SWITCH  
L2  
C
HEAT/COOL  
SWITCH  
FALL  
H1  
GREEN  
8
9
W1  
WOOD/COAL  
RELAY  
H1 ANTICIPATOR  
10  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M3725  
Fig. 63. Schematic and hookup of T874F with Q674D. Used in wood/coal applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENT  
1
W1  
B
HEAT RELAY 1  
H1  
ANTICIPATOR  
SYSTEM  
SWITCH  
B RELAY  
HEAT  
OFF  
COOL  
H1  
2
FALL  
1
2
3
4
L1  
R
(HOT)  
L2  
FAN  
K1 RELAY  
SWITCH  
G1  
L2  
L1  
5
LO  
C1  
ANTICIPATOR  
MED  
HIGH  
ON  
K2 RELAY  
K1  
K1  
K2  
G2  
RISE  
C1  
O RELAY  
K2  
K2  
O
COMPRESSOR CONTACTOR  
HI  
LO  
Y1  
MED  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
SINGLE SETPOINT LEVER AND BIMETAL.  
3-SPEED FAN SCHEMATIC  
M8005  
Fig. 64. Schematic and hookup of T874A with Q674Q. Used in fan coil applications.  
60-2485—8  
106  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
W1  
NO. 1 HEAT RELAY  
AUTO  
SWITCH  
FAN  
ON  
W2  
H1 ANTICIPATOR  
FALL  
4
B
HEAT DAMPER  
6
L1  
(HOT)  
RH  
H1  
L2  
8
9
L1  
RC  
(HOT)  
COOL DAMPER  
FAN RELAY  
L2  
SYSTEM  
SWITCH  
1
O
G
HEAT  
RISE  
C1  
OFF  
10  
C1  
COOL  
ANTICIPATOR  
11  
Y2  
NO. 1 COMP. RELAY  
Y1  
FILTER  
LED (RED)  
X1  
X2  
SERVICE LED  
YELLOW)  
(
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M5976  
Fig. 65. Schematic and hookup of T874A with Q674B. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
HEAT RELAY 1  
1
4
W1  
H1 ANTICIPATOR  
NO FAN  
SWITCH  
HEAT RELAY 2  
FALL  
W2  
RH  
H1  
5
6
L1  
(HOT)  
FALL  
H2  
NO SYSTEM  
SWITCH  
L2  
1
H2 ANTICIPATOR  
8
9
L1  
RC  
Y2  
Y1  
(HOT)  
L2  
1
10  
11  
M7011  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
Fig. 66. Schematic and hookup of T874A,D,F with Q674D. Used in standard applications.  
107  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
FAN RELAY  
1
2
X
FAN SWITCH  
G
H1  
AUTO  
ON  
C1  
H1/C1 ANTICIPATOR  
3
L1  
(HOT)  
FALL  
R
1
L2  
4
5
HEAT CHANGEOVER  
VALVE  
SYSTEM  
SWITCH  
B
FALL  
H2  
W2  
HEAT  
AUX. HT. RELAY  
6
OFF  
COOL  
COMPRESSOR  
CONTACTOR  
Y
M5998  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
Fig. 67. Schematic and hookup of T874R with Q674B. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
Y
H1  
3
H2  
ANTICIPATOR  
COMPRESSOR CONTACTOR  
2
3
G
FALL  
FAN  
SWITCH  
FAN RELAY  
C
4
5
CLOSED-DAY  
OPEN-NITE  
AUTO  
ON  
L2  
RISE  
L1  
(HOT)  
1
R
CO  
6
8
OVERRIDE  
LED (RED)  
H1  
SERVICE  
LED (RED)  
C1  
B
L
SYSTEM SWITCH  
OVERRIDE  
RISE  
B RELAY  
X
9
HEAT  
OFF  
S
COMPRESSOR  
FAULT  
C1 ANTICIPATOR  
10  
COOL  
2
JUMPER  
1
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD PROTECTION  
AS REQUIRED.  
P
W
T
COOL CHANGEOVER VALVE  
2
3
JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED.  
H2 MAKE OFFEST 8˚ F BELOW H1 MAKE.  
M101A  
Fig. 68. Schematic and hookup of T874P with Q674B. Used in heat pump applications.  
60-2485—8  
108  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
FAN SWITCH  
LO  
AUTO  
Z RELAY  
HI  
Z
CONT.  
G
SYSTEM SWITCH  
OFF  
FAN RELAY  
RISE  
C1  
COOL  
R
L1  
(HOT)  
8
9
1
L2  
COOL RELAY  
10  
C1 ANTICIPATOR  
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
Y
1
M107A  
Fig. 69. Schematic and hookup of T874V with Q674R. Used in fan coil applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
S
NO FAN  
SWITCH  
SERVICE  
LED (RED)  
H1  
FALL  
COMPRESSOR  
FAULT  
4
6
W2  
SYSTEM  
SWITCH  
H2  
AUX. HT. RELAY  
FALL  
1
8
9
HEAT  
COOL  
L2  
L1  
R
Y
(HOT)  
H1  
1
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
COMPRESSOR  
CONTACTOR  
FALL  
M1402A  
Fig. 70. Schematic and hookup of T874C with Q674S. Used in heat pump applications.  
109  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
FAN SWITCH  
AUTO  
1
4
L1  
(HOT)  
H1  
RH  
W1  
CHECK  
3
ANTICIPATOR  
HEAT RELAY 1  
HEAT RELAY 2  
L2  
1
ON  
H1  
FALL  
W2  
X1  
H2  
6
8
FALL  
H2 ANTICIPATOR  
SYSTEM  
SWITCH  
HEAT  
AUTO  
COOL  
G
RISE  
C1  
9
FAN RELAY  
2
10  
Y2  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
COMPRESSOR  
CONTACTOR 2  
Y1  
11  
COMPRESSOR  
CONTACTOR 1  
L2  
L1  
C2  
RC  
RISE  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
(HOT)  
1
M932B  
JUMPER RH, RC FOR SINGLE TRANSFORMER.  
3
OPTIONAL LED ON SOME MODELS.  
Fig. 71. Schematic and hookup of T874A-D with Q674A. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(HOT)  
L2  
RH  
W1  
H1 ANTICIPATOR  
1
FAN  
2
1
SWITCH  
HEAT RELAY 1  
AUTO  
ON  
FALL  
W2  
B
H1  
HEAT RELAY 2  
HEAT DAMPER  
COOL DAMPER  
4
6
3
H2 ANTICIPATOR  
O
H2  
FALL  
SYSTEM  
SWITCH  
8
9
G
RISE  
C1  
OFF  
FAN RELAY  
AUTO  
Y2  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
10  
COMPRESSOR  
CONTACTOR 2  
Y1  
1
1
1
COMPRESSOR  
CONTACTOR 1  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
L2  
C2  
RISE  
2
L1  
RC  
(HOT)  
2
3
JUMPER TERMINALS RC-RH FOR SINGLE SYSTEM TRANSFORMER ONLY.  
B,O TERMINALS ON SOME MODELS.  
M5122A  
Fig. 72. Schematic and hookup of T874D,E,F with Q674C. Used in standard applications.  
60-2485—8  
110  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
H ANTICIPATOR  
SUBBASE  
SYSTEM COMPONENTS  
2
Y1  
Y2  
G
H1  
REVERSING  
VALVE RELAY  
FALL  
3
4
FAN SWITCH  
AUTO  
COMPRESSOR  
CONTACTOR  
SETBACK  
ON  
FALL  
FAN RELAY  
6
8
SYSTEM  
SWITCH  
L2  
9
OPEN-NIGHT  
CLOSED-DAY  
L1  
(HOT)  
CO  
1
OFF  
RISE  
RISE  
R
L
1
0
AUTO  
SETBACK  
RELAY  
C ANTICIPATOR  
C1  
M7008  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
Fig. 73. Schematic and hookup of T874G with Q674C. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
2
3
4
Y1  
H1  
ANTICIPATOR  
COOL CHANGEOVER  
VALVE  
FALL  
H1  
FAN SWITCH  
AUTO  
FAN RELAY  
G
R
ON  
Y2  
SYSTEM  
SWITCH  
8
9
COMPRESSOR  
CONTACTOR  
OFF  
RISE  
B
AUTO  
C1  
ANTICIPATOR  
CO  
1
10  
O
X
L1  
L2  
HOT)  
(
2
RISE  
C1  
SERVICE LED  
YELLOW)  
COMPRESSOR  
FAULT  
(
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
C
SERVICE LED ON SELECT MODELS.  
M3680A  
Fig. 74. Schematic and hookup of T874H with Q674C. Used in heat pump applications.  
111  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
HEAT RELAY  
H1  
1
W1  
ANTICIPATOR  
SYSTEM SWITCH  
OFF  
FILTER LED  
YELLOW)  
(
3
X
A
AUTO  
4
8
FAN SWITCH  
SERVICE  
LED (RED)  
H1  
FALL  
FAN RELAY  
AUTO  
G
R
1
ON  
2
L1  
(HOT)  
RISE  
L2  
9
O
MOMENTARY  
CIRCUIT  
C1  
C1  
ANTICIPATOR  
O
Y
10  
COMPRESSOR CONTACTOR  
T
11  
EXTERNAL  
TEMP.  
THERMISTOR  
READOUT  
12  
T
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE.  
FILTER LED ON SELECT MODELS.  
3
M5731  
Fig. 75. Schematic and hookup of T874A with Q674C. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
W1  
W2  
1
FAN  
SWITCH  
HEAT RELAY 2  
H1 ANTICIPATOR  
FALL  
HEAT RELAY 1  
AUTO  
ON  
HEAT CHANGEOVER  
VALVE  
H1  
B
4
6
L2  
L1  
1
FALL  
RH  
(HOT)  
H2 ANTICIPATOR  
L1  
(HOT)  
H2  
RC  
8
COOL CHANGEOVER  
VALVE  
L2  
1
C1  
O
G
SYSTEM  
SWITCH  
RISE  
9
OFF  
FAN RELAY  
AUTO  
Y2  
1
0
COMPRESSOR  
CONTACTOR 1  
C1 ANTICIPATOR  
COMPRESSOR  
CONTACTOR 2  
RISE  
11  
Y1  
X
C2  
FILTER  
LED (YEL)  
3
C2 ANTICIPATOR  
2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
SERVICE  
LED (RED)  
A
2
FOR T874C, DELETE C2.  
3
FILTER LED ON SELECT MODELS.  
M7025  
Fig. 76. Schematic and hookup of T874A-D with Q674C. Used in standard applications.  
60-2485—8  
112  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
3
FAN  
SWITCH  
RESET  
LED (RED)  
X1  
FALL  
FAN RELAY  
CO  
AUTO  
ON  
G
H2  
FALL  
FALL  
L1  
RH  
(HOT)  
4
6
L2  
1
2
HEAT CHANGEOVER  
VALVE  
H1  
H1 ANTICIPATOR  
W1  
W3  
HEAT RELAY 2  
8
9
HEAT RELAY 1  
RISE  
SYSTEM  
SWITCH  
C1  
W2  
B
"
B" RELAY  
OFF  
C1  
AUTO  
ANTICIPATOR  
L1  
HOT)  
10  
RC  
(
1
L2  
1
2
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD PROTECTION  
AS REQUIRED.  
"
O" RELAY  
O
JUMPER RH AND RC FOR SINGLE  
TRANSFORMER SYSTEM.  
COMPRESSOR  
CONTACTOR  
Y1  
M4729  
Fig. 77. Schematic and hookup of T874K with Q674C. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
Y
1
2
FAN  
SWITCH  
COMPRESSOR  
CONTACTOR  
FALL  
H2  
AUTO  
G
H1  
ON  
ANTICIPATOR  
FAN RELAY  
3
4
C
R
L1  
(HOT)  
SETBACK  
CONTACT  
L2  
1
5
6
SYSTEM  
SWITCH  
B
CO  
OVERRIDE  
AUTO  
HEAT  
CHANGEOVER  
VALVE  
H1  
RISE  
8
9
L
OFF  
JUMPER  
2
S
C1  
C1  
ANTICIPATOR  
REVERSING  
VALVE  
10  
P
RISE  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
W
M7026  
JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED.  
Fig. 78. Schematic and hookup of T874P with Q674C. Used in heat pump applications.  
113  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
RESET  
X
1
FAN  
SWITCH  
RESET  
LED (RED)  
H1 ANTICIPATOR  
FALL  
G
AUTO  
ON  
FAN RELAY  
H1  
4
6
L1  
(HOT)  
R1  
SETBACK  
CONTACT  
L2  
1
H2  
2
FALL  
3
R2  
8
9
COOL  
CHANGEOVER  
VALVE  
CO  
SYSTEM  
SWITCH  
O
Y
C1  
ANTICIPATOR  
OFF  
COMPRESSOR  
CONTACTOR  
RISE  
10  
AUTO  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
RISE  
C1  
SETBACK CONTACT ON Q674C1124.  
3
H2 ON T874G.  
M7027  
Fig. 79. Schematic and hookup of T874G,H with Q674C. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
W1  
Y1  
FALL  
H1  
1
4
HEAT  
RELAY 1  
CONTACTOR  
COMPRESSOR 1  
H1 ANTICIPATOR  
FAN SWITCH  
AUTO  
G
ON  
FAN RELAY  
RC  
H2 ANTICIPATOR  
FALL  
HEAT RELAY 2  
2
6
W2  
RH  
H2  
C1  
SYSTEM  
SWITCH  
OFF  
L1  
(HOT)  
8
9
HEAT  
L2  
RISE  
1
AUTO  
COOL  
C
SERVICE  
LED (RED)  
C1 ANTICIPATOR  
Z
10  
COMPRESSOR  
FAULT  
COMPRESSOR  
CONTACTOR 2  
C2 ANTICIPATOR  
11  
Y2  
C2  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
OPTIONAL FIELDWIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.  
RISE  
M5997  
Fig. 80. Schematic and hookup of T874D with Q674E. Used in standard applications.  
60-2485—8  
114  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
CHANGEOVER  
RELAY  
FALL  
H1  
1
4
W1  
B
FAN  
SWITCH  
FAN  
RELAY  
AUTO  
ON  
FALL  
G
R
6
8
9
H2 ANTICIPATOR  
H2  
C1  
SYSTEM  
SWITCH  
COMPRESSOR  
CONTACTOR  
RISE  
W2  
Y1  
OFF  
AUTO  
C1 ANTICIPATOR  
10  
1
1
POWER SUPPLY. PROVIDE DISCONECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
L1 L2  
HOT)  
M5981  
(
Fig. 81. Schematic and hookup of T874C with Q674C. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
RH  
W1  
(HOT)  
FALL  
H1  
HEAT RELAY 1  
L2  
1
FAN  
SWITCH  
1
H1 ANTICIPATOR  
AUTO  
2
HEAT RELAY 2  
ON  
4
W2  
O
H2 ANTICIPATOR  
FALL  
6
8
3
H2  
B
SYSTEM  
SWITCH  
FAN RELAY  
RISE  
G
C1  
OFF  
HEAT  
AUTO  
COOL  
9
COMPRESSOR  
CONTACTOR 2  
C1  
ANTICIPATOR  
10  
Y2  
COMPRESSOR  
CONTACTOR 1  
C2 ANTICIPATOR  
11  
Y1  
1
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD PROTECTION  
AS REQUIRED.  
L2  
L1  
1
C2  
RC  
RISE  
(HOT)  
2
3
JUMPER RC, RH FOR SINGLE TRANSFORMER.  
O AND B TERMINALS ON SELECTED MODELS.  
M934  
Fig. 82. Schematic and hookup of T874A,C,D with Q674E. Used in standard applications.  
115  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
1
(HOT)  
L2  
H1 ANTICIPATOR  
HEAT RELAY 1  
1
W1  
FALL  
COMPRESSOR  
CONTACTOR 1  
H1  
Y1  
G
FAN  
SWITCH  
4
FAN RELAY  
AUTO  
H2 ANTICIPATOR  
ON  
RC  
W2  
FALL  
HEAT RELAY 2  
6
H2  
8
RISE  
RH  
C1  
OFF  
CHECK LED  
RED)  
(
9
HEAT  
X1  
Y2  
COMPRESSOR  
CONTACTOR 2  
AUTO  
C1 ANTICIPATOR  
10  
COOL  
C2 ANTICIPATOR  
11  
L2  
L1  
1
RISE  
1
POWER SUPPLY. PROVIDE DISCONECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
C2  
(HOT)  
M5982  
Fig. 83. Schematic and hookup of T874G with Q674C. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
R
H1 ANTICIPATOR  
COOL  
CHANGEOVER  
VALVE  
OUTDOOR  
FAN RELAY  
2
FAN  
SWITCH  
FALL  
DEFROST  
SWITCH  
H1  
DEFROST  
RELAY  
AUTO  
ON  
4
M
F
HIGH PRESSURE  
SWITCH  
COMPRESSOR  
CONTACTOR  
H2 ANTICIPATOR  
FALL  
6
8
FAN RELAY  
DEFROST  
RELAY  
H2  
SYSTEM  
SWITCH  
V
Y
C1 ANTICIPATOR  
9
OFF  
CO  
DEFROST  
RELAY  
AUX. HT.  
RELAY  
RISE  
HEAT  
AUTO  
COOL  
10  
RISE  
L2  
1
C1  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
L1  
HOT)  
(
M4666  
Fig. 84. Schematic and hookup of T874G with Q674E. Used in heat pump applications.  
60-2485—8  
116  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
HEAT RELAY 1  
1
W1  
Y1  
H1  
ANTICIPATOR  
COMPRESSOR  
CONTACTOR 1  
H1  
FALL  
FAN  
4
6
SWITCH  
FAN RELAY  
AUTO  
ON  
G
R
FALL  
L1  
(HOT)  
H2 ANTICIPATOR  
H2  
L2  
1
8
9
SYSTEM  
SWITCH  
RISE  
C1  
OFF  
HEAT  
AUTO  
COOL  
HEAT RELAY 2  
C1  
W2  
Y2  
ANTICIPATOR  
10  
COMPRESSOR  
CONTACTOR 2  
C2 ANTICIPATOR  
RISE  
11  
C2  
1
POWER SUPPLY. PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M5983  
Fig. 85. Schematic and hookup of T874A-D with Q674E. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(
HOT)  
1
L2  
H1 ANTICIPATOR  
1
2
R
COOL  
CHANGEOVER  
VALVE  
FAN  
D. F. O.  
SWITCH  
FALL  
AUTO  
H1  
ON  
3
DEFROST  
SWITCH  
DEFROST  
RELAY  
M
5
6
FALL  
H2  
HIGH  
PRESSURE  
SWITCH  
COMPRESSOR  
CONTACTOR  
H2 ANTICIPATOR  
F
V
8
SYSTEM  
SWITCH  
FAN RELAY  
OFF  
C1 ANTICIPATOR  
DEFROST RELAY  
CONTACT  
AUX. HT. RELAY  
RISE  
HEAT  
Y
9
CO  
DEFROST RELAY  
CONTACT  
AUTO  
COOL  
10  
1
L2  
C1  
RISE  
VR  
L1  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
M4667 (HOT)  
Fig. 86. Schematic and hookup of T874G with Q674E. Used in heat pump applications.  
117  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
W1  
Y1  
HEAT RELAY 1  
H1  
FALL  
FAN  
SWITCH  
COMPRESSOR  
CONTACTOR 1  
H1 ANTICIPATOR  
AUTO  
ON  
G
4
6
FAN RELAY  
L1  
(HOT)  
RC  
1
L2  
H2 ANTICIPATOR  
FALL  
W2  
B
H2  
HEAT RELAY 2  
SYSTEM  
SWITCH  
2
RISE  
OFF  
8
9
RH  
X
HEAT  
C1  
L2  
L1  
1
AUTO  
COOL  
SYSTEM  
FAULT CONTACT  
(HOT)  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
C
RISE  
C2  
COMPRESSOR  
CONTACTOR 2  
10  
LOCKOUT LED  
(RED)  
11  
Y2  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
FIELDWIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.  
M4668  
Fig. 87. Schematic and hookup of T874D with Q674E. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
W1  
G
FAN  
SWITCH  
H1  
ANTICIPATOR  
HEAT RELAY 1  
1
FALL  
H1  
AUTO  
ON  
FAN RELAY  
4
6
L1  
(HOT)  
RC  
W2  
L2  
FALL H2 ANTICIPATOR  
H2  
HEAT RELAY 2  
SYSTEM  
SWITCH  
RISE  
OFF  
8
9
RH  
C1  
HEAT  
L2  
1
AUTO  
COOL  
L1  
(HOT)  
X
C1 ANTICIPATOR  
HIGH LED (RED)  
RISE  
C2  
1
0
C2 ANTICIPATOR  
11  
Y2  
COMPRESSOR  
CONTACTOR 2  
1
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
LOW LED (GREEN)  
COMPRESSOR  
CONTACTOR 1  
M4669  
Y1  
Fig. 88. Schematic and hookup of T874B,D with Q674E. Used in standard applications.  
60-2485—8  
118  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
B
HEAT  
1
RELAY 1  
HEAT CHANGEOVER  
VALVE  
H1 ANTICIPATOR  
FALL  
W1  
AUTO  
ON  
COMPRESSOR  
CONTACTOR 1  
FAN  
SWITCH  
H1  
Y1  
G
4
6
FAN RELAY  
L1  
H2 ANTICIPATOR  
RC  
(HOT)  
H2  
HEAT RELAY 2  
FALL  
L2  
1
SYSTEM  
SWITCH  
8
9
W2  
RH  
C1  
L1  
(HOT)  
OFF  
FILTER  
LED (YEL)  
HEAT  
AUTO  
COOL  
L2  
1
RISE  
X
SERVICE  
LED (RED)  
10  
COMPRESSOR  
CONTACTOR 2  
A
C1 ANTICIPATOR  
C2 ANTICIPATOR  
1
1
1
Y2  
COOL CHANGEOVER  
VALVE  
C2  
RISE  
O
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M7023  
Fig. 89. Schematic and hookup of T874D with Q674E. Used in standard applications.  
THERMOSTAT  
SUBBASE  
FILTER LED (YEL)  
SERVICE  
SYSTEM COMPONENTS  
X2  
A2  
1
4
H1 ANTICIPATOR  
FALL  
LED (RED)  
HEAT RELAY 1  
W1  
H1  
FILTER  
LED (YEL)  
NO FAN  
SWITCH  
X1  
SERVICE  
LED (RED)  
5
6
A1  
W2  
T RELAY  
H2 ANTICIPATOR  
HEAT RELAY 2  
T
FALL  
RISE  
H2  
7
8
L1  
RC  
(HOT)  
HEAT  
CHANGEOVER  
VALVE  
SYSTEM  
SWITCH  
L2  
1
OFF  
C1  
B
AUTO  
L1  
(HOT)  
9
RH  
COOL  
CHANGEOVER  
VALVE  
L2  
1
10  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
O
COMPRESSOR  
CONTACTOR 2  
1
1
Y2  
COMPRESSOR  
CONTACTOR 1  
C2  
RISE  
12  
Y1  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M7022  
Fig. 90. Schematic and hookup of T874D with Q674G. Used in standard applications.  
119  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
4
L1  
HOT)  
L2  
H1  
RH  
W1  
(
NO FAN  
SWITCH  
ANTICIPATOR  
HEAT RELAY 1  
HEAT RELAY 2  
1
H1  
FALL  
W2  
B
H2  
6
8
FALL  
H2 ANTICIPATOR  
SYSTEM  
SWITCH  
HEAT DAMPER  
COOL DAMPER  
OFF  
O
RISE  
C1  
AUTO  
9
2
Y2  
10  
COMPRESSOR  
CONTACTOR 2  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
Y1  
11  
COMPRESSOR  
CONTACTOR 1  
L2  
L1  
C2  
RC  
RISE  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
(HOT)  
1
M3201B  
JUMPER RH, RC FOR SINGLE TRANSFORMER.  
Fig. 91. Schematic and hookup of T874A-F,Q with Q674G. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
H1 ANTICIPATOR  
1
W1  
NO FAN  
SWITCH  
3
CHANGEOVER  
RELAY  
FALL  
B
H1  
4
6
W2  
H2 ANTICIPATOR  
FAN RELAY  
G
FALL  
H2  
SYSTEM  
SWITCH  
OFF  
Y1  
8
9
COMPRESSOR  
CONTACTOR  
1
L2  
AUTO  
C1  
R
L1  
(
HOT)  
C1 ANTICIPATOR  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
10  
M6008A  
RISE  
Fig. 92. Schematic and hookup of T874C with Q674G. Used in heat pump applications.  
60-2485—8  
120  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
HEAT FAN RELAY  
FALL  
H1  
1
W1  
NO FAN  
SWITCH  
H1 ANTICIPATOR  
HEAT RELAY  
4
6
W2  
RH  
H2  
ANTICIPATOR  
L1  
(HOT)  
H2  
FALL  
RISE  
SYSTEM  
SWITCH  
L2  
1
8
OFF  
HEAT  
COMPRESSOR  
CONTACTOR 1  
C1  
AUTO  
COOL  
Y1  
9
C1 ANTICIPATOR  
L1  
10  
RC  
(HOT)  
L2  
1
C2 ANTICIPATOR  
RISE  
11  
Y2  
COMPRESSOR  
CONTACTOR 2  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
C2  
M4664  
Fig. 93. Schematic and hookup of T874D with Q674K. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
B
1
NO FAN  
SWITCH  
H1 ANTICIPATOR  
FALL  
HEAT CHANGEOVER  
VALVE  
W1  
HEAT  
H1  
RELAY 2  
HEAT  
RELAY 1  
4
6
W2  
RH  
L2  
1
L1  
(HOT)  
H2 ANTICIPATOR  
H2  
FALL  
L1  
(HOT)  
RC  
FILTER  
8
9
L2  
1
LED (YELLOW)  
C1  
X
SYSTEM  
SWITCH  
RISE  
A
COMPRESSOR  
CONTACTOR 1  
SERVICE  
LED (RED)  
OFF  
AUTO  
Y1  
COMPRESSOR  
CONTACTOR 2  
10  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
Y2  
11  
COOL CHANGEOVER  
VALVE  
O
T
C2  
RISE  
"T" RELAY  
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
1
M7013  
Fig. 94. Schematic and hookup of T874D with Q674G. Used in standard applications.  
121  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTATS  
SUBBASE  
SYSTEM COMPONENTS  
L1  
1
R
(HOT)  
NO FAN  
SWITCH  
FALL  
L2  
1
H1 ANTICIPATOR  
2
H1  
3
OIL RELAY  
4
5
SYSTEM  
SWITCH  
W2  
OFF  
OIL LED  
(RED)  
FALL  
WOOD  
X
WOOD/OIL  
OIL  
WOOD LED  
(GREEN)  
H2  
H2 ANTICIPATOR  
WOOD RELAY  
W1  
6
1
POWER SUPPLY. PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M5984  
Fig. 95. Schematic and hookup of T874F with Q674K. Used in wood/oil applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
W1  
W2  
FAN SWITCH  
AUTO  
H1  
NO. 1 HEAT RELAY  
FALL  
HEAT  
DAMPER  
NO. 2  
HEAT RELAY  
ON  
4
B
6
FALL  
L2  
H2 ANTICIPATOR  
8
H2  
SYSTEM  
SWITCH  
RH  
RC  
L1  
(HOT)  
1
C1  
OFF  
RISE  
AUTO  
9
O
G
FAN RELAY  
10  
COOL DAMPER  
C1 ANTICIPATOR  
NO. 1 COMPRESSOR  
CONTACTOR  
11  
Y2  
Y1  
ON LED  
YELLOW)  
(
X
A
SERVICE  
LED (RED)  
L2  
L1  
1
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
(HOT)  
C
M104A  
Fig. 96. Schematic and hookup of T874C with Q674C. Used in standard applications.  
60-2485—8  
122  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
2
Y
3
H2  
COMPRESSOR CONTACTOR  
H1  
FALL  
G
ANTICIPATOR  
FAN  
SWITCH  
FAN RELAY  
3
4
C
R
CLOSED-DAY  
OPEN-NITE  
AUTO  
ON  
L2  
5
6
L1  
(HOT)  
1
OVERRIDE  
LED (RED)  
RISE  
CO  
SERVICE  
LED (RED)  
H1  
B
SYSTEM SWITCH  
B RELAY  
8
9
L
C1  
OVERRIDE  
AUTO  
RISE  
X
COMPRESSURE FAILURE  
S
OFF  
2
JUMPER  
P
10  
W
C1 ANTICIPATOR  
COOL CHANGEOVER VALVE  
1
2
3
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
JUMPER HONEYWELL SUPPLIED, FIELD INSTALLED.  
M100A  
H2 MAKE OFFEST 8˚ F BELOW H1 MAKE.  
Fig. 97. Schematic and hookup of T874P with Q674C. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
SERVICE  
LED (RED)  
A
SYSTEM MONITOR  
W1  
W2  
1
FAN  
SWITCH  
HEAT RELAY 2  
H1 ANTICIPATOR  
FALL  
HEAT RELAY 1  
AUTO  
ON  
CHANGEOVER  
RELAY  
H1  
B
4
6
L2  
L1  
1
FALL  
RH  
(HOT)  
SYSTEM  
SWITCH  
H2 ANTICIPATOR  
L1  
(HOT)  
H2  
RC  
8
CHANGEOVER  
RELAY  
L2  
1
C1  
OFF  
HEAT  
AUTO  
COOL  
O
G
RISE  
9
FAN RELAY  
Y2  
Y1  
10  
COMPRESSOR  
CONTACTOR 1  
C1 ANTICIPATOR  
COMPRESSOR  
CONTACTOR 2  
RISE  
11  
C2  
C2 ANTICIPATOR  
2
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
T874A IS SINGLE-STAGE (NO W2 OR Y2).  
M5106A  
Fig. 98. Schematic and hookup of T874D with Q674E. Used in standard applications.  
123  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
HEAT RELAY 1  
H1 ANTICIPATOR  
1
W1  
W2  
3
SYSTEM  
SWITCH  
2
4
HEAT RELAY 2  
OFF  
FALL  
H1  
AUTO  
5
6
W3  
Y2  
4
H2 ANTICIPATOR  
FALL  
SERVICE  
LED (RED)  
FAN  
SWITCH  
A
H2  
7
8
AUTO  
G
R
C1  
L2  
ON  
2
FAN RELAY  
9
L1  
(HOT)  
RISE  
3
C1 ANTICIPATOR  
1
10  
MOMENTARY  
CIRCUIT  
O
COMPRESSOR RELAY  
Y1  
5
THERMISTER  
11  
T
T
EXTERNAL  
TEMP.  
READOUT  
12  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
4
5
H3 OFFSET 12°F FROM H2 FOR NIGHT SETBACK.  
2
3
MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE.  
H1 AND C1 ARE DPST SWITCHES.  
THERMISTOR INTERNAL TO THERMOSTAT.  
M531  
Fig. 99. Schematic and hookup of T874C with Q674C. Used in standard applications.  
60-2485—8  
124  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
H1 ANTICIPATOR  
1
W1  
HEAT RELAY 1  
3
SYSTEM  
SWITCH  
2
4
HEAT RELAY 2  
OFF  
FALL  
W2  
H1  
AUTO  
HEAT RELAY 3  
5
6
W3  
Y2  
FALL  
H3  
4
COMPRESSOR  
CONTACTOR 2  
H2 ANTICIPATOR  
SERVICE  
LED (RED)  
FAN  
SWITCH  
A
FALL  
C2  
H2  
3
ANTICIPATOR  
AUTO  
7
8
G
R
L2  
ON  
2
FAN RELAY  
C1  
L1  
(HOT)  
1
9
MOMENTARY  
CIRCUIT  
RISE  
RISE  
O
C2  
COMPRESSOR RELAY  
Y1  
10  
C2 ANTICIPATOR  
5
THERMISTER  
1
1
T
T
EXTERNAL  
TEMP.  
READOUT  
12  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
4
5
H3 OFFSET 12°F FROM H2 FOR NIGHT SETBACK.  
2
3
MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE.  
H1 AND C1 ARE DPST SWITCHES.  
THERMISTOR INTERNAL TO THERMOSTAT.  
M532  
Fig. 100. Schematic and hookup of T874W with Q674C. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
COOL CHANGEOVER  
VALVE  
2
O
G
R
AUTO  
ON  
H1/C1  
ANTICIPATOR  
H1  
FALL  
C1  
FAN RELAY  
L1  
(HOT)  
FAN SWITCH  
3
L2  
1
4
5
W
SYSTEM  
SWITCH  
AUX. HT. RELAY  
X
H2  
6
H2  
EM. HT.  
LED (RED)  
EM. HT.  
HEAT  
FALL  
ANTICIPATOR  
B
OFF  
COMPRESSOR  
CONTACTOR  
1
POWER SUPPLY. PROVIDE  
DISCONNECT MEANS AND  
OVERLOAD PROTECTION  
AS REQUIRED.  
COOL  
M3718A  
Y
Fig. 101. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
125  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
HIGH  
PRESSURE  
THERMOSTAT SWITCH  
COMPRESSOR OVERLOAD  
CONTACTOR  
SWITCH  
INTERNAL  
1
M
F
H1/C1  
ANTICIPATOR  
FAN  
SWITCH  
FALL  
2
AUTO  
FAN RELAY  
H1  
ON  
C1  
V
Y
3
4
OUTDOOR  
THERMOSTAT  
SUPPL. ELEC.  
HT. RELAY  
5
6
EM. HT.  
RELAY CONTACT  
TIME DELAY  
FAN RELAY  
FALL  
H2  
2
H2 ANTICIPATOR  
EM. HT. RELAY  
E
SYSTEM  
SWITCH  
7
EM. HT.  
HEAT  
OFF  
EM. HT.  
LED (RED)  
1
2
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD PROTECTION  
AS REQUIRED.  
X
VR  
R
FIELD WIRE JUMPER TO ALLOW SINGLE  
SYSTEM TRANSFORMER.  
COOL  
COOL CHANGEOVER  
VALVE  
L1 L2  
HOT)  
L1 L2  
(HOT)  
1
1
M4726  
(
Fig. 102. Schematic and hookup of T874J,R with Q674L. Used in heat pump applications.  
60-2485—8  
126  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
COOL CHANGEOVER VALVE  
1
L1  
HOT)  
1
O
(
H1 ANTICIPATOR  
L2  
FAN  
SWITCH  
AUTO  
ON  
G
R
2
4
FAN RELAY  
OUTDOOR  
THERMOSTAT  
FALL  
H1  
W2  
HEAT RELAY 1  
FALL  
6
H2  
HEAT RELAY HEAT RELAY 2  
CONTACT 1  
H2 ANTICIPATOR  
SYSTEM  
SWITCH  
E
HEAT RELAY  
CONTACT 2  
HEAT RELAY 3  
8
9
2
L
SUPL. HT.  
HEAT  
COMPRESSOR  
FAULT  
RISE  
SUPL. HT.  
LED (RED)  
CO  
C1 ANTICIPATOR  
OFF  
C
Y
1
0
COMPRESSOR  
CONTACTOR 1  
COOL  
C1 RISE  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
2
N.O. SWITCH – INSTALLER ADDED, TO LIGHT SUPL. HT. LED  
WHEN COMPRESSOR OPERATION IS NOT NORMAL.  
M4665  
Fig. 103. Schematic and hookup of T874G with Q674L. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
E
2
3
4
EM. HT. RELAY  
EM. HT. LED  
(RED)  
H1/C1  
ANTICIPATOR  
H1  
C1  
FAN  
X
SWITCH  
AUTO  
ON  
FALL  
B
"
B" RELAY  
R
AUX. HT. RELAY  
W2  
COMPRESSOR  
CONTACTOR  
5
6
2
H2 ANTICIPATOR  
FALL  
H
L1  
(HOT)  
H2  
SYSTEM  
SWITCH  
L2  
1
EM. HT.  
Y
HEAT  
OFF  
1
2
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD PROTECTION  
AS REQUIRED.  
Y
G
W
O
R
COM  
G
COOL  
R8233B  
OPTIONAL FIELD WIRE JUMPER TO CYCLE  
AUXILIARY HEAT RELAY H1 INSTEAD OF  
H2 (FASTER RESPONSE).  
ELEC. HT.  
RELAY  
O
EH  
M4728  
Fig. 104. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
127  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
2
H1 ANTICIPATOR  
FAN SWITCH  
AUTO  
FAN RELAY  
G
ON  
HEAT RELAY 2  
W2  
H1  
FALL  
K
L
EM. HT. RELAY  
4
SYSTEM  
MONITOR  
SWITCH  
SYSTEM  
SWITCH  
6
EM. HT. LED  
RED)  
(
IHRI  
FALL  
EM. HT.  
HEAT  
C
H2 ANTICIPATOR  
H2  
R
8
OFF  
RHI  
COMPRESSOR  
COOL  
CONTRACTOR  
C1 ANTICIPATOR  
Y
RISE  
10  
W1  
C1  
HEAT RELAY 1  
M8384  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
1
L1 L2  
HOT)  
(
Fig. 105. Schematic and hookup of T874C with Q674L. Used in heat pump applications.  
THERMOSTAT  
FALL  
SUBBASE  
SYSTEM COMPONENTS  
COOL CHANGEOVER  
VALVE  
2
3
O
FAN SWITCH  
AUTO  
H1/C1  
ANTICIPATOR  
FAN RELAY  
H1  
C1  
G
R
ON  
L1  
(HOT)  
L2  
1
4
5
6
SYSTEM  
SWITCH  
AUX. HT. RELAY  
EM. HT.  
W2  
X
EM. HT.  
LED  
(RED)  
HEAT  
OFF  
H2  
H2 ANTICIPATOR  
FALL  
COMPRESSOR  
CONTACTOR  
COOL  
1
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD PROTECTION  
AS REQUIRED.  
Y
E
EM. HT. RELAY  
M4724  
Fig. 106. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
60-2485—8  
128  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
COOL CHANGEOVER  
VALVE  
O
G
FAN  
SWITCH  
2
FAN RELAY  
AUTO  
ON  
H1  
H1  
ANTICIPATOR  
FALL  
OUTDOOR  
THERMSTAT  
3
SUPPL. HT.  
RELAY  
4
H2  
ANTICIPATOR  
5
Y1  
EM. HT.  
RELAY CONTACT  
COMPRESSOR  
CONTACTOR 2  
H2  
FALL  
E
L
8
SYSTEM  
SWITCH  
EM. HT. RELAY  
COMP.  
FAILURE  
C1 ANTICIPATOR  
C1  
EM. HT.  
RISE  
1
0
EM. HT.  
HEAT  
LED (RED)  
C
R
C2 ANTICIPATOR  
L1  
(HOT)  
OFF  
11  
COOL  
1
L2  
C2  
RISE  
Y
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
COMPRESSOR  
CONTACTOR 1  
M4727  
Fig. 107. Schematic and hookup of T874D with Q674L. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(HOT)  
R
H1/C1  
ANTICIPATOR  
FAN  
SWITCH  
L2  
1
H1  
C1  
2
3
4
FAN RELAY  
FALL  
AUTO  
ON  
G
AUX. HT. RELAY  
5
6
W
FALL  
AUX. HT.  
LED (YELLOW)  
H2  
H2  
SYSTEM  
SWITCH  
B
ANTICIPATOR  
EM. HT.  
LED (RED)  
EM. HT.  
HEAT  
OFF  
X
COOL CHANGEOVER  
VALVE  
O
1
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD PROTECTION  
AS REQUIRED.  
COOL  
COMPRESSOR  
CONTACTOR  
Y
M4725  
Fig. 108. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
129  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
AUX. HT. RELAY  
1
2
W
AUX. HT.  
LED (GREEN)  
B
H1  
H1/ C1  
ANTICIPATOR  
C1  
FALL  
3
EM. HT.  
LED (RED)  
F
FAN  
SWITCH  
AUTO  
G
4
ON  
FAN RELAY  
COMPRESSOR  
FAILURE  
L1  
5
R
(HOT)  
RESET  
HEATER  
L2  
1
H2  
X2  
T
FALL  
OUTDOOR  
THERMOSTAT  
6
SYSTEM  
SWITCH  
OUTDOOR  
THERMISTOR  
COOL  
CHANGEOVER  
VALVE  
EM. HT.  
HEAT  
O
Y
1
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD PROTECTION  
AS REQUIRED.  
OFF  
COMPRESSOR  
CONTACTOR  
COOL  
M5071  
Fig. 109. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
60-2485—8  
130  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
RESET  
SUBBASE  
SYSTEM COMPONENTS  
L1  
HOT)  
L2  
1
2
V
(
2
1
VR  
M
H1  
COMPRESSOR  
CONTACTOR  
INTERNAL  
THERMOSTAT  
ANTICIPATOR  
3
OVERLOAD  
SWITCH  
HI PRESSURE  
SWITCH  
FAN SWITCH  
FAN  
H1  
RELAY  
AUTO  
ON  
FALL  
F
L
4
5
SERVICE  
SERVICE  
LED (RED)  
OUTDOOR  
SUPL. ELEC.  
HT. RELAY  
THERMOSTAT  
S
Y
EM. HT. RELAY  
CONTACT  
TIME DELAY  
FAN RELAY  
H2  
3
FALL  
6
H2  
ANTICIPATOR  
ELEC. HT. RELAY  
SYSTEM  
SWITCH  
7
8
E
EM. HT.  
LED (YELLOW)  
EM. HT.  
HEAT  
OFF  
X
A
C815A OUTDOOR  
THERMISTOR  
C1  
ANTICIPATOR  
C1  
RISE  
COOL  
COOL CHANGEOVER  
VALVE  
10  
R
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
3
REMOVE FACTORY-INSTALLED S-Y JUMPER TO DISABLE SERVICE LIGHT.  
M2854  
2
REMOVE FACTORY INSTALLED V-VR JUMPER WHEN  
CONNECTING A TWO TRANSFORMER SYSTEM.  
Fig. 110. Schematic and hookup of T87C,R with Q674L. Used in heat pump applications.  
131  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
V
VR  
M
1
2
1
RESET  
HEATER  
L1  
(HOT)  
2
L2  
H1/ C1  
ANTICIPATOR  
3
COMPRESSOR  
CONTACTOR  
INTERNAL  
THERMOSTAT  
FAN  
SWITCH  
OVERLOAD  
SWITCH  
HIGH  
PRESSURE  
SWITCH  
4
AUTO  
F
L
ON  
SERVICE  
H1  
FAN RELAY  
C1  
FALL  
SERVICE  
LED (RED)  
OUTDOOR  
THERMOSTAT  
EM. HT.  
RELAY  
5
6
Y
EM. HT.  
RELAY  
SUPPL. ELEC.  
HT. RELAY  
EM. HT.  
RELAY  
SYSTEM  
SWITCH  
E
X
A
7
EM. HT. LED  
(YELLOW)  
EM. HT.  
HEAT  
OFF  
H2  
C815A  
OUTDOOR  
THERMISTOR  
FALL  
COOL  
COOL CHANGEOVER  
VALVE  
H2  
ANTICIPATOR  
R
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
2
REMOVE FACTORY INSTALLED V-VR JUMPER WHEN  
CONNECTING A TWO TRANSFORMER SYSTEM.  
M2851  
Fig. 111. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
60-2485—8  
132  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
COOL CHANGEOVER  
VALVE  
FALL  
C1  
2
O
FAN  
SWITCH  
FAN RELAY  
H1  
H1/C1  
ANTICIPATOR  
AUTO  
ON  
G
R
L1  
(HOT)  
3
4
L2  
COMPRESSOR  
FAILURE  
SYSTEM  
SWITCH  
1
L1  
5
H2  
ANTICIPATOR  
EM. HT.  
HEAT  
EM. HT. LED  
(RED)  
6
X
OFF  
AUX. HT. LED  
(GREEN)  
H2  
FALL  
COOL  
AUX. HT. RELAY  
W2  
COMPRESSOR  
CONTACTOR  
1
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD  
Y
E
PROTECTION AS REQUIRED.  
EM. HT. RELAY  
M8383  
Fig. 112. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
133  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
R
(HOT)  
HEAT  
L2  
EM. HT. RELAY CONTRACTOR 3  
1
H1/C1  
ANTICIPATOR  
EM. HT. RELAY  
1
2
W3  
HEAT  
CONTRACTOR 2  
OUTDOOR  
THERMOSTAT  
DEFROST RELAY  
3
H1  
C1  
HEAT  
CONTRACTOR 1  
HIGH LIMIT  
SWITCH  
W2  
B
FALL  
FAN  
SWITCH  
DEFROST  
RELAY  
REVERSING  
VALVE  
AUTO  
4
ON  
CHECK LED  
GREEN)  
(
5
L
OPTIONAL COMP.  
FAILURE DEVICE  
FALL  
H2  
X2  
SYSTEM  
SWITCH  
X1  
E
H2 ANTICIPATOR  
6
7
EM. HT.  
LED (RED)  
EM. HT. RELAY  
EM. HT.  
HEAT  
FAN RELAY  
G
OFF  
COOL  
HIGH  
PRESSURE  
SWITCH  
COMPRESSOR  
CONTACTOR  
Y
LOW AMBIENT  
CUTOFF  
COOL CHANGEOVER  
VALVE  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
O
M4720  
Fig. 113. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
60-2485—8  
134  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
M2  
OUTDOOR  
THERMOSTAT  
RESET  
HEATER  
HIGH SPEED  
COMPRESSOR  
CONTACTOR  
H1  
ANTICIPATOR  
2
3
M
FAN SWITCH  
LOW SPEED  
COMPRESSOR  
CONTACTOR  
FAN  
RELAY  
AUTO  
ON  
F
V
H1  
FALL  
L1  
4
5
(HOT)  
L2  
1
R
COOL  
2
H2  
CHANGEOVER  
SERVICE  
VALVE  
L
X
E
FALL  
6
7
H2 ANTICIPATOR  
EM. HT.  
RELAY  
EM. HT. LED  
(
YELLOW)  
OUTDOOR  
THERMOSTAT  
8
SYSTEM  
SWITCH  
SUPPL. ELEC.  
HT. RELAY  
VR  
RISE C1  
C1  
ANTICIPATOR  
EM. HT.  
HEAT  
OFF  
SERVICE  
LED (RED)  
SUPPL. ELEC.  
HT. RELAY  
10  
Y
EM. HT.  
RELAY  
COOL  
C2  
C815A OUTDOOR  
THERMISTOR  
C2  
ANTICIPATOR  
RISE  
1
A
11  
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
2
REMOVE FACTORY INSTALLED V-VR JUMPER WHEN CONNECTING  
A TWO TRANSFORMER SYSTEM.  
M2853  
Fig. 114. Schematic and hookup of T874D with Q674L. Used in heat pump applications.  
135  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
HOT) L1 L2  
(
1
H1/C1  
ANTICIPATOR  
R
FALL  
2
ODT 1  
EHR 1  
ODT 2  
H1  
RTD 1  
RTD 2  
C1  
W3  
3
4
FAN SWITCH  
AUTO  
ON  
EHR 2  
RTD 3  
RTD 1  
H2  
ANTICIPATOR  
W2  
5
6
AUX. HT.  
LED  
GREEN)  
(
H2  
2
X
FALL  
EM. HT.  
LED (RED)  
SYSTEM  
MONITOR  
SYSTEM  
SWITCH  
RD  
L
FAN RELAY  
G
O
EM. HT.  
HEAT  
OFF  
EM. HT.  
RELAY  
COOL CHANGEOVER  
VALVE  
E
COOL  
LACO  
CHP  
Y
B
COMPRESSOR  
CONTACTOR  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
AUXILIARY HEAT LED AVAILABLE ON SOME MODELS.  
M5072A  
Fig. 115. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
60-2485—8  
136  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
2
E
FAN  
SWITCH  
EM. HT. RELAY  
H1/C1  
ANTICIPATOR  
X
AUTO  
ON  
H1  
EM. HT.  
LED (RED)  
C1  
3
FALL  
B
4
5
R
AUX. HT. RELAY  
W2  
H2 ANTICIPATOR  
COMPRESSOR  
CONTACTOR  
2
SYSTEM  
SWITCH  
6
H
EM. HT.  
HEAT  
OFF  
L1  
(HOT)  
H2  
FALL  
A
L2  
1
COMP. FAULT  
LED (YELLOW)  
Y
Y
R
COOL  
COM  
1
2
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD PROTECTION  
AS REQUIRED.  
G
G
R8233B  
OPTIONAL FIELD WIRE JUMPER TO CYCLE  
AUXILIARY HEAT RELAY WITH H1 INSTEAD  
OF H2 (FASTER RESPONSE).  
W
O
ELEC.  
HT. RELAY  
O
EH  
M2857  
Fig. 116. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
137  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
HOT)  
L2  
R
(
DEFROST  
RELAY  
ENTHALPY  
CONTROL RELAY  
1
2
B
H1  
HEAT RELAY  
CONTACT 1  
FALL  
H1 ANTICIPATOR  
G
MOTOR  
3
FAN  
SWITCH  
ECONOMIZER  
RELAY  
DEFROST  
SWITCH  
3
4
OUTDOOR  
FAN RELAY 1  
AUTO  
ON  
H2 ANTICIPATOR  
ENTHALPY  
CONTROL  
DEFROST SWITCH  
RELAY  
5
2
TM1  
TM2  
LOW AMBIENT  
ENTHALPY  
CONTROL  
RELAY 2  
THERMOSTAT 1  
H2  
FALL  
OUTDOOR  
FAN RELAY 3  
OUTDOOR  
FAN RELAY 2  
6
8
1
ST STAGE LOW  
PRESSURE LIMIT  
1
ST STAGE  
SHORT  
Y1  
CYCLE  
CONTROL  
C1  
MOTOR  
1
RISE  
ENTHALPY  
CONTROL  
RELAY 1  
TIME DELAY  
HEATER  
TIME DELAY  
Y2  
C1 ANTICIPATOR  
2ND STAGE  
SHORT  
CYCLE  
MOTOR  
2
2
ND STAGE LOW  
CONTROL  
PRESSURE LIMIT  
10  
DEFROST  
RELAY  
SYSTEM  
SWITCH  
C2 ANTICIPATOR  
W
HEAT  
RELAY 1  
EM. HT.  
LED  
OUTDOOR  
THERMOSTAT  
11  
(GREEN)  
HEAT  
OFF  
X
C2  
SERVICE  
RISE  
COOL  
L
DEFROST  
RELAY  
SERVICE  
LED (RED)  
COOL CHANGEOVER  
VALVE  
O
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M7755  
OPTIONAL ECONOMIZER HOOKUP (DOTTED LINES).  
Fig. 117. Schematic and hookup of T874D with Q674L. Used in heat pump applications.  
60-2485—8  
138  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
H1  
SUBBASE  
SYSTEM COMPONENTS  
1
2
L1  
HOT)  
R
(
DEFROST  
RELAY  
L2  
ECONOMIZER  
RELAY  
1
FALL  
H2  
B
HEAT RELAY  
CONTACT 1  
FALL  
H1  
G
MOTOR  
3
ANTICIPATOR  
ECONOMIZER  
RELAY  
FAN  
SWITCH  
DEFROST  
SWITCH  
H2 ANTICIPATOR  
3
OUTDOOR  
FAN RELAY 1  
AUTO  
DEFROST  
RELAY  
ON  
4
H3  
ENTHALPY  
CONTROL  
ANTICIPATOR  
DEFROST SWITCH  
RELAY  
2
5
TM1  
TM2  
OUTDOOR  
THERMOSTAT 1  
H3  
FALL  
ECONO-  
MIZER  
RELAY 2  
OUTDOOR  
FAN RELAY 2  
OUTDOOR  
FAN RELAY 3  
6
1
ST STAGE LOW  
8
PRESSURE LIMIT  
1
ST STAGE  
C1  
SHORT  
Y1  
Y2  
RISE  
CYCLE  
CONTROL  
MOTOR  
1
ECONOMISER  
9
RELAY 1  
TIME DELAY  
HEATER  
SYSTEM  
SWITCH  
TIME DELAY  
RELAY  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
EM. HT.  
2
ND STAGE  
HEAT  
OFF  
SHORT  
DEFROST  
RELAY  
CYCLE  
CONTROL  
MOTOR  
2
2
ND STAGE LOW  
PRESSURE LIMIT  
10  
COOL  
C2  
DEFROST  
AUXILIARY  
HEAT RELAY  
RISE  
RELAY  
CONTACT  
W
AUX. HEAT  
DEFROST  
RELAY  
CONTACT  
LED (GREEN)  
COOL CHANGEOVER  
VALVE  
1
1
2
O
X
RESET HEATER  
1
EM. HEAT  
LED (RED)  
EMERGENCY  
HEAT RELAY  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
E
C815 OUTDOOR  
THERMISTOR  
OPTIONAL ECONOMIZER HOOKUP (DOTTED LINES).  
A
M7756  
Fig. 118. Schematic and hookup of T874W with Q674L. Used in heat pump applications.  
139  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
L2  
(HOT)  
1
C815A  
OUTDOOR  
THERMISTOR  
RESET  
HEATER  
1
T
H2 ANTICIPATOR  
2
W2  
FAN SWITCH  
AUX. HT. RELAY  
FAN RELAY  
AUTO  
G
R
ON  
3
4
X
H1  
SERVICE LED  
C1  
SYSTEM  
SWITCH  
(YELLOW)  
SERVICE  
FALL  
5
6
Z
EM. HT.  
HEAT  
C1  
EM. HT.  
LED (RED)  
ANTICIPATOR  
EM. HT. RELAY  
OFF  
K
COMPRESSOR  
CONTACTOR  
COOL  
Y
11  
12  
W1  
H2  
FALL  
1
H1 ANTICIPATOR  
HEAT CHANGEOVER  
RELAY  
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M5955  
Fig. 119. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1 L2  
HOT)  
(
2
3
FAN SWITCH  
FALL  
C1  
1
H1/C1  
ANTICIPATOR  
FAN RELAY  
H1  
AUTO  
ON  
G
R
4
5
AUX. HT. RELAY  
W
FALL  
H
B
H2  
"
H" RELAY  
6
H2  
EM. HT.  
ANTICIPATOR  
SYSTEM  
SWITCH  
LED (RED)  
X
T
EM. HT.  
EM. HT. RELAY  
HEAT  
OFF  
C815A1039  
THERMISTOR  
O
COOL  
CHANGEOVER VALVE (COOL)  
Y
11  
RESET HEATER  
COMPRESSOR  
CONTACTOR  
12  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M3173B  
Fig. 120. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
60-2485—8  
140  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
HOT)  
L2  
2
3
R
(
FAN  
SWITCH  
COMPRESSOR  
FAILURE  
H1 ANTICIPATOR  
1
ODT1  
EHR1  
AUTO  
ON  
RTD2  
H1  
FALL  
4
5
ODT2  
EHR2  
L
EM. HT.  
LED (RED)  
RTD1  
H2 ANTICIPATOR  
RTD3  
6
X
H2  
AUX. HT.  
LED (GRN)  
RTD1  
FALL  
W2  
G
RD  
FAN RELAY  
SYSTEM  
SWITCH  
EM. HT.  
HEAT  
8
COOL CHANGEOVER  
VALVE  
C1  
EM. HT.  
RELAY  
O
E
ANTICIPATOR  
OFF  
10  
COOL  
COMPRESSOR  
CONTACTOR  
CHP  
LACO  
C1  
Y
B
RISE  
1
HEAT CHANGEOVER  
VALVE  
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M7012  
Fig. 121. Schematic and hookup of T874C with Q674L. Used in heat pump applications.  
141  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
FAN RELAY  
FAN  
SWITCH  
G
AUTO  
ON  
2
L2  
FALL  
1
R
L1  
H1  
C1  
H1/C1  
(HOT)  
ANTICIPATOR  
3
W2  
AUX. HT. RELAY  
EM. HT. RELAY  
K
L
4
CO  
SYSTEM  
SWITCH  
EM. HT. LED  
(YELLOW)  
5
EM. HT.  
HEAT  
FALL  
C
H2  
H2  
ANTICIPATOR  
OFF  
SERVICE  
LED (RED)  
6
COMPRESSOR  
CONTACTOR  
COOL  
Y
1
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD  
W1  
Z
PROTECTION AS REQUIRED.  
CHANGEOVER  
VALVE  
SERVICE  
M8379  
Fig. 122. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
60-2485—8  
142  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
HOT)  
L2  
(
ODT 1  
EHR 1  
1
2
RTD 2  
RTD 3  
H1/C1  
ANTICIAPTOR  
H1  
C1  
RTD 1  
FALL  
3
4
ODT 2  
EHR 2  
FAN  
SWITCH  
AUTO  
ON  
R
L
5
H2  
EM. HT.  
LED (RED)  
COMPRESSOR  
MONITOR  
H2  
ANTICIPATOR  
FALL  
6
X
AUX. HT.  
LED  
RTD 1  
(GREEN)  
W2  
8
SYSTEM  
SWITCH  
RD  
FAN RELAY  
EM. HT.  
HEAT  
G
10  
2
COOL  
CHANGEOVER VALVE  
OFF  
1
2
POWER SUPPLY. PROVIDE  
DISCONNECT MEANS AND  
OVERLOAD PROTECTION  
AS REQUIRED.  
O
E
EM. HT. RELAY  
COOL  
LACO  
CHP  
CONNECT CHANGEOVER  
RELAY TO B FOR HEAT  
CHANGEOVER, TO O FOR  
COOL CHANGEOVER.  
Y
B
COMPRESSOR  
CONTACTOR  
2
HEAT  
CHANGEOVER VALVE  
M1030A  
Fig. 123. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
143  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
L2  
(HOT)  
1
FALL  
R
FAN  
SWITCH  
COMPRESSOR CONTACTOR  
H1  
Y
2
3
AUTO  
ON  
G
H1  
FAN RELAY  
HEAT RELAY 1  
ANTICIPATOR  
2
4
W2  
H2  
EM. HT. OR  
SUPL. HT.  
LED (RED)  
OUTDOOR  
THERMOSTAT  
ANTICIPATOR  
FALL  
5
H2  
L
6
8
HEAT RELAY HEAT RELAY 2  
CONTACT 1  
2
SYSTEM  
SWITCH  
C
HEAT RELAY  
CONTACT 2  
RISE  
EM. HT. OR  
SUPL. HT.  
HEAT RELAY 3  
9
E
X
C1 ANTICIPATOR  
HEAT  
CO  
10  
OFF  
"
X" RELAY  
COOL  
"P" RELAY  
RISE  
CO  
P
C1  
11  
O
COOL  
CHANGEOVER VALVE  
12  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
ON MODELS INCLUDING EXTERNAL JUMPER, W2=W1 AND L=F.  
M8003  
Fig. 124. Schematic and hookup of T874J with Q674L. Used in heat pump applications.  
60-2485—8  
144  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SYSTEM COMPONENTS  
L1  
SUBBASE  
R
L
(HOT)  
L2  
2
1
EM. HT.  
H1/C1  
ANTICIPATOR  
LED (RED)  
AUX. HT.  
RELAY  
FAN  
3
3
SWITCH  
W3  
AUTO  
H1  
C1  
2
FALL  
FALL  
ON  
4
X
H2  
AUX. HT.  
LED (GRN)  
AUX. HT.  
RELAY  
ANTICIPATOR  
H2  
6
W2  
G
SYSTEM  
SWITCH  
FAN RELAY  
EM. HT.  
HEAT  
OFF  
COOL CHANGEOVER  
VALVE  
O
E
COOL  
EM. HT. RELAY  
Y
B
COMPRESSOR  
CONTACTOR  
"
B" RELAY  
1
2
3
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M3683A  
TERMINAL LABELED C/X ON SOME MODELS.  
W3 TERMINAL AVAILABLE ON SOME MODELS ONLY.  
Fig. 125. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
145  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
COOL CHANGEOVER  
VALVE  
L1  
1
O
(HOT)  
H1 ANTICIPATOR  
L2  
1
FAN  
SWITCH  
FAN RELAY  
AUTO  
G
R
2
4
ON  
FALL  
H1  
OUTDOOR  
THERMOSTAT  
W2  
FALL  
HEAT RELAY 1  
6
8
H2  
H2 ANTICIPATOR  
C1 ANTICIPATOR  
HEAT RELAY HEAT RELAY 2  
CONTACT 1  
E
SYSTEM  
SWITCH  
CO  
HEAT RELAY HEAT RELAY 3  
CONTACT 2  
2
9
RISE  
SUPL. HT.  
HEAT  
L
10  
SUPL. HT.  
LED (RED)  
COOL  
C1  
RISE  
C
Y
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
COMPRESSOR  
CONTACTOR 1  
N.O. SWITCH INSTALLER ADDED, TO LIGHT EM. HT. LED WHEN COMPRESSOR OPERATION IS NOT NORMAL.  
M4722  
Fig. 126. Schematic and hookup of T874G with Q674P. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
HOT)  
(
R
ODT1  
EHR1  
2
L2  
RTD1  
RTD1  
1
H1 ANTICIPATOR  
FALL  
FAN SWITCH  
H1  
W3  
3
AUTO  
ON  
RTD2  
RTD3  
ODT2  
EHR2  
4
5
FALL  
H2  
W2  
H2 ANTICIPATOR  
SYSTEM SWITCH  
AUX.HT.  
LED (GREEN)  
X
EM. HT.  
HEAT  
OFF  
EM. HT.  
LED (RED)  
6
8
COMPRESSOR  
FAILURE  
RD  
L
FAN RELAY  
RISE  
G
O
COOL  
C1  
EM. HT.  
RELAY  
COOL CHANGEOVER  
VALVE  
E
10  
COMPRESSOR  
CONTACTOR  
C1 ANTICIPATOR  
CHP  
LACO  
1
POWER SUPPLY. PROVIDE  
DISCONNECT MEANS AND  
OVERLOAD PROTECTION  
AS REQUIRED.  
Y
B
M5652A  
Fig. 127. Schematic and hookup of T874C with Q674L. Used in heat pump applications.  
60-2485—8  
146  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(HOT)  
H1/C1  
ANTICIPATOR  
R
A
ODT1  
RD  
L2  
2
3
FALL  
1
SERVICE  
LED (RED)  
FAN  
SWITCH  
RTD1  
EHR1  
ODT2  
EHR2  
H1  
W3  
C1  
AUTO  
ON  
RTD2  
RTD1  
RTD3  
4
5
W2  
FALL  
H2 ANTICIPATOR  
AUX. HT.  
LED  
SYSTEM  
SWITCH  
(GREEN)  
H2  
EM. HT.  
HEAT  
OFF  
X
6
EM. HT.  
LED  
SYSTEM  
MONITOR  
(YELLOW)  
RD  
L
COOL  
FAN RELAY  
G
O
1
POWER SUPPLY. PROVIDE  
DISCONNECT MEANS AND  
OVERLOAD PROTECTION  
AS REQUIRED.  
COOL CHANGEOVER EM. HT. RELAY  
VALVE  
E
COMPRESSOR  
CONTACTOR  
CHP  
LACO  
Y
B
M5653A  
Fig. 128. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
FAN RELAY  
2
AUTO  
G
R
FAN  
SWITCH  
H1 ANTICIPATOR  
ON  
H1  
L1  
FALL  
3
4
(HOT)  
1
L2  
W
X
H2 ANTICIPATOR  
EM. HT. RELAY  
AUX. HT. RELAY  
FALL  
RISE  
SYSTEM  
SWITCH  
6
H2  
EM. HT.  
B
EM. HT.  
LED (RED)  
HEAT  
OFF  
COOL  
CO  
C1  
8
9
COOL CHANGEOVER VALVE  
O
Y
C1  
ANTICIPATOR  
RISE  
10  
COMPRESSOR  
CONTACTOR  
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
1
M102A  
Fig. 129. Schematic and hookup of T874G with Q674L. Used in heat pump applications.  
147  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
2
O
G
COOL  
CHANGEOVER VALVE  
FAN  
SWITCH  
H1  
C1  
AUTO  
ON  
FALL  
FAN RELAY  
L1  
HOT)  
L2  
H1/C1  
ANTICIPATOR  
R
(
1
3
4
W1  
2
AUX. HT.  
LED  
EM. HT. RELAY  
(YELLOW)  
SYSTEM  
SWITCH  
5
6
E
X
COMPRESSOR  
FAILURE  
EM. HT.  
HEAT  
CHECK  
LED  
(RED)  
H2  
FALL  
H2 ANTICIPATOR  
OFF  
C
COOL  
11  
C815A OUTDOOR  
THERMISTOR  
SYSTEM  
LED (GREEN)  
RESET  
1
2
T
Y
COMPRESSOR  
CONTACTOR  
1
2
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD PROTECTION  
AS REQUIRED.  
M1628A  
FACTORY-INSTALLED JUMPER.  
Fig. 130. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
60-2485—8  
148  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(
HOT)  
H1/C1 ANTICIPATOR  
L2  
2
AUTO  
ON  
FAN  
SWITCH  
R
1
3
4
W2  
L
H1  
C1  
HCR 1  
RESET  
HEATER  
FALL  
SYSTEM  
SWITCH  
ODT  
C
G
SUPL. HT.  
LED (RED)  
FAN RELAY  
SUPL. HT.  
HEAT  
6
COOL CHANGEOVER  
VALVE  
2
H2 ANTICIPATOR  
O
E
Y
H2  
FALL  
COOL  
HCR 2  
HCR 3  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
FOR Q674L1454, IS "OFF".  
COMPRESSOR  
CONTACTOR  
HCR 1  
HCR 2  
M4723  
Fig. 131. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
149  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
O
2
FAN  
SWITCH  
COOL CHANGEOVER  
VALVE  
FALL  
C1  
FAN RELAY  
H1  
AUTO  
ON  
G
R
L1  
HOT)  
H1/C1  
ANTICIPATOR  
(
3
4
1
L2  
3R  
W1  
SYSTEM  
SWITCH  
AUX. HT.  
LED  
(YELLOW)  
SEQ 1  
5
6
2
EM. HT.  
SEQ 2  
HEAT  
H2  
E
FALL  
H2  
OFF  
ANTICIPATOR  
EM. HT. RELAY  
COOL  
4R  
EM. HT.  
LED  
RED)  
4R  
(
X
C
SYSTEM  
LED  
5R  
C815A  
OUTDOOR  
THERMISTOR  
11  
4R  
HPS  
(GREEN)  
12  
T
Y
RESET  
COMPRESSOR  
CONTACTOR  
4R  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
REMOVE JUMPER FOR INDEPENDENT CONTROL OF W1 AND E TERMINALS.  
M1858  
Fig. 132. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
FAN  
RELAY  
FAN  
SWITCH  
G
R
1
2
H1/C1  
ANTICIPATOR  
L1  
(HOT)  
AUTO  
ON  
L2  
1
H1  
C1  
K
AUX. HT.  
FALL  
EM. HT.  
RELAY  
RELAY  
W2  
L
3
4
EM. HT.  
LED (YEL)  
SYSTEM  
SWITCH  
COMPRESSOR  
FAILURE  
C
Z
5
6
EM. HT.  
HEAT  
OFF  
RESET  
LED (RED)  
H2 ANTICIPATOR  
W1 RELAY  
CO  
H2  
W1  
Y
FALL  
COOL  
COMPRESSOR  
CONTACTOR  
M2018  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
Fig. 133. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
60-2485—8  
150  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
RTD 1  
ODT 1  
EHR 1  
ODT 2  
1
2
RTD 2  
H1  
C1  
FALL  
EHR 2  
RDT 3  
FAN RELAY  
L1  
H1/C1  
ANTICIPATOR  
FAN SWITCH  
3
AUTO  
ON  
G
R
4
(HOT)  
1
L2  
H2  
ANTICIPATOR  
5
W2  
E
AUX. HT.  
LED (GREEN)  
RTD 1  
EM. HT. RELAY  
6
8
COMP.  
FAILURE  
RD  
FALL  
H2  
L
SYSTEM  
SWITCH  
EM. HT.  
LED (RED)  
CHANGEOVER  
VALVE (HEAT)  
EM. HT.  
HEAT  
OFF  
B
X
COMPRESSOR  
CONTACTOR  
COOL  
CHP  
LACO  
10  
Y
CHANGEOVER VALVE (COOL)  
O
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
M106A  
Fig. 134. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
151  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
FAN  
SWITCH  
L1  
(HOT)  
R
H1/C1  
ANTICIPATOR  
AUTO  
ON  
L2  
1
2
3
W2  
HCR 1  
L
H1  
SUPL. HT.  
LED (RED)  
C1  
RESET  
ODT  
HCR 1  
HCR 2  
FALL  
HEATER  
C
G
4
6
SYSTEM  
SWITCH  
FAN RELAY  
SUPL. HT.  
HEAT  
O
COOL  
CHANGEOVER VALVE  
H2 ANTICIPATOR  
OFF  
E
Y
COOL  
H2  
HCR 2  
HCR 3  
FALL  
COMPRESSOR  
CONTACTOR  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M2017  
Fig. 135. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
G
1
FAN RELAY  
AUX. HEAT  
1
C1  
ANTICIPATOR  
W
U
AUX. HT.  
LED (GRN)  
H1  
FAN  
SWITCH  
RELAY  
ANTICIPATOR  
2
3
AUTO  
ON  
EM. HT.  
LED (RED)  
B
F
COMP.  
FAILURE  
H1  
C1  
2
4
5
6
FALL  
L2  
RESET  
R
T
L1  
HOT)  
(
H2  
SYSTEM  
SWITCH  
FALL  
X2  
O
EM. HT.  
HEAT  
OFF  
C815A OUTDOOR  
THERMISTOR  
O.D.  
STAT  
COOL CHANGEOVER  
VALVE  
COOL  
COMPRESSOR  
CONTACTOR  
1
FIELD REMOVABLE JUMPER  
Y
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M2012  
Fig. 136. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
60-2485—8  
152  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
RTD 1  
ODT 1  
EHR 1  
ODT 2  
1
2
3
RTD 2  
H1  
C1  
FALL  
H1/C1  
ANTICIPATOR  
EHR 2  
RDT 3  
FAN RELAY  
L1  
W3  
FAN SWITCH  
AUTO  
ON  
G
R
4
(HOT)  
1
L2  
H2  
ANTICIPATOR  
5
W2  
E
AUX. HT.  
LED (GREEN)  
RTD 1  
EM. HT. RELAY  
6
COMP.  
RD  
FAILURE  
EM. HT.  
LED  
FALL  
H2  
SYSTEM  
SWITCH  
L
(RED)  
CHECK  
CHANGEOVER  
VALVE (HEAT)  
LED (RED)  
EM. HT.  
HEAT  
B
X
OFF  
COMPRESSOR  
CONTACTOR  
COOL  
CHP  
LACO  
Y
CHANGEOVER VALVE (COOL)  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
O
M105A  
Fig. 137. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
153  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
2
J
R1 NO2  
S1 RELAY  
S1 NC  
H1  
S
G
R
FALL  
FAN SWITCH  
SOLIENOID  
RELAY  
FAN RELAY  
H1 ANTICIPATOR  
AUTO  
ON  
L1  
(HOT)  
3
4
2
L2  
1
C
H2 ANTICIPATOR  
FALL  
AUX. HT. RELAY  
5
H2  
H2  
SYSTEM SWITCH  
COMPRESSOR  
CONTACTOR  
R1 NC1  
7
8
HEAT  
OFF  
RISE  
H1  
C1  
R2 NO1  
COOL  
9
REVERSING  
VALVE  
C1 ANTICIPATOR  
10  
O
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
FIELD REMOVABLE JUMPER  
R1 RELAY  
M103A  
Fig. 138. Schematic and hookup of T874L with Q674B. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
2
FAN RELAY  
AUTO  
ON  
H1 ANTICIPATOR  
G
R
FAN  
SWITCH  
L1  
(HOT)  
FALL  
H1  
L2  
1
4
6
B
SYSTEM  
SWITCH  
W1  
H2 ANTICIPATOR  
COMPRESSOR  
RELAY  
AUX. HT.  
HEAT PUMP  
HEAT PUMP  
LED (GREEN)  
AUX. HT. RELAY  
H2  
C1  
FALL  
RISE  
2
STG. HEAT  
8
W2  
C
OFF  
AUX. HT  
LED (RED)  
C1 ANTICIPATOR  
COOL  
COOL CHANGEOVER  
VALVE  
10  
O
C2 ANTICIPATOR  
Y1  
COMPRESSOR  
CONTACTOR 1  
11  
Y2  
COMPRESSOR  
CONTACTOR 2  
C2  
RISE  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M4730  
Fig. 139. Schematic and hookup of T874D with Q674F. Used in heat pump applications.  
60-2485—8  
154  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
FALL  
SUBBASE  
SYSTEM COMPONENTS  
L1  
1
(HOT)  
L2  
1
H1 ANTICIPATOR  
2
T
W3  
U
H1  
C815A OD THERMISTOR  
H2  
H2 ANTICIPATOR  
3
AUX. HT. RELAY  
FALL  
FALL  
FAN SWITCH  
AUTO  
AUX. HT.  
LED  
(GREEN)  
H3 ANTICIPATOR  
4
G
ON  
FAN RELAY  
H3  
R
EM. HT.  
LED (RED)  
5
E
L
6
EM. HT. RELAY  
RESET  
COMPRESSOR  
MONITOR  
CHECK LED  
(RED)  
RISE  
X
B
8
SYSTEM  
SWITCH  
C1  
EM.HT.  
HEAT  
HEAT CHANGEOVER  
RELAY  
9
2
COOL CHANGEOVER  
RELAY  
C1 ANTICIPATOR  
OFF  
1
0
1
O
COMPRESSOR  
CONTACTOR 1  
COOL  
C2 ANTICIPATOR  
RISE  
Y1  
1
COMPRESSOR  
CONTACTOR 2  
C2  
12  
Y2  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
CONNECT CHANGEOVER RELAY TO 'O' TERMINAL FOR CHANGEOVER IN COOLING OR TO 'B' TERMINAL FOR CHANGEOVER IN HEATING.  
M156A  
Fig. 140. Schematic and hookup of T874W with Q674L. Used in heat pump applications.  
155  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
R
(HOT)  
FAN  
SWITCH  
HEAT RELAY 1  
L2  
FALL  
H1  
1
1
W1  
H1  
FAN RELAY  
AUTO  
ON  
ANTICIPATOR  
G
4
6
HEAT RELAY 2  
FALL  
W2  
H2  
C1  
EM. HT. LED  
(RED)  
H2  
SYSTEM  
SWITCH  
OFF  
ANTICIPATOR  
X2  
E
EM. HT. RELAY  
RISE  
EM. HT.  
HEAT  
8
9
COMPRESSOR  
CONTACTOR 2  
AUTO  
COOL  
C1  
Y2  
Y1  
ANTICIPATOR  
COMPRESSOR  
CONTACTOR 1  
10  
C2  
C2  
ANTICIPATOR  
RISE  
11  
M8376  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
Fig. 141. Schematic and hookup of T874C with Q674F. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
R
(HOT)  
FALL  
FAN  
SWITCH  
L2  
1
H1  
AUTO  
ON  
1
H1 ANTICIPATOR  
W1  
HEAT RELAY 1  
4
6
H2 ANTICIPATOR  
W2  
B
HEAT RELAY 2  
FALL  
H2  
X2  
X1  
SYSTEM  
SWITCH  
CHECK  
LED (RED)  
OFF  
E
RISE  
EM. HT.  
HEAT  
EM. HT. RELAY  
FAN RELAY  
C1  
G
8
9
AUTO  
COOL  
Y2  
C1  
COMPRESSOR  
CONTACTOR 2  
ANTICIPATOR  
10  
C2  
Y1  
O
ANTICIPATOR  
11  
COMPRESSOR  
CONTACTOR 1  
M5985  
RISE  
1
POWER SUPPLY. PROVIDE DISCONECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
C2  
Fig. 142. Schematic and hookup of T874C,D with Q674F. Used in standard applications.  
60-2485—8  
156  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
Y1  
FALL  
H1 ANTICIPATOR  
COMPRESSOR  
CONTACTOR  
FAN  
SWITCH  
H1  
2
4
FAN RELAY  
AUTO  
ON  
G
R
FALL  
L1  
(
HOT)  
6
L2  
H2  
SYSTEM  
SWITCH  
1
H2  
ANTICIPATOR  
OFF  
AUTO  
W1  
C
8
9
RISE  
AUX. HT. RELAY  
CO  
AUX. HT. LED  
(RED)  
C1  
ANTICIPATOR  
O
COOL  
CHANGEOVER VALVE  
10  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
C1  
M8378  
RISE  
Fig. 143. Schematic and hookup of T874G with Q674B. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
L2  
(HOT)  
1
R
FAN  
SWITCH  
FALL  
COMPRESSOR CONTACTOR  
Y
H1  
AUTO  
ON  
2
G
FAN RELAY  
3
W2  
HEAT RELAY 1  
H1 ANTICIPATOR  
H2 ANTICIPATOR  
OUTDOOR  
THERMOSTAT  
4
SUPP. HT.  
LED (RED)  
5
L
HEAT RELAY  
CONTACT 1  
HEAT RELAY 2  
HEAT RELAY 3  
H2 FALL  
C
E
6
8
HEAT RELAY  
CONTACT 2  
RISE  
9
SYSTEM  
SWITCH  
X
P
CO  
C1 ANTICIPATOR  
"P" RELAY  
"
X" RELAY  
SUPL. HT.  
10  
ON  
COOL CHANGEOVER  
VALVE  
OFF  
RISE  
CO  
C1  
1
1
2
O
1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M5956  
Fig. 144. Schematic and hookup of T874J with Q674J. Used in heat pump applications.  
157  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
HOT) L1 L2  
(
1
V
Y
FAN  
SWITCH  
DEFROST  
RELAY  
H1  
SUP. ELEC.  
HT. RELAY  
ANTICIPATOR  
1
AUTO  
ON  
OUTDOOR  
THERMOSTAT  
FALL  
2
H1  
TIME DELAY  
FAN RELAY  
EM. HT. RELAY  
4
6
FAN RELAY  
SYSTEM  
SWITCH  
F
E
FALL  
H2  
ANTICIPATOR  
EM. HT. RELAY  
OFF  
EM. HT.  
LED (RED)  
H2  
EM. HT.  
HEAT  
8
9
COOL CHANGEOVER  
VALVE  
FALL  
AUTO  
R
CO  
COOL  
C1 ANTICIPATOR  
COMPRESSOR  
CONTACTOR  
INTERNAL  
THERMOSTAT  
10  
M
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
HIGH  
RISE  
OVERLOAD  
C1  
PRESSURE  
SWITCH  
M8375  
Fig. 145. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
W1  
Y1  
EHR  
LPCO  
EHR  
REVERSING  
RELAY  
H1  
FALL  
H1 ANTICIPATOR  
COMPRESSOR  
CONTACTOR 1  
RVR RVR  
3
4
DFR 2  
FAN  
SWITCH  
FAN RELAY  
AUTO  
H2  
G
R
ANTICIPATOR  
ON  
H2  
6
L1  
FALL  
(HOT)  
ODT 3  
L2  
HEAT  
1
RELAY 2  
8
C1  
W2  
SYSTEM  
SWITCH  
ODT 2  
HEAT RELAY 1  
RISE  
EHT  
OFF  
SUPL. HT.  
HEAT  
HEAT RELAY 3  
9
C1  
ANTICIPATOR  
E
X
C
10  
SUPL. HT.  
RELAY  
AUTO  
SUPL.  
HEAT  
LED  
COOL  
DFR 2  
COMPRESSOR  
CONTACTOR 2  
C2  
(RED)  
RISE  
ANTICIPATOR  
C2  
11  
Y2  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M7010  
Fig. 146. Schematic and hookup of T874D with Q674F. Used in heat pump applications.  
60-2485—8  
158  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
A
1
MODE SIGNAL  
2
H1  
H1  
ANTICIPATOR  
3
FALL  
FAN  
SWITCH  
2
3
4
AUTO  
ON  
G
FAN RELAY  
L1  
5
R
S
(
HOT)  
H2  
L2  
2
ANTICIPATOR  
1
SERVICE  
LED (RED)  
6
W3  
FALL  
H2  
HEAT RELAY 1  
HEAT RELAY 2  
SYSTEM  
SWITCH  
W2  
X
AUX. HT.  
LED (GRN)  
OFF  
8
9
COOL  
CHANGEOVER  
VALVE  
COOL  
AUTO  
EM. HT.  
LED (YEL)  
CO  
L
O
RISE  
HEAT  
COMPRESSOR  
CONTACTOR  
EM. HT.  
Y
EM. HT. RELAY  
MODE SIGNAL  
C1  
ANTICIPATOR  
E
T
RISE  
C1  
10  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
3
JUMPER FACTORY INSTALLED.  
M7024  
CONNECT TO Y OR W TERMINAL WITH FACTORY INSTALLED JUMPER.  
Fig. 147. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
COOL CHANGEOVER  
VALVE  
H1 ANTICIPATOR  
1
2
O
DEFROST BLOWER SPEED  
RELAY  
RELAY  
FAN  
SWITCH  
BLOWER RELAY  
AUTO  
ON  
FALL  
G
H1  
L1  
R
(HOT)  
4
L2  
1
6
SYSTEM  
SWITCH  
FALL  
DEFROST  
AUX. HT. RELAY  
EM. HT. RELAY  
RELAY  
H2 ANTICIPATOR  
OFF  
EM. HT.  
LED  
W2  
H2  
8
EM. HT.  
HEAT  
(RED)  
E
C
RISE  
CO  
9
AUTO  
LOCKOUT  
THERMOSTAT  
COOL  
CONTRACTOR  
COOL  
C1  
ANTICIPATOR  
Y
C1  
RISE  
10  
M8382  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
Fig. 148. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
159  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
FALL  
SUBBASE  
SYSTEM COMPONENTS  
EMR4  
2R  
1
W1  
Y1  
H1  
1R  
H1 ANTICIPATOR  
FALL  
4R2  
2R2  
4
5R  
3R  
G
EMR4  
H2  
H2  
6
W2  
ANTICIPATOR  
EMR2  
THERMAL SWITCHES  
FOR HEATING  
RISE  
8
ELEMENTS  
HTR 1  
FAN  
SWITCH  
HTR 3  
EMR3  
C1  
AUTO  
ON  
HTR 2  
9
OUTDOOR  
C1  
RISE  
RC  
X1  
THERMOSTAT  
ANTICIPATOR  
10  
2
3
C2  
EM. HT. LED  
ANTICIPATOR  
C2  
SYSTEM  
SWITCH  
3R1  
11  
Z
OFF  
EM. HT.  
HEAT  
1
2
3
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
EMR1  
EMR1  
OPTIONAL FIELD WIRE JUMPER TO ALLOW  
SINGLE SYSTEM TRANSFORMER.  
RH  
E
AUTO  
COOL  
FOR Q674F1048, DELETE C2 STAGE.  
EM. HT. RELAY  
L1  
(
HOT) L2  
L1 L2  
1
(HOT)  
1
M8380  
Fig. 149. Schematic and hookup of T874C with Q674F. Used in heat pump applications.  
60-2485—8  
160  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
COOL CHANGEOVER VALVE  
R
H1 ANTICIPATOR  
1
2
INTERNAL  
THERMOSTAT  
COMPRESSOR  
CONTACTOR  
FALL  
M
H1  
OVERLOAD  
SWITCH  
HI PRESSURE  
SWITCH  
FAN SWITCH  
FAN  
AUTO  
ON  
RELAY  
3
5
F
Y
OUTDOOR  
THERMOSTAT  
SUPL. ELEC.  
HT. RELAY  
FALL  
H2  
EM. HT. RELAY  
CONTACT  
TIME DELAY  
FAN RELAY  
H2 ANTICIPATOR  
6
8
SYSTEM  
SWITCH  
TIME DELAY  
FAN RELAY  
RISE  
OFF  
EM. HT.  
HEAT  
E
X
EM. HEAT  
LED (RED)  
C1  
SYSTEM  
MONITOR  
RISE  
1
9
COOL  
AUTO  
L1  
HOT  
C1  
CO  
ANTICIPATOR  
VR  
V
L2  
2
10  
L2  
1
L1  
HOT  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
2
REMOVE FACTORY INSTALLED V-VR JUMPER WHEN CONNECTING  
A TWO TRANSFORMER SYSTEM.  
M2852A  
Fig. 150. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
161  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L2  
EM. HT. RELAY  
CONTACT 1  
L1  
HOT)  
H1  
(
ANTICIPATOR  
1
R
1
W2  
FAN  
SWITCH  
T6031 REFRIGERATON/  
TEMPERATURE  
CONTROLLER  
EM. HT.  
LED  
(RED)  
2
AUTO  
FALL  
H1  
ON  
EM. HT.  
E
4
6
2
EM. HT. RELAY  
X
H
SYSTEM  
SWITCH  
H2  
ANTICIPATOR  
OFF  
FALL  
Y
G
O
EM. HT.  
HEAT  
R8233B  
H2  
COMPRESSOR  
CONTACTOR  
Y
R
COM  
AUTO  
COOL  
8
9
G
EM.  
HT.  
CO  
W
O
RISE  
SEQUENTIAL  
RELAY  
FAN  
C1  
ANTICIPATOR  
C
DF  
L2  
RS  
1
0
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
1
C1  
RISE  
L1  
(HOT)  
REVERSING  
SOLENOID  
FAN  
2
OPTIONAL FIELD WIRE JUMPER TO CYCLE W2 WITH H1 IN EM. HT.  
(FASTER RESPONSE).  
M4710  
Fig. 151. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
60-2485—8  
162  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1 L2  
HOT)  
1
(
HEAT RELAY  
1
W1  
COMPRESSOR  
CONTRACTOR 1  
FALL  
H1  
Y1  
FAN SWITCH  
AUTO  
H1 ANTICIPATOR  
FAN RELAY  
G
ON  
4
6
RC  
HEAT RELAY 2  
3
FALL  
W2  
RH  
H2 ANTICIPATOR  
H2  
SYSTEM  
SWITCH  
EM. HT. RELAY  
RISE  
OFF  
8
E
B
EM. HT.  
HEAT  
C1  
9
AUTO  
10  
2
RISE  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
COOL  
X2  
X1  
EM. HEAT  
LED (RED)  
11  
C2  
COMPRESSOR  
CONTRACTOR 2  
O
Y2  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
1
2
3
FACTORY SUPPLIED FIELD INSTALLED JUMPER TO E-X2 FOR CONSTANT POWER TO EM HT LIGHT IN EM HT POSITION.  
OPTIONAL FIELDWARE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.  
L1 L2  
(HOT)  
M8377  
Fig. 152. Schematic and hookup of T874D with Q674F. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
COOL CHANGEOVER  
VALVE  
1
O
G
H1  
ANTICIPATOR  
FAN RELAY  
AUTO  
ON  
2
L1  
HOT)  
L2  
(
FAN  
SWITCH  
H1  
FALL  
1
4
6
R
OUTDOOR  
THERMOSTAT  
W2  
E
SYSTEM  
SWITCH  
FALL  
AUX. HT. RELAY  
H2 ANTICIPATOR  
OFF  
H2  
8
9
EM. HT.  
HEAT  
EM. HT.  
RELAY  
AUX. HT. RELAY  
CONTACT  
C1  
RISE  
EM. HT. LED  
(RED)  
AUTO  
X
COOL  
CO  
RISE  
C1 ANTICIPATOR  
Y
10  
COMPRESSOR  
CONTACTOR  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M8381  
Fig. 153. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
163  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
EM. HT. RELAY  
CONTACT 1  
1
2
R
1
H1 ANTICIPATOR  
L1  
L2  
(HOT)  
FAN  
SWITCH  
W2  
AUTO  
E
T6031  
REFRIGERATION  
TEMPERATURE  
CONTROLLER  
ON  
FALL  
H1  
EM. HT.  
LED (RED)  
4
6
8
X
EM. HT.  
2
H2 ANTICIPATOR  
H
EM. HT. RELAY  
SYSTEM  
SWITCH  
COMPRESSOR  
CONTACTOR  
A
OFF  
H2  
COMP. FAULT  
LED (YELLOW)  
EM. HT.  
FALL  
HEAT  
AUTO  
COOL  
Y
Y
R
COM  
G
G
SEQUENTIAL  
RELAY  
R8233B  
9
W
O
C
EH  
H1 ANTICIPATOR  
CO  
O
RISE  
10  
FAN  
DF RS  
FAN  
C1  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
L1  
L2  
(HOT)  
RISE  
2
OPTIONAL FIELD WIRE JUMPER TO CYCLE W2 WITH H1  
IN EM. HEAT(FASTER RESPONSE).  
REVERSING  
SOLENOID  
M2858  
Fig. 154. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
60-2485—8  
164  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
HOT)  
H1 ANTICIPATOR  
R
(
2
3
RTD1  
OTD1  
EHR1  
ODT2  
EHR2  
FAN  
SWITCH  
L2  
1
RTD2  
RTD3  
AUTO  
ON  
2
H1  
FALL  
W3  
W2  
4
H2  
ANTICIPATOR  
5
6
H2  
FALL  
AUX. HT.  
LED (GRN)  
SYSTEM  
SWITCH  
RTD1  
X
OFF  
COOL  
AUTO  
HEAT  
SYSTEM  
MONITOR  
8
9
EM. HT.  
LED (RED)  
FAN  
RELAY  
L
RISE  
G
C1  
ANTICIPATOR  
RD  
COOL  
CHANGEOVER VALVE  
CHANGEOVER  
EM. HT.  
10  
O
E
EM. HT.  
RELAY  
CHP  
RISE  
C1  
COMPRESSOR  
CONTACTOR  
LACO  
Y
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M1589  
W3 TERMINAL ON SELECT MODELS.  
Fig. 155. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
165  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
L2  
(
HOT)  
1
COOL  
H1  
CHANGEOVER VALVE  
ANTICIPATOR  
FALL  
1
2
O
FAN  
SWITCH  
H1  
FAN RELAY  
ON  
G
R
ON  
4
AUX. HT.  
RELAY  
CONTACT  
OUTDOOR  
THERMOSTAT  
FALL  
EM. HT.  
RELAY  
H2 ANTICIPATOR  
E
H2  
6
8
SYSTEM  
SWITCH  
L1  
RISE  
OFF  
EM. HT.  
HEAT  
COMPRESSOR  
FAILURE  
EM. HT. LED  
(RED)  
CO  
9
X
AUTO  
C1 ANTICIPATOR  
EM. HT. LED  
COOL  
(GREEN)  
AUX. HT. RELAY  
10  
RISE  
C1  
W2  
COMPRESSOR CONTACTOR  
Y
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M5720  
Fig. 156. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
COOL CHANGEOVER  
VALVE  
1
Y1  
L1  
(HOT)  
FAN SWITCH  
FALL  
2
FAN RELAY  
L2  
AUTO  
H1 ANTICIPATOR  
3
G
R
H1  
ON  
DEFROST  
RELAY  
TIME DELAY  
RELAY 2  
CHECK LED  
(GREEN)  
4
X
H2 ANTICIPATOR  
FALL  
6
W2  
E
TIME DELAY  
RELAY 1  
H2  
SYSTEM  
SWITCH  
8
EM. HT.  
OFF  
EM. HT.  
HEAT  
LED (RED)  
CO  
C1  
RISE  
LOCKOUT  
RELAY  
9
C1 ANTICIPATOR  
AUTO  
10  
COOL  
HI PRESSURE  
SWITCH  
COMPRESSOR  
CONTACTOR  
W1  
C1  
M2860  
RISE  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
Fig. 157. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
60-2485—8  
166  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
HOT) L2  
(
1
1
2
O
E
H1 ANTICIPATOR  
COOL CHANGEOVER VALVE  
EM. HT. RELAY  
FAN  
SWITCH  
H1  
AUTO  
ON  
FALL  
G
FAN RELAY  
2
4
6
B
HEAT CHANGEOVER VALVE  
R
H2  
W2  
H2 ANTICIPATOR  
SYSTEM  
SWITCH  
FALL  
AUX. HT. RELAY  
OFF  
EM. HT.  
HEAT  
L1  
8
9
COMPRESSOR  
FAILURE  
CO  
EM. HT. LED  
(RED)  
RISE  
C1  
C1 ANTICIPATOR  
AUTO  
X
Y
COOL  
AUX. HT. LED (GREEN)  
RISE  
10  
COMPRESSOR CONTACTOR  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
2
B TERMINAL ON SELECT MODELS.  
M5721  
Fig. 158. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
167  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
COOL CHANGEOVER VALVE  
L2  
1
O
G
H1 ANTICIPATOR  
L1  
HOT)  
(
1
FAN RELAY  
FAN SWITCH  
AUTO  
HEAT RELAY  
CONTACT  
2
4
OFF  
R
H1  
AUX. HT. RELAY  
FALL  
W
OUTDOOR  
THERMOSTAT  
SYSTEM  
SWITCH  
6
E
FALL  
RISE  
HEAT RELAY EM. HT.  
H2 ANTICIPATOR  
8
CONTACT  
RELAY  
H2  
EM.HT.  
AUTO  
EM. HT. LED  
9
(RED)  
CO  
X
OFF  
COMPRESSOR  
CONTACTOR  
LIMIT  
C1 ANTICIPATOR  
Y
10  
RISE  
C1  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M5722  
Fig. 159. Schematic and hookup of T874G with Q674J. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
FALL  
O
2
FAN  
COOL CHANGEOVER VALVE  
SWITCH  
H1  
H1 ANTICIPATOR  
H2 ANTICIPATOR  
G
R
AUTO  
3
4
FAN RELAY  
L1  
ON  
(HOT)  
L2  
1
FALL  
5
6
W
H2  
AUX. HT. RELAY  
RISE  
SYSTEM  
SWITCH  
X
CO  
EM. HT. RELAY  
8
9
EM. HT.  
AUTO  
OFF  
EM. HT.  
LED (RED)  
B
COMPRESSOR  
CONTACTOR  
C1 ANTICIPATOR  
1
RISE  
Y
0
C1  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M5723  
Fig. 160. Schematic and hookup of T874G with Q674J. Used in heat pump applications.  
60-2485—8  
168  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
COOL CHANGEOVER VALVE  
1
1
2
O
L1  
(HOT)  
H1 ANTICIPATOR  
FAN  
SWITCH  
L2  
AUTO  
ON  
G
R
FAN RELAY  
H1  
OUTDOOR  
THERMOSTAT  
FALL  
H2  
4
6
W2  
EM. HT. RELAY 1  
EM. HT. RELAY EM. HT. RELAY 2  
CONTACT 1  
H2 ANTICIPATOR  
FALL  
SYSTEM  
SWITCH  
E
2
EM. HT. RELAY EM.HT.  
8
9
CONTACT 2  
RELAY 3  
CO  
C1 ANTICIPATOR  
L
SUPL. HT.  
ON  
RISE  
SUPL. HT.  
LED (RED)  
C
Y
OFF  
COMPRESSOR  
CONTACTOR 1  
C1  
10  
RISE  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
2
N.O. SWITCH — INSTALLER ADDED, TO LIGHT EM. HT. LED  
WHEN COMPRESSOR OPERATION IS NOT NORMAL.  
M5724  
Fig. 161. Schematic and hookup of T874G with Q674J. Used in heat pump applications.  
169  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THEROMSTAT  
SUBBASE  
SYSTEM COMPONENTS  
C815A OUTDOOR  
THERMISTOR  
T
1
2
FAN RELAY  
FALL  
H1  
FAN SWITCH  
G
AUTO  
ON  
COOL  
CHANGEOVER VALVE  
H1 ANTICIPATOR  
O
R
3
4
1
FALL  
H2  
L1  
(HOT)  
L2  
OUTDOOR  
THERMOSTAT  
5
X2  
AUX. HT. LED  
(GREEN)  
AUX. HT. RELAY  
RESET HEATER  
6
8
W
B
SYSTEM SWITCH  
EM. HT.  
RISE  
CO  
AUTO  
OFF  
EM. HT.  
LED (RED)  
EM. HT. RELAY  
F
Y
9
RISE  
C1  
C1  
10  
1
ANTICIPATOR  
COMPRESSOR  
CONTACTOR  
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M5725  
Fig. 162. Schematic and hookup of T874G with Q674J. Used in heat pump applications.  
60-2485—8  
170  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L2  
L1  
(HOT)  
HEAT DAMPER  
1
B
H1  
ANTICIPATOR  
HEAT RELAY 1  
FAN RELAY  
1
W1  
G
FAN  
SWITCH  
H1  
AUTO  
ON  
FALL  
4
6
H2  
HEAT RELAY 2  
ANTICIPATOR  
W2  
R
SYSTEM  
SWITCH  
1
AUTO  
OFF  
8
9
H2  
FALL  
S1  
RESET CIRCUIT  
RESET  
1
COOL  
CHANAGEOVER VALVE  
CO  
O
FALL  
10  
C1  
S2  
RESET CIRCUIT  
ANTICIPATOR  
C1  
Y
RISE  
SERVICE LED (RED)  
COMPRESSOR  
RELAY  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
X
2
3
H2 HAS 10¡F FIXED SETBACK FROM H1 ON T874G1485, 0-12¡F  
ADJUSTABLE ON T874G1535.  
ON LED (YELLOW)  
A
C
RESET IN MOMENTARY POSITION, SPRING RETURN TO OFF UPON  
SWITCH RELEASE.  
M1820C  
Fig. 163. Schematic and hookup of T874G with Q674C. Used in standard applications.  
171  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(
HOT)  
1
L2  
H1  
ANTICIPATOR  
2
O
Y
COOL CHANGEOVER  
VALVE  
FALL  
RISE  
3
FAN SWITCH  
AUTO  
H1  
COMPRESSOR  
CONTACTOR  
G
R
4
6
ON  
FAN RELAY  
2
SYSTEM SWITCH  
L
CO  
8
9
OFF  
MALFUNCTION  
LED (RED)  
HEAT CHANGEOVER  
VALVE  
B
C1  
ANTICIPATOR  
AUTO  
RISE  
10  
X
MALFUNCTION  
SWITCH  
C1  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
M5726  
R-L JUMPER SUPPLIED BY HONEYWELL.  
Fig. 164. Schematic and hookup of T874H with Q674C. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
1
2
(HOT)  
1
L2  
FALL  
H1  
3
J
R1 N.O.2  
S1 RELAY  
S1 N.C.  
H1 ANTICIPATOR  
S
3
4
FAN  
SWITCH  
SOLENOID RELAY  
2
AUTO  
G
R
ON  
H2 ANTICIPATOR  
FAN RELAY  
5
C
H2  
H2  
FALL  
7
8
AUX. HT. RELAY  
R1 N.C.1  
COMPRESSOR  
CONTACTOR  
SYSTEM  
SWITCH  
H1  
OFF  
R2 N.O. 1  
REV. VALVE  
R1 RELAY  
AUTO  
9
3
C1  
C1  
ANTICIPATOR  
RISE  
10  
O
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
2
FIELD REMOVABLE JUMPER.  
M5727  
3
H1 AND C1 ARE DPST SWITCHES.  
Fig. 165. Schematic and hookup of T874L with Q674C. Used in heat pump applications.  
60-2485—8  
172  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(HOT)  
FALL  
H1  
FAN  
SWITCH  
1
L2  
1
AUTO  
ON  
W1  
H1 ANTICIPATOR  
HEAT RELAY 1  
AUX. HT. LED  
(
GREEN)  
4
6
X
EM. HT. LED  
RED)  
(
W2  
FALL  
H2  
HEAT RELAY 2  
EM. HT. RELAY  
RH  
L
SYSTEM  
SWITCH  
H2 ANTICIPATOR  
OFF  
EM. HT.  
HEAT  
8
9
SYSTEM  
MONITOR  
RISE  
C1  
E
AUTO  
G
COOL  
FAN RELAY  
10  
RC  
Y1  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
COMRESSOR CONTACTOR 1  
COMRESSOR CONTACTOR 2  
11  
Y2  
RISE  
C2  
L2  
1
L1  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
(HOT)  
M5728  
Fig. 166. Schematic and hookup of T874D with Q674F. Used in standard applications.  
173  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
HOT) L1 L2  
(
1
R
ODT 1  
EHR 1  
ODT 2  
H1 ANTICIPATOR  
FALL  
2
RTD 1  
RTD 2  
H1  
FAN SWITCH  
3
4
AUTO  
ON  
H2  
ANTICIPATOR  
EHR 2  
RTD 3  
RTD 1  
5
W2  
H2  
FALL  
AUX. HT.  
LED (GREEN)  
X
SYSTEM  
SWITCH  
EM. HT.  
COMPRESSOR  
FAILURE  
LED (RED)  
RD  
OFF  
EM. HT.  
HEAT  
L
7
FALL  
CHANGEOVER  
G
B
FAN RELAY  
AUTO  
HEAT  
8
9
CHANGEOVER  
VALVE  
COOL  
EM. HT.  
RELAY  
E
Y
10  
C1  
ANTICIPATOR  
EHT1  
LACO  
CHP  
COMPRESSOR  
CONTACTOR  
C1  
RISE  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M1592A  
Fig. 167. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
60-2485—8  
174  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
W3 RELAY  
W3  
O
COOL CHANGEOVER  
VALVE  
L
COMPRESSOR  
MONITOR  
H1  
ANTICIPATOR  
FAN RELAY  
FAN  
SWITCH  
1
2
G
AUTO  
ON  
C ANTICIPATOR  
L1  
R
(HOT)  
L2  
1
H1  
W2  
C
3
EM. HT.  
LED (RED)  
AUX. HT. RELAY  
EM. HT. RELAY  
FALL  
SYSTEM  
SWITCH  
4
5
6
AUX. HT.  
LED (GRN)  
E
X
EM. HT.  
HEAT  
H2  
ANTICIPATOR  
3
H2  
OFF  
HEAT  
CHANGEOVER  
VALVE  
FALL  
X2  
COOL  
B
11  
W1 RELAY  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
W1  
COMPRESSOR  
RELAY  
2
3
REMOVE JUMPER WHEN W1 RELAY IS USED.  
FACTORY-INSTALLED JUMPER.  
2
M5067  
Y
Fig. 168. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
175  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
O
G
FALL  
H1  
FAN SWITCH  
H1 ANTICIPATOR  
COOL CHANGEOVER  
VALVE  
AUTO  
ON  
2
FAN RELAY  
B
3
B RELAY  
W3  
4
6
AUX HT. RELAY  
L1  
(HOT)  
R
SYSTEM  
SWITCH  
L2  
H2  
E
L
ANTICIPATOR  
1
OFF  
EM. HT. RELAY  
H2 FALL  
EM. HT.  
HEAT  
EM. HT.  
LED (RED)  
AUTO  
COOL  
2
X
RISE  
8
9
AUX. HT.  
LED (GREEN)  
C1  
AUX. HT. RELAY  
W2  
Y
C1 ANTICIPATOR  
RISE  
1
0
COMPRESSOR  
CONTACTOR  
1
1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
CO  
12  
2
3
TERMINAL LABELED C/X ON SOME MODELS.  
W3 TERMINAL ON SOME MODELS ONLY.  
M5986A  
Fig. 169. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
60-2485—8  
176  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
W3  
W1 RELAY  
W3 RELAY  
W1  
H1  
FALL  
2
B RELAY  
H1 ANTICIPATOR  
FAN SWITCH  
B
3
FAN RELAY  
AUTO  
ON  
G
4
5
L1  
(HOT)  
R
AUX. HT. RELAY  
L2  
1
6
W2  
SYSTEM  
SWITCH  
H2  
AUX. HT.  
ANTICIPATOR  
OFF  
LED (GREEN)  
EM. HT.  
H2  
3
X
HEAT  
8
FALL  
EM. HT.  
LED (RED)  
AUTO  
COOL  
9
CO  
COMPRESSOR  
FAULT  
L
C1 ANTICIPATOR  
E
RISE  
COOL  
CHANGEOVER  
10  
EM. HT.  
RELAY  
VALVE  
RISE  
O
COMPRESSOR  
CONTACTOR  
C1  
2
1
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
Y
2
3
ON SOME MODELS, Y TERMINAL MAY BE LABELED Y1.  
M5987A  
EMERGENCY HEAT RUNS CONTINUOUSLY WHEN SWITCH IN IN EM. HT. POSITION.  
Fig. 170. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
177  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
R
(HOT)  
2
3
1
L2  
FALL  
Y
H1  
FAN  
SWITCH  
O.D.T.  
COMPRESSOR  
CONTACTOR  
H1 ANTICIPATOR  
AUTO  
ON  
G
4
FAN RELAY  
H2 ANTICIPATOR  
HCR1  
HCR2  
5
W1  
F
EM. HT. LED  
(RED)  
FALL  
H2  
HCR1  
6
8
9
C
E
2
CO  
SYSTEM  
SWITCH  
HCR2  
HCR3  
RISE  
C1 ANTICIPATOR  
EM. HT.  
AUTO  
OFF  
X
1
0
1
"X" RELAY  
"
P" RELAY  
P
1
C1  
RISE  
CO  
O
1
2
COOL CHANGEOVER  
VALVE  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
EXTERNAL JUMPER SUPPLIED BY HONEYWELL.  
2
M5729  
Fig. 171. Schematic and hookup of T874J with Q674J. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
FAN  
SWITCH  
2
H1 ANTICIPATOR  
3
FAN RELAY  
AUTO  
G
R
ON  
4
O
FALL  
FAULT  
LED  
COOL  
CHANGEOVER  
VALVE  
H1  
2
(RED)  
8
C
RISE  
CO  
C1 ANTICIPATOR  
SYSTEM  
SWITCH  
CHECK  
FILTER  
LED (YELLOW)  
3
9
HEAT  
L1  
(HOT)  
10  
OFF  
L2  
1
COOL  
11  
12  
Y
C1  
COMPRESSOR  
CONTACTOR  
M1401  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
RISE  
Fig. 172. Schematic and hookup of T874H with Q674B. Used in heat pump applications.  
60-2485—8  
178  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
FAN  
SWITCH  
2
H1 ANTICIPATOR  
3
FAN RELAY  
AUTO  
ON  
G
R
4
O
FALL  
FAULT  
LED  
COOL  
CHANGEOVER  
VALVE  
H1  
2
(RED)  
8
C
RISE  
CO  
C1 ANTICIPATOR  
SYSTEM  
SWITCH  
CHECK  
FILTER  
LED (YELLOW)  
3
9
OFF  
L1  
(HOT)  
10  
AUTO  
L2  
1
11  
12  
Y
C1  
COMPRESSOR  
CONTACTOR  
M1400  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
RISE  
Fig. 173. Schematic and hookup of T874H with Q674C. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
2
HA  
FAN  
SWITCH  
3
FAN RELAY  
AUTO  
ON  
G
H1  
EM.. HT. RELAY  
FALL  
4
5
X2  
T
H2  
ODA  
C815A  
OUTDOOR  
THERMISTOR  
FALL  
1
L1  
HOT)  
L2  
R
F
6
(
"F" RELAY  
C1  
8
9
SYSTEM  
SWITCH  
EM. HT.  
AUX. HT. RELAY  
RISE  
AUTO  
W
EM. HT.  
LED (RED)  
OFF  
2
CA  
10  
U
AUX. HT.  
C2  
LED (GREEN)  
B
COOL CHANGEOVER  
VALVE  
RISE  
O
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
COMPRESSOR  
CONTACTOR  
REMOVABLE JUMPER.  
Y
M1403  
Fig. 174. Schematic and hookup of T874G with Q674J. Used in heat pump applications.  
179  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
COOL  
H1 ANTICIPATOR  
1
2
O
FAN RELAY  
FAN  
SWITCH  
CHANGEOVER VALVE  
ON  
AUTO  
G
R
L1  
(HOT)  
FALL  
L2  
1
4
H.C.R. 1  
H.C.R.2  
H2  
O.D.T.  
ANTICIPATOR  
W2  
6
H.C.R. 1  
FALL  
8
SYSTEM  
SWITCH  
H.C.R. 2  
H.C.R.3  
E
L
C1 ANTICIPATOR  
SUPL. HT.  
ON  
9
CO  
MANUAL  
(RED)  
RISE  
OFF  
AUTO  
(YEL)  
C
10  
Y
HEAT PUMP  
(GRN)  
DEFROST  
(RED)  
C1  
RISE  
COMPRESSOR  
CONTACTOR  
D
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M2112A  
Fig. 175. Schematic and hookup of T874G with Q674J. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
2
Y1  
Y2  
FALL  
COOL  
H1 ANTICIPATOR  
CHANGEOVER VALVE  
H1  
3
4
COMPRESSOR  
CONTACTOR  
AUTO  
ON  
FALL  
2
G
FAN RELAY  
L2  
L1  
SETBACK  
OPEN-NIGHT  
CLOSED-DAY  
FAN SWITCH  
1
6
SYSTEM  
SWITCH  
(HOT)  
R
L
RISE  
SETBACK RELAY  
8
9
OFF  
CO  
AUTO  
X1  
LED  
10  
C
3
LED  
RISE  
C1 ANTICIPATOR  
X2  
C1  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
SETBACK STAGE OFFSET 12°F (7°C) FROM H1 STAGE.  
LEDS ON SOME MODELS.  
M5730  
3
Fig. 176. Schematic and hookup of T874G with Q674C. Used in standard applications.  
60-2485—8  
180  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
LOCKOUT  
(RESET) RELAY  
FAN  
SWITCH  
X
H1 ANTICIPATOR  
H1  
1
RESET LED  
RED)  
(
AUTO  
ON  
G
FALL  
FAN RELAY  
4
L1  
(HOT)  
R1  
6
L2  
SYSTEM SWITCH  
3
H2  
1
R2  
OFF  
FALL  
AUTO  
7
2
B
CO  
HEAT CHANGEOVER  
VALVE  
8
RISE  
2
O
COOL  
CHANGEOVER VALVE  
9
C1 ANTICIPATOR  
Y
10  
COMPRESSOR  
CONTACTOR  
C1  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
RISE  
USE EITHER 'B' OR 'O' ONLY FOR SYSTEM CHANGEOVER. 0.8A AT 30 VAC MAXIMUM LOAD CURRENT.  
o o  
SECOND STAGE HEAT MAKES 12 F (7 C) AFTER FIRST STAGE HEAT TO PROVIDE SETBACK  
3
M114C  
Fig. 177. Schematic and hookup of T874G,H with Q674C. Used in standard applications.  
THERMOSTAT  
FALL  
SUBBASE  
SYSTEM COMPONENTS  
CHANGEOVER RELAY  
H1  
W1  
W2  
1
3
FAN  
SWITCH  
H1 ANTICIPATOR  
AUX.HT. RELAY  
AUTO  
ON  
L1  
(HOT)  
1
L2  
R
L
4
6
FALL  
SERVICE  
LED (RED)  
H2 ANTICIPATOR  
SYSTEM  
SWITCH  
H2  
C0  
OFF  
X
8
9
COOL  
EM, HT. LED  
YELLOW)  
(
AUTO  
HEAT  
FAN RELAY  
G
RISE  
C1 ANTICIPATOR  
1
EM.HT.  
COMPRESSOR RELAY  
EM.HT. RELAY  
0
C
K
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M18623  
Fig. 178. Schematic and hookup of T874N with Q674F. Used in heat pump applications.  
181  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
OUTDOOR  
REVERSING  
VALVE  
1
W1  
DEFROST  
RELAY  
THERMOSTAT  
H1  
ANTICIPATOR  
EM.HT. RELAY  
CONTACT  
HEAT  
RELAY 2  
2
4
EM.HT. RELAY  
CONTACT  
HEAT  
RELAY 3  
H1  
W3  
FALL  
FAN SWITCH  
AUTO  
FAN RELAY  
H2  
G
R
ANTICIPATOR  
ON  
5
1
L1  
(HOT)  
L2  
H2  
FALL  
6
W2  
E
HEAT  
RELAY 1  
SYSTEM  
SWITCH  
EM. HT.  
LED (RED)  
OFF  
EM. HT.  
RELAY  
X
L
EM. HT.  
CHECK  
LED  
(GREEN)  
8
OPTIONAL  
COMPRESSOR  
FAILURE DEVICE  
HEAT  
AUTO  
RISE  
9
C1  
HIGH  
PRESSURE  
SWITCH  
COMPRESSOR  
CONTACTOR  
ANTICIPATOR  
COOL  
C1  
1
CO  
Y
10  
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M3686  
Fig. 179. Schematic and hookup of T874N with Q674F. Used in heat pump applications.  
60-2485—8  
182  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
HOT)  
L2  
(
FAN DELAY  
RELAY  
1
R-11  
R-11  
ELEC. HT.  
RELAY STG. 1  
CHANGEOVER VALVE  
1
W1  
Y1  
FALL  
H1  
COMPRESSOR  
CONTACTOR  
R-6  
OVERLOAD  
R-10  
R-8  
H1  
ANTICIPATOR  
FAN  
SWITCH  
FAN RELAY  
AUTO  
ON  
R-6  
G
R-1  
R-2  
4
FALL  
H1  
R
ELEC. HT. RELAY  
STG. 2  
R-10  
H2  
ANTICIPATOR  
6
8
W2  
E
EM. HT.  
LED  
EM. HT. RELAY  
(
RED)  
C1  
RISE  
X2  
SYSTEM  
SWITCH  
R-5  
R-5  
T2  
2
9
R-6  
(
HEAT PUMP  
EM. HT.  
FILTER  
LED  
(YELLOW)  
C1 ANTICIPATOR  
OPERATION) R-10  
10  
RISE  
AUTO  
OFF  
C2 ANTICIPATOR  
RANDOM START  
R-8 (OPT.)  
(BIOLERLESS  
OPERATION ) R-11  
C2  
R-3  
11  
Y2  
X1  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
FILTER LED ON SOME MODELS.  
M5957  
Fig. 180. Schematic and hookup of T874A,D with Q674J. Used in heat pump applications.  
183  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENT  
L1 L2  
HOT)  
(
FALL  
CO  
2
3
TIME  
CLOCK  
1
Y
H2  
FALL  
COMPRESSOR  
RELAY  
FAN  
SWITCH  
4
6
AUTO  
G
R
ON  
FALL  
H1  
FAN RELAY  
H1  
ANTICIPATOR  
W
8
RISE  
W2  
REVERSING  
VALVE  
SYSTEM  
SWITCH  
C1  
9
COMPRESSOR  
FAULT LED (RED) COMPRESSOR  
FAULT  
C1  
ANTICIPATOR  
OFF  
10  
A
AUTO  
M18587  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
Fig. 181. Schematic and hookup of T874K with Q674C. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
OUTDOOR  
RESET  
1
2
T
H1/C  
ANTICIPATOR  
AUX. HT.  
FAN  
H1  
W2  
H2  
FAN  
SWITCH  
AUTO  
ANTICIPATOR  
FALL  
3
G
R
4
5
6
ON  
RESET  
H2  
EM. HT.  
E
B
W89  
HEAT  
PUMP  
SYSTEM  
SWITCH  
FALL  
EM. HT.  
CONTROL  
PANEL  
EM. HT.  
LED (YELLOW)  
HEAT  
OFF  
EM. HT. LIGHT  
X
SERVICE  
LED (RED)  
COOL  
SERVICE  
LIGHT  
L
O
Y
COOL/HEAT  
COMPRESSOR  
M3951  
Fig. 182. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
60-2485—8  
184  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
2
O
H1  
FALL  
ANTICIPATOR  
FAN  
SWITCH  
COOL CHANGEOVER  
VALVE  
H1  
AUTO  
G
ON  
2BH  
FAN RELAY  
4
6
R
H2  
O. D. S.  
ANTICIPATOR  
FALL  
H2  
1BH  
SH  
E
SYSTEM  
SWITCH  
L1  
RISE  
CO  
8
9
EM. HT.  
LED (RED)  
COMPRESSOR  
FAILURE  
X
C1  
EM. HT.  
ON  
ANTICIPATOR  
AUX. HT.  
LED (GREEN)  
1BH  
10  
W
Y
OFF  
RISE  
C1  
COMPRESSOR  
CONTACTOR  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
1
L1 L2  
(HOT)  
M3950  
Fig. 183. Schematic and hookup of T874G with Q674J. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
HEAT RELAY 1  
H1  
ANTICIPATOR  
1
W1  
W2  
NO  
FAN  
SWITCH  
FALL  
H1  
1
HEAT RELAY 2  
L2  
4
6
H2  
RH  
RC  
L1  
(HOT)  
ANTICIPATOR  
FALL  
H2  
L1  
(HOT)  
SYSTEM  
SWITCH  
L2  
RISE  
C1  
1
8
9
OFF  
COMPRESSOR  
CONTACTOR 1  
C1  
ANTICIPATOR  
AUTO  
1
0
C2  
Y1  
Y2  
ANTICIPATOR  
11  
RISE  
C2  
COMPRESSOR  
CONTACTOR 2  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
M3953  
Fig. 184. Schematic and hookup of T874A,F with Q674G. Used in standard applications.  
185  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
L2  
(HOT)  
H1  
ANTICIPATOR  
HEAT RELAY  
1
1
W1  
G
FALL  
AUTO  
FAN  
SWITCH  
H1  
ON  
FAN RELAY  
RC  
W2  
4
HEAT RELAY 2  
H2  
SYSTEM  
SWITCH  
ANTICIPATOR  
RH  
FALL  
H2  
6
IGNITION  
RELAY  
OFF  
RISE  
C1  
8
9
HEAT  
B
AUTO  
COOL  
C1  
ANTICIPATOR  
COMPRESSOR  
CONTACTOR 1  
10  
C2  
Y1  
Y2  
ANTICIPATOR  
RISE  
C2  
11  
COMPRESSOR  
CONTACTOR 2  
1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
L1 L2  
HOT)  
(
M3954  
Fig. 185. Schematic and hookup of T874D with Q674E. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
FALL  
H1  
1
W1  
H1  
1
ANTICIPATOR  
HEAT RELAY 1  
4
5
L2  
L1  
NO  
FAN  
SWITCH  
RH  
W2  
B
(HOT)  
H2  
HEAT RELAY 2  
FAN RELAY  
FALL  
H2  
ANTICIPATOR  
6
7
8
9
SYSTEM  
SWITCH  
OFF  
RISE  
AUTO  
FAN RELAY  
C1  
O
C1  
L2  
L1  
ANTICIPATOR  
10  
RC  
Y2  
(HOT)  
RISE  
C2  
11  
1
C2  
ANTICIPATOR  
COMPRESSOR  
CONTACTOR 2  
12  
Y1  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
COMPRESSOR  
CONTACTOR 1  
M3955  
Fig. 186. Schematic and hookup of T874D with Q674G. Used in standard applications.  
60-2485—8  
186  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
R4  
FALL  
H1  
HEAT RELAY 2  
2
3
R3  
R2  
FAN  
HEAT RELAY 1  
H1  
SWITCH  
ANTICIPATOR  
HIGH  
HI SPEED  
FAN RELAY  
LOW  
R1  
C
HIGH  
PRESSURE TEMP.  
SWITCH  
HIGH  
LO SPEED  
FAN RELAY  
4
5
LR  
SWITCH  
H2  
ANTICIPATOR  
R5  
X
FALL  
H2  
COOL  
CONTACTOR  
LOCKOUT  
RELAY  
SYSTEM  
SWITCH  
1
RISE  
C1  
L2  
HEAT  
OFF  
8
R
1
L1  
(HOT)  
C1  
ANTICIPATOR  
COOL  
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
10  
M3956  
Fig. 187. Schematic and hookup of T874C with Q674B. Used in standard applications.  
THERMOSTAT  
H1  
SUBBASE  
SYSTEM COMPONENTS  
HEAT RELAY 1  
ANTICIPATOR  
FALL  
H1  
1
W1  
RH  
1
4
L2  
NO  
FAN  
5
6
L1  
(HOT)  
H2  
SWITCH  
HEAT RELAY 2  
FALL  
ANTICIPATOR  
W2  
T
H2  
7
8
SYSTEM  
SWITCH  
FAN RELAY  
RISE  
C1  
B
AUTO  
9
O
C1  
L2  
L1  
ANTICIPATOR  
1
0
RC  
Y2  
(HOT)  
1
RISE  
C2  
1
1
C2  
ANTICIPATOR  
COMPRESSOR  
CONTACTOR 2  
12  
Y1  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
COMPRESSOR  
CONTACTOR 1  
M3958  
Fig. 188. Schematic and hookup of T874D with Q674G. Used in standard applications.  
187  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
FALL  
H1  
1
W1  
B
4
M839  
ANTICIPATOR  
NO  
MOTOR  
FALL  
H2  
5
6
FAN  
SWITCH  
L1  
W2  
RH  
RC  
Y
L2  
NO  
SYSTEM  
SWITCH  
R
8
9
Y2  
Y1  
10  
11  
M3960  
Fig. 189. Schematic and hookup of T874F with Q674D. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
V
1
2
VR  
RESET  
H1  
OG  
IN STAT  
1
ANTICIPATOR  
M
L1  
FAN  
SWITCH  
FALL  
H1  
2
COMPRESSOR  
CONTACTOR  
(HOT)  
L2  
AUTO  
ON  
HI PR  
3
F
L
SERVICE  
RELAY  
L1  
FAN RELAY  
4
(HOT)  
L2  
5
EM. HT. RELAY  
O. D. S.  
EM. HT.  
1
H2  
3
ANTICIPATOR  
SERVICE  
LED (RED)  
H2  
6
ELEC. HT. RELAY  
FALL  
Y
7
8
E
SYSTEM  
SWITCH  
ELEC. HT. RELAY  
EM. HT. LED  
YELLOW)  
RISE  
(
EM. HT.  
C1  
X
ANTICIPATOR  
C1  
HEAT  
10  
A
R
OFF  
C815A  
OUTDOOR THERMISTOR  
COOL  
COOL CHANGEOVER  
VALVE  
1
2
3
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
OPTIONAL REMOVABLE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.  
WIRE JUMPER FOR SERVICE LIGHT.  
M3978  
Fig. 190. Schematic and hookup of T874C with Q674L. Used in heat pump applications.  
60-2485—8  
188  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
2
3
Z
FAN  
FALL  
SWITCH  
"
Z" RELAY  
H1/C1  
ANTICIPATOR  
LO  
H1  
C1  
AUTO  
O
HI  
COOL CHANGE-  
OVER VALVE  
CONT.  
G
R
FAN RELAY  
L2  
L1  
4
6
(HOT)  
H2  
AUX. HT. RELAY  
ANTICIPATOR  
1
FALL  
H2  
W2  
C
SYSTEM  
SWITCH  
W1  
HEAT  
OFF  
HEAT RELAY  
COOL  
COOL  
RELAY  
Y
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M3965  
Fig. 191. Schematic and hookup of T874R with Q674B. Used in heat pump applications.  
THERMOSTAT  
H1  
SUBBASE  
SYSTEM COMPONENTS  
HEAT RELAY 1  
ANTICIPATOR  
FALL  
H1  
1
W1  
SYSTEM  
SWITCH  
OFF  
4
6
H2  
AUTO  
HEAT RELAY 2  
ANTICIPATOR  
FALL  
W2  
H2  
FILTER  
LED  
(
YELLOW)  
X
A
SERVICE  
LED (RED)  
RISE  
C1  
FAN  
SWITCH  
8
9
AUTO  
G
R
L2  
L1  
ON  
2
FAN RELAY  
(HOT)  
O
O
1
C1  
MOMENTARY  
CIRCUIT  
ANTICIPATOR  
10  
COMPRESSOR  
CONTACTOR 1  
C2  
ANTICIPATOR  
Y1  
Y2  
11  
RISE  
C2  
COMPRESSOR  
CONTACTOR 2  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE.  
M3959  
Fig. 192. Schematic and hookup of T874D with Q674C. Used in standard applications.  
189  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
FAN  
SWITCH  
L1  
(HOT)  
H1  
RH  
W1  
ANTICIPATOR  
L2  
AUTO  
ON  
H1  
FALL  
1
HEAT RELAY 1  
HEAT RELAY 2  
4
6
W2  
B
H2  
FALL  
H2 ANTICIPATOR  
CHANGEOVER  
RELAY (HEAT)  
O
SYSTEM  
SWITCH  
CHANGEOVER  
RELAY (COOL)  
8
9
OFF  
2
G
HEAT  
AUTO  
COOL  
RISE  
C1  
FAN RELAY  
Y2  
COMPRESSOR  
CONTACTOR 2  
10  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
Y1  
1
COMPRESSOR  
CONTACTOR 1  
L2  
11  
RC  
L1  
(HOT)  
C2  
RISE  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M3203B  
JUMPER RH, RC FOR SINGLE TRANSFORMER.  
Fig. 193. Schematic and hookup of T874D with Q674E. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
2
3
Y1  
COOL  
CHANGEOVER VALVE  
FAN RELAY  
FALL H1  
AUTO  
ON  
ANTICIPATOR  
H1  
G
R
FAN  
SWITCH  
CHECK  
LED  
DR  
TDR 2  
(
GREEN)  
4
6
HBTH  
FALL  
H2  
X
ANTICIPATOR  
H2  
W2  
E
TDR 1  
SYSTEM  
SWITCH  
OFF  
RISE  
CO  
8
9
C
EM. HT.  
EM. HT.  
LED (RED)  
COMPRESSOR  
CONTACTOR  
C1  
HEAT  
AUTO  
COOL  
ANTICIPATOR  
W1  
10  
HPA  
1
RISE  
C1  
L1 L2  
(HOT)  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M3977  
Fig. 194. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
60-2485—8  
190  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
COOL  
CHANGEOVER  
VALVE  
(HOT)  
L2  
H1 ANTICIPATOR  
1
1
2
4
O
G
H1  
FAN SWITCH  
FAN RELAY  
FALL  
AUTO  
ON  
"
B" RELAY  
B
R
EM. HT.  
RELAY  
SYSTEM  
SWITCH  
H2  
H2  
6
8
E
L
FALL  
ANTICIPATOR  
OFF  
EM. HT.  
HEAT  
EM. HT. LED  
RED)  
COMPRESSOR  
FAULT  
CO  
(
RISE  
X
9
AUX.  
HT. LED  
GREEN)  
AUTO  
COOL  
W2  
(
AUX. HT. RELAY  
C1 ANTICIPATOR  
10  
Y
COMPRESSOR  
CONTACTOR  
C1  
RISE  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M2974  
Fig. 195. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
HOT)  
L2  
COOL  
CHANGEOVER  
VALVE  
(
H1 ANTICIPATOR  
1
1
2
4
O
H1  
FAN SWITCH  
FAN RELAY  
FALL  
G
R
AUTO  
ON  
H.C.R.1  
W2  
H2  
O.D.T.  
H2  
6
8
FALL  
ANTICIPATOR  
E
SYSTEM  
SWITCH  
H.C.R.1  
H.C.R.2  
H.C.R.2  
CO  
RISE  
SUPL. HT.  
L
9
SUPL. HT.  
LED  
ON  
H.C.R.3  
C
(RED)  
OFF  
C1 ANTICIPATOR  
10  
Y
C1  
COMPRESSOR  
CONTACTOR  
RISE  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M2975  
Fig. 196. Schematic and hookup of T874G with Q674J. Used in heat pump applications.  
191  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
FAN RELAY  
1
2
3
4
5
6
G
W
AUX. HEATER  
RELAY  
AUX. HT.  
LED (GREEN)  
2
AUTO  
ON  
U
B
H1  
C1  
EM. HT.  
LED (RED)  
COMPRESSOR  
MONITOR  
FALL  
FAN  
SWITCH  
F
1
L1  
R
(HOT)  
L2  
H2  
FALL  
SYSTEM  
SWITCH  
EM. HT.  
HEAT  
T
OUTDOOR  
THERMISTOR  
X2  
OFF  
OUTDOOR  
THERMOSTAT  
11  
COOL  
O
Y
COOL  
CHANGEOVER  
VALVE  
COMPRESSOR  
RELAY  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
M2970  
FIELD REMOVABLE JUMPER.  
Fig. 197. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(
HOT)  
STAGE 1 HEAT RELAY  
L2  
1
W1  
1
H1  
FAN  
FALL  
SWITCH  
COMPRESSOR  
CONTACTOR  
AUTO  
H1 ANTICIPATOR  
Y1  
G
3
4
ON  
FAN RELAY  
H2  
H2  
6
7
FALL  
ANTICIPATOR  
R
STAGE 2  
HEAT RELAY  
SYSTEM  
SWITCH  
C1  
RISE  
OFF  
HEAT  
AUTO  
COOL  
W2  
8
9
10  
C2 ANTICIPATOR  
M2976  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
Fig. 198. Schematic and hookup of T874L with Q674E. Used in standard applications.  
60-2485—8  
192  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
W3 RELAY  
L1  
(HOT)  
L2  
H1 ANTICIPATOR  
FAN SWITCH  
W3  
1
2
FAN RELAY  
H1  
AUTO  
ON  
FALL  
G
R
3
4
AUX. HT. RELAY  
EM. HT. RELAY  
H2  
W2  
H2  
FALL  
ANTICIPATOR  
AUX. HT. LED  
(GREEN)  
5
SYSTEM  
SWITCH  
E
EM. HT.  
LED (RED)  
OFF  
EM. HT.  
HEAT  
COMPRESSOR  
FAULT  
8
9
CO  
L
X
B
RISE  
CHECK  
LED  
(RED)  
AUTO  
COOL  
C1 ANTICIPATOR  
C1  
1
0
HEAT CHANGEOVER  
VALVE  
1
1
2
O
RISE  
COOL CHANGEOVER  
RELAY  
1
Y
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
COMPRESSOR  
CONTACTOR  
M2977  
Fig. 199. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(HOT)  
L2  
1
1
T
H1  
RISE  
C1  
OUTDOOR  
THERMOSTAT  
FAN SWITCH  
H2 ANTICIPATOR  
SEQ 2  
W2  
2
3
4
AUTO  
ON  
OUTDOOR  
THERMOSTAT  
FAN RELAY  
G
R
5
H2  
C1 ANTICIPATOR  
SERVICE  
LED  
FALL  
SYSTEM  
SWITCH  
(YELLOW)  
6
EM. HT.  
X
Z
K
SERVICE  
HEAT  
OFF  
SEQ 1  
11  
EM. HT.  
LED (RED)  
COMPRESSOR  
CONTACTOR  
COOL  
H1 ANTICIPATOR  
12  
Y
HEAT CHANGEOVER  
VALVE  
W1  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M2978  
Fig. 200. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
193  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
C815A  
OUTDOOR  
THERMISTOR  
(HOT)  
RESET  
L2  
1
1
T
H1  
C1  
H2  
OUTDOOR  
THERMOSTAT  
ANTICIPATOR  
SEQ 2  
FAN SWITCH  
AUTO  
RISE  
W2  
2
3
4
ON  
OUTDOOR  
THERMOSTAT  
FAN RELAY  
G
5
H2  
C1 ANTICIPATOR  
SERVICE  
LED  
RISE  
SYSTEM  
SWITCH  
R
X
(YELLOW)  
6
EM. HEAT  
HEAT  
SERVICE  
Z
K
OFF  
11  
EM. HT.  
LED (RED)  
COMPRESSOR  
CONTACTOR  
COOL  
SEQ 1  
H1 ANTICIPATOR  
12  
Y
HEAT CHANGEOVER  
VALVE  
W1  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M2979  
Fig. 201. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
THERMOSTAT  
H1  
SUBBASE  
SYSTEM COMPONENTS  
A2  
L1  
HOT)  
L2  
(
SERVICE  
LED (RED)  
FALL  
HEAT RELAY 1  
1
1
4
W1  
H1 ANTICIPATOR  
SERVICE  
LED (RED)  
NO  
FAN  
SWITCH  
5
A1  
H2  
HEAT RELAY 2  
H2  
6
7
W2  
FALL  
ANTICIPATOR  
"
T" RELAY  
T
8
9
C1  
RC  
RISE  
FAN RELAY B  
FAN RELAY O  
SYSTEM  
SWITCH  
B
OFF  
10  
RH  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
AUTO  
1
L1  
HOT)  
L2  
O
1
1
2
(
C2  
RISE  
1
Y2  
COMPRESSOR  
CONTACTOR 2  
Y1  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED  
COMPRESSOR  
CONTACTOR 1  
M2980  
Fig. 202. Schematic and hookup of T874D with Q674G. Used in standard applications.  
60-2485—8  
194  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(
HOT)  
COMPRESSOR  
CONTACTOR  
L2  
1
Y
CO  
FAN SWITCH  
FALL  
FAN RELAY  
2
AUTO  
ON  
G
R
3
HEAT CHANGEOVER  
VALVE  
4
6
W
H1  
FALL  
H1 ANTICIPATOR  
SYSTEM  
SWITCH  
COMP.  
FAULT  
(RED)  
W2  
COMPRESSOR  
FAULT  
8
9
OFF  
A
C1  
RISE  
AUTO  
10  
C1 ANTICIPATOR  
M2981  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
Fig. 203. Schematic and hookup of T874L with Q674C. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
HEAT RELAY 1  
L1  
(HOT)  
L2  
1
W1  
1
FAN  
H1  
SWITCH  
HEAT RELAY 2  
FALL  
AUTO  
W2  
R
H1 ANTICIPATOR  
ON  
4
LED  
RED)  
X
2
(
H2  
H2  
B
6
8
EM. HT. RELAY  
FALL  
ANTICIPATOR  
E
SYSTEM  
SWITCH  
OFF  
FAN RELAY  
C1  
G
RISE  
EM. HT.  
HEAT  
COMPRESSOR  
CONTACTOR 2  
9
Y2  
Y1  
AUTO  
COOL  
1
0
COMPRESSOR  
CONTACTOR 1  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
1
1
C2  
RISE  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
LED IS NOT LABELED. JUMPER W2 TO X FOR AUXILIARY HEAT INDICATION. JUMPER E TO X FOR  
EMERGENCY HEAT INDICATION. CONNECT SYSTEM MONITOR TO X TO IDENTIFY WHEN SYSTEM  
NEEDS TO BE CHECKED.  
M2982A  
Fig. 204. Schematic and hookup of T874D with Q674F. Used in standard applications.  
195  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(
HOT)  
COOL CHANGEOVER  
VALVE  
L2  
H1 ANTICIPATOR  
1
2
3
Y1  
Y2  
H1  
COMPRESSOR  
CONTACTOR  
FALL  
FAN SWITCH  
FAN RELAY  
AUTO  
G
R
4
6
8
ON  
L
SYSTEM  
SWITCH  
LED  
(RED)  
CO  
RISE  
X1  
C
OFF  
9
AUTO  
2
LED  
(RED)  
C1 ANTICIPATOR  
10  
X2  
C1  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
LEDS ON SOME MODELS.  
M2983  
RISE  
Fig. 205. Schematic and hookup of T874H with Q674C. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(HOT)  
L2  
2
R
Y
COMPRESSOR  
CONTACTOR  
1
H1  
FAN SWITCH  
H1 ANTICIPATOR  
3
FALL  
AUTO  
ON  
FAN RELAY  
4
H2  
ANTICIPATOR  
G
H.C.R.1  
5
H2  
W2  
FALL  
6
8
SUPL. HT.  
LED (RED)  
SYSTEM  
SWITCH  
L
O.D.T.  
CO  
RISE  
SUPL. HT.  
ON  
H.C.R.1  
H.C.R.2  
9
C
E
C1 ANTICIPATOR  
OFF  
10  
H.C.R.2  
H.C.R.3  
11  
O
12  
COOL  
RISE  
CHANGEOVER  
VALVE  
CO  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M2984  
C1  
Fig. 206. Schematic and hookup of T874J with Q674J. Used in heat pump applications.  
60-2485—8  
196  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(HOT)  
2
R
Y
L2  
COMPRESSOR  
CONTACTOR  
1
H1  
FAN SWITCH  
H1 ANTICIPATOR  
3
FALL  
AUTO  
ON  
FAN RELAY  
H.C.R.1  
4
H2  
G
ANTICIPATOR  
5
H2  
W2  
FALL  
6
8
SUPL. HT.  
LED (RED)  
SYSTEM  
SWITCH  
L
O.D.T.  
CO  
RISE  
SUPL. HT.  
H.C.R.1  
H.C.R.2  
H.C.R.2  
9
HEAT  
C
E
C1 ANTICIPATOR  
OFF  
10  
COOL  
H.C.R.3  
11  
O
12  
COOL CHANGEOVER  
VALVE  
RISE  
M2985  
CO  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
C1  
Fig. 207. Schematic and hookup of T874J with Q674L. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
HEAT RELAY 1  
L1  
HOT)  
L2  
(
1
W1  
H1  
1
HEAT RELAY 2  
FALL  
NO  
W2  
RH  
H1 ANTICIPATOR  
FAN  
SWITCH  
4
5
6
2
H2  
H2  
RC  
Y2  
FALL  
ANTICIPATOR  
1
8
9
COMPRESSOR  
CONTACTOR 2  
L1  
(HOT)  
C1  
RISE  
Y1  
L2  
NO  
SYSTEM  
SWITCH  
COMPRESSOR  
CONTACTOR 1  
10  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
RC-RH REMOVABLE JUMPER WHEN SPECIFIED.  
M2986  
11  
C2  
RISE  
Fig. 208. Schematic and hookup of T874D with Q674D. Used in standard applications.  
197  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
R
(HOT)  
EM. HT.  
RELAY  
EM. HT.  
L2  
LED (RED)  
1
H1  
C1  
L
H1/C1  
ANTICIPATOR  
FAN SWITCH  
AUTO  
AUX. HT.  
LED  
X
RISE  
2
3
4
AUX. HT. RELAY  
FAN RELAY  
(GREEN)  
ON  
W2  
G
6
COOL  
SYSTEM  
SWITCH  
CHANGEOVER  
VALVE  
H2 ANTICIPATOR  
EM. HEAT  
HEAT  
O
E
H2  
FALL  
EM. HT. RELAY  
OFF  
COMPRESSOR  
CONTACTOR  
COOL  
Y
B
’"B" RELAY  
M2987  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
Fig. 209. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
FAN RELAY  
L1  
(HOT)  
H1  
L2  
1
G
1
FALL  
FAN  
H1 ANTICIPATOR  
SWITCH  
AUTO  
COOL  
CHANGEOVER  
VALVE  
2
3
R
O
ON  
HEAT  
CHANGEOVER  
VALVE  
HCO  
CCO  
FALL  
4
6
FILTER  
LED  
(YELLOW)  
B
F
L
SYSTEM  
SWITCH  
H2  
H2  
OFF  
HEAT  
AUTO  
FALL  
ANTICIPATOR  
8
RESET  
LED  
C1  
RISE  
(RED)  
COMPRESSOR  
CONTACTOR 1  
COOL  
9
Y1  
Y2  
1
0
C1 ANTICIPATOR  
C2 ANTICIPATOR  
COMPRESSOR  
CONTACTOR 2  
1
1
C2  
M2988  
RISE  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
Fig. 210. Schematic and hookup of T874Y with Q674E. Used in heat pump applications.  
60-2485—8  
198  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(HOT)  
L2  
W1 RELAY  
FAN RELAY  
H1 ANTICIPATOR  
1
2
3
4
W1  
FAN SWITCH  
AUTO  
H1  
FALL  
G
R
ON  
AUX. HT. RELAY  
SYSTEM  
SWITCH  
W2  
AUX. HT.  
LED  
(GREEN)  
OFF  
EM. HT.  
HEAT  
H2  
H2  
6
8
FALL  
ANTICIPATOR  
X
L
EM. HT.  
LED (RED)  
AUTO  
COOL  
RISE  
COMPRESSOR  
FAULT  
C1  
C1  
ANTICIPATOR  
10  
Y1  
COMPRESSOR  
CONTACTOR  
M2989  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
Fig. 211. Schematic and hookup of T874G with Q674F. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
HEAT RELAY 1  
(HOT)  
1
W1  
L2  
H1  
FAN  
SWITCH  
HEAT RELAY 2  
1
FALL  
W2  
RH  
AUTO  
H1 ANTICIPATOR  
ON  
4
6
8
2
H2  
H2  
RC  
G
FAN RELAY  
FALL  
ANTICIPATOR  
SYSTEM  
SWITCH  
Y2  
C1  
OFF  
HEAT  
AUTO  
COOL  
RISE  
COMPRESSOR  
CONTACTOR 2  
9
Y1  
1
COMPRESSOR  
CONTACTOR 1  
L1  
(HOT)  
10  
C1 ANTICIPATOR  
C2 ANTICIPATOR  
L2  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
11  
M2990  
RC -RH REMOVABLE JUMPER WHEN SPECIFIED.  
C2  
RISE  
Fig. 212. Schematic and hookup of T874A with Q674E. Used in standard applications.  
199  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(HOT)  
1
L2  
1
2
SYSTEM  
SWITCH  
RELAY 1  
N.O. 2  
S1  
RELAY  
H1  
H1 ANTICIPATOR  
3
FALL  
OFF  
H1  
AUTO  
COMPRESSOR  
CONTACTOR  
S1  
4
RELAY N.C.  
Y
R
C
H2  
5
H2 ANTICIPATOR  
FALL  
7
8
FIELD  
REMOVABLE  
JUMPER  
FAN  
SWITCH  
AUX. HT. RELAY  
COMPRESSOR  
H2  
L
LO  
RISE  
CO  
9
MED  
CHECK  
R1 RELAY N.C. 1 CONTACTOR  
LED (RED)  
HIGH  
ON  
10  
C1 ANTICIPATOR  
COOL  
R2  
CHANGEOVER  
RELAY  
VALVE  
N.O 1  
O
R1 RELAY  
K1 RELAY  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
G1  
G2  
K2 RELAY  
M2991  
Fig. 213. Schematic and hookup of T874L with Q674C. Used in heat pump applications.  
60-2485—8  
200  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
H1  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(HOT)  
1
2
L2  
FALL  
1
SYSTEM  
SWITCH  
H1 ANTICIPATOR  
AUX. HT. RELAY  
R1 RELAY  
HEAT  
H1  
R
OFF  
C1 ANTICIPATOR  
COOL  
O
3
4
COOL  
CHANGEOVER  
VALVE  
L
C1  
FAN  
RISE  
SWITCH  
R2  
RELAY  
N.O. 1  
5
LO  
COMPRESSOR  
CONTACTOR  
MED  
C
Y
CHECK  
LED (RED)  
HIGH  
ON  
COMPRESSOR  
CONTACTOR  
11  
S1 RELAY N.C.  
12  
K1 RELAY  
G1  
G2  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
K2 RELAY  
M2992  
Fig. 214. Schematic and hookup of T874A with Q674B. Used in standard applications.  
201  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(HOT)  
1
L2  
1
2
SYSTEM  
SWITCH  
RELAY 1  
N.O. 2  
S1  
RELAY  
H1  
H1 ANTICIPATOR  
3
FALL  
FALL  
HEAT  
OFF  
H1  
COMPRESSOR  
CONTACTOR  
S1  
4
RELAY N.C.  
COOL  
Y
R
C
H2  
5
H2 ANTICIPATOR  
FIELD  
REMOVABLE  
JUMPER  
7
8
AUX. HT. RELAY  
COMPRESSOR  
FAN  
SWITCH  
H2  
L
LO  
RISE  
C1  
MED  
CHECK  
LED (RED)  
9
R1 RELAY N.C. 1 CONTACTOR  
HIGH  
ON  
1
0
1
C1 ANTICIPATOR  
COOL  
R2  
1
CHANGEOVER  
RELAY  
VALVE  
N.O. 1  
O
R1 RELAY  
K1 RELAY  
12  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
G1  
G2  
K2 RELAY  
M2993  
Fig. 215. Schematic and hookup of T874L with Q674B. Used in heat pump applications.  
60-2485—8  
202  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
COOL CHANGEOVER  
VALVE  
O
G
FAN  
1
SWITCH  
FAN RELAY  
L2  
H1  
H1  
AUTO  
ON  
ANTICIPATOR  
1
FALL  
L1  
(HOT)  
2
R
3R  
4
6
SEQ 2  
SEQ 1  
W1  
FALL  
AUX. HT.  
LED  
2
H2  
(YELLOW)  
E
H2 ANTICIPATOR  
SYSTEM  
SWITCH  
EM. HT.  
RELAY  
4R  
X
C
RISE  
EM. HT.  
AUTO  
OFF  
4R  
8
9
CHECK  
LED  
(RED)  
5R  
CO  
SYSTEM  
LED  
GREEN)  
10  
(
HPS  
4R  
C1  
ANTICIPATOR  
RISE  
Y
C1  
COMPRESSOR  
4R  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED. CONTACTOR  
M1629  
2
REMOVE JUMPER FOR INDEPENDENT CONTROL OF W1 AND E TERMINALS.  
Fig. 216. Schematic and hookup of T874G with Q674J. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
D. P.  
HEAT CHANGEOVER VALVE  
1
W1  
ODT  
H1  
FALL  
HEAT  
CONTACTOR #2  
EHR  
EHR  
2
H1 ANTICIPATOR  
W3  
4
5
HEAT  
CONTACTOR #3  
FAN SWITCH  
1
AUTO  
ON  
G
R
L2  
FAN RELAY  
H2  
ANTICIPATOR  
L1  
HEAT CONTACTOR #1  
(HOT)  
6
W2  
X
H2  
FALL  
SYSTEM  
SWITCH  
CHECK LED  
(GREEN)  
OPTIONAL  
COMPRESSOR FAILURE  
OFF  
AUTO  
8
9
L
C1  
RISE  
CO  
Y
COMPRESSOR  
CONTACTOR  
C1 ANTICIPATOR  
10  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M5900  
Fig. 217. Schematic and hookup of T874N with Q674C. Used in heat pump applications.  
203  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
R
(HOT)  
L2  
1
L
2
EM. HT.  
H1/C1  
ANTICIPATOR  
LED (RED)  
AUX. HT.  
RELAY  
FAN  
3
3
4
SWITCH  
AUTO  
W3  
H1  
C1  
2
FALL  
FALL  
ON  
X
H2  
AUX. HT.  
LED (GRN)  
AUX. HT.  
RELAY  
ANTICIPATOR  
H2  
6
W2  
G
SYSTEM  
SWITCH  
FAN RELAY  
EM. HT.  
HEAT  
OFF  
COOL CHANGEOVER  
VALVE  
O
E
COOL  
EM. HT. RELAY  
Y
B
COMPRESSOR  
CONTACTOR  
"
B" RELAY  
1
2
3
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M3683A  
TERMINAL LABELED C/X ON SOME MODELS.  
W3 TERMINAL AVAILABLE ON SOME MODELS ONLY.  
Fig. 218. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
60-2485—8  
204  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
CONTROL MODULE  
1
W1  
H1  
HEAT RELAY 1  
HEAT RELAY 2  
2
FALL  
W2  
W3  
H1  
ANTICIPATOR  
SYSTEM  
SWITCH  
OFF  
4
AUTO  
5
6
Y2  
A
FALL  
SERVICE  
LED (RED)  
FAN RELAY  
H2  
ANTICIPATOR  
7
3
FAN SWITCH  
G
R
H2  
C1  
L1  
(HOT)  
AUTO  
ON  
8
9
L2  
1
2
RISE  
MONENTARY  
CIRCUIT  
O
COMPRESSOR CONTACTOR 1  
10  
Y1  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE.  
2
3
o
M5901  
H2 OFFSET 12 F FROM H1.  
Fig. 219. Schematic and hookup of T874C with Q674C. Used in standard applications.  
205  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
CONTROL MODULE  
HEAT RELAY #1  
1
2
SYSTEM  
SWITCH  
H1  
W1  
W2  
FALL  
OFF  
HEAT RELAY #2  
HEAT RELAY #3  
H1  
ANTICIPATOR  
AUTO  
4
5
W3  
Y2  
COMPRESSOR CONTACTOR #2  
H3  
FALL  
SYSTEM MONITOR  
6
7
A
H2  
ANTICIPATOR  
SERVICE  
LED (RED)  
H2  
FAN RELAY  
L2  
FALL  
G
R
O
1
FAN  
SWITCH  
L1  
(HOT)  
RISE  
C1  
AUTO  
8
9
ON  
MOMENTARY  
CIRCUIT  
2
10  
COMPRESSOR CONTACTOR #1  
Y1  
RISE  
C2  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
MOMENTARY POSITION. SPRING RETURN TO "ON" UPON SWITCH RELEASE.  
M5929  
Fig. 220. Schematic and hookup of T874W with Q674C. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
2
Y1  
H1 ANTICIPATOR  
3
COOL CHANGEOVER  
VALVE  
H1  
FAN SWITCH  
1
AUTO  
ON  
FALL  
G
R
L2  
L1  
FAN RELAY  
4
(HOT)  
COMPRESSOR  
CONTACTOR  
Y2  
B
RISE  
CO  
8
O
X
9
SYSTEM  
SWITCH  
SERVICE  
LED (YELLOW)  
C1 ANTICIPATOR  
OFF  
10  
AUTO  
X1  
C
RISE  
C1  
24 VAC  
FILTER LED (RED)  
X2  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
M5902  
Fig. 221. Schematic and hookup of T874H with Q674C. Used in heat pump applications.  
60-2485—8  
206  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(HOT)  
R
H1 ANTICIPATOR  
L2  
2
FALL  
SYSTEM  
MONITOR  
1
H1  
3
FAN SWITCH  
L
FAN RELAY  
AUTO  
ON  
4
8
G
W
MALFUNCTION HEAT RELAY  
LED (RED)  
SYSTEM  
SWITCH  
C
C1  
HIGH SPEED  
LED (YELLOW)  
RISE  
OFF  
9
LOW  
SPEED  
LED  
C1  
ANTICIPATOR  
COMPRESSOR  
CONTACTOR 1  
HEAT  
AUTO  
COOL  
10  
(GREEN)  
Y1  
C2  
ANTICIPATOR  
C2  
11  
COMPRESSOR  
CONTACTOR 2  
RISE  
Y2  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M5920  
Fig. 222. Schematic and hookup of T874B with Q674E. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
(HOT)  
2
R
FAN SWITCH  
AUTO  
H1  
FALL  
L2  
1
H1  
ANTICIPATOR  
3
ON  
L
4
FAN RELAY  
H2  
H2 ANTICIPATOR  
G
FALL  
5
7
AUX. HT. RELAY  
EM.HT. RELAY  
W2  
E
RISE  
C1  
AUX. HT.  
LED (RED)  
MALFUNCTION  
LED (RED)  
8
9
SYSTEM  
SWITCH  
C
OFF  
HIGH SPEED  
LED (YELLOW)  
EM. HT.  
C1  
ANTICIPATOR  
LOW SPEED  
LED (GREEN)  
COMPRESSOR  
CONTACTOR 1  
HEAT  
AUTO  
COOL  
1
0
C2  
Y1  
C2  
ANTICIPATOR  
RISE  
COMPRESSOR  
CONTACTOR 2  
1
1
CO  
1
Y2  
O
RISE  
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
COOL  
CHANGEOVER VALVE  
M5923  
Fig. 223. Schematic and hookup of T874S with Q674F. Used in heat pump applications.  
207  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
FALL  
SUBBASE  
SYSTEM COMPONENTS  
CONTROL MODULE  
1
HEAT CHANGEOVER VALVE  
H1  
B
HEAT RELAY #1  
H1  
ANTICIPATOR  
W1  
COMPRESSOR CONTACTOR #1  
4
Y1  
FAN  
SWITCH  
FAN RELAY  
AUTO  
ON  
G
H2  
ANTICIPATOR  
L1  
(HOT)  
RC  
H2  
6
L2  
1
FALL  
HEAT RELAY #2  
W2  
RH  
SYSTEM  
SWITCH  
L1  
HOT)  
L2  
8
9
(
OFF  
1
C1  
RISE  
SERVICE  
LED (RED)  
HEAT  
AUTO  
COOL  
SYSTEM MONITOR  
A
Y2  
O
10  
COMPRESSOR CONTACTOR #2  
COOL CHANGEOVER VALVE  
11  
C2  
RISE  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M5927  
Fig. 224. Schematic and hookup of T874A,D with Q674E. Used in standard applications.  
60-2485—8  
208  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
CONTROL MODULE  
HEAT RELAY #1  
1
W1  
FALL  
H1  
HEAT RELAY #2  
W2  
FAN  
SWITCH  
H1  
ANTICIPATOR  
HEAT DAMPER  
B
AUTO  
ON  
4
6
L1  
(HOT)  
RH  
1
L2  
L2  
L1  
H2  
ANTICIPATOR  
1
RC  
(HOT)  
H2  
COOL DAMPER  
FALL  
O
G
SYSTEM  
SWITCH  
8
9
FAN RELAY  
C1  
RISE  
OFF  
COMPRESSOR CONTACTOR #2  
AUTO  
Y2  
10  
COMPRESSOR CONTACTOR #1  
SYSTEM MONTIOR  
1
1
Y1  
A
C2  
1
RISE  
SERVICE  
LED (RED)  
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M5928  
Fig. 225. Schematic and hookup of T874D with Q674C. Used in standard applications.  
209  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
CONTROL MODULE  
SYSTEM MONITOR  
A2  
FALL  
SERVICE  
LED (RED)  
HEAT RELAY #1  
H1  
1
4
W1  
A1  
NO FAN  
SWITCH  
SERVICE  
LED (RED)  
SYSTEM MONITOR  
H1  
ANTICIPATOR  
HEAT RELAY #2  
T RELAY  
W2  
5
6
T
L1  
(HOT)  
RC  
H2  
1
H2  
L2  
FALL ANTICIPATOR  
SYSTEM  
SWITCH  
FAN RELAY B  
7
8
B
OFF  
L2  
L1  
AUTO  
1
RH  
O
(HOT)  
C1  
RISE  
FAN RELAY O  
9
COMPRESSOR CONTACTOR #2  
COMPRESSOR CONTACTOR #1  
1
0
Y2  
Y1  
1
1
2
C2  
1
RISE  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M5930  
Fig. 226. Schematic and hookup of T874G with Q674G. Used in standard applications.  
60-2485—8  
210  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
1
2
FAN  
SWITCH  
W3 RELAY  
L1  
(
L2  
HOT)  
CO  
W3  
G
(HEAT)  
AUTO  
ON  
FAN RELAY  
FALL  
FALL  
H1  
ANTICIPATOR  
3
R
4
5
AUX. HT.  
RELAY  
W2  
H2  
EM. HT.  
RELAY  
H2 ANTICIPATOR  
E
AUX.  
HT. LED  
COMPRESSOR  
FAULT  
H1  
FALL  
(GREEN)  
6
SYSTEM  
SWITCH  
X1  
CHECK  
LED (RED)  
CO  
COOL)  
8
9
OFF  
(
EM. HT.  
HEAT  
X2  
RISE  
EM. HT.  
LED (RED)  
X
AUTO  
COOL  
10  
C1  
ANTICIPATOR  
COOL CHANGEOVER  
RELAY  
O
B
C1  
RISE  
11  
HEAT CHANGEOVER  
RELAY  
W1 RELAY  
W1  
2
COMPRESSOR  
CONTACTOR  
Y1  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
W1 - Y1 JUMPER IS Y TERMINAL; REMOVE JUMPER WHEN W1 RELAY IS USED.  
2
M1230B  
Fig. 227. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
211  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
HOT)  
L2  
(
1
R
1
FAN  
SWITCH  
Y1  
H1  
FALL  
C1  
2
COMP. RELAY  
O.L.  
IN. STAT.  
HI. PRO.  
AUTO  
G
L
H1/C1 ANTICIPATOR  
ON  
FAN RELAY  
3
4
SENSOR  
LED (RED)  
SERVICE  
H2 ANTICIPATOR  
2
O.D.S.  
EM. HT. RELAY  
5
6
W1  
E
EM. HT.  
ELECTRIC  
HEAT RELAY  
FALL  
H2  
SYSTEM  
SWITCH  
AUX. HT.  
LED  
(GREEN)  
ELECTRIC  
HEAT RELAY  
EM. HT.  
LED (YELLOW)  
EM. HT.  
HEAT  
OFF  
C
C815A OUTDOOR  
THERMISTOR  
COOL  
T
11  
RESET  
O
12  
COOL CHANGEOVER  
VALVE  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
REMOVABLE JUMPER (INSTALLED).  
M3259  
Fig. 228. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
60-2485—8  
212  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
HOT)  
L2  
R
(
1
1
2
H1 ANTICIPATOR  
FAN  
SWITCH  
COMP. RELAY  
O.L.  
IN. STAT.  
HI. PRO  
Y1  
G
AUTO  
ON  
H2 ANTICIPATOR  
3
4
5
FAN RELAY  
SERVICE  
LED (RED)  
H1  
FALL  
L
SERVICE  
FALL  
H2  
2
O.D.S.  
EM. HT. RELAY  
6
W1  
E
RESET  
SYSTEM  
SWITCH  
OFF  
ELECTRIC  
HT. RELAY  
EM. HT.  
8
9
RISE  
CO  
AUX. HT.  
LED  
GREEN)  
EM. HT.  
HEAT  
EM. HT.  
LED (YELLOW)  
ELECTRIC  
HT. RELAY  
(
C1 ANTICIPATOR  
C
T
10  
COOL  
AUTO  
C815A OUTDOOR  
THERMISTOR  
RISE  
C1  
11  
O
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
REMOVABLE JUMPER (INSTALLED).  
COOL CHANGEOVER  
VALVE  
M3264  
2
Fig. 229. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
W3 RELAY  
W3  
O
L
COOL  
CHANGEOVER VALVE  
H1  
ANTICIPATOR  
1
CHECK  
LED (RED)  
COMPRESSOR  
MONITOR  
FAN  
SWITCH  
C ANTICIPATOR  
2
FAN RELAY  
G
R
AUTO  
ON  
1
L1  
(HOT)  
L2  
H1  
C
W2  
E
FALL  
3
4
AUX. HT. RELAY  
SYSTEM  
SWITCH  
EM. HT.  
LED  
(RED)  
AUX. HT.  
LED  
EM .HT.  
HEAT  
OFF  
EM. HT. RELAY  
(GREEN)  
5
X
B
H2  
ANTICIPATOR  
H2  
6
COOL  
HEAT  
FALL  
CHANGEOVER VALVE  
Y
1
1
COMPRESSOR  
RELAY  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
M5068  
Fig. 230. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
213  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
2
O
L
H1  
H1  
COOL  
CHANGEOVER  
VALVE  
ANTICIPATOR  
FALL  
FAN  
3
4
SWITCH  
COMPRESSOR  
FAULT  
EM. HT.  
LED (RED)  
FAN RELAY  
AUTO  
ON  
G
R
1
H2 ANTICIPATOR  
FALL  
L1  
5
8
9
(HOT)  
L2  
EM. HT. RELAY  
H2  
SYSTEM  
SWITCH  
E
X
OFF  
AUX. HT.  
AUX. HT. RELAY  
EM. HT.  
LED (GREEN)  
W2  
C1  
HEAT  
AUTO  
ANTICIPATOR  
10  
HEAT CHANGEOVER  
VALVE  
2
B
COOL  
C1  
RISE  
W3 RELAY  
1
1
W3  
Y
COMPRESSOR  
RELAY  
12  
H1  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
ONLY TERMINAL B OR O TO BE USED. 0.8A MAX.  
CO  
RISE  
M5152  
Fig. 231. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
H1  
HEAT RELAY 1  
ANTICIPATOR  
FALL  
H1  
1
W1  
RH  
1
NO FAN  
SWITCH  
4
L2  
L1  
(HOT)  
5
6
H2  
HEAT RELAY 2  
FALL  
ANTICIPATOR  
W2  
T
H2  
7
8
SYSTEM  
SWITCH  
FAN RELAY  
RISE  
C1  
OFF  
B
AUTO  
9
O
C1  
L2  
L1  
ANTICIPATOR  
1
0
RC  
Y2  
(HOT)  
1
RISE  
C2  
1
1
2
C2  
ANTICIPATOR  
COMPRESSOR  
CONTACTOR 2  
1
Y1  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
COMPRESSOR  
CONTACTOR 1  
M3957  
Fig. 232. Schematic and hookup of T874D with Q674G. Used in standard applications.  
60-2485—8  
214  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
2
FALL  
H1  
H1  
COMPRESSOR  
HIGH SPEED  
ANTICIPATOR  
Y1  
H2  
AUX. HT.  
FAN  
ANTICIPATOR  
W2  
3
4
5
AUTO  
ON  
G
R
FALL  
H3  
FAN  
SWITCH  
H3  
ANTICIPATOR  
FALL  
H2  
6
8
EM. HT.  
E
B
W89  
HEAT  
PUMP  
CONTROL  
PANEL  
SYSTEM  
SWITCH  
RISE  
C1  
EM. HT.  
EM. HT.  
LED (YELLOW)  
9
C1  
ANTICIPATOR  
HEAT  
OFF  
EM. HT. LIGHT  
X
10  
C2  
SERVICE  
LED (RED)  
ANTICIPATOR  
COOL  
RISE  
SERVICE LIGHT  
C2  
L
COOL  
CHANGEOVER  
11  
O
COMPRESSOR  
LOW SPEED  
Y
T
OUTDOOR  
RESET  
RESET  
12  
M3952  
Fig. 233. Schematic and hookup of T874W with Q674L. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
H1  
COMPRESSOR  
CONTACTOR  
ANTICIPATOR  
FALL  
H1  
1
2
FAN  
SWITCH  
Y1  
FAN RELAY  
AUTO  
ON  
G
R
L2  
4
H2  
L1  
(HOT)  
ANTICIPATOR  
FALL  
6
8
1
H2  
W1  
C
SYSTEM  
SWITCH  
AUX. HT. RELAY  
RISE  
CO  
HEAT  
OFF  
9
AUX. HEAT  
LED (RED)  
COOL  
10  
C1  
ANTICIPATOR  
COOL  
CHANGEOVER  
VALVE  
RISE  
C1  
O
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M3961  
Fig. 234. Schematic and hookup of T874G with Q674B. Used in heat pump applications.  
215  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
OTD1  
L1  
H1 ANTICIPATOR  
R
(HOT)  
2
3
RTD1  
FAN  
SWITCH  
L2  
1
EHR1  
ODT2  
EHR2  
RTD2  
AUTO  
ON  
H1  
FALL  
W2  
4
5
H2  
RTD3  
ANTICIPATOR  
AUX. HT.  
LED (GRN)  
SYSTEM  
SWITCH  
H2  
FALL  
RTD1  
EM. HT.  
LED (RED)  
X
OFF  
SYSTEM  
MONITOR  
8
9
COOL  
AUTO  
HEAT  
FAN  
RELAY  
L
RISE  
C1  
G
RD  
ANTICIPATOR  
COOL  
CHANGEOVER VALVE  
CHANGEOVER  
EM. HT.  
10  
O
E
EM. HT.  
RELAY  
CHP  
RISE  
C1  
COMPRESSOR  
CONTACTOR  
LACO  
Y
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M7064  
Fig. 235. Schematic and hookup of T874G and Q674F. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
CONTROL MODULE  
W1  
W2  
1
FAN  
SWITCH  
HEAT RELAY 2  
H1 ANTICIPATOR  
FALL  
HEAT RELAY 1  
HEAT DAMPER  
AUTO  
ON  
H1  
B
4
6
FALL  
RH  
1
1
H2 ANTICIPATOR  
H2  
RC  
8
COOL DAMPER  
C1  
O
G
SYSTEM  
SWITCH  
RISE  
9
OFF  
FAN RELAY  
AUTO  
Y2  
1
0
COMPRESSOR  
RELAY 1  
COMPRESSOR  
RELAY 2  
RISE  
11  
Y1  
A
C2  
SERVICE  
LED (RED)  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M7570  
Fig. 236. Schematic and hookup of T874A-D with Q674C. Used in standard applications.  
60-2485—8  
216  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
SYSTEM COMPONENTS  
SUBBASE  
THERMOSTAT  
L1  
(HOT)  
H1 ANTICIPATOR  
R
1
2
FAN SWITCH  
AUTO  
L2  
1
FAN RELAY  
ON  
FALL  
G
B
3
4
5
H1  
H2 ANTICIPATOR  
LOW LED  
(YELLOW)  
HEAT 1  
HEAT 2  
SYSTEM  
SWITCH  
FALL  
H2  
W1  
6
8
HEAT  
OFF  
HI LED  
(GREEN)  
C1  
W2  
Y
RISE  
COOL  
10  
COMPRESSOR  
CONTACTOR  
C1 ANTICIPATOR  
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
M7716  
1
Fig. 237. Schematic and hookup of T874C with Q674B. Used in standard applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
2
X
H1  
FAN SWITCH  
AUTO  
CHECK  
LED (RED)  
ANTICIPATOR  
G
R
FALL  
H1  
ON  
FAN RELAY  
B RELAY  
L1  
(HOT)  
4
6
L2  
1
B
HEAT PUMP  
RELAY  
H2  
ANTICIPATOR  
SYSTEM  
SWITCH  
W1  
W2  
AUX. HT.  
RELAY  
FALL  
AUX. HT.  
H2  
HT. PUMP  
AUX. HT.  
LED (RED)  
2
STAGE HT.  
8
C
OFF  
COOL  
CHANGEOVER  
VALVE  
2
C1  
RISE  
COOL  
C1  
O
ANTICIPATOR  
10  
Y1  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
FACTORY INSTALLED JUMPER BETWEEN TERMINALS W1 AND Y1.  
COMPRESSOR  
CONTACTOR  
M7719  
Fig. 238. Schematic and hookup of T874C with Q674F. Used in heat pump applications.  
217  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
FAN RELAY  
1
2
G
H1  
ANTICIPATOR  
W
FAN SWITCH  
AUTO  
AUX. HT.  
LED (GREEN)  
2
AUX. HT.  
RELAY  
U
B
H1  
ON  
EM. HT.  
LED (RED)  
C1  
FALL  
COMPRESSOR  
MONITOR  
3
F
L1  
4
5
6
R
(HOT)  
H2  
OUTDOOR  
SENSOR  
FALL  
SYSTEM  
SWITCH  
L2  
1
T
EM. HT.  
HEAT  
OFF  
X2  
O
COOL  
CHANGEOVER  
OUTDOOR  
VALVE  
THERMOSTAT  
COOL  
11  
RESET  
COMPRESSOR  
CONTACTOR  
Y
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
M7744  
2
FIELD REMOVABLE JUMPER.  
Fig. 239. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
4
W1  
H1  
ANTICIPATOR  
SYSTEM  
HEAT  
RELAY  
OFF  
2
ON  
B
R
B RELAY  
L2  
L1  
H1  
FALL  
L1  
(HOT)  
L2  
1
FAN  
LO  
K1  
K2  
K1  
K2  
8
9
C1  
MED  
HI  
G1  
K2  
RISE  
K1 RELAY  
K2 RELAY  
HI  
MED  
LO  
C1  
G2  
Y1  
ANTICIPATOR  
10  
3
SPEED FAN SCHEMATIC  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
COMPRESSOR  
CONTACTOR  
M7745  
FAN CONTINUOUS IN ON POSITION.  
Fig. 240. Schematic and hookup of T874A with Q674W. Used in standard applications.  
60-2485—8  
218  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
H1  
SUBBASE  
SYSTEM COMPONENTS  
L1  
2
R
(HOT)  
L2  
1
ANTICIPATOR  
FAN SWITCH  
3
4
Y
G
H1  
AUTO  
ON  
COMPRESSOR  
CONTACTOR  
FAN RELAY  
FALL  
H2  
ANTICIPATOR  
5
6
W2  
SUPL. HEAT  
LED (RED)  
HEAT  
CHANGEOVER  
VALVE NO. 1  
L
H2  
FALL  
C
8
9
SYSTEM  
SWITCH  
C1  
HEAT  
HEAT  
O.D.T.  
ANTICIPATOR  
CHANGEOVER CHANGEOVER  
VALVE NO. 1  
VALVE NO. 2  
SUPL. HT.  
HEAT  
CO  
E
10  
HEAT  
HEAT  
CHANGEOVER  
VALVE NO. 3  
RISE  
CHANGEOVER  
VALVE NO. 2  
OFF  
11  
COOL  
X
P
C1  
RISE  
X RELAY  
CO  
12  
P RELAY  
O
COOL CHANGEOVER  
VALVE  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M7742  
Fig. 241. Schematic and hookup of T874J with Q674L. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
B
H1 ANTICIPATOR  
1
HEAT DAMPER  
FAN  
SWITCH  
W1  
G
HEAT RELAY 1  
HEAT RELAY 2  
AUTO  
ON  
FALL  
H1  
FAN RELAY  
4
W2  
R
6
8
9
L1  
(HOT)  
SYSTEM  
SWITCH  
H2 ANTICIPATOR  
L2  
1
H2  
FALL  
OFF  
OVERRIDE  
CIRCUIT  
S1  
CHANGEOVER  
VALVE  
AUTO  
OVERRIDE  
2
O
RISE  
C0  
OVERRIDE  
CIRCUIT  
S2  
C1 ANTICIPATOR  
Y
SERVICE  
LED (RED)  
10  
COMPRESSOR  
RELAY  
RISE  
X
C1  
ON LED (YEL)  
A
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
OVERRIDE IS MOMENTARY POSITION. SPRING RETURN TO (OFF)  
UPON SWITCH RELEASE.  
M7212  
C
Fig. 242. Schematic and hookup of T874G with Q674C. Used in standard applications.  
219  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
1
O
FALL  
H1  
FAN SWITCH  
H1 ANTICIPATOR  
COOL CHANGEOVER  
VALVE  
AUTO  
ON  
2
G
B
FAN RELAY  
B RELAY  
4
6
L1  
(HOT)  
R
E
SYSTEM  
SWITCH  
L2  
H2  
ANTICIPATOR  
OFF  
1
EM. HT. RELAY  
H2 FALL  
EM. HT.  
L
EM. HT.  
LED (RED)  
HEAT  
AUTO  
COOL  
2
X
RISE  
8
AUX. HEAT  
LED (GREEN)  
C1  
AUX. HEAT RELAY  
9
W2  
Y
C1 ANTICIPATOR  
10  
COMPRESSOR  
CONTACTOR  
1
1
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
RISE  
CO  
M7715  
12  
TERMINAL LABELED C/X ON SOME MODELS.  
Fig. 243. Schematic and hookup of T874G with Q674F. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
2
R
(HOT)  
H1  
L2  
1
ANTICIPATOR  
FAN SWITCH  
3
4
Y
G
H1  
AUTO  
ON  
COMPRESSOR  
CONTACTOR  
FAN RELAY  
FALL  
H2  
ANTICIPATOR  
5
6
W2  
SUPL. HEAT  
LED (RED)  
HEAT  
CHANGEOVER  
VALVE NO. 1  
L
H2  
FALL  
C
8
9
C1  
HEAT  
CHANGEOVER  
VALVE NO. 1  
HEAT  
CHANGEOVER  
VALVE NO. 2  
O.D.T.  
ANTICIPATOR  
SYSTEM  
SWITCH  
CO  
SUPL. HT.  
E
10  
HEAT  
CHANGEOVER  
VALVE NO. 2  
HEAT  
CHANGEOVER  
VALVE NO. 3  
RISE  
ON  
11  
OFF  
X
P
C1  
RISE  
X RELAY  
CO  
12  
P RELAY  
O
COOL CHANGEOVER  
VALVE  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
M7743  
Fig. 244. Schematic and hookup of T874J with Q674J. Used in heat pump applications.  
60-2485—8  
220  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
2
3
O
H1/C1  
ANTICIPATOR  
FAN SWITCH  
COOL CHANGEOVER  
AUTO  
ON  
VALVE  
G
H1  
FALL  
FAN RELAY  
C1  
B
B RELAY  
L1  
(
HOT)  
R
E
4
6
L2  
SYSTEM  
SWITCH  
1
EM. HT. RELAY  
H2  
EM. HT.  
HEAT  
L
ANTICIPATOR  
EM. HT.  
LED (RED)  
FALL  
OFF  
2
H2  
X
COOL  
AUX. HT.  
LED (GREEN)  
AUX. HT. RELAY  
W2  
Y
1
2
POWER SUPPLY. PROVIDE DISCONNECT  
MEANS AND OVERLOAD PROTECTION  
AS REQUIRED.  
COMPRESSOR  
CONTACTOR  
M7718  
TERMINAL LABELED C/X ON SOME MODELS.  
Fig. 245. Schematic and hookup of T874R with Q674L. Used in heat pump applications.  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
H1 ANTICIPATOR  
1
W1  
W2  
NO FAN  
SWITCH  
HEAT RELAY 1  
FALL  
H1  
4
6
HEAT RELAY 2  
L2  
L1  
RH  
SYSTEM  
SWITCH  
(HOT)  
1
H2 ANTICIPATOR  
OFF  
H2  
C1  
FALL  
RISE  
AUTO  
8
9
L1  
(HOT)  
RC  
L2  
1
1
0
Y1  
Y2  
COOL CHANGEOVER  
VALVE  
11  
M7717  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
Fig. 246. Schematic and hookup of T874C with Q674G. Used in standard applications.  
221  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
FALL  
SUBBASE  
SYSTEM COMPONENTS  
1
H1 ANTICIPATOR  
2
T
H1  
C815A OUTDOOR  
THERMISTOR  
W3  
H2  
H2 ANTICIPATOR  
3
FALL  
FALL  
AUX. HT. RELAY  
FAN SWITCH  
AUTO  
AUX. HEAT  
LED (GREEN)  
H3 ANTICIPATOR  
4
G
R
ON  
FAN RELAY  
H3  
L1  
(HOT)  
5
L2  
1
EM. HEAT  
LED (RED)  
E
6
EM. HT. RELAY  
RESET  
X1  
CHECK LED  
(
YELLOW)  
C
B
RISE  
CHANGEOVER  
RELAY (HEAT)  
2
8
SYSTEM  
SWITCH  
C1  
CHANGEOVER  
RELAY (COOL)  
EM.HT.  
HEAT  
9
O
C1 ANTICIPATOR  
OFF  
1
0
1
X2  
Y1  
COMPRESSOR  
CONTACTOR 1  
COOL  
C2 ANTICIPATOR  
RISE  
1
COMPRESSOR  
CONTACTOR 2  
C2  
12  
Y2  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
CONNECT CHANGEOVER RELAY TO 'O' TERMINAL FOR CHANGEOVER IN COOLING OR TO 'B' TERMINAL FOR CHANGEOVER IN HEATING.  
M6999  
Fig. 247. Schematic and hookup of T874W with Q674L. Used in heat pump applications.  
60-2485—8  
222  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
SUBBASE  
SYSTEM COMPONENTS  
L1  
2
R
(HOT)  
FAN SWITCH  
AUTO  
H1  
FALL  
L2  
1
H1  
ANTICIPATOR  
3
ON  
L
4
FAN RELAY  
H2  
H2 ANTICIPATOR  
G
FALL  
5
7
AUX. HT. RELAY  
EM.HT. RELAY  
W2  
E
RISE  
C1  
AUX. HT.  
LED (RED)  
MALFUNCTION  
LED (RED)  
8
9
SYSTEM  
SWITCH  
C
OFF  
HIGH SPEED  
LED (YELLOW)  
EM. HT.  
C1  
ANTICIPATOR  
LOW SPEED  
LED (GREEN)  
COMPRESSOR  
CONTACTOR 1  
HEAT  
AUTO  
COOL  
1
0
C2  
Y1  
C2  
ANTICIPATOR  
RISE  
COMPRESSOR  
CONTACTOR 2  
1
1
CO  
1
Y2  
O
RISE  
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
COOL  
CHANGEOVER VALVE  
M5923  
Fig. 248. Schematic and hookup of T874Y with Q674F. Used in heat pump applications.  
223  
60-2485—8  
href="
T874 MULTISTAGE THERMOSTATS AND Q674 SUBBASES  
THERMOSTAT  
FALL  
SUBBASE  
SYSTEM COMPONENTS  
HEAT RELAY 1  
W1  
G
H1  
1
3
FAN  
SWITCH  
FAN RELAY  
H1 ANTICIPATOR  
AUTO  
ON  
2
RC  
W2  
HEAT RELAY 2  
HEAT DAMPER  
4
6
FALL  
B
H2 ANTICIPATOR  
H2  
SERVICE  
LED (RED)  
C
X
L1  
SYSTEM  
SWITCH  
(HOT)  
1
8
9
L2  
RH  
O
C1  
HEAT  
OFF  
COOL DAMPER  
RISE  
COOL  
C1 ANTICIPATOR  
COMPRESSOR CONTACTOR 1  
COMPRESSOR CONTACTOR 2  
1
0
Y1  
Y2  
C2 ANTICIPATOR  
RISE  
1
1
C2  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.  
FIELD WIRE JUMPER TO ALLOW SINGLE SYSTEM TRANSFORMER.  
M18622  
Fig. 249. Schematic and hookup of T874C with Q674B. Used in heat pump applications.  
Home and Building Control Home and Building Control  
Honeywell  
985 Douglas Drive North  
Golden Valley, MN 55422  
Honeywell Limited-Honeywell Limitée  
35 Dynamic Drive  
Scarborough, Ontario  
M1V 4Z9  
1
Printed in U.S.A. on recycled  
paper containing at least 10%  
post-consumer paper fibers.  
60-2485—8 J.H. Rev. 3-01  
www.honeywell.com