Home

href="
T8624C,D (5-1-1 Day  
®
Programming) Chronotherm  
III Fuel Saver Thermostats  
The T8624C,D Chronotherm III Program-  
mable Fuel Saver Thermostats provide auto-  
matic control of multistage heating/cooling sys-  
tems and offer users the highest standard of  
comfort and convenience available with energy  
savings.  
Different schedules may be selected for week-  
days, Saturday and Sunday.  
Can be programmed in hand (with batteries in-  
stalled) or on wall to provide up to four tempera-  
ture settings per day.  
Large digital clock (liquid crystal display) indi-  
cates continuous time, day, current period and  
room temperature.  
Adaptive Intelligent Recovery™ brings room tem-  
perature to programmed temperature at pro-  
grammed time, maximizing comfort and energy  
savings.  
Models available with automatic or manual heat/  
cool changeover.  
Batteries included provide power to maintain  
clock and memory during power failures.  
Switching subbase with wiring terminals included.  
Powered directly from control transformer, re-  
quiring an extra (24V) wire to thermostat.  
Fan operation switch to select either independent  
or direct thermostat control of fan in heating  
included on back of select models.  
Temperature control program maintains tempera-  
ture within 1° F of setpoint.  
Temporary program override available by using:  
WARMER and COOLER keys.  
SKIP next period key.  
CHANGE to last period key.  
HOLD TEMP key provided for indefinite pro-  
gram override (vacation/holiday).  
Installer self-test and time delay override save  
installation time.  
SYSTEM light-emitting diode (LED) indicates  
system is energized.  
CONTENTS  
Specifications ................................................. 2  
Ordering Information ..................................... 2  
Selection/Application ..................................... 4  
Installation ..................................................... 5  
Checkout....................................................... 11  
Programming the Thermostat ......................14  
Operating the Thermostat ............................ 18  
Troubleshooting ........................................... 21  
Glossary ....................................................... 22  
C.H. • 9-93 • ©Honeywell Inc. 1993 • Form Number 68-0134  
href="
T8624C,D  
SPECIFICATIONS • ORDERING INFORMATION  
Specifications  
IMPORTANT: The specifications given in this publi-  
cation do not include normal manufacturing toler-  
ances. Therefore, this unit may not exactly match  
the listed specifications. Also, this product is tested  
under closely controlled conditions, and some mi-  
nor differences in performance can be expected if  
those conditions are changed.  
SETPOINT RANGE: 45° F to 88° F [7° C to 31° C].  
CALIBRATION: Self-calibrating thermostat and  
thermometer to ±1° F.  
SHIPPING TEMPERATURE: -20° F to +120° F [-29° C  
to +49° C].  
CYCLES PER HOUR ADJUSTMENT:  
Heating: First stage of 2-stage heat models—fixed at  
3
cph. Second stage of 2-stage heat models or heat  
®
TRADELINE MODELS  
stage of single-stage heat models—factory-set at  
6 cph; field-adjustable to 1,3,6 or 9 cph.  
Cooling: Factory-set at 3 cph (not field adjustable);  
minimum off-time of five minutes.  
TRADELINE models (see Table 1) are selected and  
packaged to provide ease of stocking and handling  
and also maximum replacement value.  
LIGHT-EMITTING DIODE (LED): SYSTEM LED  
lights during thermostat ON cycle.  
FINISH: Beige matte with decorative brushed metal  
faceplate or Premier White™.  
VOLTAGE RATING: 15 to 30 Vac.  
DIMENSIONS: Thermostat (mounted on subbase)—7 in.  
[178 mm] long, 5-5/16 in. [135 mm] high, 1-3/4 in.  
[44 mm] deep. See Fig. 1 for subbase dimensions.  
TYPICAL KEYPAD: See Fig. 2.  
CURRENT RATING: 1.6A maximum total per stage.  
OPERATING HUMIDITY RANGE: 5 to 90 percent  
relative humidity, noncondensing.  
OPERATING AMBIENT TEMPERATURE RANGE:  
ACCESSORIES:  
TG586A Locking Cover.  
4
0° F to 110° F [4° C to 43° C].  
TG512 Versaguard™ Universal Thermostat Guard.  
TABLE 1—TRADELINE MODELS.  
Thermostat  
Model  
Number  
Stages  
Changeover  
Type  
Switching  
System  
Heat  
Cool  
Fan  
Application  
T8624C  
T8624D  
T8624D  
2
2
2
1
2
2
Auto  
Auto  
HEAT-AUTO-COOL-OFF  
HEAT-AUTO-COOL-OFF  
HEAT-OFF-COOL  
ON-AUTO  
ON-AUTO  
ON-AUTO  
Multistage  
Multistage  
Multistage  
Manual  
Ordering Information  
When purchasing replacement and modernization products from your TRADELINE® wholesaler or your distributor, refer to the  
TRADELINE Catalog or price sheets for complete ordering number, or specify—  
1
2
. Model number.  
. Number of heat and cool stages desired.  
3. System, fan switching desired.  
4. Application.  
If you have additional questions, need further information or would like to comment on our products or services, please write or  
phone:  
1
2
. Your local Honeywell Home and Building Control Sales Office (check white pages of your phone directory).  
. Home and Building Control Customer Satisfaction  
Honeywell Inc., 1885 Douglas Drive North  
Minneapolis, Minnesota 55422-4386 (612) 951-1000  
In Canada—Honeywell Limited/Honeywell Limitee, 740 Ellesmere Road, Scarborough, Ontario M1P 2V9. 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.  
2
href="
T8624C,D  
SPECIFICATIONS  
Fig. 1—T8624 Subbase mounting dimensions in in. [mm].  
3
3
1
2
1
[
50]  
1
3
1
16  
[
46]  
3
4
32  
[
104]  
5
16  
135]  
5
[
5
1
3
[83]  
6
3
4
4
[121]  
7
[179]  
M5181A  
Fig. 2—Typical thermostat keypad.  
AM  
SYSTEM  
ROOM  
HEAT ON  
WED  
LEAVE  
TEMPERATURE  
PRESENT  
SETTING  
RUN  
PROGRAM  
PERIOD  
TIME  
SET  
SKIP  
NEXT  
PRESENT  
DAY/TIME  
WAKE  
SLEEP  
LEAVE  
DAY  
AHEAD  
WARMER  
COOLER  
PERIOD  
HOLD  
TEMP  
SET  
HEAT/COOL  
BACK  
CHANGE  
TO LAST  
PERIOD  
RETURN  
FAN  
HEAT AUTO COOL OFF  
ON  
AUTO  
M2998  
3
68-0134  
href="
T8624C,D  
SELECTION/APPLICATION  
Selection/Application  
The T8624 Thermostat uses the latest microelec-  
tronic design and control technology to provide home  
and building owners with the highest level of comfort  
available and optimal energy savings in a package that is  
easy to use and easy to live with.  
The following section is a guide to selection and  
application of the best thermostat to meet individual  
needs.  
Fan switching; does fan come on automatically  
from thermostat on cooling only (typical gas/  
oil heating), or on call for cool and heat (typical  
electric heat with single speed fan)?  
Existing wiring  
Are there enough conductors to operate the equip-  
ment and the thermostat? Can a new cable be  
pulled?  
IMPORTANT: The T8624 requires an additional con-  
ductor to transformer common to provide continu-  
ous 24V power for thermostat operation.  
PROGRAMMING  
Does the thermostat selected accommodate the  
customers daily schedule, lifestyle or work schedule?  
Daily  
Temperature  
SECURITY  
Does the thermostat selected provide access to  
Device  
Programming  
Selection  
T8624C,D  
5-1-1 (Mon-Fri,  
Sat, Sun)  
4 heat and  
4 cool  
Typical  
Application  
Access  
Device  
Free access to  
programming  
and adjustment/ commercial  
Home or  
owner-occupied  
T8624A,C,D  
T8621A,C,D  
7-day (each  
day different)  
4 heat and  
4 cool  
override.  
building.  
Restricted  
access to  
device.  
Public  
building.  
T8624 with  
TG512 Locking  
Guard or  
T8600,01,02,03* 5-1-1 (Mon-Fri,  
Sat, Sun)  
4 heat and  
4 cool  
TG586A  
Locking Cover.  
The choices are:  
programmming and the override features that will best  
suit the application? The choices are:  
*
Model not currently available to control multistage  
equipment.  
SINGLE-STAGE HEAT PUMPS  
If home/building owner has a single-stage heat pump,  
one option is to use a T8624C or D (see Fig. 8).  
IF NEW CONSTRUCTION APPLICATION, CON-  
SIDER:  
The T8624C is a two-stage heating, one-stage cool-  
ing programmable thermostat. The T8624D is a two-  
stage heating, two-stage cooling programmable thermo-  
stat. What both thermostats have in common is separate  
W1 and W2 (first and second stage heat) terminals. In  
both cases, the W1 can be used for changeover in heat-  
ing.  
For single-stage compressor applications (both first-  
Equipment type (see manufacturer specifications).  
Staging required.  
System switching required.  
Fan switching required.  
Control wiringnumber of conductors required  
to operate equipment and thermostat.  
IMPORTANT: The T8624 requires an additional con-  
stage heating and first-stage cooling energized through  
ductor to transformer common to provide continu-  
the Y terminal), simply jumper Y1 and W1.  
Note that the recovery algorithm of the T8624 may  
cause the compressor to cycle on and off during recov-  
ous 24V power for thermostat operation.  
IF RETROFIT/REPLACEMENT APPLICATION,  
ery.  
CONSIDER:  
Equipment requirements.  
Although the cycle rate for the first stages of heat and  
cool are set for hot water systems, the second stage of the  
T8624 must be adjusted. Turn the cycle rate adjustment  
screws to the hot water setting on both the T8624C and  
D to achieve the cycle rate appropriate for heat pumps.  
If changeover is utilized in the cooling mode, apply a  
normally closed relay.  
Staging (heat stages, cool stages).  
System switching (manual: HEAT-OFF-COOL;  
automatic: HEAT-AUTO-COOL-OFF). Emer-  
gency heat for heat pump application not pro-  
vided on T8624.  
The above application should be used only on single-  
stage heat pumps.  
4
href="
T8624C,D  
INSTALLATION  
Installation  
or disconnects. Remove any existing wallplate or sub-  
base from wall. To avoid miswiring later, label each  
wire color with the letter or number on the wiring termi-  
nal as the wire is removed.  
RECYCLING NOTICE  
If this control is replacing a control that contains  
mercury in a sealed tube, do not place your old control in  
the trash. Contact your local waste management author-  
ity for instructions regarding recycling and the proper  
disposal of your old control.  
NEW INSTALLATION  
Run cable to a hole at the selected wall location for the  
thermostat, and pull about 3 in. [76 mm] of wire through  
the opening. Color-coded, 18-gauge thermostat cable with  
at least one conductor for each wiring terminal is recom-  
mended. Good service practice recommends selecting  
cable with one or two more conductors than the immedi-  
ate application requires.  
If you have any questions, call Honeywell Inc. at 1-  
00-468-1502.  
8
COMPATIBILITY  
The T8624 Thermostats will replace most heating/  
cooling system thermostats. As long as ac power is  
continuously available to the transformer, the thermostat  
will be compatible with any low-volt control system.  
MOUNTING SUBBASE  
IMPORTANT: Before mounting, set the system switch  
IMPORTANT: The T8624 requires an additional con-  
ductor to transformer common to provide continu-  
ous 24V power for thermostat operation.  
to the OFF position.  
NOTE: The subbase does not require leveling for proper  
operation, but only for appearance.  
WHEN INSTALLING THIS PRODUCT…  
1
. Read these instructions carefully. Failure to follow  
them could damage the product or cause a hazardous  
condition.  
Fig. 3—Removing thermostat from subbase.  
2
. Check the ratings given on the product to make  
sure the product is suitable for your application.  
. Installer must be a trained, experienced service  
technician.  
3
4
. Allow thermostat to warm to room temperature  
before operating.  
5
. After installation is complete, check out product  
operation as provided in these instructions.  
CAUTION  
!
HEAT AUTO COOL  
OFF  
FAN  
ON  
AUTO  
Disconnect power supply to prevent electrical  
shock or equipment damage.  
M 844  
LOCATION  
Install thermostat and subbase about 5 ft [1.5m] above  
the floor in an area with good air circulation at room  
temperature.  
Do not install thermostat where it may be affected by:  
drafts or dead spots behind doors, in corners or  
under cabinets.  
hot or cold air from ducts.  
radiant heat from sun or appliances.  
concealed pipes and chimneys.  
unheated (uncooled) areas such as an outside wall  
behind the thermostat.  
Remove thermostat from subbase (Fig. 3).  
Mount the subbase directly onto the wall with the  
screws and anchors included. If drywall construction,  
use plastic anchors. Use the subbase as a template, and  
with a pencil, mark the two mounting screw positions  
(Fig.  
4).  
Use  
3/16 in. bit to drill holes for anchors. Gently tap anchors  
into holes until they are flush with the wall surface.  
Thread wires through the center opening of the subbase.  
Then mount the subbase using the two screws provided.  
Gently tighten the screws, level the top surface of the  
subbase, and securely tighten the screws.  
REPLACING AN EXISTING THERMOSTAT  
Turn off thermostat power at furnace or boiler. A two-  
transformer system may require turning off two switches  
5
68-0134  
href="
T8624C,D  
INSTALLATION  
Fig. 4—Mounting subbase on wall.  
Fig. 5—Restrict wiring to recessed area  
surrounding terminals.  
WALL  
FOR STRAIGHT  
INSERTION –  
STRIP 5/16 in. [8 mm]  
WIRES THROUGH  
WALL OPENING  
FOR WRAPAROUND –  
STRIP 7/16 in. [11 mm]  
RESTRICT  
WIRING TO  
THIS AREA  
FRONT VIEW OF  
TERMINAL AREA  
WALL  
ANCHORS  
(
2)  
WIRING TO BE BELOW  
THIS SURFACE  
TOP SURFACE  
OF SUBBASE  
MOUNTING  
HOLES  
MOUNTING  
SCREWS (2)  
SUBBASE  
CROSS-SECTIONAL VIEW OF  
TERMINAL AREA  
M 847  
M846  
WIRING  
In multistage heat systems, the cycle rate adjustment  
applies to the highest stage of heat only. Screws should  
be backed out about one-half to one turn, or be turned in  
until tight. See Fig. 9.  
All wiring must comply with local electrical codes  
and ordinances.  
Disconnect power before wiring to prevent electrical  
shock or equipment damage.  
The shape of the terminal barrier permits insertion of  
straight or conventional wraparound wiring connections.  
Either method is acceptable.  
Push excess wire back into the hole, and plug the hole  
with nonhardening caulk, putty or insulation to prevent  
drafts from affecting thermostat operation.  
TIME/TEMPERATURE CONVERSION  
(SOME MODELS)  
The display readout may be converted between 12  
and 24 hour clock or °C and °F using screws 2A and 2B  
as indicated in Fig. 9.  
FAN OPERATION OPTION SWITCH  
(SELECT MODELS ONLY)  
NOTE: Restrict wiring to the recessed area surrounding  
the terminals (Fig. 5) to assure thermostat/subbase  
contact.  
Select models include a fan operation option switch  
on the subbase that is visible before the thermostat is  
mounted on the subbase. The switch should be in electric  
heat position for electric heating systems that do not  
have independent fan control.  
Refer to Figs. 6-8 for typical hookups of subbase and  
thermostat.  
ADJUSTING CYCLE RATE  
INSTALLING BATTERIES  
To customize the thermostat cycling performance to  
various types of heating equipment, cycle rate adjust-  
ment screws are provided on the back of the thermostat  
to provide optimum room temperature control.  
Three AAA alkaline batteries are included to provide  
backup to prevent program loss in case of power outage.  
Install batteries in back of thermostat as shown in Fig.  
1
0.  
Without battery backup, the program will remain  
NOTE: Most applications will not require a change in  
cycle rate.  
about 30 seconds in event of power loss.  
IMPORTANT: When batteries are first installed, the  
display will flash 1:00 PM and 32°. The tempera-  
ture will stay at 32° F until the thermostat is  
powered from the system wiring.  
The room air temperature will normally vary slightly  
from the comfort temperature setting with the cycling of  
the furnace or air conditioner.  
The heating cycle rate of this thermostat is factory-set  
for gas/oil warm air heating. The cooling cycle rate is  
factory-set and cannot be adjusted. The heating cycle  
rate can be adjusted by turning one or both cycle rate  
adjustment screws located on the back of the thermostat.  
When the batteries are low, the display will flash  
REPL BAT. Homeowner will have 20-30 seconds to  
install new batteries after removing old batteries from  
back of thermostat. After 20-30 seconds, it will be nec-  
essary to reprogram. REPL BAT indication will disap-  
6
href="
T8624C,D  
INSTALLATION  
Fig. 6T8624C 2-stage heat/1-stage cool thermostat with HEAT-AUTO-COOL-OFF system and AUTO-ON  
fan switching.  
HEATING  
TRANSFORMER  
1
L1  
(HOT)  
R
4
2
HIGH  
LIMIT  
L2  
3
POWER  
SUPPLY  
C
HIGH  
LIMIT  
HEAT 1  
HEAT 2  
HEAT RELAY 1  
HEAT RELAY 2  
W1  
W2  
SYSTEM  
SWITCH  
HEAT  
THERMOSTAT  
LOGIC CIRCUIT  
AUTO  
COOL  
OFF  
COOLING  
COOL  
CONTACTOR  
Y1  
G
FAN  
SWITCH  
SUBBASE  
LOGIC/  
CONTROL  
CIRCUIT  
FAN RELAY  
AUTO  
ON  
2
L1  
(HOT)  
RC  
L2  
1
COOLING  
TRANSFORMER  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
3
NOMINAL 24 Vac POWER MUST BE PRESENT BETWEEN R AND C FOR  
THERMOSTAT OPERATION.  
FOR SINGLE TRANSFORMER SYSTEM JUMPER R AND RC.  
4
DENOTES THERMOSTAT TO SUBBASE INTERCONNECTION.  
M5233  
7
68-0134  
href="
T8624C,D  
INSTALLATION  
Fig. 7T8624D 2-stage heat/2-stage cool thermostat with HEAT-AUTO-COOL-OFF system and AUTO-ON  
fan switching.  
L1  
(HOT)  
R
4
2
L2  
1
HIGH  
LIMIT  
3
HEATING  
TRANSFORMER  
HEAT RELAY 1  
POWER  
SUPPLY  
C
HIGH  
LIMIT  
HEAT 1  
HEAT 2  
SYSTEM  
SWITCH  
W1  
W2  
HEAT RELAY 2  
HEAT  
THERMOSTAT  
LOGIC  
CIRCUIT  
AUTO  
COOL  
OFF  
COOLING  
CONTACTOR 2  
COOL 2  
COOL 1  
5
Y2  
SUBBASE  
LOGIC/  
CONTROL  
CIRCUIT  
Y1  
FAN  
SWITCH  
COOLING  
CONTACTOR 1  
AUTO  
G
ON  
FAN RELAY  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
2
L1  
(HOT)  
RC  
2
3
FOR SINGLE TRANSFORMER SYSTEM, JUMPER R AND RC.  
L2  
1
COOLING  
TRANSFORMER  
NOMINAL 24 Vac POWER MUST BE PRESENT BETWEEN  
R AND C FOR THERMOSTAT OPERATION.  
4
5
DENOTES THERMOSTAT TO SUBBASE INTERCONNECTION.  
AVAILABLE ON T8624D MODELS ONLY.  
M3765  
8
href="
T8624C,D  
INSTALLATION  
Fig. 8T8624D 2-stage heat/2-stage cool thermostat with HEAT-OFF-COOL system and AUTO-ON fan  
switching; auto fan on heat and cool; convertible to auto fan on cool only.  
L1  
HOT) L2  
(
1
HEATING  
TRANSFORMER  
R
5
4
POWER  
SUPPLY  
C
HIGH  
LIMIT  
FAN  
OPERATION  
SWITCH  
3
HIGH  
LIMIT  
W1  
STAGE 1  
ELECTRIC  
HEAT RELAY  
HEAT 1  
W2  
HEAT 2  
NON-ELECTRIC  
2
SYSTEM  
SWITCH  
STAGE 2  
HEAT RELAY  
HEAT  
THERMOSTAT  
LOGIC CIRCUIT  
B
OFF  
HEATING DAMPER OR  
CHANGEOVER RELAY  
COOL  
COOLING DAMPER OR  
CHANGEOVER RELAY  
O
STAGE 2  
COOLING RELAY  
Y2  
COOL 1  
COOL 2  
STAGE 1  
COOLING RELAY  
SUBBASE  
LOGIC/  
CONTROL  
CIRCUIT  
Y1  
G
FAN  
SWITCH  
FAN RELAY  
AUTO  
ON  
3
RC  
COOLING  
TRANSFORMER  
1
L1  
L2  
(HOT)  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD  
PROTECTION AS REQUIRED.  
3
FOR ELECTRIC HEAT APPLICATIONS (AUTO FAN OPERATES WITH W1  
AND Y1), USE ONLY ONE TRANSFORMER; JUMPER R AND RC. SET  
SWITCH TO ELECTRIC POSITION.  
FOR GAS OR OIL APPLICATIONS OR ELECTRIC HEAT APPLICATIONS  
WHERE THE FAN OPERATION IS CONTROLLED INDEPENDENTLY OF  
THE THERMOSTAT (AUTO FAN OPERATES WITH Y1 ONLY), TWO  
TRANSFORMERS MAY BE USED. SET SWITCH TO NONELECTRIC  
POSITION.  
4
5
NOMINAL 24 VAC POWER MUST BE PRESENT BETWEEN R AND C FOR  
THERMOSTAT OPERATION.  
DENOTES THERMOSTAT TO SUBBASE INTERCONNECTION.  
M1016D  
9
68-0134  
href="
T8624C,D  
INSTALLATION  
After replacing the batteries, reprogramming will be nec-  
essary.  
Fig. 9Cycle rate adjustment.  
1
A
1B  
2B  
2
A
1
BATTERY PLACEMENT  
(
NOTE CORRECT PLUS  
CYCLES  
PER HOUR  
TIME/TEMP  
DISPLAY  
AND MINUS DIRECTION)  
M 372A  
SYSTEM  
GRAVITY  
1A  
1B  
2A  
IN  
2B  
OUT 1/2  
OUT 1/2  
AIR/WATER TO 1 TURN TO 1 TURN  
1
3
24 HR  
12 HR  
HOT  
WATER  
OUT 1/2  
TO 1 TURN  
OUT 1/2  
TO 1 TURN  
IN  
GAS/OIL  
IN  
IN  
If the display goes off when power is lost, either the  
backup batteries need to be replaced or are not installed.  
When power is restored, the display will flash 1:00 PM  
as a reminder to reprogram.  
WARM AIR (FACTORY SETTING)  
6
9
o
o
C
F
IN  
ELECTRIC  
WARM AIR  
OUT 1/2  
TO 1 TURN  
OUT 1/2  
TO 1 TURN  
IN  
1
SCREWS 2A, 2B AVAILABLE ON SOME MODELS ONLY.  
M311A  
MOUNTING THE THERMOSTAT  
With system switch set to OFF, hang the thermostat  
on the tabs at the top of the subbase (Fig. 11A). Swing  
down and press on lower edge until thermostat snaps in  
place (Fig. 11B). Open cover and tighten the captive  
mounting screws (Fig. 11C).  
pear when thermostat is mounted back on the subbase.  
IMPORTANT: For proper thermostat operation, al-  
ways replace dead batteries with new alkaline  
batteries. We recommend Energizer® batteries.  
SETTING DAY AND TIME  
Restore 24V power to the thermostat. When power is  
applied to the thermostat, the display will read 1:00 PM  
and room temperature. It will go off for a few seconds,  
then begin to flash on and off. Set present day and time.  
If batteries are completely dead, the display will go  
blank when the thermostat is removed from the subbase.  
Fig. 10Battery placement.  
SET  
PRESENT  
.
POWER OUTAGES  
Press DAY/TIME  
Backup batteries will hold the programming and keep  
the display on during most power outages. Once the  
power is restored, the system will resume normal opera-  
tion.  
Press  
DAY  
to set the current day. Each press of  
the DAY key advances the display one day.  
BACK  
Press TIME  
or  
to set the current time.  
AHEAD  
If the display will not come on:  
Check the mounting of the thermostat to the sub-  
base. If loose or misaligned, remove thermostat  
and reinstall on the subbase, making sure it is  
firmly attached.  
Check to see that heat or cool system power is on.  
Check voltage between R and C; it should be 24 to  
3
0 Vac.  
1
0
href="
T8624C,D  
INSTALLATION • CHECKOUT  
Fig. 11Mounting thermostat on subbase.  
A.  
B.  
PM  
SYSTEM  
RETU RM ON  
N
HEAT ON  
FAN  
AUTO  
ON AUTO  
HEAT AUTO COOL  
OFF  
C.  
PM  
SYSTEM  
RETU RM ON  
N
HEAT ON  
TEMPERATURE  
PR OR GU RN AM  
P
S
R
E
ET ST EI N  
G
NT  
PERIOD  
LEAVE  
TIME  
DP RA SEY ES/ T TEI MN ET  
HT EO ML DP  
P NES ERK XII OP  
DAY  
WAKE  
SLEEP  
AHEAD  
BACK  
WARMER  
COOLER  
T
D
SET  
HEAT/COOL  
RETURN  
CT OH A  
L
N
A
GS ET  
PERIOD  
M3764  
Checkout  
HEATING  
Move the system switch to COOL and the fan switch  
Move the system switch to HEAT and the fan switch  
to AUTO. Press WARMER key until the setting is about  
to AUTO. Press COOLER key until the setting is about  
10° F [6° C] below room temperature. The cooling  
equipment and fan should start (both stages if multi-  
stage). Press WARMER key until the setting is about  
10° F [6° C] above room temperature. The cooling  
equipment and fan equipment should stop.  
1
0° F [6° C] above room temperature. Heating should  
start (both stages if multistage), and the fan should run  
may be a short delay on forced air systems). Press  
(
COOLER key until the setting is about 10° F [6° C]  
below room temperature. The heating equipment should  
shut off, followed by the fan.  
NOTE: On an AUTO changeover thermostat, the heat-  
ing temperature must be set at least 3° F [2° C] below  
the cooling temperature, or display will flash.  
NOTE: On an AUTO changeover thermostat, the cool-  
ing temperature must be set at least 3° F [2° C] above  
the heating temperature, or display will flash.  
FAN  
Move the system switch to OFF, and the fan switch to  
ON. The fan should run continuously. When the fan  
switch is in the AUTO position, the fan operates directly  
with the thermostat call for cooling and also with the  
COOLING  
CAUTION  
!
Do not operate cooling if outdoor temperature  
is below 50° F [10° C]. Refer to manufacturer  
recommendations.  
NOTE: When cooling setting is changed, thermostat  
will wait up to five minutes before turning on the  
cooling equipment. This delay is to protect the com-  
pressor.  
1
1
68-0134  
href="
T8624C,D  
CHECKOUT  
System  
Switch  
Position  
Press  
This  
Key  
Look For This Response  
Key  
Down  
Key Released  
OFF  
06  
Blank  
WARMER  
COOLER  
02  
Blank  
0
0
0
0
5
4
1
0
Blank  
AHEAD  
BACK  
Blank  
Blank  
LEAVE  
RETURN  
WAKE  
REPL  
AM  
PM BAT  
SET  
PT  
SUN MON TUE WED THU FRI SAT COOL ON HEAT ON  
Blank  
WAKE LEAVE RETURN SLEEP TEMPORARY  
M410C  
(
CHECK  
12  
08  
See note A  
EACH  
POSITION)  
OFF  
Blank  
SLEEP  
DAY  
1
3
Microprocessor  
mask no. and  
revision no.  
RUN  
PROGRAM  
SET  
HEAT/COOL  
09  
14  
14  
Blank  
Look For This Response  
System  
Switch  
Position  
Press  
This  
Key  
SET  
PRESENT  
DAY/TIME  
Blank  
Key  
Down  
Key Released  
Blank  
HEAT or  
AUTO  
1
SET  
PRESENT  
DAY/TIME  
1st stage heating  
and SYSTEM  
LED on.  
OFF  
CHANGE  
TO LAST  
PERIOD  
03  
07  
15  
15  
SKIP  
NEXT  
PERIOD  
Blank  
Blank  
SET  
PRESENT  
DAY/TIME  
14  
14  
14  
2nd stage heating  
also on.  
PRESENT  
SETTING  
SET  
PRESENT  
DAY/TIME  
2nd stage heating  
off.  
COOL or  
AUTO  
with fan in  
PRESENT  
SETTING  
1st stage cooling,  
fan and SYSTEM  
LED on.  
SET  
PRESENT  
DAY/TIME  
1st stage heating  
and SYSTEM  
LED off.  
(
AUTO)  
15  
15  
15  
2nd stage cooling  
also on.  
PRESENT  
SETTING  
NOTE: If single-stage heating system, press key twice  
instead of four times; once to turn on heating and  
SYSTEM LED, second time to turn off.  
PRESENT  
SETTING  
2nd stage cooling  
off.  
OFF  
HOLD  
TEMP  
10  
Blank  
PRESENT  
SETTING  
1st stage cooling,  
fan and SYSTEM  
LED off.  
RUN  
PROGRAM  
11  
Normal operating  
display.  
NOTE: If single-stage cooling system, press key twice  
instead of four times; once to turn on cooling, fan  
and SYSTEM LED, second time to turn off.  
END SELF-TEST  
(
continued)  
1
2
href="
T8624C,D  
CHECKOUT  
Second  
Digit  
Stages of  
Heat  
Cool  
0
1
2
3
4
5
6
2
2
1
1
0
1
2
1
2
1
2
2
0
0
Cycle Rate Setting (cph at 50% on  
time for stage 1 on 1-heat models,  
stage 2 on 2-heat models)  
First Digit  
0
1
2
3
1
3
9
6
M5734  
Third  
Digit  
Manual or Auto  
Changeover  
System Switch  
Position  
Fourth  
Digit  
Clock  
(hrs)  
System Switch  
Position  
Degrees  
0
1
3
4
5
Manual  
Auto  
HEAT or OFF  
HEAT or OFF  
AUTO  
0
F
12  
COOL, AUTO  
or OFF  
1
F
24  
COOL, AUTO  
or OFF  
Auto  
Manual  
Auto  
COOL  
2
3
4
F
F
12  
24  
12  
HEAT  
HEAT  
COOL  
C
COOL, AUTO  
or OFF  
5
C
24  
COOL, AUTO  
or OFF  
6
7
C
C
12  
24  
HEAT  
HEAT  
1
3
68-0134  
href="
T8624C,D  
PROGRAMMING THE THERMOSTAT  
Programming the Thermostat  
IMPORTANT: With Adaptive Intelligent Recovery™,  
program the times for when the homeowner wants  
the home comfortable. The thermostat will decide  
how early to begin the temperature changes.  
NOTE: Some models will show 32° F instead of the  
current temperature, indicating the thermostat is op-  
erating on backup batteries until the thermostat is  
mounted on the wallplate and the system is powered.  
STEP 1  
SET THE CURRENT DAY AND  
TIME  
SET  
PRESENT  
DAY/TIME  
definitions of unfamiliar  
words.  
PM  
MON  
M5015  
This thermostat can be programmed either  
on the wall or in hand. SEE PAGE 5 TO  
FIND OUT HOW TO REMOVE THE  
THERMOSTAT FROM THE SUBBASE.  
Press and release. The display  
shows 1:00 PM MON.  
PM  
DAY  
TUE  
M5016  
M5017  
Press and hold until the current  
day appears in the display.  
PM  
AHEAD  
BACK  
TUE  
Always press the keys with fingertip or  
similar blunt tool. Sharp instruments like a  
pen or pencil point can damage the key-  
board.  
Press and hold until the current  
time appears in the display. Be  
sure AM or PM appears as desired.  
NOTE: Check the glossary, page 22, for  
STEP 2  
SET THE PROGRAM SCHEDULE  
AND HEATING TEMPERATURES  
Press and release. Note that  
the display shows WAKE and  
AM  
SET  
PT  
WAKE  
MON TUE WED THU FRI  
HEAT  
WAKE  
the preprogrammed time and  
temperature.  
M5018  
Before Beginning…  
The schedule form on page 22 provides the  
homeowner an opportunity to plan the  
schedule.  
If the display reads COOL,  
press and release to switch to  
AM  
SET  
HEAT/COOL  
SET  
PT  
MON TUE WED THU FRI  
HEAT  
WAKE  
HEAT.  
M5018  
Now…  
Start by programming the WAKE time  
and temperature for weekdays.  
If display reads SAT or SUN,  
press and hold until MON  
AM  
SET  
PT  
DAY  
MON TUE WED THU FRI  
HEAT  
WAKE  
TUE WED THU FRI appears.  
M5018  
The thermostat requires a program for  
WAKE. You can program LEAVE, RE-  
TURN and SLEEP or not, as desired.  
Press and hold until the dis-  
play shows the desired start-  
ing time.  
AM  
SET  
PT  
AHEAD  
BACK  
MON TUE WED THU FRI  
WAKE  
HEAT  
M5019  
Press and hold until the dis-  
play shows the desired tem-  
perature.  
AM  
SET  
PT  
WARMER  
COOLER  
MON TUE WED THU FRI  
WAKE  
HEAT  
M5020  
If the display starts to blink while holding down TEM-  
PERATURE WARMER or COOLER, the setting limit  
has been reached. If the thermostat can switch automati-  
cally between heating and cooling, the heating tempera-  
ture must be at least three degrees below the air condi-  
tioning temperature. For example, if the cooling setting  
1
4
href="
T8624C,D  
PROGRAMMING THE THERMOSTAT  
is 75° F, the maximum heating setting is  
2° F.  
temperature disappear from  
the display.  
SET  
PT  
LEAVE  
7
MON TUE WED THU FRI  
LEAVE  
HEAT  
Program the LEAVE time and tempera-  
ture, if desired.  
M5021  
Press and release. The display  
shows LEAVE, but no time  
or temperature.  
AM  
SET  
PT  
NOTE: The LEAVE, RETURN or SLEEP  
program may be canceled by holding  
down the period key until the time and  
AHEAD  
BACK  
MON TUE WED THU FRI  
LEAVE  
HEAT  
M5022  
Press and hold until the dis-  
play shows the desired starting time.  
AM  
SET  
PT  
WARMER  
COOLER  
MON TUE WED THU FRI  
LEAVE  
HEAT  
M5023  
Press and hold until the display shows the  
desired temperature.  
Press and release. The display  
shows RETURN, but no time  
or temperature.  
SET  
PT  
RETURN  
MON TUE WED THU FRI  
RETURN  
ON HEAT  
M5024  
Program the RETURN time and tempera-  
ture, if desired.  
Press and hold until the dis-  
play shows the desired start-  
ing time.  
SET  
PT  
PM  
MON TUE WED THU FRI  
RETURN  
AHEAD  
BACK  
HEAT  
M5025  
SET  
PT  
PM  
MON TUE WED THU FRI  
RETURN  
WARMER  
COOLER  
Press and hold until the dis-  
play shows the desired tem-  
perature.  
HEAT  
M5026  
Program the SLEEP time and temperature, if desired.  
SLEEP  
PM  
MON TUE WED THU FRI  
SP ET T  
Press and release. The dis-  
HEAT  
play shows SLEEP and the  
pre-programmed time and  
temperature.  
SLEEP  
M5027  
SET  
PT  
PM  
MON TUE WED THU FRI  
AHEAD  
BACK  
HEAT  
Press and hold until the dis-  
play shows the desired start-  
ing time.  
SLEEP  
M5060  
SET  
PT  
PM  
MON TUE WED THU FRI  
SLEEP  
WARMER  
COOLER  
HEAT  
M5028  
Press and hold until the display shows the  
desired temperature.  
Set the SATURDAY sched-  
ule. Use the same procedure  
as for weekdays.  
SET  
PT  
PM  
SAT  
DAY  
HEAT  
SLEEP  
M5029  
WAKE  
SLEEP  
LEAVE  
Press and release until SAT ap-  
pears on the display.  
RETURN  
Press WAKE, LEAVE, RE-  
TURN or SLEEP to select the  
time period.  
AHEAD  
BACK  
WARMER  
COOLER  
Use the AHEAD/BACK keys  
to set the time and the WARMER/COOLER  
keys to set the temperature.  
Set the SUNDAY schedule.  
Use the same procedure as for  
weekdays.  
SET  
PT  
PM  
DAY  
SUN  
HEAT  
SLEEP  
M5030  
1
5
68-0134  
href="
T8624C,D  
PROGRAMMING THE THERMOSTAT  
WAKE  
SLEEP  
LEAVE  
Press and hold until SUN ap-  
pears on the display.  
RETURN  
Press WAKE, LEAVE, RE-  
TURN or SLEEP to select  
the time period.  
AHEAD  
BACK  
WARMER  
COOLER  
Use the AHEAD/BACK keys  
to set the time and the  
WARMER/COOLER keys to set the temperature.  
This completes setting the program schedule and heat-  
ing temperatures. To set air conditioning, go to Step 3.  
If cooling temperatures are not being pro-  
grammed, skip Step 3 and press the RUN  
PROGRAM key.  
AM  
SET  
PT  
WAKE  
First program the WAKE tem-  
perature for weekdays.  
SUN  
HEAT  
WAKE  
M5031  
STEP 3  
SET THE COOLING TEMPERA-  
TURES  
Press and release. The display shows WAKE and the  
time and temperature pro-  
SET  
HEAT/COOL  
AM  
SET  
PT  
grammed for heating.  
SUN  
COOL  
The program times are the same for both  
heating and cooling. Only the cooling tem-  
peratures need to be programmed if the  
thermostat has already been programmed  
for heating. To set times as the cooling  
temperatures are programmed, use the TIME  
AHEAD and BACK keys as described in  
Step 2. If the times are changed for cooling,  
they are also being changed for heating.  
WAKE  
M5032  
Press and release so COOL  
shows on the display, along  
with the preprogrammed cool-  
ing temperature.  
AM  
SET  
PT  
DAY  
MON TUE WED THU FRI  
WAKE  
COOL  
M5033  
If display reads SAT or SUN,  
press and hold until MON  
TUE WED THU FRI appears.  
AM  
SET  
PT  
WARMER  
COOLER  
MON TUE WED THU FRI  
COOL  
WAKE  
M5034  
Press and hold until the dis-  
play shows the desired temperature.  
If the display blinks while holding down TEMPERA-  
TURE WARMER or COOLER, the setting limit has  
been reached. If the thermostat can switch automatically  
between heating and cooling, the cooling temperature  
must be at least three degrees higher than the corre-  
sponding heating temperature. For example, if the heat-  
ing setting is 70° F, the mini-  
mum  
cooling  
setting  
is  
desired, the heating tempera-  
ture first must be lowered ac-  
cordingly.  
AM  
SET  
PT  
LEAVE  
7
3° F. If a lower cooling temperature is  
MON TUE WED THU FRI  
LEAVE  
COOL  
M5035  
Program the LEAVE tempera-  
ture, if desired.  
AM  
SET  
PT  
WARMER  
COOLER  
MON TUE WED THU FRI  
LEAVE  
COOL  
Press and release. The display  
M5036  
shows LEAVE, the time programmed for  
heating, and  
8° F.  
RETURN  
PM  
MON TUE WED THU FRI  
RETURN  
SP ET T  
Press and hold until the dis-  
play shows the desired tem-  
perature.  
COOL  
7
M5037  
1
6
href="
T8624C,D  
PROGRAMMING THE THERMOSTAT  
Program the RETURN tem-  
SET  
PT  
PM  
MON TUE WED THU FRI  
RETURN  
WARMER  
COOLER  
perature,  
desired.  
if  
COOL  
M5038  
Press and release. The display shows RE-  
TURN, the time programmed for heating,  
a
n
d
SET  
PT  
SLEEP  
PM  
MON TUE WED THU FRI  
SLEEP  
78° F.  
COOL  
M5039  
Press and hold until the  
display shows the desired tem-  
perature.  
SET  
PT  
PM  
MON TUE WED THU FRI  
SLEEP  
WARMER  
COOLER  
COOL  
M5040  
Program the SLEEP tempera-  
ture, if desired.  
SET  
PT  
PM  
SAT COOL  
DAY  
SLEEP  
Press and release.  
Press and hold until the dis-  
play shows the desired tem-  
perature.  
M5041  
WAKE  
SLEEP  
LEAVE  
Set the cooling temperatures  
for the SATURDAY schedule.  
Use the same procedure as for  
weekdays.  
RETURN  
WARMER  
COOLER  
Press and hold until SAT ap-  
pears on the display.  
to select the time period.  
SET  
PT  
PM  
DAY  
SUN  
COOL  
SLEEP  
M5042  
Press WAKE, LEAVE, RETURN or SLEEP  
WAKE  
SLEEP  
LEAVE  
Use the WARMER/COOLER  
keys to set the temperature.  
RETURN  
Set the cooling temperatures for  
the SUNDAY schedule. Use the  
same procedure as for weekdays.  
WARMER  
COOLER  
Press and hold until SUN ap-  
pears on the display.  
Press WAKE, LEAVE, RE-  
TURN or SLEEP to select the  
time period.  
RUN  
PROGRAM  
SET  
PT  
PM  
TUE  
LEAVE  
M5043  
1
7
68-0134  
href="
T8624C,D  
PROGRAMMING THE THERMOSTAT • OPERATING THE THERMOSTAT  
Use the WARMER/COOLER keys to set the tempera-  
ture.  
SET THE SYSTEM AND FAN  
SWITCHES ON THE SUB-  
BASE.  
FAN  
ON  
AUTO  
You have completed programming the cooling tempera-  
tures.  
Depending on thermostat model,  
some of the switch positions shown  
may not be available on the ther-  
mostat. Note the positions provided  
on the subbase, then set the  
switch(es) as desired.  
FAN  
Press and release to start the program.  
ON  
AUTO  
Go to Step 4.  
M3763  
STEP 4  
First set the fan switch.  
FAN ON: The fan runs continuously. Use for improved  
air circulation during special occasions or for more effi-  
cient  
electronic  
air  
cleaning.  
FAN AUTO: Normal setting  
for most homes. The fan goes  
on and off with the air condi-  
tioner in summer. In winter, the  
HEAT  
AUTO COOL OFF  
fan  
on  
most  
systems starts a few minutes  
after the furnace comes on. It  
stops a few minutes after the  
furnace goes off. The fan starts  
and stops with the furnace in  
some electric heat systems and  
with the compressor in heat  
pump systems.  
HEAT AUTO COOL OFF  
HEAT AUTO COOL OFF  
Then set the system switch.  
HEAT AUTO  
COOL OFF  
M3762  
HEAT: The thermostat controls  
your heating system.  
AUTO (select models only): The thermostat controls  
either your heating or cooling system, depending on  
room temperature.  
OFF: Both the heating and cooling systems are off.  
This completes the programming of the thermostat.  
OpeCOOL: The thermostat controls your cooling system.  
rating the Thermostat  
If the thermostat is removed from the wall to program, replace it following the procedure on page 5.  
TEMPORARILY CHANGING THE PROGRAM  
These features allow the program to be customized for  
those times when someone comes home early, or stays  
up late, or plans to be out for the evening.  
To keep the current temperature through the  
next program period:  
Press and release. The name  
of the period to be skipped  
will flash in the display until  
the next regularly scheduled  
period starts.  
SKIP  
NEXT  
PERIOD  
PM  
TUE  
LEAVE RETURN  
M5044  
To go back to the temperature of the previ-  
ous program period:  
Press and release. The dis-  
play will show the name of  
the previous period and flash  
TEMPORARY until the next  
regularly scheduled period starts.  
CHANGE  
TO LAST  
PERIOD  
PM  
TUE  
WAKE  
TEMPORARY  
M5045  
1
8
href="
T8624C,D  
OPERATING THE THERMOSTAT  
To temporarily raise or lower the tempera-  
ture for the current period only:  
Press and hold until the de-  
WARMER  
COOLER  
sired temperature is reached.  
The display will flash TEM-  
PORARY until the next pro-  
grammed time period starts.  
HEAT  
TEMPORARY  
M5046  
With the system switch at the  
AUTO position, press and  
hold down the key to alter-  
nate between heating and cool-  
ing temperature settings for  
temporary override.  
PRESENT  
SETTING  
Press and release to cancel  
any of the temporary settings.  
RUN  
PROGRAM  
PM  
TUE  
LEAVE  
M5047  
PERMANENTLY CHANGING THE  
PROGRAM  
WAKE  
SLEEP  
LEAVE  
Press and release the desired  
period key.  
If the schedule changes or a different tem-  
perature is desired, any setting can be up-  
dated without affecting other program set-  
tings.  
RETURN  
DAY  
Press and hold until the desired  
day schedule shows on the dis-  
play.  
AHEAD  
BACK  
Press and hold the Time or Tem-  
perature keys until the display  
shows the desired new program.  
WARMER  
COOLER  
RUN  
PROGRAM  
Press and release to return to  
normal operation.  
HOLD  
TEMP  
SET  
PT  
MANUALLY OPERATING THE  
THERMOSTAT  
Press and release.  
HEAT  
M5048  
This feature is particularly useful when on  
vacation or other extended absences. It does  
not cancel the program.  
SET  
PT  
WARMER  
COOLER  
Press and hold to change the  
temperature setting. After a  
few seconds, the display will  
show the current temperature.  
OHEAT  
M5049  
PRESENT  
SETTING  
SET  
PT  
Press and release to check the  
temperature setting.  
OHEAT  
M5050  
Press and hold down to alter-  
nate between heating and  
cooling temperature settings.  
RUN  
PROGRAM  
PM  
Press and release to cancel  
hold.  
TUE  
LEAVE  
M5051  
1
9
68-0134  
href="
T8624C,D  
OPERATING THE THERMOSTAT  
NOTE: Moving the system switch also can-  
cels hold.  
CANCELING THE PROGRAM  
SETTINGS  
day and Sunday settings are  
canceled separately.  
SLEEP  
MON TUE WED THU FRI  
LEAVE  
HEAT  
M5052  
Press and hold the desired pe-  
riod key until the time and temperature clear from the  
display (about three seconds).  
LEAVE  
The thermostat requires time and tempera-  
ture settings in the WAKE period, but any of  
the others can be canceled. Weekday, Satur-  
RETURN  
RUN  
PROGRAM  
PM  
MON  
RETURN  
Press and release to return to  
M5053  
Check all the stored settings without affecting the per-  
normal operation.  
manent program.  
SET  
PT  
WAKE  
SLEEP  
LEAVE  
PM  
MON TUE WED THU FRI  
SLEEP  
OHEAT  
CHECKING THE PROGRAM TIMES  
AND TEMPERATURES  
Press and release the desired  
period key. The start time and  
M5054  
temperature setting will appear on the display.  
RETURN  
DAY  
SET  
PT  
Press and release to display  
the next daily time and tem-  
perature for that period.  
PM  
SAT  
OHEAT  
SLEEP  
M5055  
RUN  
PROGRAM  
PM  
Press and release to return to  
MON  
normal operation.  
RETURN  
M5056  
PRESENT  
SETTING  
SET  
PT  
CHECKING THE CURRENT  
TEMPERATURE SETTING  
Press and release. The dis-  
play will show the current  
temperature setting for sev-  
OHEAT  
M5057  
Press a single key to compare current room  
temperature to the current temperature set-  
ting at any time.  
eral seconds, then revert to the room temperature.  
To check the heating and cooling settings with the sys-  
tem switch at the AUTO position, press and hold down  
to alternate between the heating and cooling settings.  
PRESENT  
SETTING  
During recovery from energy savings, the setting dis-  
played will not match the programmed setting. This is  
because the thermostat gradually changes the tempera-  
ture setting during recovery to provide most efficient use  
of the heating or cooling equipment.  
2
0
href="
T8624C,D  
TROUBLESHOOTING  
SYMPTOM  
POSSIBLE CAUSE  
ACTION  
CHECK POWER TO FURNACE OR AIR CONDITIONER.  
ROOM TEMPERATURE DISPLAY  
IS 32˚  
F.  
NO ac POWER TO THERMOSTAT  
ON-OFF SWITCH  
FUSE OR CIRCUIT BREAKER  
LOOSE 24V CONNECTION  
AT THERMOSTAT  
AT FURNACE /AIR CONDITIONER  
INCORRECT WIRING  
CHECK WIRING DIAGRAM  
FURNACE OR AIR CONDITIONER  
WON'T OPERATE.  
NO ac POWER TO THERMOSTAT  
CHECK POWER TO FURNACE OR AIR CONDITIONER.  
ON-OFF SWITCH  
FUSE OR CIRCUIT BREAKER  
LOOSE 24V CONNECTION  
AT THERMOSTAT  
AT FURNACE /AIR CONDITIONER  
INCORRECT WIRING  
CHECK WIRING DIAGRAM  
THERMOSTAT INOPERATIVE  
CONDUCT SELF-TEST; SEE CHECKOUT.  
ADJUST TEMPERATURE BY PUSHING WARMER/  
COOLER KEYS.  
PRESENT SETTING TOO LOW/HIGH  
SYSTEM SWITCH ON THERMOSTAT  
IN WRONG POSITION.  
RESET THERMOSTAT SYSTEM SWITCH.  
MINIMUM-OFF TIMES IN THERMOSTAT  
IN OPERATION ON COOLING  
WAIT 5 -10 MIN. OR USE SELF-TEST IN THERMOSTAT.  
SEE CHECKOUT.  
INCORRECT WIRING  
CHECK CIRCUIT DIAGRAM.  
CONSULT FURNACE OR AIR CONDITIONER  
INSTRUCTIONS.  
FURNACE OR AIR CONDITIONER  
INOPERATIVE  
PARTIAL DISPLAY  
NO DISPLAY  
INOPERATIVE THERMOSTAT  
NO POWER TO THERMOSTAT  
REPLACE THERMOSTAT.  
CHECK THAT HEAT OR COOL SYSTEM POWER IS ON.  
THERMOSTAT MOUNTED  
INCORRECTLY ON BASE.  
SEE INSTALLATION INSTRUCTIONS FOR CORRECT  
MOUNTING.  
PRESENT SETTING APPEARS  
INACCURATE.  
NORMAL OPERATION THERMOSTAT TURNS ON  
HEATING/COOLING EARLY TO MEET TEMPERATURE  
SETTING AT PROGRAMMED TIMES.  
RECOVERY CAN BE ENDED BY PUSHING WARMER/  
COOLER KEYS.  
THERMOSTAT IS IN RECOVERY  
MODE.  
CANNOT TEMPORARILY OVERRIDE  
BOTH HEATING AND COOLING  
SETTINGS IN AUTO MODE.  
PRESS AND HOLD DOWN PRESENT SETTING KEY TO  
ALTERNATE BETWEEN HEATING AND COOLING SETTINGS.  
NOT USING PRESENT SETTING KEY.  
THERMOSTAT TEMPERATURE NEEDS  
TO BE ADJUSTED ON A REGULAR  
BASIS.  
REPROGRAM THERMOSTAT TO MAKE PERMANENT  
CHANGE IN PROGRAM. WARMER/COOLER KEYS ARE  
TEMPORARY UNLESS PERIOD KEY IS PRESSED FIRST.  
WARMER/COOLER KEYS BEING  
USED TO ADJUST TEMPERATURE  
PROGRAM IS LOST DUE TO POWER  
OUTAGE OR DISPLAY GOES BLANK  
WHEN POWER IS TURNED OFF.  
BATTERIES ARE INCORRECTLY  
INSTALLED.  
REMOVE AND REPLACE PER MARKINGS ON THERMOSTAT.  
REPLACE BATTERIES.  
BATTERIES ARE DEAD.  
DISPLAY FLASHES WHILE  
PROGRAMMING.  
CHECK PROGRAMMING INSTRUCTIONS FOR CORRECT  
PROGRAM SEQUENCE.  
IMPROPER PROGRAM SEQUENCE  
AUTOMATIC THERMOSTAT HEATING  
OR COOLING TEMPERATURE CAN  
NOT BE SET CLOSER THAN 3 F.  
O
SET HEATING AND COOLING TEMPERATURES 3 F OR  
MORE APART.  
O
DISPLAY FLASHES DURING  
OPERATION.  
PROGRAMMING HAS BEEN LOST  
BECAUSE OF A POWER OUTAGE.  
REPROGRAM ACCORDING PROGRAMMING INSTRUCTIONS  
(MAKE SURE BATTERIES ARE INSTALLED).  
M5234A  
2
1
68-0134  
href="
T8624C,D  
GLOSSARY  
Recovery  
The time when the thermostat operates the heating or  
air conditioning equipment to return the home from the  
energy saving temperature to the comfort temperature.  
The thermostat starts the recovery period early so the  
home will be at the comfort setting by the time the  
homeowner has chosen.  
Troubleshooting  
Glossary  
Saturday program schedule  
The schedule of WAKE, LEAVE, RETURN and  
SLEEP period start times and temperatures programmed  
to run on Saturdays.  
Comfort temperature  
Setback  
The temperature desired when active and occupying  
the home.  
Reducing the temperature in the home for a set period  
in heating for energy savings. The lower temperature is  
the energy saving temperature.  
Energy-saving temperature  
The lower (heating) or higher (cooling) temperature  
that allows savings on heating and cooling costs when  
asleep or away. Also called the setback (heating) or  
Setup  
Raising the temperature in the home for a set period  
in cooling for energy savings. The higher temperature is  
the energy saving temperature.  
Temperature  
Start  
Time  
Period  
WAKE  
Heating Cooling  
Setpoint  
6:00 AM  
70° F  
78° F  
The thermostat temperature setting the homeowner  
selects. The thermostat turns the heating or cooling  
equipment on and off to maintain this temperature at the  
thermostat location until another temperature setting  
LEAVE  
RETURN  
SLEEP  
——— No program ————  
——— No program ————  
(
setpoint) goes into effect.  
10:00 PM  
60° F  
78° F  
Sunday program schedule  
setup (cooling) temperature.  
The schedule of WAKE, LEAVE, RETURN and  
SLEEP period start times and temperatures programmed  
to run on Sundays.  
Period key  
One of the four keysWAKE, LEAVE, RETURN or  
SLEEPto check or program the start time and  
temperatue for a time period.  
SYSTEM light  
This light glows whenever the thermostat is calling  
for heating or air conditioning.  
Preprogrammed schedule  
This is the schedule programmed into the thermostat  
at the factory. It sets a night program that provides  
energy savings when homeowner sets no program, or if  
personal program is lost for any reason. The program,  
which is the same for all days of the week, is:  
Time period  
One of four program periods: WAKE, LEAVE, RE-  
TURN and SLEEP available with the thermostat. One  
period begins when the previous program period ends:  
WAKEThe time period that the house is at a com-  
fortable temperature while the family gets up and gets  
ready to leave for work or school. This is the only  
period that must contain a time and temperature.  
LEAVEThe time period that the temperature can  
be set back (winter) or set up (summer) for energy  
Program  
The times and temperatures homeowner sets to define  
the comfort and energy saving periods for each day  
schedule.  
home.  
RETURNThe time period that the house is at a comfortable st ea mv i pn eg rsa t bu er ec af ou rs ef a mt h ie lyfa cmt ii vl yi ti ei ss i un s tuh ae l leyv e an wi na gy b fe rf oo mr e  
bedtime.  
SLEEPThe time period that the temperature can be set back (winter) or set up (summer) for energy savings  
because the family is sleeping. It can be set to start at the familys normal bedtime. Often the SLEEP program is set  
only for the heating season so family members can sleep cool in the cooling season.  
Weekday program schedule  
The schedule of WAKE, LEAVE, RETURN and SLEEP period start times and temperatures programmed to run  
Monday through Friday.  
2
2
2
3
68-0134  
href="
Home and Building Control  
Honeywell Inc.  
Home and Building Control  
Honeywell LimitedHoneywell Limitée  
740 Ellesmere Road  
1985 Douglas Drive North  
Golden Valley, MN 55422  
Scarborough, Ontario  
M1P 2V9  
Printed in U.S.A.