Honeywell T8700C Thermostat User Manual

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T8700B,C  
An Electronic Round™  
Programmable Thermostat  
PRODUCT DATA  
FEATURES  
Attractive neutral styling complements any decor.  
Easy-to-use means fewer homeowner questions and  
increased homeowner satisfaction.  
Large easy-to-read display.  
Keys located near the display for easy access.  
Fan and System switches are located on the top of the  
wallplate to eliminate accidental setting changes.  
Quick and easy installation.  
Two-period programming for added energy savings.  
Manual changeover from heat to cool eliminates  
unexpected system operation (T8700C).  
°F or °C temperature display for added model  
flexibility.  
T8700C  
Selectable heating cycle rate (1, 3, 6 or 9 cph) allows a  
variety of applications and reduced inventory.  
Cooling (T8700C) cycle rate fixed at 3 cph (the standard  
setting for compressors) allows a speedy installation.  
APPLICATION  
Programming permanently held in memory (no  
batteries needed) and retained during power outages  
for increased installer and homeowner convenience.  
The T8700 Electronic Round™ Programmable Thermostats  
provide single-stage, programmable temperature control for  
4V heating and/or cooling systems. See Table 1 for model  
2
Compatible with most equipment and application  
needs including gas, oil and electric forced air;  
condensing gas furnaces; hydronic heat; and gravity  
and radiant heat systems.  
descriptions.  
Table 1.T8700 Thermostat Description.  
Wiring  
System  
Selection  
Fan  
Terminals  
Used  
Powerstealing eliminates need to run additional wires.  
Model  
Selection  
T8700B1007  
T8700B1015  
T8700C1005  
HEAT-OFF  
HEAT-OFF  
NONE  
R,W  
Contents  
ON-AUTO  
ON-AUTO  
R,G,W  
R,G,W,Y  
HEAT-OFF-  
COOL  
Application........................................................................... 1  
Features .............................................................................. 1  
Specifications ...................................................................... 2  
Ordering Information ........................................................... 2  
Installation ........................................................................... 3  
Settings and Adjustments ................................................... 6  
Setting the Clock ................................................................. 7  
Programming....................................................................... 7  
Operation ............................................................................ 8  
Checkout ............................................................................. 10  
Troubleshooting ................................................................... 11  
®
U.S. Registered Trademark  
Copyright © 1998 Honeywell Inc.  
All Rights Reserved  
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T8700B,C AN ELECTRONIC ROUND™ PROGRAMMABLE THERMOSTAT  
Cycle Rates (at 50 Percent Load):  
SPECIFICATIONS  
Heating: Selectable at 1, 3, 6 or 9 cph. See Table 2 for  
heating cycle rates and corresponding system equipment.  
Cooling (T8700C): Fixed at 3 cph.  
IMPORTANT  
The specifications given in this publication do not  
include normal manufacturing tolerances; therefore,  
an individual unit might not exactly match the listed  
specifications. Also, this product is tested and  
calibrated under closely controlled conditions and  
some minor differences in performance can be  
expected if those conditions are changed.  
Table 2. Heating Cycle Rates.  
Cycles per  
System  
Hour (cph)  
Steam, Gravity  
1
3
6
9
Hydronic Heat, Condensing Gas Furnaces  
Gas or Oil Forced Air  
T8700 TRADELINE® models include a thermostat, wallplate,  
decorator cover plate and owner’s guide. The package also  
includes a resistor for use with Taco zone valves. See Fig. 11.  
Electric Furnace  
Power:  
Finish:  
T8700: Premier White® color.  
T8700: 24 Vac nominal, 18 to 30 Vac, 60 Hz.  
Electrical Ratings:  
Dimensions:  
See Fig. 1.  
Heating: .02 to 1.2A run; 3.5A inrush.  
Cooling: .02 to 1.2A run; 6.0A inrush.  
Fan: .02 to 0.5A run; 2.5A inrush.  
1-1/2  
5-1/2  
Current Draw:  
4-1/4  
T8700 Power Stealing Thermostat requires only 2.5 mA  
current draw when the thermostat calls for heat or cool and is  
compatible with most 24V systems. It can be used in most  
non-millivolt applications. See Power Stealing in the Operation  
section.  
3-1/2  
Temperature Adjustment:  
Setpoint temperature is adjusted by using the  
or  
keys.  
One press changes the setpoint one degree; pressing and  
holding changes the setpoint several degrees.  
PM  
Temperature Setting Range:  
40°F (4°C) to 99°F (37°C).  
Set  
Operational Ambient Temperature Range:  
0°F (4°C) to 110°F (43°C).  
3
Shipping Temperature Range:  
20°F (29°C) to 120°F (49°C).  
DECORATOR  
COVER PLATE  
T8700  
THERMOSTAT  
M12579  
-
Operating Relative Humidity:  
% to 90% RH, noncondensing.  
Fig. 1.T8700 Thermostat dimensions (T8700C shown).  
5
ORDERING INFORMATION  
When purchasing replacement and modernization products from your TRADELINE® wholesaler or distributor, refer to the  
TRADELINE® Catalog or price sheets for the complete ordering number.  
1
. Order number.  
2. Accessory, if desired.  
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 Home and Building Control Sales Office (check white pages of your phone directory).  
Home and Building Control Customer Logistics  
Honeywell Inc., 1985 Douglas Drive North  
Minneapolis, Minnesota 55422-4386  
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.  
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T8700B,C AN ELECTRONIC ROUND PROGRAMMABLE THERMOSTAT  
INSTALLATION  
Location  
Install the thermostat about 5 ft (1.5m) above the floor in an  
area with good air circulation at average temperature. See  
Fig. 2. Do not install the thermostat where it can be affected by:  
When Installing this Product…  
1
. Read these instructions carefully. Failure to follow them  
could damage the product or cause a hazardous  
condition.  
Drafts or dead spots behind doors and in corners.  
Hot or cold air from ducts.  
Radiant heat from the sun or appliances.  
Concealed pipes and chimneys.  
Unheated (uncooled) areas such as an outside wall  
behind the thermostat.  
2
. Check the ratings given in the instructions and on the  
product to make sure the product is suitable for your  
application.  
3. Installer must be a trained, experienced service  
technician.  
Mounting Decorator Cover  
Plate and Wallplate to Wall  
4
. After installation is complete, check out product  
operation as provided in these instructions.  
IMPORTANT  
CAUTION  
Position and level the wallplate for appearance only.  
The thermostat functions properly even when not  
level.  
Damage To Heating/Cooling System Possible.  
Be careful when handling wires during installation.  
Disconnect power at furnace or at main breaker/fuse  
box before starting installation.  
Mount decorator cover plate (if desired), wallplate, T8700 and  
the screws as follows; see Fig. 3:  
1
. Place the decorator cover plate and the wallplate on the  
desired wall location.  
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.  
2
. Pull the thermostat wire through the entrance hole on  
the decorator cover plate, then through the wallplate  
entrance hole.  
3
4
5
. Plug the wiring hole behind the thermostat to prevent  
drafts from affecting the thermostat.  
. Select the two mounting holes that best fit the  
application.  
. Fasten the decorator cover plate and the wallplate to  
the wall using the provided anchors (if necessary) and  
screws.  
Contact your local waste management authority for  
instructions regarding recycling and the proper  
disposal of an old control containing mercury in a  
sealed tube.  
YES  
NO  
NO  
5
FEET  
[
1.5 METERS]  
NO  
M12524  
Fig. 2.Typical thermostat location.  
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T8700B,C AN ELECTRONIC ROUND™ PROGRAMMABLE THERMOSTAT  
ROUTE WIRING AS  
SHOWN THROUGH  
ALTERNATE MOUNTING  
SCREW HOLE  
WALL  
ENTRANCE  
HOLE  
MOUNTING  
SCREW  
HOLE  
DECORATOR  
PLASTIC SCREW  
COVER PLATE  
ANCHOR (2)  
R
WALLPLATE  
1
G
O
F
F
H A  
E
T
O
L
O
C
F
A
N
Y
O
N
W
O
ALTERNATE  
MOUNTING  
SCREW HOLE  
MOUNTING  
SCREW HOLE  
WIRING ENTRANCE HOLE  
M12529  
Fig. 4.T8700C wallplate wiring connections.  
Refer to Table 1 for T8700B wiring connections.)  
(
1
WHEN USING WALL ANCHORS, DRILL 3/16 INCH HOLES FOR  
DRYWALL, 7/32 INCH HOLES FOR PLASTER OR WOOD.  
M12532A  
The shape of the terminals permits insertion of straight or  
wraparound wiring connections; either method is acceptable.  
See Fig. 5.  
Fig. 3. Mounting decorator cover plate  
and wallplate on wall (T8700C shown).  
Wiring  
FOR WRAPAROUND, STRIP  
CAUTION  
7/16 IN. (11 mm)  
Damage To Heating/Cooling System Possible.  
Be careful when handling wires  
during installation.  
FOR STRAIGHT INSERTION,  
STRIP 5/16 IN. (8 mm)  
Disconnect power at furnace or at main breaker/fuse  
box.  
M12537  
IMPORTANT  
Use an 18-gauge maximum wire for wiring the  
T8700 Thermostat.  
Fig. 5. Wiring connections.  
The T8700 Thermostat steals power through the heating and/or  
cooling system controls and is adaptable to most, 24 Vac  
systems. Refer to Fig. 6 through 11 for typical wiring hookups.  
All wiring must comply with local electrical codes and  
ordinances. A letter is located near each terminal for  
identification.  
NOTE: To ensure proper mounting of thermostat, restrict all  
wiring to the left side of the terminals. See Fig. 4.  
T8700B  
R
G
W
FAN  
RELAY  
HEATING  
PRIMARY  
CONTROL  
1
L1  
HOT)  
(
24V  
L2  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
M16005B  
Fig. 6.T8700B1007 Heat Only wiring diagram  
T8700B1015 Heat Only with Fan includes dotted line.  
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T8700B,C AN ELECTRONIC ROUND PROGRAMMABLE THERMOSTAT  
T8700  
T8700  
W
T8700  
W
T8700  
W
R
G
Y
R
R
R
COOLING  
CONTACTOR  
L2  
L1  
W
(
HOT)  
2
2
2
FAN  
RELAY  
HEATING  
1
PRIMARY  
CONTROL  
1
L1  
HOT)  
(
24V  
V8043E  
3
V8043E  
3
V8043E  
3
L2  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
M13207  
Fig. 7.T8700C heat-cool wiring diagram in single trans-  
former system with gas or electric heat/electric cooling.  
T
T
B1  
B2  
TO  
BURNER  
CONTROL  
CIRCUIT  
T8700  
R
1
2
G
COOLING  
CONTACTOR  
C1 C2  
Y
W
FAN  
RELAY  
CIRCULATOR  
1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
L1  
HOT)  
T
T
(
1
2
3
CONNECT V8043E YELLOW LEADWIRE TO THERMOSTAT.  
CONNECT V8043E RED LEADWIRES TO AQUASTAT®.  
OIL PRIMARY  
CONTROL  
L1  
HOT)  
L2  
(
24V  
M12623  
L2  
Fig. 10.T8700B1007 Heat Only wiring diagram  
for controlling 2-wire hot water zone valves.  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
M12526  
Fig. 8.T8700C heat-cool wiring diagram  
in oil heating/electric cooling system.  
THERMOSTAT T8700B  
(
Oil primary has its own transformer.)  
T8700  
R
R
W
TACO ZONE VALVE  
W
1
RESISTOR  
L1  
HOT)  
BLACK  
R841C  
L1  
HOT)  
(
1
2
3
2
(
L2  
1
L2  
BLUE  
RED  
SWITCH  
HEATER  
BIMETAL  
SWITCH  
RESISTANCE  
HEATER  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS  
AND OVERLOAD PROTECTION AS REQUIRED.  
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
M12527B  
CONNECT 7870 OHM RESISTOR TO THE TACO ZONE  
VALVE TERMINALS 1 AND 2. (TO ORDER, USE PART  
NO. 4074EYC.)  
Fig. 9.T8700B1007 Heat Only wiring diagram in  
electric baseboard or ceiling cable system.  
M13178  
Fig. 11.T8700B1007 Heat Only diagram used with TACO  
zone valves.The 7870 OHM resistor is included.  
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T8700B,C AN ELECTRONIC ROUND™ PROGRAMMABLE THERMOSTAT  
Adjust Fan Operation Switch  
SETTINGS AND ADJUSTMENTS  
The thermostat fan operation switch, labeled Fuel switch, is set  
at the factory in the F position. See Fig. 12.This is the correct  
setting for most systems. If this system is an electric heat  
system, set the switch to the E position. The E setting allows the  
fan to turn on immediately with the heating or cooling  
Setting Fan and System Switches  
Fan and system settings are controlled manually using the  
switches located at the top of the thermostat wallplate. See  
Fig. 14 for switch locations.  
equipment in a system where the G terminal is connected.  
TIME/TEMPERATURE  
DISPLAY  
FAN SWITCH  
(SOME MODELS)  
FUEL SWITCH  
CONNECTOR  
1
SYSTEM SWITCH  
E
F
PM  
Set  
1
T8700C AND T8700B WITH FAN ONLY.  
M12531A  
DECREASE  
SETTING  
INCREASE  
SETTING  
Fig. 12. Fuel switch, rear view of thermostat.  
M12546A  
Mounting Thermostat to Wallplate  
Fig. 14.T8700 time/temperature display  
and System/Fan switches (T8700C shown).  
1
. Align and attach bottom center notch on the thermostat  
with bottom center tab on wallplate.  
2. Next align tabs and connector at top of thermostat to  
the pins on the wallplate. Press firmly to attach.  
Fan Switch  
The Fan switch settings for the T8700B1015 with Fan and  
T8700C are:  
PINS  
ON: The fan runs continuously. Use to improve air circulation.  
AUTO: Normal setting for most homes. In cooling, the fan  
starts and stops with the cooling equipment. In heating,  
the heating system directly controls the fan equipment.  
The fan may start a few minutes after the heating  
equipment turns on (for most systems). When the  
thermostat Fuel switch is set to the E position for electric  
heat, the fan starts and stops with heating equipment.  
Slide the Fan switch on the thermostat to the desired fan  
setting.  
Set  
System Switch  
BOTTOM CENTER  
NOTCH  
The T8700B System switch controls the thermostat as follows:  
HEAT: The thermostat controls the heating system.  
OFF: Heating is off.  
A
B
ALIGN AND ATTACH BOTTOM CENTER NOTCHS ON  
THERMOSTAT/WALLPLATE.  
ALIGN PINS ON WALLPLATE WITH CONNECTOR ON  
THERMOSTAT. PRESS FIRMLY TO ATTACH.  
M13208  
The T8700C System switch controls the thermostat as  
follows:  
Fig. 13. Mounting thermostat to wallplate.  
COOL: The thermostat controls the cooling system.  
OFF: Both heating and cooling are off.  
HEAT: The thermostat controls the heating system.  
NOTE: To remove the thermostat from the wallplate, grasp  
the thermostat on both sides and pull the thermostat  
straight out.  
Slide the System switch on the thermostat to the desired  
system setting.  
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T8700B,C AN ELECTRONIC ROUND PROGRAMMABLE THERMOSTAT  
2
. Set your WAKE time.  
SETTING THE CLOCK  
AM  
a. Press the  
once.You will see a  
flashing WAKE time.  
key  
1. To set the current time:  
M12507  
a. Press the key  
PM  
once.You will see a  
flashing clock.  
b. Use the keys to set your desired WAKE  
or  
time. The WAKE time is now set.  
M12506  
b. Use the  
or  
keys to set the current time.  
3. Set your WAKE  
SET  
temperature.  
c. Press the  
key until End is displayed.  
AM  
a. Press the  
key  
once.You will see a  
flashing WAKE  
temperature.  
M12508  
PROGRAMMING  
The thermostat is preprogrammed for your convenience with  
the following time and temperature settings, see Table 3.  
b. Use the keys to set your desired WAKE  
or  
temperature. The WAKE temperature is now set.  
Table 3. Preprogrammed Time/Temperature Settings.  
4
. Set your SLEEP time.  
a. Press the key  
Heating  
Setpoint  
Cooling  
a
PM  
Period  
WAKE  
Start Time  
6:00 AM  
Setpoint  
once.You will see a  
flashing SLEEP time.  
70°F (21°C)  
78°F (25.5°C)  
82°F (28°C)  
M12509  
SLEEP  
10:00 PM  
62°F (16.5°C)  
b. Use the keys to set your desired SLEEP  
or  
a
T8700C only.  
time. The SLEEP time is now set.  
WAKE is the time period when you want the house at a  
comfortable temperature during the day.  
SLEEP is the time period you can set for an energy-saving  
temperature while you sleep.  
5
. Set your SLEEP  
temperature.  
SET  
PM  
a. Press the  
key  
once.You will see a  
flashing SLEEP  
temperature.  
M12510  
NOTE: The heating and cooling program times are the  
same. Changing your cooling WAKE time also  
changes your heating WAKE time.  
b. Use the keys to set your desired SLEEP  
or  
The following is a heating program example. The System  
switch is in the HEAT position. To change to the cooling  
program (T8700C), move the System switch to the COOL  
position and enter the cooling temperature settings.  
temperature. The SLEEP temperature is now set.  
6
. Run program.  
a. Press the  
once.You have  
key  
IMPORTANT  
completed your  
When programming the T8700B, first move the  
System switch to the heat position.  
program changes.  
End is displayed for  
five seconds indica-  
ting the end of  
programming. The  
thermostat then  
M12511  
To program your ownTime and Temperature settings  
follow steps 1 through 6.  
PM  
1. Set the current time.  
displays the current  
time and room temperature.  
M12542  
a. Press the  
once.You will see a  
flashing clock.  
key  
PM  
NOTE: To exit the programming mode at any time, press the  
key until End is displayed.  
M12506  
b. Use the  
or  
keys to set the current time. The  
clock is now set.  
Preprogrammed Time and Temperature settings.  
After the clock is set, you can use the preprogrammed  
Time and Temperature settings, (see table 3) press the  
key until End is displayed.  
The preprogrammed Temperature settings can now be  
used.  
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T8700B,C AN ELECTRONIC ROUND™ PROGRAMMABLE THERMOSTAT  
2
. Select Cycles Per Hour.  
The display changes to  
show current cycle  
rate setting.  
Operating the Thermostat  
To Display Temperature  
Setting.  
once to  
SET  
AM  
Press  
or  
display present tempera-  
ture setting. After approxi-  
mately five seconds, the  
M12520  
a. Use  
or  
to  
select 1, 3, 6, or 9 cph.  
Refer to Table 4.  
M12512  
thermostat displays current time and room temperature.  
Table 4. Heating Cycle Options  
To Make a Temporary  
Temperature Change.  
SET  
Program  
Setting  
(cph)  
a. Press or  
until  
AM  
desired temperature  
is displayed.  
System  
M12513  
Steam, Gravity  
1
3
6
9
Hydronic Heat, Condensing Gas Furnaces  
Gas or Oil Forced Air  
Electric Heat  
b. TEMPORARY is  
displayed. The  
TEMPORARY  
AM  
TEMPORARY  
change is in effect  
until the next  
program period.  
M12514  
3. Select Fahrenheit - CelsiusTemperature.  
a. Press  
display the current  
F or °C setting.  
to  
NOTE: To cancel your TEMPORARY change, press  
until End is displayed.  
°
b. Use  
or  
to  
To Use Hold Function.  
M12521  
choose between °C  
and °F.  
To hold the thermostat at one temperature indefinitely,  
program both WAKE and SLEEP to the same  
temperature.  
4
. Clock Format.  
a. Press  
to  
Installer Setup  
The following instructions provide the information necessary  
to change the heating cycle rate, select either Fahrenheit  
display the current  
12- or 24-hour clock  
setting.  
(F °) or Celsius (C °) and 12- or 24-hour clock format.  
M12522  
b. Use  
or  
to  
NOTE: To exit at any time, press until End is displayed.  
choose either a 12- or 24-hour clock format.  
Press once to exit  
Installer Setup. Upon  
exiting, the temperature  
setting will be at 52°F  
1
. Enter Installer Setup.  
a. Use or keys  
to set the  
SET  
AM  
temperature set-  
point to 52°F (11°C).  
(or 11°C). Press  
times to return the  
thermostat to the normal operating mode with End  
appearing on the display.  
six  
M12518  
M12519  
M12504  
M12511  
b. After the thermostat  
reverts back to  
TEMPORARY  
AM  
displaying room  
temperature  
(approximately  
five seconds),  
simultaneously  
press and  
keys  
and hold for three  
seconds. Release  
the keys after the  
display changes.  
c. Press  
within  
five seconds.  
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T8700B,C AN ELECTRONIC ROUND PROGRAMMABLE THERMOSTAT  
Fan Control  
OPERATION  
The FAN switch settings for the T8700B1015 with Fan and  
T8700C are ON and AUTO.  
Zero Droop Performance  
ON: The fan runs continuously.  
The T8700 Thermostat can control temperature closer to  
setpoint than electromechanical thermostats. This is because  
proportional plus integral control (P + I) maintains a constant  
indoor temperature independent of the outdoor temperature.  
This feature allows the T8700 Thermostat to provide tight  
temperature control with virtually no noticeable swings in  
temperature, a condition referred to as droop. This zero droop  
performance provides improved comfort and occupants do not  
need to continually adjust thermostat settings to be  
AUTO: In cooling, the fan starts and stops with the cooling  
equipment. In heating, the fan starts a few minutes after  
the heating equipment turns on. With the Fuel switch in  
the E position for electric heat, the fan starts and stops  
with the heating equipment.  
Heat Mode  
With the T8700 system switch in the HEAT position, the  
thermostat controls the heating system. On a call for heat, the  
W terminal is energized and a flame icon  
digital display.  
comfortable, even during extreme weather.  
shows on the  
Power Stealing  
If the Fuel switch is in the E position, both the W and G  
terminals are energized on a call for heat.  
The T8700 Thermostat steals power through the heating and/or  
cooling system controls; therefore, it can be used in applications  
where it is not possible to run additional wires. See Fig. 15.  
Cool Mode  
The T8700 Thermostat requires only 2.5 mA of load current  
when the heating and/or cooling is on. When the heating and/or  
cooling is off, the thermostat operates at 0.1 mA. This low  
current draw allows the T8700C to be used with most 24V  
heating and/or cooling systems.  
With the T8700C System switch in the Cool position, the  
thermostat controls the cooling system. On a call for cool,  
the G and Y terminals are energized and a snowflake icon  
shows on the digital display. A flashing snowflake indicates  
that the minimum-off timer is in effect.  
The T8700 Thermostat operates only when mounted on the  
wallplate with 24V applied. Batteries are not required for  
operation. Temperature setpoints, programming and  
configuration settings are retained permanently in memory.  
Minimum Off-Timer T8700C  
A minimum off-timer for the T8700C assures that the cooling  
compressor does not come on again for at least five minutes  
after it turns off. The minimum-off timer is triggered when the  
compressor turns off or when the System switch is changed.  
If the compressor turns off when the setpoint is changed, the  
minimum-off timer is triggered. Power interruption and power  
restoration also trigger the minimum off-timer.  
Sequence of Operations  
The Heat and Cool outputs are transistor controlled. A loss of ac  
power or a change in the System switch setting can turn off  
outputs. Table 5 shows the Fan and System sequence of  
operations.  
L1  
L2  
(HOT)  
1
R
G
FAN SWITCH  
ON  
FAN RELAY  
THERMISTOR  
SENSOR  
AUTO  
THERMOSTAT  
LOGIC  
HEAT RELAY  
COOL RELAY  
SYSTEM SWITCH  
HEAT  
W
Y
OFF  
COOL  
POWER  
SUPPLY  
MOSFET  
LOGIC AND  
CONTROL  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
MOSFET  
M10360  
Fig. 15.T8700C power stealing internal schematic.  
68-0197—1  
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T8700B,C AN ELECTRONIC ROUND™ PROGRAMMABLE THERMOSTAT  
Table 5. Sequence of Operations.  
Fan Switch Settings  
System Switch Settings  
Call for Action  
None  
Energize Terminals  
Display Icons  
None  
AUTO  
ON  
OFF  
Any  
None  
G
Any  
None  
b
b
AUTO  
AUTO  
COOL  
Cooling  
G, Y  
a
HEAT  
Heating  
W,G  
a
b
When fuel switch is in the E position. (T8700B with Fan and T8700C).  
T8700C only.  
IMPORTANT  
CHECKOUT  
A mimimum off-timer for the T8700C assures that the  
cooling compressor does not come on again for at  
least five minutes after it turns off. The minimum-off  
timer is triggered when the compressor turns off or  
when the System switch is changed. If the compressor  
turns off when the setpoint is changed, the minimum-  
off timer is triggered. Power interruption and power  
restoration also trigger the minimum off-timer.  
Heating (T8700B,C)  
1
. Slide the System switch to HEAT and the Fan switch to  
AUTO. (For T8700B1007 Heat Only model, a Fan switch  
is not an option).  
2
. Press and hold the  
key to raise the temperature  
setting several degrees above the room temperature  
the heating equipment should start. In conventional  
systems, the system turns on the fan through a limit  
control. When using the thermostat with the fuel switch  
set to the E position for electric heat, the fan starts  
immediately.  
1
. Slide the System switch to COOL and the Fan switch to  
AUTO.  
2
. To start the cooling equipment, press the  
key to  
lower the temperature setting several degrees below  
room temperature. The fan starts and stops with the  
cooling equipment.  
key to raise the temperature setting above  
3
. Press the  
key to lower the temperature setting below  
the room temperature. Heating equipment should stop.  
3
. Press the  
the room temperature. Cooling system should shut down.  
Cooling (T8700C)  
Fan (T8700B1015 with Fan, T8700C)  
CAUTION  
Operating at too low of an outdoor temperature  
1
. Slide the System switch to OFF and the Fan switch to  
ON. The Fan should run continuously.  
Equipment Damage Possible.  
2
. Slide the Fan switch to AUTO. In heating, the fan is  
controlled directly by the heating equipment and starts  
a few minutes after the heating equipment turns on (for  
most systems). When using the thermostat with the  
Fuel switch set to the E position for electric heat, the fan  
starts and stops with the heating equipment. In cooling,  
the fan starts and stops with the cooling equipment.  
can cause compressor damage.  
Do not attempt to operate cooling when outdoor  
temperature is below 50°F (10°C). Refer to  
manufacturer recommendations.  
Make certain all equipment responds properly to the  
thermostat.  
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T8700B,C AN ELECTRONIC ROUND PROGRAMMABLE THERMOSTAT  
TROUBLESHOOTING  
Symptom  
Possible Cause  
No ac power.  
Corrective Action  
Heating/cooling  
equipment does not  
operate.  
Check power to heating/cooling equipment:  
On/Off switch.  
Fuse or circuit breaker.  
Loose 24V connection: at thermostat; at furnace/air  
conditioner.  
Incorrect wiring: check appropriate wiring diagram.  
Thermostat inoperative.  
Incorrect wiring.  
See Checkout section.  
Check wiring.  
Heating/cooling equipment  
inoperative.  
Consult equipment manufacturer instructions.  
System switch on thermostat in  
wrong position.  
Reset System switch.  
Flashing  
Snowflake  
Minimum-off timer in thermostat  
operating for cooling.  
Wait five minutes or follow steps in Checkout section.  
Partial display.  
Still in installer setup mode.  
Damaged thermostat.  
See Installer Setup section for instructions on how to exit.  
Replace thermostat.  
Displaying only time  
Power to thermostat is currently  
Check the power to thermostat.  
and not temperature. interrupted.  
Blank display. No power to thermostat.  
Check the power to thermostat.  
Thermostat mounted incorrectly on See installation instructions for correct mounting.  
wallplate.  
Temperature display Thermostat is configured  
Reconfigure display. See Installer Set-up for instructions to  
change display.  
is incorrect.  
incorrectly for °F or °C.  
Cannot change  
temperature setting.  
Upper or lower temperature  
setpoints were reached.  
Check temperature setpoints; temperature setting range is  
40°F (4°C) to 99°F (37°C).  
Time loss.  
Power to thermostat was  
interrupted longer than 20  
minutes.  
Reset clock. See Setting The Clock  
68-0197—1  
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1
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Home and Building Control  
Honeywell Inc.  
Honeywell Plaza  
P.O. Box 524  
Minneapolis MN 55408-0524  
Home and Building Control  
Honeywell Limited-Honeywell Limitée  
155 Gordon Baker Road  
North York, Ontario  
Honeywell Asia Pacific Inc.  
Room 3213-3225  
Sun Hung Kai Centre  
No. 30 Harbour Road  
Wanchai  
M2H 3N7  
Hong Kong  
Honeywell Latin American Region  
Honeywell Europe S.A.  
3 Avenue du Bourget  
1140 Brussels  
4
80 Sawgrass Corporate Parkway  
Suite 200  
Sunrise FL 33325  
Belgium  
Printed in U.S.A. on recycled  
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mer paper fibers.  
www.honeywell.com/yourhome  

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