The T8700 Electronic Round™ Programmable Thermostats provide single-stage, programmable temperature control for 24V heating and/or cooling systems. See Table 1 for model descriptions.
Table 1. T8700 Thermostat Description.
Model | System Selection | Fan Selection | Wiring Terminals Used |
T8700B1007 | HEAT-OFF | NONE | R,W |
T8700B1015 | HEAT-OFF | ON-AUTO | R,G,W |
T8700C1005 | HEAT-OFF- COOL | ON-AUTO | R,G,W,Y |
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. 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.
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.
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System | Cycles per Hour (cph) |
Steam, Gravity | 1 |
Hydronic Heat, Condensing Gas Furnaces | 3 |
Gas or Oil Forced Air | 6 |
Electric Furnace | 9 |
Finish:
T8700: Premier White® color.
Dimensions:
See Fig. 1.
When Installing this Product…
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 authority for instructions regarding recycling and the proper disposal of an old control containing mercury in a sealed tube.
Fig. 2. Typical thermostat 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:
Mounting Decorator Cover Plate and Wallplate to Wall
IMPORTANT
Position and level the wallplate for appearance only. The thermostat functions properly even when not level.
Mount decorator cover plate (if desired), wallplate, T8700 and the screws as follows; see Fig. 3:
CAUTION
Damage To Heating/Cooling System Possible. Be careful when handling wires during installation.
Disconnect power at furnace or at main breaker/fuse box.
IMPORTANT
Use an 18-gauge maximum wire for wiring the T8700 Thermostat. 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.
The shape of the terminals permits insertion of straight or wraparound wiring connections; either method is acceptable. See Fig. 5.
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.
Adjust Fan Operation Switch
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 equipment in a system where the G terminal is connected.
Mounting Thermostat to Wallplate
Setting Fan and System Switches
Fan and system settings are controlled manually using the switches located at the top of the thermostat wall plate. See Fig. 14 for switch locations.
Fan Switch
The Fan switch settings for the T8700B1015 with Fan and T8700C are:
System Switch
The T8700B System switch controls the thermostat as follows:
The T8700C System switch controls the thermostat as follows:
The thermostat is preprogrammed for your convenience with the following time and temperature settings, see Table 3.
Table 3. Preprogrammed Time/Temperature Settings.
Period | Start Time | Heating Setpoint | Cooling Setpointa |
WAKE | 6:00 AM | 70°F (21°C) | 78°F (25.5°C) |
SLEEP | 10:00 PM | 62°F (16.5°C) | 82°F (28°C) |
a T8700C only.
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 the temperature while you sleep.
NOTE: The heating and cooling program times are the same. Changing your cooling WAKE time also changes your heating WAKE time.
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.
IMPORTANT
When programming the T8700B, first move the System switch to the heat position.
To program your own Time and Temperature settings follow steps 1 through 6.
To Display Temperature Setting.
Press
To Make a Temporary Temperature Change.
NOTE: To cancel your TEMPORARY change, press until
To Use Hold Function.
To hold the thermostat at one temperature indefinitely, program both WAKE and SLEEP to the same temperature.
Installer Setup
The following instructions provide the information necessary to change the heating cycle rate, select either Fahrenheit (F °) or Celsius (C °) and 12- or 24-hour clock format.
NOTE: To exit at any time, press
System | Program Setting (cph) |
Steam, Gravity | 1 |
Hydronic Heat, Condensing Gas Furnaces | 3 |
Gas or Oil Forced Air | 6 |
Electric Heat | 9 |
Press
Zero Droop Performance
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 comfortable, even during extreme weather.
Power Stealing
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. 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.
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.
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.
Fan Control
The FAN switch settings for the T8700B1015 with Fan and T8700C are ON and AUTO.
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 shows on the digital display.
If the Fuel switch is in the E position, both the W and G terminals are energized on a call for heat.
Cool Mode
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.
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.
Table 5. The sequence of Operations.
Fan Switch Settings | System Switch Settings | Call for Action | Energize Terminals | Display Icons |
AUTO | OFF | None | None | None |
ON | Any | Any | G | None |
AUTO | COOLb | Coolingb | G, Y | |
AUTO | HEAT | Heating | W,Ga |
Heating (T8700B, C)
CAUTION
Equipment Damage Possible.
Operating at too low of an outdoor temperature can cause compressor damage. Do not attempt to operate cooling when the outdoor temperature is below 50°F (10°C). Refer to manufacturer recommendations.
IMPORTANT
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.
Fan (T8700B1015 with Fan, T8700C)
Symptom | Possible Cause | Corrective Action |
Heating/cooling equipment does not operate. | No ac power. | 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. | See the Checkout section. | |
Incorrect wiring. | Check wiring. | |
Heating/cooling equipment is inoperative. | Consult equipment manufacturer instructions. | |
The system switched on the thermostat in wrong position. | Reset the 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. | See Installer Setup section for instructions on how to exit. |
Damaged thermostat. | Replace thermostat. | |
Displaying only time and not temperature. | Power to the thermostat is currently interrupted. | Check the power to the thermostat. |
Blank display. | No power to the thermostat. | Check the power to the thermostat. |
The thermostat is mounted incorrectly on the wallplate. | See installation instructions for correct mounting. | |
The temperature display is incorrect. | The thermostat is configured incorrectly for °F or °C. | Reconfigure display. See Installer Set-up for instructions to change display. |
Cannot change the 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 the thermostat was interrupted for longer than 20 minutes. | Reset clock. See Setting The Clock |
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 M2H 3N7
Honeywell Asia Pacific Inc.
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