Honeywell T8775A, T8775C Installation Guide
Non-Programmable Thermostats
The T8775A,C Thermostats provide single-stage
temperature control for 24V systems. The
T8775A,C models include a thermostat, wallplate
(for wiring and mounting thermostat), mounting
screws, wall anchors, and a 4074 FAB resistor.
MERCURY 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.
INSTALLATION
When Installing this Product…
1. Read these instructions carefully. Failure to
follow them could damage the product or
cause a hazardous condition.
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.
4. After installation is complete, check out product operation as provided in these instructions.
CAUTION
Electrical Shock or Equipment Damage
Hazard.
Can shock individuals or short
equipment circuitry.
Disconnect power supply before
installation.
® U.S. Registered Trademark • Patents Pending
© 2004 Honeywell International Inc.
All Rights Reserved
T8775A,C
The Digital Round
INSTALLATION INSTRUCTIONS
Location
Install the thermostat about 5 ft (1.5m) above the
floor in an area with good air circulation at average
temperature. Do not install the thermostat where it
can be affected by:
— 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.
Mounting Wallplate to Wall
Mount the T8775A,C wallplate, with the screws
provided. See Fig. 1.
WALL ANCHORS (2)
WALL PLATE
WIRING HOLE
1 INCH SCREW (2)
1 WHEN USING WALL ANCHORS, DRILL 3/16 IN. HOLES
FOR DRYWALL, 7/32 IN. HOLES FOR PLASTER.
Fig. 1. Mounting wallplate to wall.
™
1
M19499
69-1677ES—1
T8775A,C THE DIGITAL ROUND™ NON-PROGRAMMABLE THERMOSTATS
Wiring
IMPORTANT
Use 18-gauge wire to wire the T8775A,C
Thermostats.
All wiring must comply with local electrical codes
and ordinances. Disconnect the power supply to
prevent electrical shock or equipment damage.
Refer to Fig. 2 through 6 for typical wiring hookups.
R
W
1
Fig. 4. Typical hookup of T8775C in heat-cool system
O
Rc
2
R
HEATING
RELAY OR
VALVE COIL
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
2 FACTORY INSTALLED JUMPER.
with single transformer.
B
G
Y
W
COMPRESSOR
CONTACTOR
FAN
RELAY
M19515
1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
HEATING
RELAY OR
VALVE COIL
M19513
Fig. 2. Typical hookup of T8775A in a heat-only system.
O
B
Rc
2
G
Y
R
W
1
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
2 FACTORY INSTALLED JUMPER.
Fig. 3. Typical hookup of T8775C in heat-only system
HEATING
RELAY OR
VALVE COIL
with fan.
FAN
RELAY
M19514
69-1677ES—1 2
B
Rc
G
2
Y
R
W
COMPRESSOR
CONTACTOR
HEATING
RELAY OR
1
VALVE COIL
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
REMOVE FACTORY INSTALLED JUMPER BETWEEN R AND RC.
2
Fig. 5. Typical hookup of T8775C in heat-cool system
Fig. 6. Typical hookup of T8775C in single-stage heat
with two transformers.
4
O
B
Rc
G
2
Y
3
R
W
COMPRESSOR
CONTACTOR
1
1 POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
2 FACTORY INSTALLED JUMPER.
3 USE A JUMPER WIRE (NOT SUPPLIED) TO CONNECT W TO Y.
4 USE EITHER O OR B FOR HEAT PUMP CHANGEOVER.
pump system.
FAN
RELAY
FAN
RELAY
HEAT
CHANGEOVER
VALVE
CHANGEOVER
COOL
VALVE
1
M19517
M19516
T8775A,C THE DIGITAL ROUND™ NON-PROGRAMMABLE THERMOSTATS
CUSTOMIZE THERMOSTAT
Setting Fuel Switch (T8775C only)
The fuel switch is preset at the factory in the F
position. See Fig. 7. This is the correct setting for gas
or oil systems. If the T8775C is being installed on an
electric heat system, or a heat pump, set the switch to
the E position. The E setting allows the fan to turn on
immediately with the heating equipment in a system
where the G terminal is connected.
FUEL SWITCH
Fig. 7. Fuel switch.
DIP Switch
To adjust the heat cycle rate or the Fahrenheit/Celsius
indication, locate DIP switch 1, 2 and 3 on the back of
the thermostat. See Fig. 8.
BACK OF THERMOSTAT
M19497
Table 1. Heat Cycle Rate.
Cycles
DIP
Switch
1
DIP
Switch
2
Heating System
Steam, Gravity 1 On On
High Efficiency Warm Air
(90%+ efficiency), Hot Water,
Heat Pump
Gas or Oil Warm Air (factory
setting)
Electric Warm Air 9 On Off
In Floor Radiant Heat Check with manufacturer
Per
Hour
3OffOn
6OffOff
for recommended cycle
rate.
Fahrenheit/Celsius Indication
Use DIP switch 3 to set the desired temperature
indication. See Table 2.
Table 2. Temperature Indication.
Fahrenheit/Celsius
Display DIP Switch 3
Fahrenheit (factory setting) Off
Celsius On
Mounting Thermostat to Wallplate
ENGAGE TABS
AT BOTTOM OF
THERMOSTAT
AND WALL PLATE.
PRESS UPPER
EDGE OF CASE
TO LATCH
1 2 3
ON
DIP SWITCH
M19567
Fig. 8. DIP switch.
Set Heat Cycle Rate
Use DIP switches 1 and 2 to set the heat cycle rate.
See Table 1.
M19498
Fig. 9. Mounting thermostat to wallplate.
OPERATION
Setting SYSTEM and FAN Switches (T8775C only)
System and fan settings are controlled manually by
using the switches located at the top of the
thermostat. See Fig. 10.
3 69-1677ES—1
T8775A,C THE DIGITAL ROUND™ NON-PROGRAMMABLE THERMOSTATS
(T8775C ONLY)
(T8775C ONLY)
SELECTS
COOL/OFF/HEAT
DISPLAYS ROOM
OR SET TEMPERATURE
SELECTS
ON/AUTO
ROOM
SHOWS THAT THE
SET
CURRENT ROOM
TEMPERATURE IS
DISPLAYED.
SHOWS THAT THE
CURRENT TEMPERATURE
SETPOINT IS DISPLAYED.
DISPLAYS AND ADJUSTS
TEMPERATURE SETPOINT/TURNS
BACKLIGHT ON
Fig. 10. T8775 Thermostat (features and operation).
SYSTEM Switch
Heat: The thermostat controls the heating
system.
Off: Both heating and cooling systems are off.
Cool: The thermostat
system.
controls the cooling
FAN Switch
Auto: The fan only runs with the heating and
cooling system.
On: The fan runs continuously. Use for
improved air circulation.
CHECKOUT
NOTE: Temperature setpoint range is 40°F to 90°F
(4°C to 32°C) in heating and 45°F to 99°F
(7°C to 37°C) in cooling.
Heating
1. Slide the SYSTEM switch to Heat and the FAN
switch to Auto (T8775C only).
2. Raise the temperature setpoint several degrees
above the room temperature.
3. A flame will appear in the display and the
heat should turn on.
4. Lower the temperature setpoint below the room
temperature.
5. The flame will disappear from the display
and the heat should turn off.
Cooling (T8775C only)
CAUTION
Low Temperature Hazard.
Operating at too low of an outdoor
temperature may cause compressor
damage.
Do not operate cooling if outdoor temperature
is below 50°F (10°C). Refer to manufacturer’s
recommendations.
NOTE: If a call for cooling is made before the com-
pressor has been off for five minutes, or if a
power interruption occurs while the compressor is running, the thermostat will go
into a five-minute delay to protect the compressor. The snowflake will flash during
this delay.
1. Slide the SYSTEM switch to Cool and the FAN
switch to Auto.
2. Lower the temperature setpoint several
degrees below the room temperature.
3. After approximately five minutes, the thermostat will display a solid snowflake and the
cooling should turn on.
4. Raise the temperature setpoint above the room
temperature.
5. The snowflake will disappear from the display and the cooling should turn off.
Fan
1. Slide the SYSTEM switch to Off and the FAN
switch to On. The fan should run continuously.
2. Slide the FAN switch to Auto. The fan should
turn off.
M19520
Automation and Control Solutions
Honeywell International Inc. Honeywell Limited-Honeywell Limitée
1985 Douglas Drive North 35 Dynamic Drive
Golden Valley, MN 55422 Scarborough, Ontario
69-1677ES—1 J.S. Rev. 6-04 Printed in Hungary www.honeywell.com/yourhome
M1V 4Z9
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