Honeywell T8775A, T8775C Installation Guide

T8775A,C

The Digital Round™

Non-Programmable Thermostats

INSTALLATION INSTRUCTIONS

	The T8775A,C Thermostats provide single-stage	Location
	temperature control for 24V systems. The	Install the thermostat about 5 ft (1.5m) above the
	T8775A,C models include a thermostat, wallplate
		floor in an area with good air circulation at average
	(for wiring and mounting thermostat), mounting
		temperature. Do not install the thermostat where it
	screws, wall anchors, and a 4074 FAB resistor.
		can be affected by:
		— drafts or dead spots behind doors and in
	MERCURY NOTICE	corners.
		— hot or cold air from ducts.
	If this control is replacing a control that	— radiant heat from the sun or appliances.
		— concealed pipes and chimneys.
	contains mercury in a sealed tube, do not
		— unheated (uncooled) areas such as an outside
	place your old control in the trash.
		wall behind the thermostat.
	Contact your local waste management	Mounting Wallplate to Wall
	authority for instructions regarding
	recycling and the proper disposal of an old	Mount the T8775A,C wallplate, with the screws
	control containing mercury in a sealed
		provided. See Fig. 1.
	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.

WALL ANCHORS (2)

WALL PLATE

1

WIRING HOLE
1 INCH SCREW (2)	M19499

1WHEN USING WALL ANCHORS, DRILL 3/16 IN. HOLES FOR DRYWALL, 7/32 IN. HOLES FOR PLASTER.

Fig. 1. Mounting wallplate to wall.

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All Rights Reserved

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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

HEATING 1 RELAY OR VALVE COIL

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

M19513

Fig. 2. Typical hookup of T8775A in a heat-only system.

	O
	B
2	Rc
	G

RY

W

1	HEATING	FAN
	RELAY OR
	VALVE COIL	RELAY

O

B

2 Rc G

RY W

1	HEATING	COMPRESSOR	FAN
	RELAY OR	CONTACTOR	RELAY
	VALVE COIL
	1 POWER SUPPLY. PROVIDE DISCONNECT MEANS
	AND OVERLOAD PROTECTION AS REQUIRED.

2 FACTORY INSTALLED JUMPER.

M19515

Fig. 4. Typical hookup of T8775C in heat-cool system with single transformer.

	Rc	B
		G
	2
		Y
	R
		W

		COMPRESSOR
		CONTACTOR
	HEATING	FAN
1	RELAY OR	RELAY	1
	VALVE COIL

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

2REMOVE FACTORY INSTALLED JUMPER BETWEEN R AND RC.

M19517

Fig. 5. Typical hookup of T8775C in heat-cool system with two transformers.

1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

2 FACTORY INSTALLED JUMPER.

M19514

Fig. 3. Typical hookup of T8775C in heat-only system with fan.

		4
		O
		B
		Rc
	2	G
		Y 3
	R
		W

HEAT COMPRESSOR CHANGEOVER CONTACTOR VALVE

1	FAN	COOL
	RELAY	CHANGEOVER
		VALVE
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.

M19516

Fig. 6. Typical hookup of T8775C in single-stage heat pump system.

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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

M19497

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

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M19567

DIP SWITCH

Fig. 8. DIP switch.

Set Heat Cycle Rate

Use DIP switches 1 and 2 to set the heat cycle rate. See Table 1.

Table 1. Heat Cycle Rate.

	Cycles	DIP	DIP
	Per	Switch	Switch
Heating System	Hour	1	2
Steam, Gravity	1	On	On
High Efficiency Warm Air	3	Off	On
(90%+ efficiency), Hot Water,
Heat Pump
Gas or Oil Warm Air (factory	6	Off	Off
setting)
Electric Warm Air	9	On	Off
In Floor Radiant Heat	Check with manufacturer
	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	DIP Switch 3
Display
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

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.

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T8775A,C THE DIGITAL ROUND™ NON-PROGRAMMABLE THERMOSTATS

		(T8775C ONLY)
(T8775C ONLY)		SELECTS
SELECTS		ON/AUTO
COOL/OFF/HEAT
	ROOM	SHOWS THAT THE
	SET
		CURRENT ROOM
		TEMPERATURE IS
		DISPLAYED.
		SHOWS THAT THE
		CURRENT TEMPERATURE
DISPLAYS ROOM		SETPOINT IS DISPLAYED.
OR SET TEMPERATURE	DISPLAYS AND ADJUSTS
	TEMPERATURE SETPOINT/TURNS
	BACKLIGHT ON		M19520

Fig. 10. T8775 Thermostat (features and operation).

SYSTEM Switch

Heat:	The thermostat controls the heating
Off:	system.
	Both heating and cooling systems are off.
Cool:	The thermostat controls the cooling
	system.

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 compressor 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 thermo-

stat 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.

Automation and Control Solutions

Honeywell International Inc.	Honeywell Limited-Honeywell Limitée
1985 Douglas Drive North	35 Dynamic Drive
Golden Valley, MN 55422	Scarborough, Ontario
	M1V 4Z9

69-1677ES—1 J.S. Rev. 6-04

Printed in Hungary

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