T8775A,C The Digital Round

™

Non-Programmable Thermostats

APPLICATION

The T8775A and T8775C Thermostats provide single-stage, non-programmable temperature control for 24 Vac systems with manual changeover from heat to cool.

The T8775A controls 2-wire heating-only systems.

The T8775C controls gas, oil or electric heating and cooling systems.

PRODUCT DATA

FEATURES

• Attractive styling complements any decor.

• Simple to use. Turn the dial to adjust the setpoint temperature.

• Large easy-to-read display. The temperature reading is easily seen from a distance.

• Backlit display. On-demand backlighting makes it easy to read the display in a dark room or hallway.

• No batteries required. The setpoint temperature is held permanently in memory in the event of a power failure.

• Powered through heating-cooling system controls.

• System and Fan switches on the T8775C model.

• Manual changeover from heat to cool on T8775C model.

• Easy installation and set up saves time and increases installer productivity.

• Easily configurable by the use of DIP switches.

• Fahrenheit or Celsius temperature display for added flexibility.

• Selectable heating cycle rates (1, 3, 6, 9 CPH) for a variety of applications.

• Cooling cycle rate is fixed at 3 CPH. This is the standard compressor setting.

• Minimum off-time for the compressor in the cooling mode. Protects and extends the life of the equipment.

• Decorative cover plate is available to cover marks on the wall or to mount the T8775 Thermostat to an electrical box.

Contents

Application.........................................................................1

Features ............................................................................1

Specifications ....................................................................2

Ordering Information .........................................................2

Installation .........................................................................3

Wiring ................................................................................4

Customize Thermostat ......................................................5

Set System and Fan Switches ..........................................6

Checkout ...........................................................................7

Troubleshooting Guide ......................................................8

® U.S. Registered Trademark • Patents Pending

Copyright © 2004 Honeywell International Inc.

All Rights Reserved 68-0279

T8775A,C THE DIGITAL ROUND

™

NON-PROGRAMMABLE THERMOSTATS

SPECIFICATIONS

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.

Models: T8775A and T8775C TRADELINE® models include a thermostat, wallplate for mounting and wiring, mounting hardware, 4074FAB resistor, installation instructions and an owner’s guide.

Electrical Ratings:

24 Vac nominal: 18 Vac to 30 Vac, 60Hz.

Heating: .02 to 1.5 A run; 3.5A inrush.

Cooling: .02 to 1.5 A run; 6.0 A inrush.

Fan: .02 to 0.5 A run; 2.5A inrush.

Temperature Ratings:

Setting Range:

40°F to 90°F (4.5°C to 32.0°C) in heating.

45°F to 99°F (7.0°C to 37.0°C) in cooling.

Ambient Range:

40°F to 110°F (4.4°C to 43.3°C).

Shipping Temperature Range:

-20°F to 120°F (-28.9°C to 48.9°C).

Humidity Ratings: 5% to 90% RH, non-condensing.

Mounting Hardware:

Sheet metal screws: Two 1-in. (25 mm) 4-24, type AB.

Drywall anchors: Two conical anchors, 3/16 in. (5 mm) diameter by ¾ in. (19 mm) length.

4074 FAB Resistor:

1 Kohm, 3 Watts.

Installation Instructions packed with resistor.

Batteries: Not required.

Finish: Premier White®.

Accessories:

50000066-001 Decorative Cover Plate. Used to cover wall marks, or to mount T8775 Thermostat to an electrical box.

32007680-001 Cover Ring.

Dimensions: See Fig. 1.

1-7/16

(37)

2-5/8 (67)

3-11/16

(94)

ROOM

SET

M19676

Fig. 1. T8775 Thermostat dimensions in in. (mm).

ORDERING INFORMATION

When purchasing replacement and modernization products from your TRADELINE® wholesaler or distributor, refer to the

TRADELINE® Catalog or price sheets for complete ordering number.

If you have additional questions, need further information, or would like to comment on our products or services, please write or phone:

1.

Your local Honeywell Automation and Control Products Sales Office (check white pages of your phone directory).

2.

Honeywell Customer Care

1885 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.

68-0279 2

T8775A,C THE DIGITAL ROUND

™

NON-PROGRAMMABLE THERMOSTATS

INSTALLATION

NO

YES

ROOM

SET

NO

5 FEET

[1.5 METERS]

NO

M19716A

Fig. 2. Typical thermostat location.

Separate Wallplate from Thermostat

1.

Place your thumbs on top of the thermostat and wallplate. Use your thumbs to pull the thermostat away from the wallplate. See Fig. 3.

Mount wallplate to wall (See Fig. 4) as follows:

TOP OF

THERMOSTAT

WALL PLATE

WALL ANCHORS (2)

WALL PLATE

1

M19679

Fig. 3. Separate wallplate from thermostat.

Mount Wallplate to Wall

NOTE: Level wallplate for appearance only. The thermostat functions normally even when not mounted level.

3

WIRING HOLE

1 INCH SCREW (2) M19499

1 WHEN USING WALL ANCHORS, DRILL 3/16 IN. HOLES

FOR DRYWALL, 7/32 IN. HOLES FOR PLASTER.

Fig. 4. Mount wallplate to wall.

1.

Pull the thermostat wires through the wiring hole on the wallplate.

2.

Use a pencil to mark the center of the screw holes on the left and right sides of the wallplate.

3.

Remove the wallplate from the wall and drill two 3/16 in.

(5 mm) holes in the wall (if drywall) at the locations you marked. For materials such as plaster, drill 7/32 in.

(6 mm) holes where marked.

68-0279

T8775A,C THE DIGITAL ROUND

™

NON-PROGRAMMABLE THERMOSTATS

4.

Tap the provided wall anchors into the drilled holes until they are flush with the wall.

5.

Pull the thermostat wires through the wiring hole on the wallplate and reposition the wallplate over the wall anchors.

6.

Attach the wallplate to the wall with the screws provided.

7.

After wiring the wallplate, plug the hole to prevent drafts from affecting the thermostat; see Wiring section.

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.

NOTE: To ensure proper mounting of thermostat, restrict all wiring to the shaded area. See Fig. 5.

Refer to Fig. 7 through 11 for typical wiring diagrams.

1

R

W

HEATING

RELAY OR

VALVE COIL

1

POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

M19513

Fig. 7. Typical hookup of T8775A in a heat-only system.

MOUNTING

HOLES 2 Rc

O

R

B

G

Y

W

1

HEATING

RELAY OR

VALVE COIL

FAN

RELAY

WIRING

HOLE

RESTRICT WIRING

TO SHADED AREA

M19680

Fig. 5. Restrict T8775 wiring to shaded area.

The shape of the terminals permits insertion of straight or wraparound wiring connections; either method is acceptable.

See Fig. 6.

1 POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

2 FACTORY INSTALLED JUMPER.

M19514

Fig. 8. Typical hookup of T8775C in heat-only system with fan.

2

Rc

O

R

B

G

Y

W

FOR STRAIGHT INSERTION

STRIP 5/16 IN. (8 MM).

FOR WRAPAROUND

INSERTION STRIP

7/16 IN. (11 MM).

M19496

Fig. 6. T8775 wiring connections.

1

HEATING

RELAY OR

VALVE COIL

COMPRESSOR

CONTACTOR

FAN

RELAY

1 POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

2 FACTORY INSTALLED JUMPER.

M19515

Fig. 9. Typical hookup of T8775C in heat-cool system with single transformer.

68-0279 4

T8775A,C THE DIGITAL ROUND

™

NON-PROGRAMMABLE THERMOSTATS

2

Rc

R

B

G

Y

W

1

HEATING

RELAY OR

VALVE COIL

COMPRESSOR

CONTACTOR

FAN

RELAY

1

1 POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

2 REMOVE FACTORY INSTALLED JUMPER BETWEEN R AND RC.

M19517

Fig. 10. Typical hookup of T8775C in heat-cool system with two transformers.

M19497 FUEL SWITCH

Fig. 12. Fuel switch.

DIP Switch

To adjust the heat cycle rate or the Fahrenheit/Celsius temperature display, locate DIP switch 1, 2 and 3 on the back of the thermostat. See Fig. 13.

BACK OF THERMOSTAT

2

R

Rc

O

4

B

G

Y

W

3

1

COMPRESSOR

CONTACTOR

FAN

RELAY

HEAT

CHANGEOVER

VALVE

COOL

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

CUSTOMIZE THERMOSTAT

Setting Fuel Switch (T8775C only)

The fuel switch is preset at the factory in the F position. See

Fig. 12. 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 position allows the fan to turn on immediately with the heating equipment in a system where the G terminal is connected.

M19567

DIP SWITCH

Fig. 13. 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.

Heating System

Steam, Gravity

High Efficiency Warm Air (90%+ efficiency), Hot Water, Heat Pump

Gas or Oil Warm Air (factory setting)

Electric Warm Air

In Floor Radiant Heat

Cycles

Per

Hour

DIP

Switch

1

DIP

Switch

2

1 On On

3 Off On

6

9

Off

On

Off

Off

Check with manufacturer for recommended cycle rate.

5 68-0279

T8775A,C THE DIGITAL ROUND

™

NON-PROGRAMMABLE THERMOSTATS

Fahrenheit/Celsius Indication

Use DIP switch 3 to set the desired temperature indication. See

Table 2.

Table 2. Temperature Indication.

Fahrenheit/Celsius Display

Fahrenheit (factory setting)

Celsius

Off

On

DIP Switch 3

Mount Thermostat to Wallplate (see Fig. 14)

ENGAGE TABS

AT BOTTOM OF

THERMOSTAT

AND WALL PLATE.

PRESS UPPER

EDGE OF CASE

TO LATCH

(T8775C ONLY)

SELECTS

COOL/OFF/HEAT

ROOM

SET

(T8775C ONLY)

SELECTS

ON/AUTO

SHOWS THAT THE

CURRENT ROOM

TEMPERATURE IS

DISPLAYED.

DISPLAYS ROOM

OR SET TEMPERATURE

SHOWS THAT THE

CURRENT TEMPERATURE

SETPOINT IS DISPLAYED.

DISPLAYS AND ADJUSTS

TEMPERATURE SETPOINT/TURNS

BACKLIGHT ON

M19681

Fig. 15. T8775 Thermostat (features and operation).

CO

OL

ER

WARM

ER

ROOM

SET M19498

Fig. 14. Mount thermostat to wallplate.

SET SYSTEM AND FAN SWITCHES

(T8775C ONLY)

SYSTEM Switch: (See Fig.15)

Heat: The thermostat controls the heating system.

Off: Both the heating and cooling systems are off.

Cool: The thermostat controls the cooling system.

FAN Switch: (See Fig.15)

Auto: The fan only runs with the heating and cooling system.

On: The fan runs continuously. Use for improved air circulation.

FEATURES AND OPERATION

Features and operation of The Digital Round TM Thermostat (see

Fig. 15 and 16):

• Simple to use.

Turn the dial to adjust the temperature setting.

• Large easy-to-read display.

The temperature reading is easily seen from a distance.

• Backlit display. On-demand backlighting makes it easy to read the display in a dark room or hallway.

• No batteries required.

The temperature setting is held permanently in memory in the event of a power failure.

Fig. 16. T8775 Thermostat.

M19582

Backlit Display

Push the backlight button to turn on the backlight (See Fig.

15).

Display Temperature Setpoint

1.

Turn the dial one click to display the temperature setpoint. An indicator points to Set when the temperature setpoint is displayed (see Fig.17).

ROOM

SET

M19489

Fig. 17. Temperature setpoint display.

2.

If a change to the temperature setpoint is not made within five seconds, the display will switch to the current room temperature. An indicator points to Room when the room temperature is displayed (see Fig. 18).

68-0279 6

T8775A,C THE DIGITAL ROUND

™

NON-PROGRAMMABLE THERMOSTATS

ROOM

SET

M19490

Table 3. T8775 Power Stealing.

System Switch

Power Stealing Circuit

T8775A

Heat R and W

T8775C

R and W

Off

Cool

—

—

R and W

Rc and Y

Fig. 18. Room temperature display.

Adjust Temperature Setpoint

Turn the dial clockwise to raise the temperature setpoint. Turn the dial counterclockwise to lower the temperature setpoint

(see Fig. 16).

The T8775 Thermostat only operates when mounted on the wallplate with 24 Vac applied. Batteries are not required for operation because the temperature setpoint is permanently retained in memory.

Power Stealing

The T8775 thermostat steals power from R and W or Rc and

Y depending on the system switch position. See Table 3.

Sequence of Operations

See Table 4 for Sequence of Operations.

Auto

On

On

On

Fan Switch Settings

Auto

Auto

Table 4. Sequence of Operations.

System Switch Settings

Off

Heat

Call for Action

None

Heating

Cool Cooling

Energize Terminals

None

W a

Y,G

Display Icons

None

Flame

Snowflake

None Off

Heat

Fan

Heating

Cool Cooling

G

W,G

Y,G

Flame

Snowflake a

If fuel switch is set to E, both W and G are energized in a call for heat.

CHECKOUT

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.

Minimum Off-Timer

The minimum off-timer in the T8775C Thermostat assures that the cooling compressor does not turn on for at least five minutes after it turns off. The snowflake will flash in the display if there is a call for cooling during the 5-minute off-time.

The following activates the 5-minute minimum-off timer:

• Initial startup

• Power interruption

• Compressor turns off:

— Setpoint is raised above the room temperature

— System switch is changed from the cool mode

— Thermostat ends the call for cooling

NOTE: The 5-minute minimum-off timer does not apply to heating.

7

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.

A snowflake will appear in the display and the cooling should turn on.

4.

Raise the temperature setpoint several degrees above the room temperature.

5.

The snowflake will disappear from the display and the cooling should turn off.

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.

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.

NOTE: Make sure that all equipment responds properly to the thermostat.

68-0279

T8775A,C THE DIGITAL ROUND

™

NON-PROGRAMMABLE THERMOSTATS

TROUBLESHOOTING GUIDE

HEATING OR COOLING EQUIPMENT

WILL NOT OPERATE.

PARTIAL DISPLAY

NO AC POWER TO THERMOSTAT.

THERMOSTAT INOPERATIVE.

PRESENT SETTING TOO LOW/HIGH.

SYSTEM SWITCH ON THERMOSTAT

IN WRONG POSITION.

MINIMUM-OFF TIME IN COOLING.

INCORRECT WIRING.

HEATING OR COOLING EQUIPMENT

INOPERATIVE.

INOPERATIVE THERMOSTAT.

• CHECK POWER TO HEATING AND COOLING EQUIPMENT

– FUSE OR CIRCUIT BREAKER

– LOOSE 24V CONNECTION:

– AT FURNACE/AIR CONDITIONER

– INCORRECT WIRING (SEE WIRING DIAGRAMS)

SEE CHECKOUT SECTION.

ADJUST TEMPERATURE BY TURNING DIAL CLOCKWISE OR

COUNTER-CLOCKWISE.

RESET THERMOSTAT SYSTEM SWITCH.

WAIT UP TO FIVE MINUTES FOR THE COOLING EQUIPMENT

TO TURN ON.

CHECK WIRING DIAGRAMS.

CONSULT EQUIPMENT MANUFACTURER INSTRUCTIONS.

REPLACE THERMOSTAT.

NO DISPLAY NO POWER TO THERMOSTAT.

TEMPERATURE DISPLAY IS

INCORRECT.

TEMPERATURE SETTINGS WILL NOT

CHANGE. (EX: CANNOT SET THE

HEATING HIGHER OR THE

COOLING LOWER).

FAN DOES NOT OPERATE PROPERLY

IN HEAT OR COOL MODES.

THERMOSTAT MOUNTED

INCORRECTLY ON WALLPLATE.

THERMOSTAT IS CONFIGURED FOR

F OR C DISPLAY.

THE UPPER OR LOWER

TEMPERATURE LIMITS WERE

REACHED.

INCORRECT WIRING.

CHECK FUEL SWITCH POSITION.

HEATING OR COOLING EQUIPMENT

INOPERATIVE.

• CHECK POWER TO HEATING AND COOLING EQUIPMENT

– FUSE OR CIRCUIT BREAKER

– LOOSE 24V CONNECTION:

– AT FURNACE/AIR CONDITIONER

– INCORRECT WIRING (SEE WIRING DIAGRAM)

SEE MOUNT THERMOSTAT TO WALLPLATE SECTION.

RECONFIGURE THE DISPLAY. SEE CUSTOMIZE

THERMOSTAT SECTION.

CHECK THE TEMPERATURE SETPOINTS; TEMPERATURE

SETTING RANGE IS 40 F TO 90 F (4.5 C TO 32 C) IN HEATING

AND 45 F TO 99 F (7 C TO 37 C) IN COOLING.

CHECK WIRING DIAGRAMS.

SEE CUSTOMIZE THERMOSTAT SECTION.

CONSULT EQUIPMENT MANUFACTURER INSTRUCTIONS.

M19684

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

68-0279 J.S. 4-04

Printed in U.S.A. on recycled paper containing at least 10% post-consumer paper fibers.

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