Honeywell THE DIGITAL ROUND CT8775A User manual

OWNER’S GUIDE
® U.S. Registered Trademark • Patents Pending
Copyright © 2004 Honeywell International Inc.
All Rights Reserved 69-1676—1
CT8775A,C
THE DIGITAL ROUND™NON-PROGRAMMABLE THERMOSTATS
CT8775A Heat Only Thermostat (20 to 30 Vac) and
CT8775C Heating-Cooling Thermostat (20 to 30 Vac)
Para obtener un documento con las instrucciones en español, por favor visite
nuestro sitio de web a: www.honeywell.com/yourhome.
Pour obtenir des notices techniques en français, veuillez consulter notre site web
www.honeywell.com/yourhome.
Contents
Step 1. Prepare for Installation .................................................................................................................................. 3
Step 2. Remove Old Thermostat ............................................................................................................................... 4
Step 3. Special Installations........................................................................................................................................ 4
Step 4. Label Thermostat Wires ................................................................................................................................. 5
Step 5. Separate Wallplate from Thermostat.............................................................................................................. 5
Step 6. Mount Decorator Cover Plate and Thermostat Wallplate............................................................................... 5
Step 7. Wire Wallplate Terminals................................................................................................................................ 8
Step 8. Customize the Thermostat ............................................................................................................................. 10
Step 9. Mount the Thermostat .................................................................................................................................... 11
Step 10. Set the System and Fan Switches ............................................................................................................... 12
Step 11. Operating the Thermostat............................................................................................................................. 13
Step 12. Check Operation of Heating and/or Cooling System ................................................................................... 13
If You Have A Problem ............................................................................................................................................... 15
Wiring Diagrams......................................................................................................................................................... 16

69-1676—1 2
Enjoy the benefits of The Digital RoundTM Thermostat by Honeywell.
•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.
This manual answers many of the questions that can arise as you become familiar and
comfortable with your Honeywell thermostat — the state of the art in home comfort
controls.
Read these instructions carefully. Failure to follow these instructions can damage the
product or cause a hazardous condition.
MERCURY NOTICE
If this thermostat 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.
C
O
O
L
E
R
W
A
R
M
E
R
ROOM
SET
M19582
M10614
MERCURY
SWITCH
TYPICAL LOCATION OF A MERCURY
SWITCH IN A THERMOSTAT

3 69-1676—1
STEP 1. PREPARE FOR INSTALLATION
❑Check Table 1, the compatibility chart, to make sure the thermostat is compatible with your system. If your system
is not compatible, call Honeywell Customer Care, toll-free, 1-800-468-1502.
Table 1. Compatibility Chart.
aCompatible with 2-wire Honeywell zone valves. Not compatible with Taco zone valves and 2- or 3-wire White-
Rodgers zone valves (No. 1311 and 1361).
bNot compatible with any 120/240 volt system.
Package Contents
• Thermostat • Decorator cover plate • Screws and wall anchors
• Wiring labels • Owner’s Guide
Tools for Installation
• Screwdriver • Drill • Hammer
• Needle nose pliers • Drill bits (3/16 in. drywall,
7/32 in. plaster)
System Type
Compatibility with
CT8775A
Compatibility with
CT8775C
Gas or Oil Warm Air Yes Yes
Electric Warm Air No Yes
Gas or Oil Hot Water YesaYe sa
Gas or Oil Steam Yes Yes
Gas or Oil Gravity Yes Yes
Gas Millivolt No No
Electric Air Conditioning No Yes
Baseboard Electric (120/240 line volt)bNo No
Single Stage Heat Pump No Yes
Multistage Heat Pumps/Multistage Equipment No No

69-1676—1 4
STEP 2. REMOVE OLD THERMOSTAT
❑Test your heating and cooling systems to make sure they work properly. If either system does not work, contact
your local heating/air-conditioning dealer. To avoid compressor damage, do not operate the cooling system when
outdoor temperature is below 50°F (10°C).
❑Turn off power to the system at the furnace or the fuse/circuit breaker panel.
❑Carefully unpack your new thermostat and decorator cover plate. Save package of screws, instructions, and
receipt.
❑Remove the cover from the old thermostat. If the cover does not snap off when pulled firmly from the top or bottom,
check for a screw or screws that may be used to lock on the cover.
❑Loosen the screw or screws (if present) holding the thermostat to the wallplate and lift the thermostat away. Do not
disconnect wires.
STEP 3. SPECIAL INSTALLATIONS
Read this section if you are replacing:
• A thermostat that has wires connected to C or C1 terminals.
• A thermostat that is connected to six or more wires.
• A thermostat that is connected to three wires on a warm air heating only system.
• A thermostat that is connected to three wires on a zoned hot water heating system.
NOTE: If none of the special installations apply to your particular application, please skip to Step 4.
Replacing a thermostat that has wires connected to C or C1 terminals
If you are replacing a thermostat that has one or two wires connected to C or C1 terminals, do not allow them to touch,
or you can damage the transformer. Wrap the wires separately using electrical tape. Place the wires where they will
not interfere with the operation of the new thermostat. Continue with the installation at Step 4.
Replacing a thermostat that is connected to six or more wires
If you are replacing a thermostat that is connected to six or more wires (excluding wires connected to C or C1
terminals), you may have a multistage heat pump or other multistage system. If you have either one of these systems,
return the product to the place of purchase. This thermostat is not compatible with these systems. For information
about which thermostats will work with your system, call Honeywell Customer Care, at 1-800-468-1502.

5 69-1676—1
Replacing a thermostat that is connected to three wires on a warm air heating only system
If you are replacing a thermostat that is connected to three wires on a warm air heating only system and could turn the
fan on by setting the thermostat fan switch to ON, the CT8775C Thermostat will work with your system. Continue with
the installation at Step 4. If you purchased a CT8775A thermostat, return the product to the place of purchase. The
CT8775A thermostat is not compatible with this application.
Replacing a thermostat that is connected to three wires on a zoned hot water heating system
If you are replacing a thermostat that is connected to three wires on a zoned hot water heating system, the
CT8775A,C thermostats will only work if an isolation relay is installed. For details, call your local heating and/or cooling
contractor.
STEP 4. LABEL THERMOSTAT WIRES
❑Disconnect the wires from the old thermostat. As you disconnect each wire, attach
the enclosed labels with the old terminal designation. Wrap the wires around a
pencil as shown to keep them from falling back into the wall.
STEP 5. SEPARATE WALLPLATE FROM
THERMOSTAT
❑Remove cover from thermostat. Separate the wallplate from the
thermostat by placing your thumb on the top between the
wallplate and the thermostat and pulling the thermostat away from
the wallplate. See the illustration at the right.
STEP 6. MOUNT DECORATOR COVER PLATE
AND THERMOSTAT WALLPLATE
❑The decorator cover plate and wallplate can be mounted directly
on the wall or onto an electrical box.
❑To mount directly to the wall, see Fig. 1.
❑To mount onto an electrical box, see Fig. 2.
WIRES THROUGH
WALL OPENING
M5136
WALL PLATE
THERMOSTAT
COVER REMOVED
M19492

69-1676—1 6
Mount Decorator Cover Plate (Optional) and Wallplate Directly to Wall
❑If using the decorator cover plate, pull the wires through
the wiring hole on the decorator cover plate. Position the
decorator cover plate against the wall so that the UP
indicator in the middle of the decorator cover plate is
pointing up.
❑Position the wallplate:
❑If using the decorator cover plate, pull the wires
through the wiring hole on the wallplate and place
the wallplate over the decorator cover plate. Turn
the wallplate until the wiring holes are aligned and
the two screw holes on the left and right side of the
wallplate line up with the screw holes on the
decorator cover plate. You will be inserting the
screws through these holes into the wall.
❑If attaching the wallplate directly to the wall, pull the
wires through the wiring hole on the wallplate and
position it so that the UP indicator on the wallplate is
pointing up.
❑Use a pencil to mark the center of the screw holes on the
left and right sides of the wallplate.
❑Remove the wallplate and decorator cover plate (if used)
and drill two 3/16 in. holes in the wall (if drywall) at the
locations you marked. For materials such as plaster, drill
7/32 in. holes where marked. Gently tap the provided
anchors into the drilled holes until they are flush with the
wall.
❑Pull the wires through the wiring holes and reposition the
decorator cover plate (if used) and wallplate over the
screw holes.
❑Attach the decorator cover plate (if used) and wallplate to
the wall with two 1-in. screws.
Fig. 1. Mount decorator cover plate (optional) and
wallplate directly to wall (heating-cooling wallplate
shown).
M19493
WALL ANCHORS (2)
WIRING HOLES
DECORATOR COVER PLATE
WALL PLATE
1 INCH
SCREW (2)

7 69-1676—1
.
Mount Decorator Cover Plate (Required) and Wallplate onto Electrical Box
❑Pull the wires through the wiring hole on the
decorator cover plate.
❑Place the decorator cover plate against the electrical
box so that the UP indicator in the middle of the
decorator cover plate is pointing up.
❑Line up the screw slots on the decorator cover plate
with the electrical box screw holes, and attach the
decorator cover plate to the electrical box with two
1/2 in. screws.
❑Pull the wires through the wiring hole on the
wallplate.
❑Place the wallplate over the decorator cover plate.
Turn the wallplate until the wiring holes are aligned
and the two screw holes on the left and right side of
the wallplate line up with the screw holes on the
decorator cover plate.
❑Attach the wallplate to the decorator cover plate with
the two 3/8 in. screws.
Fig. 2. Mount decorator cover plate (required) and
wallplate onto electrical box (heating-cooling wallplate
shown).
1
TROUS DE CÂBLAGE
PLAQUE D'ADAPTATION DÉCORATIVE
PLAQUE DE
COMMUTATION
VIS 1/2 PO (2)
VIS 3/8
PO (2)
BOÎTE ÉLECTRIQUE
MF19494
1 SI LA BOÎTE ÉLECTRIQUE EST
HORIZONTALE, MONTER LA PLAQUE
D'ADAPTATION DÉCORATIVE DANS
LA POSITION ILLUSTRÉE, MAIS
INSÉRER LES VIS DANS LE TROU DE
MONTAGE «A».
A

69-1676—1 8
STEP 7. WIRE WALLPLATE TERMINALS
IMPORTANT
All wiring must comply with local codes and ordinances. If
unsure about household wiring procedures, call your local
heating/air conditioning contractor.
❑Refer to the labels you placed on the wires when you removed the
old thermostat (see illustration).
❑Match the letter of your old thermostat wire with the corresponding
terminal letter on your new thermostat. Refer to Table 2.
IMPORTANT
Remove the factory-installed jumper connecting terminals R
and Rc on the CT8775C Thermostat if wires will be con-
nected to both of these terminals.
❑For wiring diagrams, see pp 16-17.
❑Loosen the terminal screws. Slip each wire beneath its matching
terminal. Wraparound and straight connections are both acceptable,
(see illustration). Tighten the terminals.
❑Plug the hole in the wall with insulation to help prevent drafts from
adversely affecting thermostat operation.
M19495
FACTORY
INSTALLED JUMPER
Y
G
R
W
M19496
FOR WRAPAROUND
INSERTION STRIP
7/16 IN. (11 MM).
FOR STRAIGHT INSERTION
STRIP 5/16 IN. (8 MM).

9 69-1676—1
Table 2. Terminal Designations on Old and New Thermostats.
NOTES:
1. If wires were connected to both Rh and R terminals on the old thermostat, remove jumper between R and Rc on
the new thermostat and connect Rh to R and R to Rc.
2. If wires will be connected to both R and Rc on the new thermostat, remove jumper between R and Rc.
3. Do not connect both O and B when wiring to a single stage heat pump. Connect O to O. Tape off B with electri-
cal tape and do not use.
4. Tape off wire with electrical tape and do not use.
Terminal on
Old
Thermostat
Connect to Terminals
on CT8775A
Connect To Terminals
on CT8775C Description
R
Rh (see Note 1)
4
V
RR
(see Note 2) Power
Rc
R (see Note 1)
—Rc
(see Note 2) Power for cooling
W, W1, H W W Heat
Y, Y 1, M — Y Cooling
G, F — G Fa n
O — O Changeover in cool. (Single stage heat pump
only).
B (see Note 3) —B(see Note 3) Changeover in heat. (Single stage heat pump
only).
C (see Note 4)
X (see Note 4)
B (see Note 3)
Do not connect. Do not connect. Transformer common
W2, H2Do not continue
installation. Call 1-800-
468-1502.
Do not continue
installation. Call 1-800-
468-1502.
Second stage heat.
Y2Second stage cool.

69-1676—1 10
STEP 8. CUSTOMIZE THE THERMOSTAT
Set Fuel Switch (CT8775C Only)
❑To adjust the fuel switch, locate the switch labeled E/F on the wallplate
(see Fig. 3). The fuel switch is factory set in the F position. This is the
correct setting for gas or oil systems. If you have an electric heat
system, or a heat pump, set the switch to E. The E setting allows the
fan to turn on immediately with the heating system where the G
terminal is connected.
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. 4.
Set Heat Cycle Rate
❑Use DIP switches 1 and 2 to set the heat cycle rate. See Table 3.
NOTE: The CT8775A,C Thermostats will provide optimal temperature
control if DIP switches 1 and 2 are set according to your partic-
ular heating system.
Fig. 3. Fuel switch.
Fig. 4. DIP switch.
M19497
FUEL SWITCH
ON
1 2 3
M19567
BACK OF THERMOSTAT
DIP SWITCH