1
CT87A,B,J Round® Thermostat
LOW VOLTAGE (15 TO 30 VAC),
THERMOSTAT AND MOUNTING HARDWARE
Installation Instructions
Verify that you have the correct thermostat
Using the compatibility chart
below, verify that you purchased
the correct CT87Thermostat for
your heating/cooling system. If
you are unsure which model is
right for your system, visit
www.honeywell.com/
yourhome or call Honeywell
Customer Care at
1-800-468-1502.
Compatible with:
Heating/Cooling system
Heating only: Gas or oil fueled warm air, steam, or hot
water heat
Cooling only: Electric air conditioning Yes* Yes Yes
Heating and cooling: Gas or oil fueled warm air,
steam, or hot water heat with electric air conditioning
Single stage heat pump: Outdoor heating/cooling unit
(compressor) with no auxiliary or backup heat.
Electric heat furnace with or without cooling: No No
Electric baseboard: Electric heating strips located just
above the floor, usually 120-240 volts
Multistage: A conventional system with more than one
stage, or an outdoor heating/cooling unit (compressor)
with auxiliary or backup heat.
CT87A CT87B CT87J
Yes Yes No
No
No No Yes
No No No
No No No
Yes No
Yes
* CT87A is compatible with 2-wire cooling-only systems.
® U.S. Registered Trademark
Copyright © 2002 Honeywell
All Rights Reserved
69-0274-6
CT87A,B,J ROUND® THERMOSTAT
2
3
Prepare for installation
1. Carefully unpack your new thermostat; rough handling may affect its
accuracy. Save your receipt and identify the following parts:
• CT87 Thermostat
• Screws: two 1-in. sheet metal screws, two 1/2-in. binding head
screws, and two 1/4-in. round head screws
• Wallplate (CT87A) or subbase (CT87B, CT87J)
• Cover ring (select models only). Necessary if installing on an
outlet box. Optional if installing directly on the wall; can be used to
hide wall marks.
• These Installation Instructions and the Installation Quick Guide.
• Wiring labels
2. Gather these tools:
Required Tools Optional Tools
• Flat blade
screwdriver
• Spirit level
• Hand or power drill with 1/16-in. drill bit
• Wire cutter/stripper or sharp knife
• Pencil
Remove the old thermostat
1. Turn off power to the heating/cooling system at the main fuse/circuit
breaker panel.
2. Remove the cover of your old thermostat. You may need to unscrew
the cover if it is locked on.
3. Locate the heat anticipator adjustment scale and lever on the old
thermostat (Fig. 1).
Fig. 1. Mercury switch location.
MERCURY
SWITCH
OLD THERMOSTAT
ANTICIPATOR
SCALE
LEVER
TYPICAL LOCATION OF A
MERCURY SWITCH IN
A THERMOSTAT
In the box below, record the
number that the adjustment lever
points to. This is the current (amp)
rating of your heating system.
Current setting:
If you cannot find the heat
anticipator setting on the old
thermostat, you can use a
standard setting for your type of
system when you reach Step 8 of
M20206
this installation.
4. Unscrew and remove the old thermostat wallplate from the wall, but
do not disconnect the wires.
69-0274-6 2
CT87A,B,J ROUND® THERMOSTAT
H
4
5. Label the wires using the wiring
labels that came with the CT87.
Fig. 2. Labeling wires.
Identify each wire using the letter
of the terminal on the old thermo-
stat (Fig. 2). Do not label the wires
by color.
6. Disconnect the wires from the old
thermostat and wrap them around
a pencil to keep them from
falling
back into the wall (Fig. 3).
Fig. 3. Wrapping wires.
WIRES THROUG
MERCURY NOTICE
WALL OPENING
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 this
control, or of an old control containing mercury in a sealed tube.
Install the cover ring and wallplate or subbase
If installing on the wall
Refer to Fig. 4 as you work.
M19086
M20133
Fig. 4. Installing wallplate/subbase on the wall (wallplate shown).
COVER RING
WALLPLATE
THERMOSTAT
NO. 4 X 1 INCH
SHEET METAL SCREWS (2)
3 69-0274-6
WIRING OPENING
M20188
CT87A,B,J ROUND® THERMOSTAT
7
1
R
H
S
1. If using the cover ring: Position the cover ring against the wall so
that the arrow in the middle of the cover ring is pointing up.
2. Position the wallplate or subbase.
• If using cover ring: Place the wallplate/subbase over the cover
ring. Rotate the wallplate/subbase until the wiring openings are
aligned and the two screw holes on the left and right side of the
wallplate/subbase align with the screw holes on the cover ring.
You will be inserting screws through these holes into the wall.
• If attaching wallplate directly to the wall: Position so that the
UP indicator on the wallplate is on top.
• If attaching subbase directly to the wall: Position so that the
fan and heating/cooling switches are on the top.
3. Use a pencil to mark the center of the screw holes on the left and
right sides of the wallplate or subbase.
4. Remove the wallplate/subbase and cover ring, and drill two 1/16-in.
holes at the locations you marked.
5. Reposition the cover ring (if used) and wallplate/subbase over the
holes, pull the wires through the wiring opening, and loosely insert
the two 1-in. screws into the drilled holes.
If installing on an outlet box
Refer to Fig. 5 as you work.
Fig. 5. Installing wallplate/subbase on an outlet box (subbase shown).
69-0274-6 4
1/2 IN. BINDING
HEAD SCREW (2)
1
2
COVER RING
SUBBASE
/4 IN.
OUND
EAD
CREW (2)
1
THE TWO INNER HOLES ARE USED WITH WALLPLATE.
2
IF OUTLET BOX IS HORIZONTAL, MOUNT COVER RING IN
POSITION SHOWN, BUT FASTEN WITH SCREWS THROUGH "A".
OUTLET BOX
THERMOSTAT
WIRING HOLE
A
M2018
CT87A,B,J ROUND® THERMOSTAT
5
G
)
O
T
W
1. Place the cover ring against the outlet box so that the arrow in the
middle of the cover ring is pointing up.
2. Pull the wires through the wiring hole on the bottom left side of the
cover ring.
3. Align the screw slots on the cover ring with the outlet box screw
holes, and attach the cover ring to the outlet box with two 1/2-in.
screws.
4. Place the wallplate or subbase over the cover ring so that the wiring
holes line up, and pull the wires through.
5. Loosely attach the wallplate/subbase to the cover ring with two 1/4-
in. screws, through the screw holes on the left and right sides of the
wallplate/subbase.
Level the wallplate or subbase
IMPORTANT: The wallplate/subbase must be level to maintain accurate thermostat temperature.
1. Rotate the wallplate/subbase until level as shown in Fig. 6.
To level the subbase, use the leveling posts directly below the Heat
and Fan indicators.
Fig. 6. Leveling the wallplate.
SPIRIT
LEVEL
2. Tighten the mounting screws after making sure that the wallplate or
subbase is level.
PENING FOR
HERMOSTAT
IRING
5 69-0274-6
LEVELIN
POSTS (2
MOUNTING
SLOTS
M3319A
CT87A,B,J ROUND® THERMOSTAT
F
C
S
]
6
Wire the thermostat
1. Use the wiring cross-reference table below to match each old
thermostat wire with its corresponding terminal on the CT87 wallplate
or subbase. See Fig. 8 through 13 wiring diagrams.
Wiring Cross-reference
Connect to
Wire Label
CT87A
R, RH, 4, V R RH R
Rc, R
W, W1, H W W W
, M Y Y Y
Y, Y
1
G, F
B See Fig. 9
O
See Fig. 13
*Never attach wires to both the B and O terminals.
2. Strip the wire insulation as needed to fit the wires underneath the ter-
minal screws (Fig. 7).
Fig. 7. Fitting wires under the terminal screws.
OR STRAIGHT
ONNECTION—
TRIP 5/16 in. [8 mm]
Connect to
CT87B
Connect to
CT87J
Rc
GG
B*
O*
P
FOR WRAPAROUND
CONNECTION—
STRIP 7/16 in. [11 mm
3. Loosen the terminal screws and slip each wire beneath its matching
terminal.
4. Securely tighten the terminal screws.
5. Push any excess wire back into the wall.
69-0274-6 6
BARRIER
M1279
CT87A,B,J ROUND® THERMOSTAT
3
4
5
M
Fig. 8. CT87A for a 2-wire heating only system.
CT87A WALLPLATE
POWER
R
Y
W
HEAT
Fig. 9. CT87A for a 3-wire hot water heating only system.
CT87A WALLPLATE
R
Y
W
R
W
B
WIRE LABELS
(LETTERS
ON ORIGINAL
THERMOSTAT
TERMINALS)
Fig. 10. CT87B for a 4-wire heating/cooling system.
TO
SYSTEM
M2018
3-WIRE
HOT WATER
ZONE VALVE
M2018
JUMPER R
O
•
L
O
O
C
R
CT87B SUBBASE
F
T
A
E
H
•
F
F
RH G
C
W
A
N
O
N
•
A
U
T
O
POWER
FAN
COOL
Y
HEAT
H TO RC
7 69-0274-6
TO
SYSTE
M2018
CT87A,B,J ROUND® THERMOSTAT
5
M
6
M
8
M
Fig. 11. CT87B for a 5-wire heating/cooling system.
T
A
E
H
•
F
F
O
•
L
O
O
C
H G
R
C
R
W
Fig. 12. CT87J for a 4-wire single stage heat pump.
T
A
E
H
•
F
F
O
•
L
O
O
C
WG
Y
P
B
JUMPER W TO Y
CT87B SUBBASE
F
A
N
O
N
•
A
U
T
O
Y
HEATING
POWER
FAN
COOLING
POWER
COOL
TO
SYSTEM
TO
SYSTE
HEAT
M2022
CT87J SUBBASE
F
A
N
O
N
•
A
U
T
O
R
O
HEAT
FAN
SYSTE
POWER
COOL
REVERSING VALVE
HEAT
REVERSING VALVE
DO NOT ATTACH WIRES
TO BOTH B AND O
TO
M2018
Fig. 13. CT87J for 4-wire single stage heat pump.
T
A
E
H
•
F
F
O
•
L
O
O
C
WG
Y
1
P
R
B
1
IF WIRES ARE ATTACHED TO Y OR W, AND P ON YOUR OLD
THERMOSTAT, CONTACT YOUR LOCAL CONTRACTOR FOR
FURTHER ASSISTANCE.
69-0274-6 8
CT87J SUBBASE
F
A
N
O
N
•
A
U
T
O
O
FAN
POWER
HEAT
REVERSING
VALVE
COOL
REVERSING
VALVE
HEAT PUMP
COMPRESSOR
DO NOT ATTACH WIRES
TO BOTH B AND O
TO
SYSTE
M2022
CT87A,B,J ROUND® THERMOSTAT
7
7
Mount the thermostat
1. Pull off the thermostat cover and discard the red plastic insert that
holds the mercury switch in place during shipping.
2. Using a pencil point, slide the heat anticipator indicator to 1.2 on the
scale as shown in Fig. 14.
IMPORTANT: This prevents the thermostat from being damaged.
Fig. 14. Adjusting heat anticipator indicator.
HEAT ANTICIPATOR INDICATOR
1.2
.6
.5
.4
.3
.2
HOLE SUITABLE FOR
PENCIL POINT
TO MOVE INDICATOR
SCALE
.15
.12
.10
M20226
3. Place the thermostat over the wallplate or subbase so that the three
captive mounting screws align with the three raised screw holes on
the wallplate/subbase.
4. Tighten the three captive mounting screws as shown in Fig. 15.
NOTE: These screws complete the installation of the
thermostat.
Fig. 15. Tightening mounting screws.
CAPTIVE SCREWS (3)
9 69-0274-6
M2022
CT87A,B,J ROUND® THERMOSTAT
T
8
9
Set the heat anticipator for your system
IMPORTANT: Setting the heat anticipator allows the thermostat to
maintain accurate temperature control.
1. Using a pencil point, move the heat anticipator pointer to the number
that you recorded in Step 3, sub-step 3. If you could not find the
anticipator setting on the old thermostat, use the setting for your type
of system shown in the table below.
Your heating system: Heat anticipator setting:
Steam 1.2
Hot water heat 0.8
High-efficiency warm air 0.8
Standard warm air 0.4
Electric heat 0.3
2. Snap on the thermostat cover.
NOTE: If the furnace stays on beyond the thermostat set temperature,
move the anticipator pointer down by .1 ampere.
If the furnace shuts off before the set temperature is reached, move the
anticipator pointer up by .1 ampere.
Never adjust the anticipator below .3 ampere.
Check heating/cooling operation
Check heating
1. Turn the transparent dial to the farthest point left.
2. If your CT87 has a subbase, set the system switch to Heat.
3. Turn the dial until the temperature on the setting scale (Fig. 16)
exceeds the room temperature that is shown on the thermometer.
The heating system should start.
4. Turn the dial until the temperature on the setting scale is below the
room temperature that is shown on the thermometer.
The heating system should stop.
69-0274-6 10
Fig. 16. Checking heating system.
SETTING SCALE
HERMOMETER
M9656
CT87A,B,J ROUND® THERMOSTAT
Check cooling
IMPORTANT: To avoid damaging the compressor in the air conditioner,
do not operate the cooling system when the outdoor temperature is
below 50°F (10°C).
1. If your CT87 has a subbase, set the System switch on the left to
Cool.
IMPORTANT: After heating is tested, wait five minutes before switch-
ing to Cool on the CT87J model.
2. Lower the temperature setting below room temperature. The cooling
system should start.
3. Raise the temperature setting above room temperature. The cooling
system should stop.
Operation
To set the temperature, turn the dial until the pointer on the top setting scale aligns with
the desired temperature.
CT87B, J switches
Switch Setting Result
System Cool The thermostat controls your cooling system.
Off Both the heating and cooling systems are off.
Heat The thermostat controls your heating system.
Fan On The fan runs continuously.
Auto The fan runs only with the heating or cooling
system.
11 69-0274-6
CT87A,B,J ROUND® THERMOSTAT
Limited One-Year Warranty
Honeywell warrants this product, excluding battery, to be free from defects in the workmanship or
materials, under normal use and service, for a period of one (1) year from the date of purchase by
the consumer. If, at any time during the warranty period, the product is defective or malfunctions,
Honeywell shall repair or replace it (at Honeywell’s option) within a reasonable period of time.
If the product is defective,
(i) return it, with a bill of sale or other dated proof of purchase, to the retailer where you purchased
it, or
(ii) package it carefully, along with proof of purchase (including date of purchase) and a short
description of the malfunction, and mail it, postage prepaid, to the following address:
Honeywell Inc. USA Honeywell Canada:
Dock 4 — MN10-3860 Honeywell Limited/Honeywell Limitée
1985 Douglas Drive North 35 Dynamic Drive
Golden Valley, MN 55422-3992 Scarborough, Ontario M1V 4Z9
This warranty does not cover removal or reinstallation costs. This warranty shall not apply if it is
shown by Honeywell that the defect or malfunction was caused by damage which occurred while
the product was in the possession of a consumer.
Honeywell’s sole responsibility shall be to repair or replace the product within the terms stated
above. HONEYWELL SHALL NOT BE LIABLE FOR ANY LOSS OR DAMAGE OF ANY KIND,
INCLUDING ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES RESULTING, DIRECTLY OR
INDIRECTLY, FROM ANY BREACH OF ANY WARRANTY, EXPRESS OR IMPLIED, OR ANY
OTHER FAILURE OF THIS PRODUCT. Some states do not allow the exclusion or limitation of
incidental or consequential damages, so this limitation may not apply to you.
THIS WARRANTY IS THE ONLY EXPRESS WARRANTY HONEYWELL MAKES ON THIS
PRODUCT. THE DURATION OF ANY IMPLIED WARRANTIES, INCLUDING THE
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, IS
HEREBY LIMITED TO THE ONE YEAR DURATION OF THIS WARRANTY. Some states do not
allow limitations on how long an implied warranty lasts, so the above limitation may not apply to
you.
This warranty gives you specific legal rights, and you may have other rights which vary from state
to state.
If you have any questions concerning this warranty, please write Honeywell Customer Care,
Honeywell Inc., 1985 Douglas Dr. N., Golden Valley, MN 55422-3992, or call 1-800-468-1502. In
Canada, write Retail Products ON15, Honeywell Limited/Honeywell Limitée, 35 Dynamic Drive,
Scarborough, Ontario M1V 4Z9.
Automation and Control Solutions
Honeywell Honeywell Limited-Honeywell Limitée
1985 Douglas Drive North 35 Dynamic Drive
Golden Valley, MN 55422 Scarborough, Ontario
69-0274-6 G.H. Rev. 08-02 www.honeywell.com/yourhome
M1V 4Z9
Printed in U.S.A. on recycled
paper containing at least 10%
post-consumer paper fibers.
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