CT31
CT31
Low-voltage Thermostat
Owner’s
Manual
Getting started
Before you begin,make sure you have:
• Screwdriver
• Hammer
• Level (optional)
• Pencil
• Drill bit (3/16” for drywall, 7/32” for plaster)
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Copyright © 2005 Honeywell International Inc.
All rights reserved.
Caution cardWire labels
Wall anchors and
mounting screws
(2 each)
CT31 thermostat
Cover plate
Check to make sure your package includes the following items:
Owner’s Manual
2
Remove your old thermostat
1
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at heating/cooling system (or fuse/circuit-breaker panel).
2 Remove cover and thermostat, but leave wallplate with wires attached.
Old thermostat
Leave wallplate in place Is there a sealed tube containing mercury?
If so, see mer
cury notice below.
Cover
MERCURY NOTICE: Do not place your old thermostat in the trash if it contains
mercury in a sealed tube. Contact your local waste management authority for
instructions regarding recycling and proper disposal.
Did you purchase right thermostat? Count wires to check.
Count the number of wires coming out of the wall and attached to terminals in
your old thermostat. If any of them are attached to a terminal marked “C” or “C1”
do not count that wire in your total.
If the total (not counting C or C1) is 4 wires or less, proceed to the next page. If
you have 5 or more wires,your new thermostat may not be compatible with your
system. Stop installation and call 1-800-468-1502 for advice.
Do you have 5 or more wires? If so, stop now.
You may have purchased the wrong replacement thermostat.
CT31 Low-voltage Thermostat
3
Label wires and remove old wallplate
Use a screwdriver to disconnect wires one by one.As you disconnect each wire,
wrap it with the label matching the letter on your old thermostat. (Adhesive labels
are supplied in your thermostat package.)
Remove the old wallplate only after all wires are labeled.Be careful not to let
loose wires fall into the wall opening.
Wrap supplied labels securely around each wire
Do not let wires fall into wall opening!
IGNORE WIRE COLORS: Use only letter designations
to identify wire types.
Mark mounting position
1 Pull wires through base (and
cover plate if desired).
2 Level base or cover plate
if desired.
3 Mark positions of
both screw holes.
Owner’s Manual
4
Connect wires
1 Match each labeled wire
with same letter
on terminal.
2 Use a screwdriver to loosen
screw terminals, wrap bare
wire securely around terminals, then tighten screws.
3 Push any excess wire back
into the wall opening.
Labels don’t match?
If labels do not match letters on
thermostat, see table below.
Existing wires Connect to:
R • RH • 4 • V Terminal “R”
W • W1 • H Terminal “W”
Y • Y1 • M Terminal “Y”
G • F Terminal “G”
Rc Stop! See note
Mount thermostat base
1 Drill holes at pencil-marked locations (3/16” holes for drywall, 7/32” holes for plaster).
2 Use hammer to
tap anchors into
holes until flush
with wall.
3 [Optional] Pull
wires through
cover plate (if
needed to cover
marks left by your
old thermostat).
4 Pull wires through
thermostat base
and insert screws.
Check level if
desired, then
tighten screws.
Thermostat base
Optional cover plate
If this wire is present, you cannot use
this thermostat with your system. See
page 2.
CT31 Low-voltage Thermostat
5
Set adjustment lever
1 Separate cover from thermostat,
and remove the plastic insert.
2 Use a pencil to move the adjust-
ment lever to the proper setting for
your system (see table below).
Finish installation
1 Mount thermostat
on base and tighten
three mounting
screws.
2 Align the 3 tabs on
the cover with slots
on the thermostat,
then push gently
until the cover
snaps into place.
3 Restore electrical
power at the heating/cooling system,
or at the fuse/
circuit-breaker
panel.
Thermostat
Cover
Base
(shown with
optional
cover plate)
Your system Setting
Gas or oil furnace
(less than 90% efficiency) 0.4
Electric furnace (any type) 0.3
High efficiency furnace
(more than 90% efficiency) 0.8
Hot water system 0.8
Gas/oil steam or gravity system 1.2
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