CONTENTS
Preparations ...........................................
Thermostat Features ..............................
Removing Old Thermostat .....................
Mounting and Wiring ..............................
New Thermostat Operation ....................
Specifications .........................................
Troubleshooting .....................................
1
2
3
4
5
6
7
Installation Instructions for
Cooling only
1C21
PREPARATIONS
YOUR THERMOSTAT REPLACES
1
Assemble tools required as shown below.
Description
1C21
Standard Heating & Cooling Systems - 4 or 5 wires
Standard Cool Only Systems
No
Yes
Yes
Yes
No
FLAT BLADE SCREWDRIVER
WIRE CUTTER/STRIPPER
Millivolt Cool Only Systems - Floor or Wall Furnaces
Standard Central Air Conditioning
HAND OR POWER
Gas or Oil Heat
DRILL WITH 3/16 INCH
DRILL BIT, IF NEEDED
Electric Furnace
No
Hydronic (Hot Water) Zone Heat - 2 Wires
Hydronic (Hot Water) Zone Heat - 3 Wires
Heat Pump (No Aux or Emergency Heat)
Heat Pump (with Aux or Emergency Heat)
Baseboard Electric Heating or Line Voltage (120 or 240 Volt)
No
SPIRIT LEVEL OR PLUMB BOB AND LINE OPTIONAL—
THERMOSTAT MUST BE LEVEL TO WORK PROPERLY
No
No
Failure to follow and read all instructions carefully be-
fore installing or operating this control could cause
personal injury and/or property damage
No
No
THERMOSTAT FEATURES
REMOVING OLDTHERMOSTAT
2
3
CAUTION
!
To prevent electrical shock and/or equipment damage,
disconnect electrical power to the system at the main
fuse or circuit breaker until installation is complete.
MOUNTING SCREWS
CAPTIVE SCREWS
Before removing wires from old thermostat’s switching subbase,
label each wire with the terminal designation it was removed from.
Some models also include an adaptor plate to cover unpainted
surfaces. Thermostat wires pass through the adaptor plate center
opening.
1. Remove Old Thermostat: A standard heat/cool thermostat
BASE
consists of two basic parts:
a. The cover, which may be either a snap-on or hinge type.
b. The base, which is removed by loosening all captive screws.
ATTENTION! This product does not contain mercury. How-
ever, this product may replace a unit which contains mercury.
Do not open mercury cells. If a cell becomes damaged, do not
touch any spilled mercury. Wearing non-absorbent gloves, take
up the spilled mercury and place into a container which can be
sealed. If a cell becomes damaged, the unit should be discarded.
COVER
Adaptor Plate
(optional)
Figure 1.
Mercury must not be discarded in household trash. When the unit
this product is replacing is to be discarded, place in a suitable
container.Refertowww.white-rodger.comforlocationtosendthe
product containing mercury.
PART NO. 37-6370B
Replaces 37-6370A
0835
TROUBLESHOOTING
7
Symptom
Possible Cause
Corrective Action
No Cool
1. Blown fuse or tripped circuit breaker.
2. Furnace power switch to OFF.
Replace fuse or reset breaker.
Turn switch to ON.
3. Furnace blower compartment door or
panel loose or not properly installed.
Replace door panel in proper position to engage
safety interlock or door switch.
4. Loose connection to thermostat or system.
Verify thermostat and system wires are securely
attached.
5. Thermostat or cooling system requires
replacement or service.
Your cooling system manufacturer or service
person can describe how to test the cooling
system to verify it is operating correctly. If the
cooling system is capable of operation and the no
cooling condition persists, replace the thermostat.
Cool Runs Constantly
1. Possible short in wiring.
2. Possible short in thermostat.
Check each wire connection to the thermostat to
verify it is neatly looped under the terminals. No
extra wire should stick out from under the
terminals.
Cooling Cycles Too Fast or Too Slow
(narrow or wide temperature swing)
1. Poor thermostat location for sensing room
temperature.
2. Cooling system over or undersized.
3. Excessive Current draw influencing thermostat.
The cycle rate for cooling can not be adjusted.
The location of the thermostat, size of the Cool
system and current draw can influence the cycle
rate. Contact a local service person for suggestions.
Thermostat Setting and Thermostat
Thermometer Disagree
1. Thermostat thermometer setting requires
adjustment.
The thermometer can be adjusted by using a
standard slotted screwdriver. Turn the thermom-
2. Thermostat setting lever requires calibration. eter pointer screw located inside the front cover
to change the setting. For calibrating the setting
lever contact a local heating and cooling service
person.
Adjusting Thermometer
1. Thermostat thermometer disagrees with
other room thermometers.
The thermometer on the thermostat is accurately
calibrated at our factory but you can adjusted it
by using a standard slotted screwdriver. Turn the
thermometer pointer screw located inside the
front cover to change the setting.
The Emerson logo is a
trademark and a service mark
of Emerson Electric Co.
White-Rodgers is a division
of Emerson Electric Co.
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