If recalibration appears necessary, proceed as
follows:
1. Place the temperature setting lever at the same setting
as the thermometer. Remove cover.
2. Insert 104994A Calibration Wrench (order separately)
onto the hex nut under the coil. See Fig. 6. Holding the setting
lever so it does not move, turn the wrench clockwise
until
the mercury drops to the right end of the tube. Remove
wrench and replace cover.
To ensure accurate temperature control, do not touch or
breathe on bimetal or thermometer.
3. Move the setting lever to a low setting. Wait at least
five minutes for temperature to stabilize.
4. Slowly move the setting lever until it reads the same as
the thermometer.
5. Remove cover. Holding the setting lever so it does not
move, reinsert wrench and carefully turn
counterclockwis
e
until the mercury drops to the le
ft
of the tube, but no farther.
6. Recheck calibration. Set the thermostat system switch
for desired operation and replace cover.
7. Adjust temperature setting lever so mercury bulb is in
position. See Fig. 1
8. Carefully replace thermostat cover.
Fig. 6—Recalibration procedure.
5
69-0434—5
COOLING
CAUTION
Do not operate cooling if outdoor temperature is
below 50
°
F [10
°
C]. Refer to manufacturer’s
recommendations.
NOTE: To prevent compressor short cycling, some manufac-
turers’ equipment includes a minimum off-timer to pro-
vide a five-minute time delay before activating the com-
pressor when the thermostat last turned the compressor
off, or from when the system first received power. This
delay protects the compressor.
With the system switch set at COOL and the fan switch set
at AUTO, move the temperature setting lever about
10
°
F [6
°
C] below room temperature. Cooling and fan should
start (see NOTE above). Move the temperature setting lever
about 10
°
F [6
°
C] above room temperature. Cooling and fan
should shut off.
FAN
With the system switch set at OFF, and the fan switch at
ON, the fan should run continuously. Move the fan switch to
AUTO. In gas- or oil-fired systems, fan operation is con-
trolled by the thermostat in cooling and by the plenum fan
control in heating. In single-stage heat pump and central
electric heat systems, fan operation is controlled by the
thermostat in both heating and cooling.
RECALIBRATION
These thermostats are calibrated at the factory and should
not need recalibration. If the thermostat seems out of adjust-
ment, first check for accurate leveling. To check calibration,
proceed as follows.
1. Move the temperature setting lever to the left end (low
end) of the temperature scale. System switch must be placed
at OFF. Wait at least five minutes.
2. Remove the thermostat cover. Move the setting lever
until the switch just makes contact. The mercury in the switch
will drop to the left end of the tube.
3. Replace cover and wait five minutes for the cover
and the thermostat to lose the heat it has gained from your
hands. If the thermometer pointer and the setting lever
indicator read approximately the same, no recalibration
is needed.
CALIBRATION
WRENCH
COIL SHOWN WITHOUT
HEAT ANTICIPATOR
M2044