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SERVICING
3. Set fan selector switch at thermostat to "ON" position.
4. With voltmeter, check for 24 volts at wires C and G.
5. No voltage, indicates the trouble is in the thermostat or
wiring.
6. Check the continuity of the thermostat and wiring. Repair
or replace as necessary.
S-3B COOLING ANTICIPATOR
The cooling anticipator is a small heater (resistor) in the ther-
mostat. During the "off" cycle it heats the bimetal element
helping the thermostat call for the next cooling cycle. This
prevents the room temperature from rising too high before the
system is restarted. A properly sized anticipator should main-
tain room temperature within 1 1/2 to 2 degree range.
The anticipator is supplied in the thermostat and is not to be
replaced. If the anticipator should fail for any reason, the ther-
mostat must be changed.
S-3C HEATING ANTICIPATOR
The heating anticipator is a wire-wound adjustable heater, which
is energized during the "ON" cycle to help prevent overheating
of the conditioned space.
The anticipator is a part of the thermostat and if it should fail for
any reason, the thermostat must be replaced. See the follow-
ing for recommended heater anticipator setting.
To determine the proper setting, use an amp meter to measure
the amperage on the "W" wire going to the thermostat.
Use an amprobe as shown below. Wrap 10 turns of thermostat
wire around the stationary jaw of the amprobe and divide the
reading by 10.
Checking Heat Anticipator Amp Draw
S-4 CHECKING TRANSFORMER AND
CONTROL CIRCUIT
A step-down transformer (208/240 volt primary to 24 volt sec-
ondary) is provided with each package unit. This allows ample
capacity for use with resistance heaters.
10 TURNS OF
THERMOSTAT WIRE
(From "W" on thermostat)
STATIONARY JAW
OF AMPROBE
READS 4 AMPS
CURRENT DRAW
WOULD BE .4 AMPS
WARNING
1. Remove control panel cover or etc. to gain access to trans-
former.
With power ON:
WARNING
LINE VOLTAGE NOW PRESENT.
2. Using a voltmeter, check voltage across secondary voltage
side of transformer (R to C).
3. No voltage indicates faulty transformer, bad wiring, or bad
splices.
4. Check transformer primary voltage at incoming line voltage
connections and/or splices.
5 If line voltage is present at the primary voltage side of the
transformer and 24 volts is not present on the secondary
side, then the transformer is inoperative. Replace.
S-7 CHECKING CONTACTOR AND/OR
RELAYS
The compressor contactor and other relay holding coils are
wired into the low or line voltage circuits. When the control
circuit is energized the coil pulls in the normally open contacts
or opens the normally closed contacts. When the coil is de-
energized, springs return the contacts to their normal position.
WARNING
DISCONNECT POWER SUPPLY BEFORE SERVICING.
1. Remove the leads from the holding coil.
2. Using an ohmmeter, test across the coil terminals.
If the coil does not test continuous, replace the relay or con-
tactor.
25
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