SERVICING
12
WARNING
High Voltage!
Disconnect all power before servicing or
installing. Multiple power sources may be present.
Failure to do so may cause property damage,
personal injury or death.
1. Remove control panel cover, or etc., to gain access
to transformer.
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.
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
High Voltage!
Disconnect all power before servicing or
installing. Multiple power sources may be present.
Failure to do so may cause property damage,
personal injury or death.
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
contactor.
Checking Contactor Contacts
WARNING
High Voltage!
Disconnect all power before servicing or
installing. Multiple power sources may be present.
Failure to do so may cause property damage,
personal injury or death.
Single Phase
1. Disconnect the wire leads from the terminal (T) side
of the contactor.
2. With power ON, energize the contactor.
WARNING
Line voltage now present.
Testing Compressor Contactor
(Single Phase)
3. Using a voltmeter, test across terminals.
A. L1 - L2 - No voltage. Check breaker or fuses on
main power supply. If voltage present, proceed to
step B.
B. T1 to T2 - Meter should read the same as L1 to
L2 in step A. If voltage readings are not the same
as step A, replace contactor.
Checking Low Pressure Control
(Heat Pump Models)
The low pressure control senses the pressure in the
suction line and will open its contacts on a drop in
pressure. The low pressure control will automatically reset
itself with a rise in pressure.
The low pressure control is designed to cut-out (open) at
approximately 22 PSIG. It will automatically cut-in (close) at
approximately 50 PSIG.
