51
SERVICING
S-4
CHECKING TRANSFORMER AND CONTROL
CIRCUIT
WARNING
HIGH VOLTAGE
Disconnect ALL power before servicing or installing
this unit. Multiple power sources may be present.
Failure to do so may cause property damage, personal
injury or death.
A step-down transformer (208/240 volt primary to 24 volt
secondary) is provided with each indoor unit. This allows ample
capacity for use with resistance heaters. The outdoor sections
do not contain a transformer (see note below).
NOTE:
ComfortNet™ ready condensing units may have
an optional 240VAC to 24VAC transformer installed. This
transformer provides 24VAC power to the unitary (UC) control in
some communicating system installation scenarios.
WARNING
Disconnect ALL power before servicing.
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 available at primary voltage side of
transformer and wiring and splices good, transformer is
inoperative. Replace.
S-6
CHECKING TIME DELAY RELAY
Time delays are used in electric heaters to sequence in multiple
electric heaters.
WARNING
Disconnect ALL power before servicing.
1. Tag and disconnect all wires from male spade connections
of relay.
2. Using an ohmmeter, measure the resistance across
terminals H1 and H2. Should read approximately 150
ohms.
3. Using an ohmmeter, check for continuity across terminals
3 and 1, and 4 and 5.
4. Apply 24 volts to terminals H1 and H2. Check for
continuity across other terminals - should test continuous.
If not as above - replace.
NOTE:
The time delay for the contacts to make will be
approximately 20 to 50 seconds and to open after the coil is de-
energized is approximately 40 to 90 seconds.
OHMMETER
TESTING COIL CIRCUIT
S-8A CHECKING UNITARY (UC) CONTROL
COMPRESSOR CONTACTOR/RELAY CONTACTS
WARNING
Disconnect ALL power before servicing.
1. Connect voltmeter to lugs (L2) and (C).
2. With power ON, provide a call for cool or heat pump to
energize the on-board compressor contactor/relay.
WARNING
Line Voltage now present.
3. Measure voltage across on-board compressor contactor/
relay contacts.
A. No voltage indicates the contacts are closed and the
contactor/relay is functioning properly.
B. A reading of approximately half of the supply voltage
(example: 115VAC for 230VAC) indicates the relay is
open. Replace UC control if relay does not close.
NOTE:
The unitary (UC) control has a built-in short cycle delay.
Ensure short cycle delay has elapsed before making voltage
measurements.
