SERVICING
43
S-4 CHECKING TRANSFORMER AND CONTROL
CIRCUIT
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.
A step-down transformer (208/240 volt primary to 24 volt sec-
ondary) is provided with each indoor unit. This allows ample
capacity for use with resistance heaters. The outdoor sec-
tions do not contain a transformer (see note below).
NOTE:
ComfortNet
TM
ready condensing units may have an
optional 240VAC to 24VAC transformer installed. This trans-
former 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 volt-
age 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 volt-
age connections and/or splices.
5 If line voltage available at primary voltage side of trans-
former and wiring and splices good, transformer is inop-
erative. 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 connec-
tions 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 termi-
nals 3 and 1, and 4 and 5.
4. Apply 24 volts to terminals H1 and H2. Check for
continuity across other terminals - should test continu-
ous. 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.
