Service Manual

SERVICING
84
ture so both stages call for heat.
2. With voltmeter, check for 24 volts at each heater relay.
3. No voltage indicates the trouble is in the thermostat or wiring.
4. Check the continuity of the thermostat and wiring. Repair or
replace as necessary.
NOTE: Consideration must be given to how the heaters are wired
(O.D.T. and etc.). Also safety devices must be checked for conti-
nuity.
S-4 CHECKING TRANSFORMER AND CONTROL CIRCUIT
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.
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 sections
do not contain a transformer (see note below).
Disconnect ALL power before servicing.
WARNING
1. Remove control panel cover, or etc., to gain access to trans-
former.
With power ON:
Line Voltage now present.
WARNING
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 trans-
former and wiring and splices good, transformer is inopera-
tive. Replace.
S-7 CHECKING CONTACTOR AND/OR RELAYS
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.
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.
NOTE: Most single phase contactors break only one side of the
line (L1), leaving 115 volts to ground present at most internal
components.
NOTE: The compressor contactor/relay in ComfortNet
TM
ready equipment is fully integrated into the unitary (UC) con-
trol. The compressor contactor/relay coil on the UC control
is non-serviceable.
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.
S-8 CHECKING CONTACTOR CONTACTS
Disconnect ALL power before servicing.
WARNING
SINGLE PHASE:
1. Disconnect the wire leads from the terminal (T) side of the
contactor.
2. With power ON, energize the contactor.
Line Voltage now present.
WARNING
3. Using a voltmeter, test across terminals.
A. L2 - T1 - No voltage indicates CC1 contacts open.
If a no voltage reading is obtained - replace the contactor.