GPC14M GPH14M Installation Manual

14
SERVICE
THE FOLLOWING INFORMATION IS FOR USE BY QUALIFIED SER-
VICE AGENCY ONLY: OTHERS SHOULD NOT ATTEMPT TO SER-
VICE THIS EQUIPMENT.
Common Causes of Unsatisfactory Operation of Heat Pump in
the Heating Cycle.
INADEQUATE AIR VOLUME THROUGH INDOOR COIL
When a heat pump is in the heating cycle, the indoor coil is func-
tioning as a condenser. The return air filter must always be clean,
and sufficient air volume must pass through the indoor coil to
prevent excessive discharge pressure, and high pressure cut out.
OUTSIDE AIR INTO RETURN DUCT
Do not introduce cold outside air into the return duct of a heat
pump installation. Do not allow air entering the indoor coil to drop
below 65° F. Air below this temperature will cause low discharge
pressure, thus low suction pressure, and excessive defrost cy-
cling resulting in low heating output. It may also cause false
defrosting.
UNDERCHARGE
An undercharged heat pump on the heating cycle will cause low
discharge pressure resulting in low suction pressure and frost
accumulation on the outdoor coil.
POOR “TERMINATING” SENSOR CONTACT
The unit’s defrost terminating sensor must make good thermal con-
tact with the outdoor coil tubing. Poor contact may not terminate the
unit’s defrost cycle quickly enough to prevent the unit from cutting out
on high discharge pressure.
MALFUNCTIONING REVERSING VALVE - THIS MAY BE DUE TO:
1. Solenoid not energized - In order to determine if the
solenoid is energized, touch the nut that holds the solenoid
cover in place with a screwdriver. If the nut magnetically
holds the screwdriver, the solenoid is energized and the
unit is in the cooling cycle.
2. No voltage at unit’s solenoid - Check unit voltage. If no
voltage, check wiring circuit.
3. Valve will not shift:
a. Undercharged - check for leaks;
b. Valve Body Damaged - Replace valve;
c. Unit Properly Charged - If it is in the heating cycle, raise
the discharge pressure by restricting airflow through
the indoor coil. If the valve does not shift, tap it lightly on
both ends with a screwdriver handle. DO NOT TAP THE
VALVE BODY. If the unit is in the cooling cycle, raise the
discharge pressure by restricting airflow through the
outdoor coil. If the valve does not shift after the above
attempts, cut the unit off and wait until the discharge
and suction pressure equalize, and repeat above steps.
If the valve does not shift, replace it.