GSX14 Service Manual

SERVICING
127
4. With power ON, close the switch.
WARNING
Line Voltage now present.
A. If the compressor starts and continues to run, the cause
for failure is somewhere else in the system.
B. If the compressor fails to start - replace.
COPELAND COMPRESSOR
03 A 12345 L
Y
EAR
MONTH
SERIAL
NUMBER
PLANT
S-17E CHECKING 3-PHASE SCROLL
COMPRESSOR ROTATION
Verify the proper rotation of Copeland scroll compressors as
follows:
NOTE: The compressor may run backwards (noisy opera-
tion) for 1 or 2 seconds at shutdown. This is normal and does
not harm the compressor.
1. Install gauges and verify that the suction pressure drops
while the discharge pressure increases.
2. Listen for normal compressor sound levels. Reverse
rotation results in elevated or unusual sound levels.
3. Reverse rotation will result in substantially reduced amp
draw from tabulated values.
To correct improper rotation, switch any two power supply
leads at the outdoor unit contactor.
The 3-phase scroll compressors are direction of rotation
sensitive. They will rotate in either direction depending on the
phasing of the power. There is no negative impact on
durability caused by operating 3-phase compressors in
reversed rotation. The compressor's internal protector will
trip, de-energizing the compressor. Continued operation of
3-phase scroll compressors with the rotation reversed will
contribute to compressor failure. All 3-phase scroll compres-
sors should be checked for correct phase rotation.
S-18 TESTING CRANKCASE HEATER (OPTIONAL
ITEM)
The crankcase heater must be energized a minimum of four
(4) hours before the condensing unit is operated.
Crankcase heaters are used to prevent migration or accumu-
lation of refrigerant in the compressor crankcase during the
off cycles and prevents liquid slugging or oil pumping on start
up.
A crankcase heater will not prevent compressor damage
due to a floodback or over charge condition.
WARNING
Disconnect ALL power before servicing.
1. Disconnect the heater lead in wires.
2. Using an ohmmeter, check heater continuity - should
test continuous. If not, replace.
NOTE: The positive temperature coefficient crankcase
heater is a 40 watt 265 voltage heater. The cool resistance
of the heater will be approximately 1800 ohms. The
resistance will become greater as the temperature of the
compressor shell increases.
S-21 CHECKING REVERSING VALVE AND
SOLENOID
Occasionally the reversing valve may stick in the heating or
cooling position or in the mid-position.
When stuck in the mid-position, part of the discharge gas
from the compressor is directed back to the suction side,
resulting in excessively high suction pressure. An increase
in the suction line temperature through the reversing valve
can also be measured. Check operation of the valve by
starting the system and switching the operation from COOL-
ING to HEATING cycle.
If the valve fails to change its position, test the voltage (24V)
at the valve coil terminals, while the system is on the
COOLING cycle.
All heat pumps and ComfortNet
TM
heat pumps wired in
legacy - If no voltage is registered at the coil terminals,
check the operation of the thermostat and the continuity of
the connecting wiring from the "O" terminal of the thermostat
to the unit.
ComfortNet heat pumps only - Check voltage (24VAC) at
the non-insulated terminal E22 on the UC control board
(RVS on silkscreen) and "C" terminal on the 7-pin or 4-pin
connector on the UC control
If voltage is registered at the coil, tap the valve body lightly
while switching the system from HEATING to COOLING, etc.
If this fails to cause the valve to switch positions, remove the
coil connector cap and test the continuity of the reversing
valve solenoid coil. If the coil does not test continuous -
replace it.
If the coil test continuous and 24 volts is present at the coil
terminals, the valve is inoperative - replace it.
S-24 TESTING DEFROST CONTROL
LEGACY MODELS:
To check the defrost control for proper sequencing, pro-
ceed as follows: With power ON; unit not running.
1. Jumper defrost thermostat by placing a jumper wire
across the terminals "DFT" and "R"/"R-DFT" at defrost
control board.
2. Connect jumper across test pins on defrost control
board.