GSZH5 Service Manual
92
SERVICING
Trouble Shooting Mechanical Failures on a Reversing
Valve by Temperature
1. When operating properly the valve contains refrigerant
gases at certain temperatures.
2. The discharge line should be the same temperature
after the valves discharge line.
3. The true suction should be the same as the suction line
is leaking
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
COOLING 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 communicating 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.
Communicating 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.
Testing Defrost Control
To check the defrost control for proper sequencing, proceed
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. Remove jumper from timer pins and jump across
test pins on defrost control board. NOTE: Do not use
3. Set thermostat to call for heating. System should go
into defrost within 21 seconds
4. Immediately remove jumper from test pins.
5. Using VOM check for voltage across terminals “C & O”.
Meter should read 24 volts.
6. Using VOM check for voltage across fan terminals DF1
and DF2 on the board. You should read line voltage
(208-230 VAC) indicating the relay is open in the
defrost mode.
7. Using VOM check for voltage across “W”/”W2” & “C”
terminals on the board. You should read 24 volts.
8. If not as above, replace control board.
9.
Remove jumper from defrost thermostat and replace
timer jumper to the desired defrost time.
before returning system to service.
Testing Defrost Thermostat
1. Install a thermocouple type temperature test lead on
the tube adjacent to the defrost control. Insulate the
lead point of contact.
2. Check the temperature at which the control closes its
contacts by lowering the temperature of the control.
Part # 0130M00009P which is used on 2 and 2.5 ton
units should close at 34°F ± 5°F. Part # 0130M00001P
or B1370803 which is used on 3 thru 5 ton units should
close at 31°F ± 3°F.
3. Check the temperature at which the control closes its
contacts by lowering the temperature of the control.
Part # 0130M00085, which is used on units with 5 mm
coils, should close at 30°F ± 5°F.
4. Check the temperature at which the control opens its
contacts by raising the temperature of the control. Part
#0130M00009P which is used on 2 and 2.5 ton units
should open at 60°F ± 5°F. Part # 0130M00001P or
B1370803 which is used on 3 thru 5 ton units should
open at 75°F ± 6°F.
5. Check the temperature at which the control opens its
contacts by raising the temperature of the control. Part
# 0130M00085, which is used on units with 5 mm coils,
should open at 60°F ± 5°F.
6. If not as above, replace control.
Each individual heater element is protected with an
automatic rest limit control connected in series with each
element to prevent overheating of components in case
approximately 150°F. to 160°F and close at approximately
110°F.