Service manual

31
Installation and Service Manual
COMPONENT DIAGNOSTICS
HOT GAS VALVE / COMPRESSOR CONTACTOR / CHECK PROCEDURE
Hot Gas Valve
Servend employs a hot gas defrost harvest method.
When the ice reaches the proper temperature, the ice
sensing thermistor initiates the board to open the hot
gas bypass valve. This electrically operated solenoid
valve will then allow hot discharge refrigerant gas as it
leaves the compressor to return to the inlet of the evapo-
rator. The flow of liquid refrigerant out of the expansion
valve will then cease. The hot refrigerant warms the
evaporator therefore allowing the ice to melt and slide
off of the evaporator.
If the hot gas fails to open, check the electric power
supply to the coil of the valve. This power supply comes
to the coil from the circuit board and should be ener-
gized when the red LED is energized. If the coil is
envergized but the valve still fails to operate, you have a
sticking valve that needs to be replaced.
A leaking valve can cause excessive freeze times,
uneven bridge thickness, high suction pressures, etc.
A leaking hot gas valve is difficult to troubleshoot.
Several methods to determine if this valve is leaking in
the closed mode is as follows:
The hand temperature method - Place your hand
on the outlet line of the valve. The outlet line of the
valve should feel ambient temperature or a little
cooler.
The use of an electronic sight glass - Can be ben-
eficial in the leak detection. Install the probes on the
oulet line of the valve, several inches apart. If there
is a small leak in the valve, the instument should
detect hot gas condensing due to the pressure drop
and cooler temperatures of the evaporator section.
Another leak detection method for the hot gas
valve is the use of a pinch off tool - By closing the
line between the hot gas valve and the evaporator,
you should be able to determine if the valve was
slightly leaking through.
Compressor Contactor
CAUTION: 230 VOLT MODELS - CONTACTOR
BREAKS ONE POWER LEG ONLY - ICE MAKER IS
STILL LIVE (HOT).
The contactor serves as the voltage supply switch
for the compressor circuit. Voltage to the coil of the
contactor is supplied by the control board relay on self-
contained models (see diagrams). Remote models are
wired directly across the supply line from the toggle
switch. The coil receives power through the low pres-
sure cut-out and thermo-disc.
Check Procedure (Single Phase)
Top two (2) screws of contactor should always have
line voltage supply present. The lower two (2) screws
should have line voltage when the contactor closes.
The contactor coil must receive line voltage from teh
control board relay. If the coil will not close the contactor:
A) Check the coil with an OHM meter for continuity.
B) *Check for proper voltage supplied to coil.
*NOTE:High impedance digital meter may show volt-
age from the control board, but that voltage may not
carry a current load. Test light 25W or higher or a
low impedance dial type meter should be used when
testing output voltage from control board.