Welbilt FB081TF, Service Manual

Page: 71 / 96

Part Number REV00 04/08/2020 71
Section 7 Component Check Procedures
LOW PRESSURE CONTROL
Function
Energizes and de-energizes the contactor coil when suction
pressure rises above or falls below set-point.
The LPCO control is closed at pressures above setpoint and
opens at pressures below set-point.
SPECIFICATIONS
Specifications
Cut-Out Cut-In
7 psig ±3 22 psig ±3
Check Procedure
1. Install gauge set and restart the ice machine and
initiate a start sequence. Watch the refrigerant
pressures when the compressor starts.
• LPCO opens above cut-out set-point - Replace the LPCO
• LPCO will not open below cut-out set-point - Replace
the LPCO.
• Refrigerant pressure drops below cut-out - Locate the
root cause - Low on refrigerant, moisture in system, txv
defective, etc.
HIGH PRESSURE CUTOUT (HPCO) CONTROL
Function
Protects the compressor by interrupting the control signal
to the control board. Excessive high side pressure operates
the HPCO. The HPCO control is normally closed, and opens
on a rise in discharge pressure.
Location
Above the ice compressor.
Specification
Refrigerant Type Cut-Out Cut-In
R404A 2413 kPa ±24.13
bar ±.69
350 psig ±10
1723 kPa 17.23 bar ±.69
250 psig ±10
R290
The HPCO automatically resets when the pressure drops below the cut-in
Check Procedure
1. Verify the filter and condenser are clean.
2. With power off, isolate by disconnecting the wiring
connectors.
3. Check continuity across the terminals with an ohm
meter.
• Low resistance = Continuity is good.
• Open (OL) = Replace HPCO.
4. Replace wires on HPCO terminals and also connect volt
meter across the HPCO terminals.
5. Install a high side gauge and initiate a start sequence.
6. Watch the refrigerant pressures when the compressor starts.
• HPCO opens below cut-out set-point - Replace
the HPCO
• HPCO opens above cut-out set-point - Locate
the root cause - Fan motor defective, dirty
condenser, refrigeration system issue, etc.