Manitowoc QD0202A, Service Manual

Page: 144 / 175

Refrigeration System Section 7
7-32
Part No. 80-1100-3
Pressure Control Specifications and
Diagnostics
FAN CYCLE CONTROL
(Self-Contained Air-Cooled Models Only)
Function
Cycles the fan motor on and off to maintain proper
operating discharge pressure.
The fan cycle control closes on an increase, and opens
on a decrease in discharge pressure.
Specifications
Check Procedure
1. Verify fan motor windings are not open or grounded,
and fan spins freely.
2. Connect manifold gauges to ice machine.
3. Hook voltmeter in parallel across the fan cycle
control, leaving wires attached.
4. Refer to chart below.
HIGH PRESSURE CUT-OUT (HPCO) CONTROL
Function
Stops the ice machine if subjected to excessive high-
side pressure.
The HPCO control is normally closed, and opens on a
rise in discharge pressure.
Specifications
Cut-out: 450 psig ±10
Cut-in: Manual or automatic reset
(Must be below 300 psig to reset).
Check Procedure
1. Set ICE/OFF/CLEAN switch to OFF, (Manual reset
HPCO reset if tripped).
2. Connect manifold gauges.
3. Hook voltmeter in parallel across the HPCO, leaving
wires attached.
4. On water-cooled models, close the water service
valve to the water condenser inlet. On self-contained
air-cooled and remote models, disconnect the fan
motor.
5. Set ICE/OFF/CLEAN switch to ICE.
6. No water or air flowing through the condenser will
cause the HPCO control to open because of
excessive pressure. Watch the pressure gauge and
record the cut-out pressure.
Replace the HPCO control if it:
• Will not reset (below 300 psig)
• Does not open at the specified cut-out point
Model Cut-In (Close) Cut-Out (Open)
Q200/Q280
Q320/Q370/Q420
Q450/Q600
250 psig ±5 200 psig ±5
Q800/Q1000
Q1300/ Q1800
275 psig ±5 225 psig ±5
At: Reading Should Be: Fan Should Be:
above cut-in 0 volts running
below cut-out line voltage off
! Warning
If discharge pressure exceeds 460 psig and the
HPCO control does not cut out, set ICE/OFF/
CLEAN switch to OFF to stop ice machine
operation.