Manitowoc Ice Chiplet QC0700 - Manual (Page 57)

Section 5 Before Calling Service
Part Number 000002688 5-5
Temperature is Too High or Low
QF400/QC700/QF800
The temperature sensor (thermistor) is mounted on the
compressor discharge line. The temperature sensor
provides input to the control board. The control board
monitors the temperature anytime the compressor is
energized.
If the thermistor detects 245°F or higher for 15
continuous seconds:
1. The ice machine will de-energize the compressor
and gear motor and initiate a SafeGuard Mode.
2. The control board “Disch Temp” light will continue to
flash twice then pause, to indicate the ice machine
has shut off on high temperature.
3. The ice machine will remain off until the toggle
switch is moved from ICE to OFF, and back to ICE.
or
Line voltage is interrupted and restored.
If the thermistor detects 155°F or less for 3
continuous minutes:
1. The control board ignores the low temperature limit
for the first 30 minutes of compressor run time.
2. The ice machine will de-energize the compressor
and gear motor, continuously flash the control board
“Disch Temp” light and initiate a 60-minute Standby
Mode.
3. After the 60-minute Standby Mode, the ice machine
will de-energize the “Disch Temp” light and initiate a
start-up sequence.
4. After 30 minutes of compressor run time, the ice
machine will check the discharge line temperature.
Discharge line temperature normal:
The ice machine continues to make ice.
Discharge line temperature below 155°F after 30
minutes of run time:
The ice machine will start another 60-minute
Standby Mode.
If the discharge line temperature drops below 155°F for
3 continuous minutes during 7 consecutive cycles the
ice machine will start a SafeGuard Mode.
During the SafeGuard Mode the ”Disch Temp” light will
continually flash to indicate a Safeguard Mode. The ice
machine remains off until:
• The toggle switch is moved from ICE to OFF, then
back to ICE.
• Line voltage is interrupted and restored.
INDICATOR LIGHT
Before 48 hours have elapsed:
After a Standby Mode has been initiated the Control
Board “Disch Temp“ light will flash anytime the toggle
switch is placed in the OFF position.
After 48 hours have elapsed:
The SafeGuard will be automatically erased from memory
and the “Disch Temp” light will not flash.
Temperature Sensor Checklist
Possible Problem List Corrective Action List
Thermistor is not properly insulated Insulate thermistor.
Thermistor loose Secure thermistor to discharge line.
Thermistor mounted in the wrong location Position thermistor on discharge line 6 in. from compressor
discharge port.
Thermistor defective Refer to CHECK PROCEDURE under “Thermistor.”
Flooding expansion valve Replace expansion valve.
Refrigerant overcharge or undercharge Recover and weigh in nameplate charge.
Low ambient temperature Verify ambient temperature remains above 45°F (7.2°C).
Defective compressor Replace compressor.
Insufficient or low water pressure Verify water pressure is between 20 and 80 psig.