Manitowoc Ice QC0700 Section, Troubleshooting, Temperature is Too High or Low QF400/QC700/QF800

Section 5 Troubleshooting

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.

Temperature Sensor Checklist

QF400/QC700/QF800

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.

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.

Part No. 80-1214-3 Revised 8/2003 5-5