Hoshizaki 73183 service manual F. Mullion/Perimeter Heater, G. Thermistors, Short-Cycle Protection

E. Compressor Overload, Short Cycle Protection, and High-Pressure Switch

1. Compressor External or Internal Overload

If combined temperature/amperage value is above the limit specified by the compressor manufacturer, the compressor overload operates independently to turn off the compressor. The compressor overload de-energizes the compressor until the temperature/amperage value returns to an acceptable level.

•If the condenser fan motor is operating and the compressor is off, it is most likely that the compressor overload opened. If both the compressor and condenser fan motor are off, it is most likely the unit is off or the high-pressure switch has opened. For further details, see "IV. Service Diagnosis."

•On refrigerators, the compressor overload is integrated with the start relay. On 1-section freezers, the compressor overload is internal. On 2-section freezers, the compressor overload is external.

2.Short-Cycle Protection

There is a 2-minute minimum off-time and on-time for the compressor.

Note: Time may vary with compressor overload or high-pressure switch activation.

3. High-Pressure Switch

If pressure on the high-side of the unit exceeds Hoshizaki specifications, the

high‑pressure switch activates and interrupts the compressor circuit, de‑energizing the compressor until the pressure returns to an acceptable level.

F. Mullion/Perimeter Heater

Refrigerators and freezers with mullions are equipped with mullion heaters. Freezers are also equipped with perimeter heaters. The heaters are energized as soon as the power switch is turned on.

G. Thermistors

The cabinet thermistor is used for cabinet temperature control and the defrost thermistor is used for defrost cycle initiation and termination. Thermistor resistance varies depending on temperature. The control module monitors the resistance to control system operation. No adjustment is required. For further details, see "IV.C. Thermistor Check."

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