| 摘要 |
A defrost system for refrigerating apparatus having a refrigerating mode and a defrosting mode including an evaporator and an electric resistance heater in heat transfer relationship with the evaporator. There is provided a timer to actuate a normally open defrost initiation switch to energize the heater periodically and initiate a defrosting mode. A defrost terminating thermostat switch is in the heater circuit and will open at a predetermined elevated temperature to deenergize the heater and close at a lower temperature. A voltage sensor across the normally open defrost initiation switch senses periodically and provides a signal when voltage in the heater circuit is interrupted. The multiple voltage sensor signals are stored in a memory bank over a predetermined period of time and when the voltage is interrupted for the predetermined period of time, an alarm is actuated to indicate failure of the defrost system.
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