In this troubleshooting situation you are dealing with equipment that has only been in operation for two months. And during that time frame, the customer has complained that at times the box temperature is higher than it should be, but the unit them seems to recover and freeze okay until the next time some of the items inside are found to be thawing.
The details on this freezer are as follows:
- The refrigeration system was field-designed and assembled with components purchased individually, and the condensing unit is sitting on top of the cabinet.
- The defrost system is hot gas, employing a timer to initiate the defrost cycle.
When you arrive to evaluate this equipment, you find all refrigerant pressures to be normal and the box temperature is near 0°. Satisfied that the freezing mode of the unit is operating according to specifications, your next step is to force a defrost mode.
When you do, you note that the evaporator fan motor shuts down and the hot gas solenoid operates normally. Figure One shows you the path of refrigerant flow during the hot gas defrost mode: from the hot gas solenoid valve, directly through the evaporator, and back to the compressor.
Near the end of the defrost mode, you find that the compressor kicks off on overload, and is not able to re-start until after an extended delay.
Your troubleshooting question: What mistake was made during the design and construction of this system, causing the compressor to shut down?
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