ESCO Commercial Refrigeration Practice Test

Defrost is ended by a control that watches the evaporator conditions, not by the compressor finishing. In most reach-in refrigerators, the defrost heater runs until a set point is reached on a temperature sensor (on the evaporator or in the air), or until a timer finishes. When the coil is sufficiently warm and the frost has melted, the control switches the heater off and returns the unit to cooling. This approach keeps frost from rebuilding while avoiding overheating.

Manual defrost isn’t typical for these systems, since they are designed to run automatically. Relying on a fixed duration alone is less reliable because frost buildup and temperatures vary; temperature sensing provides a more accurate termination.