ESCO Commercial Refrigeration Practice Test

Defrost termination is determined by how the control system knows when frost has melted and the evaporator is ready to resume cooling. In practice, most commercial units use either a defrost timer or a temperature sensor. A timer stops the defrost after a set interval, which works in simpler or older systems. A temperature sensor ends defrost when the evaporator temperature reaches a predefined level, indicating frost is melted and the surface is ready for efficient cooling. Some modern controls combine both approaches or use temperature feedback to optimize defrost duration. The other ideas—requiring manual defrost, having the compressor end defrost, or ending strictly after a fixed time without temperature feedback—don’t match typical automatic control practices and can lead to improper defrost outcomes.