In a refrigeration system, which device is used to control defrost cycles?

In a refrigeration system, which device is used to control defrost cycles?

• A. Disconnect switch
• B. Defrost relay
• C. Potential relay
• D. High pressure safety switch

Answer: (B)

Defrost cycles are controlled by a switching device that energizes and then stops the defrost heater at the scheduled time or temperature. The defrost relay serves this exact role: it receives a control signal from the defrost timer or control board and closes to power the defrost heater during the cycle, then opens to end the cycle. This keeps frost buildup in check without running the heater continuously. The other components have different functions. A disconnect switch is just a manual power cutoff for maintenance, not an automatic defrost control. A potential relay (start relay) is used to aid compressor start-up, not to manage defrost. A high pressure safety switch monitors system pressure and interrupts operation if it gets too high, serving as a protective device rather than a defrost controller.

Defrost cycles are controlled by a switching device that energizes and then stops the defrost heater at the scheduled time or temperature. The defrost relay serves this exact role: it receives a control signal from the defrost timer or control board and closes to power the defrost heater during the cycle, then opens to end the cycle. This keeps frost buildup in check without running the heater continuously.

The other components have different functions. A disconnect switch is just a manual power cutoff for maintenance, not an automatic defrost control. A potential relay (start relay) is used to aid compressor start-up, not to manage defrost. A high pressure safety switch monitors system pressure and interrupts operation if it gets too high, serving as a protective device rather than a defrost controller.