Defrost termination can be controlled by which of the following methods?

Defrost termination can be controlled by which of the following methods?

• A. Time
• B. Humidity
• C. Flow rate
• D. Sound level

Answer: (A)

Defrost termination is about ending the cycle at the point where frost has melted enough to restore heat transfer, while keeping energy use reasonable. The most common and straightforward way to achieve this is by a timer that ends defrost after a preset duration. This approach is simple, reliable, and doesnures a consistent cycle length regardless of varying conditions, so the evaporator can return to normal operation in a predictable way. Using elapsed time works well because it doesn’t depend on sensors that may be harder to calibrate or prone to drift. Humidity sensing would require an evaporator-surface humidity sensor and a robust threshold, which isn’t always practical. Flow-rate-based termination would need precise flow measurements that don’t directly reflect frost melt and can be affected by fan speed and ducting. Sound level isn’t a reliable indicator of frost status. So terminating defrost by time is the best-fit method in typical practice.

Defrost termination is about ending the cycle at the point where frost has melted enough to restore heat transfer, while keeping energy use reasonable. The most common and straightforward way to achieve this is by a timer that ends defrost after a preset duration. This approach is simple, reliable, and doesnures a consistent cycle length regardless of varying conditions, so the evaporator can return to normal operation in a predictable way.

Using elapsed time works well because it doesn’t depend on sensors that may be harder to calibrate or prone to drift. Humidity sensing would require an evaporator-surface humidity sensor and a robust threshold, which isn’t always practical. Flow-rate-based termination would need precise flow measurements that don’t directly reflect frost melt and can be affected by fan speed and ducting. Sound level isn’t a reliable indicator of frost status. So terminating defrost by time is the best-fit method in typical practice.