Defrost termination is achieved by time, pressure, and temperature. Which of the following is NOT used as a termination method?

Defrost termination is achieved by time, pressure, and temperature. Which of the following is NOT used as a termination method?

• A. Humidity
• B. Time
• C. Pressure
• D. Temperature

Answer: (A)

Defrost termination is driven by signals that reflect the actual state of the frost melt and the refrigerant circuit. Time provides a safe upper limit so the defrost cycle can’t run indefinitely if conditions don’t change. Temperature feedback is essential because when the outdoor coil reaches a set temperature, enough ice has melted for normal operation to resume. Pressure feedback helps confirm that the refrigerant flow and phase conditions are returning to normal, signaling that the cycle can end. Humidity doesn’t directly indicate the ice condition on the coil or the refrigerant state, so it isn’t used to terminate defrost. Relying on humidity would lead to inconsistent termination since outdoor moisture can vary without corresponding to the melt status.

Defrost termination is driven by signals that reflect the actual state of the frost melt and the refrigerant circuit. Time provides a safe upper limit so the defrost cycle can’t run indefinitely if conditions don’t change. Temperature feedback is essential because when the outdoor coil reaches a set temperature, enough ice has melted for normal operation to resume. Pressure feedback helps confirm that the refrigerant flow and phase conditions are returning to normal, signaling that the cycle can end. Humidity doesn’t directly indicate the ice condition on the coil or the refrigerant state, so it isn’t used to terminate defrost. Relying on humidity would lead to inconsistent termination since outdoor moisture can vary without corresponding to the melt status.