Defrost systems can be terminated by

Defrost systems can be terminated by

• A. Time
• B. Pressure
• C. Temperature
• D. Any of the above

Answer: (D)

Defrost termination is determined by stopping conditions that show the ice has melted and the system can return to normal operation. A timer can terminate defrost after a predetermined duration, ensuring the cycle ends even if sensors don’t reach a specific setpoint. A temperature sensor on the evaporator coil provides a direct indication that the coil has warmed enough and frost has melted, so the cycle ends when the coil reaches the defined temperature. A pressure switch or sensor can also signal the end of defrost by detecting that refrigerant pressures have returned to normal after heating, indicating the system can resume regular cooling. Because different control schemes use different signals to determine completion, any of these methods can terminate a defrost cycle. Modern controls may even combine two or more of these signals for reliability.

Defrost termination is determined by stopping conditions that show the ice has melted and the system can return to normal operation. A timer can terminate defrost after a predetermined duration, ensuring the cycle ends even if sensors don’t reach a specific setpoint. A temperature sensor on the evaporator coil provides a direct indication that the coil has warmed enough and frost has melted, so the cycle ends when the coil reaches the defined temperature. A pressure switch or sensor can also signal the end of defrost by detecting that refrigerant pressures have returned to normal after heating, indicating the system can resume regular cooling. Because different control schemes use different signals to determine completion, any of these methods can terminate a defrost cycle. Modern controls may even combine two or more of these signals for reliability.