During defrost cycles, which device is used to disable the compressor circuit?

• A. Low ambient control
• B. High pressure switch
• C. Thermostat
• D. Fan control

Answer: (A)

Defrost cycles require temporarily preventing the compressor from running so the outdoor coil can heat and melt the frost without pulling heat from the indoor space. A low ambient control is the device designed to disable the compressor circuit when outdoor temperatures are below a set point, ensuring the defrost process can occur efficiently and safely. The high pressure switch protects the system from abnormally high pressures and isn’t specific to defrost timing; a thermostat governs indoor temperature, and fan control only affects the outdoor fan, not the compressor circuit.