What device prevents the compressor from re-starting immediately after shutdown due to pressure build-up?

What device prevents the compressor from re-starting immediately after shutdown due to pressure build-up?

• A. defrost control
• B. compressor short-cycle timer
• C. thermostat
• D. blower relay

Answer: (B)

A compressor short-cycle timer is the device that prevents the compressor from restarting too soon after it shuts off. When the compressor stops, refrigerant pressures on the high side can stay elevated and the motor oil needs time to redistribute. If the compressor were allowed to restart immediately, it would experience a high inrush current and mechanical stress from starting under those unfavorable conditions, which hastens wear and increases the risk of nuisance trips or damage. The timer creates a brief delay, typically a couple of minutes, giving pressures to equalize and the system to stabilize before allowing a restart. Defrost control is for managing the defrost cycle on heat pumps, not for delaying compressor restart. The thermostat simply senses room temperature to call for heating or cooling; it doesn’t impose a restart delay after shutdown. The blower relay controls the indoor fan, not the compressor restart timing. So the compressor short-cycle timer is the component that specifically handles delaying re-start after shutdown due to pressure build-up.

A compressor short-cycle timer is the device that prevents the compressor from restarting too soon after it shuts off. When the compressor stops, refrigerant pressures on the high side can stay elevated and the motor oil needs time to redistribute. If the compressor were allowed to restart immediately, it would experience a high inrush current and mechanical stress from starting under those unfavorable conditions, which hastens wear and increases the risk of nuisance trips or damage. The timer creates a brief delay, typically a couple of minutes, giving pressures to equalize and the system to stabilize before allowing a restart.

Defrost control is for managing the defrost cycle on heat pumps, not for delaying compressor restart. The thermostat simply senses room temperature to call for heating or cooling; it doesn’t impose a restart delay after shutdown. The blower relay controls the indoor fan, not the compressor restart timing. So the compressor short-cycle timer is the component that specifically handles delaying re-start after shutdown due to pressure build-up.