The low - pressure switch opens its contacts

The low - pressure switch opens its contacts

• A. On a drop in discharge pressure
• B. On a drop in suction pressure
• C. At the end of each operating cycle
• D. At the beginning of each operating cycle

Answer: (B)

The test centers on how a low-pressure switch uses the suction (low) side to protect the system. This switch is wired to monitor suction pressure, and its contacts open when that pressure falls below a safe setpoint. When suction pressure drops, it means the evaporator may be starved of refrigerant, the compressor could be at risk of oil starvation, or the system could be damaged by improper boiling. Opening the contacts cuts power to the compressor, stopping the cycle to prevent damage. This isn’t triggered by changes on the discharge side, nor is it tied to the start or end of an operating cycle. It’s a protective, pressure-threshold device that responds specifically to suction pressure levels.

The test centers on how a low-pressure switch uses the suction (low) side to protect the system. This switch is wired to monitor suction pressure, and its contacts open when that pressure falls below a safe setpoint. When suction pressure drops, it means the evaporator may be starved of refrigerant, the compressor could be at risk of oil starvation, or the system could be damaged by improper boiling. Opening the contacts cuts power to the compressor, stopping the cycle to prevent damage.

This isn’t triggered by changes on the discharge side, nor is it tied to the start or end of an operating cycle. It’s a protective, pressure-threshold device that responds specifically to suction pressure levels.