Attempting to start a compressor against a(n) _________ in the discharge side can damage the compressor.

Attempting to start a compressor against a(n) _________ in the discharge side can damage the compressor.

• A. high-pressure safety switch
• B. low-pressure switch
• C. overload relay
• D. condenser fan

Answer: (A)

The important idea is protection against starting a compressor when the discharge side already has high pressure. If the compressor tries to start while the discharge is pressurized, it has to work against a large head, which can cause a surge of current, excessive torque, and heat that can damage internal components. A high-pressure safety switch sits in the discharge path and will trip or shut off the compressor when discharge pressure exceeds a safe limit, preventing startup under those unsafe conditions. The other devices don’t provide that specific protection: a low-pressure switch guards against suction-side problems (like low refrigerant), not high head pressure; an overload relay protects the motor from overheating during normal operation but isn’t a preventive measure specific to starting against high discharge pressure; and a condenser fan is part of heat rejection and doesn’t prevent startup against high back pressure.

The important idea is protection against starting a compressor when the discharge side already has high pressure. If the compressor tries to start while the discharge is pressurized, it has to work against a large head, which can cause a surge of current, excessive torque, and heat that can damage internal components. A high-pressure safety switch sits in the discharge path and will trip or shut off the compressor when discharge pressure exceeds a safe limit, preventing startup under those unsafe conditions.

The other devices don’t provide that specific protection: a low-pressure switch guards against suction-side problems (like low refrigerant), not high head pressure; an overload relay protects the motor from overheating during normal operation but isn’t a preventive measure specific to starting against high discharge pressure; and a condenser fan is part of heat rejection and doesn’t prevent startup against high back pressure.