Capacity control of a reciprocating hermetic compressor is typically achieved through the operation of which component?

• A. Hot gas bypass valve
• B. Thermostatic expansion valve
• C. Condenser fan
• D. Suction pressure regulator

Answer: (A)

Capacity control in a reciprocating hermetic compressor is achieved with a hot gas bypass valve. By routing part of the high‑pressure discharge gas back to the suction side, the valve raises the suction pressure and lowers the compressor’s pressure ratio, effectively unloading the cylinders and reducing the amount of refrigerant the compressor moves. This allows the system to modulate capacity without stopping the compressor. The other components serve different roles (the thermostatic expansion valve controls evaporator refrigerant flow, the condenser fan affects heat rejection, and a suction pressure regulator isn’t the typical primary method for trimming compressor capacity).