What is the function of a contactor in an HVAC system?

What is the function of a contactor in an HVAC system?

• A. It regulates refrigerant flow to the evaporator.
• B. It senses room temperature and adjusts setpoint.
• C. It acts as a fuse for the compressor.
• D. It is an electromagnetic switch that closes or opens the power circuit to the compressor and outdoor fan when the control circuit energizes the control relay.

Answer: (D)

The main idea is that a contactor acts as a heavy-duty switch controlled by a low-voltage signal. It uses an electromagnetic coil; when the control circuit energizes the coil, the contacts close and power flows to the outdoor compressor and condenser fan. When the control signal drops, the coil releases and the contacts open, cutting power. This lets the thermostat or control circuit safely switch high-current equipment without running that load through the low-voltage controls. It isn’t used to regulate refrigerant flow, sense room temperature, or act as a fuse.

The main idea is that a contactor acts as a heavy-duty switch controlled by a low-voltage signal. It uses an electromagnetic coil; when the control circuit energizes the coil, the contacts close and power flows to the outdoor compressor and condenser fan. When the control signal drops, the coil releases and the contacts open, cutting power. This lets the thermostat or control circuit safely switch high-current equipment without running that load through the low-voltage controls. It isn’t used to regulate refrigerant flow, sense room temperature, or act as a fuse.