Which device is typically used to switch large electrical loads in HVAC systems?

• A. Relay
• B. Contactor
• C. Starter
• D. Switch

Answer: (B)

Contactor is the device typically used to switch large electrical loads in HVAC systems. Think of it as a heavy-duty relay designed to handle the high current drawn by motors, compressors, and large fans. It is controlled by a low-voltage coil from the control circuit or thermostat, and when energized, it closes the main contacts to supply power to the equipment. Contactors are built to handle inductive inrush and continuous loads, and they often come in multiple poles to match the motor or equipment configuration. A starter may include overload protection and is used specifically for starting motors, while a general switch or a smaller relay isn’t suited for reliably switching such high loads in an HVAC environment.