NATE Air Conditioning and Heat Pumps Practice Exam

Which of the following electrical components is a power-passing device?

1. Fan motor

2. Fan switch

3. Relay coil

4. Transformer primary coil

The correct answer is: Fan switch

The fan switch is a power-passing device because it directly controls the flow of electrical current to the fan motor. When the switch is turned on, it completes the circuit, allowing electricity to flow to the fan motor, thereby enabling it to operate. This function is crucial in HVAC systems as the fan motor is responsible for circulating air, either in heating or cooling modes. The fan motor, while integral to the system, is not a power-passing device in the same context as the fan switch, since it consumes power rather than controls its distribution. The relay coil serves as an electromagnetic switch that activates the relay to open or close a circuit but does not pass power to the load itself. Similarly, the transformer primary coil operates by stepping down voltage or current in the transformer but does not directly control or pass power in the way a switch does.