Heating, Ventilation, and Air Conditioning (HVAC ) Electrical Practice Test

What is the minimum number of wires required between two Start/Stop push button controls?

1. 1

2. 2

3. 3

4. 4

The correct answer is: 3

In a typical control circuit for a motor, the minimum number of wires required between two Start/Stop push button controls is determined by the need for operational functionality and safety. For the Start/Stop control mechanism to work effectively, one wire is needed for the power supply and another for the return path. However, the Start and Stop functions necessitate additional wiring for proper control signaling and operation. Specifically, one wire is used for the Start button, usually wired to supply voltage, and another wire is used for the Stop button, which usually connects to the control circuit to break the circuit. A third wire is often required for a common return path or to connect back to the control panel or relay. This setup allows the Start button to momentarily engage the circuit while the Stop button can open it, thus stopping the motor. Thus, three wires are essential to ensure that all necessary connections are made for both the Start and Stop functions, allowing the circuit to operate correctly. This configuration also ensures that the system can be safely engaged or disengaged from operation.