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

Which switch impacts the operation of the blower motor in AUTO mode?

1. The thermal expansion valve

2. The high pressure switch

3. The thermostat setting

4. The relay control

The correct answer is: The thermostat setting

The thermostat setting plays a crucial role in determining how and when the blower motor operates in AUTO mode. When the thermostat is set to a desired temperature, it monitors the ambient temperature of the space. If the temperature rises above or falls below this setpoint, the thermostat signals the HVAC system to either heat or cool the area. In AUTO mode, the blower motor will operate when needed, based on the signals received from the thermostat to either distribute warm or cool air as per the set temperature. In this context, other components like the thermal expansion valve, high pressure switch, and relay control have their specific functions. The thermal expansion valve regulates the flow of refrigerant in the system, while the high pressure switch monitors system pressure and can protect against issues like refrigerant flooding. The relay control is essential for connecting electrical circuitry, but it does not dictate the operating conditions of the blower motor. Therefore, the thermostat setting is the key factor influencing the blower motor's operation in AUTO mode.