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

What voltage is found from terminal Y to the output side of the coil on line #11?

1. 24 volts

2. 0 volts

3. 120 volts

4. 240 volts

The correct answer is: 0 volts

To understand why the voltage from terminal Y to the output side of the coil on line #11 is 0 volts, consider the typical arrangement of control circuits in HVAC systems. Terminal Y is often associated with the thermostat, which sends a signal to energize the contactor and start the compressor or the fan. When this terminal is not energized, which is often the case when the system is not calling for cooling or heating, there will be no voltage present at the coil output of line #11. In HVAC systems, when the control circuit is de-energized, it results in a scenario where the voltage measured across terminals that would normally carry current to activate the devices will read 0 volts. This is a standard condition of electrical control circuits when they are not engaged in operation. In contrast, other voltage levels such as 24 volts, 120 volts, or 240 volts would indicate that the control or power circuit is energized. However, in this specific scenario, identifying that the Y terminal is not engaged confirms that no voltage is present at the coil, leading to the conclusion that the voltage measured is indeed 0 volts.