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

What voltage is across L1 to L2 in the schematic?

1. 120 volts

2. 240 volts

3. 480 volts

4. 0 volts

The correct answer is: 240 volts

In a typical two-phase electrical system, the voltage measured across L1 and L2 is indicative of the difference in potential between these two phases. When both L1 and L2 are derived from a split-phase power supply, they are out of phase with each other by 180 degrees. In a residential or light commercial setting, when each phase has a nominal voltage of 120 volts to a neutral wire, the voltage across L1 and L2 will combine to result in 240 volts. This is a common configuration used for powering larger appliances that require more voltage, such as electric dryers and ovens. Therefore, observing the system can confirm that when measuring the voltage between the two live conductors, the reading will yield 240 volts as the correct answer. This illustrates the typical workings of a split-phase system, facilitating applications that necessitate higher electrical power.