A residential mid or high efficiency furnace or power vented water heater works on which power supply?

• A. 240/1/60
• B. 240/3/60
• C. 120/3/60
• D. 120/1/60

Answer: (D)

These appliances run on standard household electrical power. The blower and power-venting components, along with the control electronics, are designed for 120-volt single-phase power at 60 Hz. That means a typical residential circuit provides one hot and one neutral (120/1/60), which is what these units expect.

The other options would supply either higher voltage or three-phase power, which isn’t how residential gas furnaces and power-vented water heaters are wired. They don’t require the heavier or three-phase power these alternatives imply. So the correct supply is 120/1/60.