Wiring a 220 Volt Furnace

By Dave Rongey Summary: Electrical Wiring Question: 220v electric furnace hook up. for a furnace. I have installed a 220v electric furnace but have not finished the wire hook up and need some help.

How to Wire a 220Volt Electric Furnace

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Electrical Question from Ray
Wiring Project: A 220v electric furnace hook up.
Additional Info: I have installed a 220v electric furnace but have not finished the wire hook up.
The wiring diagram shows L1 and L2 for the hot sides (red and black) and the ground is separate. There is not a place to hook up the neutral (white) wire.

Some info I have found shows that a furnace can be run with only two hot lines and a ground line. I have already wired my whole house, garage, hot tub, and shop and all is up to the electrical code. I don't want to make a boo boo now. Any info to would be helpful.
Thanks Ray


Hi Ray,
I understand your question, a lot of people get confused with 220 Volt circuits and just what to do with the extra white wire. I remember long ago asking my Dad about this as well.

220Volt or 240Volt Circuit
The bottom line is this, if the nameplate calls for a 220 or 240 volt circuit then with few exceptions is there ever a need for a neutral wire. One exception would be hot tubs where there is a GFCI breaker installed which has a separate neutral.

If there is no termination for a neutral and the instructions do not call for a 3-wire circuit with a ground then a neutral is not needed. But with equipment such as air conditioners, and in this case a 220 volt electric furnace, a neutral is not needed, only the ground wire.

What to Do with a Spare Wire
So just cap the neutral off because its a spare wire, (better to have too many than not enough!). In the future I'm sure we will start to see a required neutral which has already begun with electric ranges and clothes dryers.

L1 and L2 Wiring
As you mentioned, the L1 and L2 are the 2 hot lines coming in and it does not matter which one goes where.

Make sure your ground wire is attached to the provided ground lug or terminal, and back at the panel bond the ground as well. It sounds like you have been busy wiring your home, good for you!
Did you include interlinked smoke detectors and GFI's in the appropriate locations? I'll bet you did if it is all up to code.
Let me know if this helps.