I would like to hook up a 240 garage heater with wire I had used for a old hot tub. The wire has 4 wires ,red, black, white and ground. The hook up on the heater only has 2 hook ups for a black and white wires and a ground. Can I hook it up with the hot tub wire and what would I do with the red wire. Thanks

  • What make and model is the heater? Can you post photos of its nameplate for that matter? Nov 23, 2020 at 23:50
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    A 240V heater should have a red and black wire. Or black and black. Or any colors that are not white, gray or green. Your neutral from the wall will not be used. Cap it off. Nov 24, 2020 at 0:05

2 Answers 2


Maybe! but read the instructions for over-current protection of your 240 volt heater, you might have to swap out the breaker. Also, make sure the wire gauge size is good for the heater. Larger than needed is OK, smaller is obviously not. As always, wire size, breaker rating and device amperage requirements all need to be considered. But just having an extra conductor in a cable isn't an issue, to actually answer your question. Use the red & black as the hots, the bare copper or green wire as the ground and cap off the white. Double check your voltages to make sure nobody monkeyed anything up.

IMPORTANT UPDATE: JACK mentioned the possibility of this being a 120 volt heater due to the black and white wires. CRITICAL that you make sure this is actually a 240 volt heater. If not, well, lets just say it will get very hot very quickly and probably start a fire if over-temp devices don't trip. Sorry for my answer...it was clearly limited to other possibilities.

  • OP said "240". Either way, no big deal, as long as it is done correctly. Just a matter of hot + neutral (for 120) vs. hot + hot (for 240). Nov 23, 2020 at 23:21
  • Yes, the original question was just about the number of conductors, which if go unused isn't an issue, but JACK made a great point that the OP might have missed. Thanks for the comment. Nov 23, 2020 at 23:23

It appears that you have a 120 volt heater and you should be able to hook it up to your hot tub wires. You would then just disconnect your red wire in the panel. Provide some name plate pictures and we can further help you out with breaker size and actual hookup.

  • Oh man! I missed that. good call, Jack. I assumed OP knew enough that he had a 240 volt heater. I'll update my answer to reflect that (and give credit) to you. Nov 23, 2020 at 23:16

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