I have an old wall mounted electric heater. It takes 240v. I only see two wires that it’s connected to and at the breaker box it’s only connected to one breaker. The breaker that it’s on only has one switch. It’s not like a double breaker that I see for laundry dryers.

How is this 240v device only connected to a single breaker?

I 'know' this because that is the only breaker that causes my non-contact voltage detector to beep.

Updated breaker closeup schematic wiring diagram

  • 3
    add a photo of the breaker showing the wiring.
    – Jasen
    Commented May 1 at 10:05
  • 1
    Some double breakers have only one switch. Does the breaker have two screws with wires on them(like double breakers)?
    – crip659
    Commented May 1 at 10:40
  • 5
    In Europe, this is the norm :)
    – fraxinus
    Commented May 1 at 11:01
  • 3
    Easy way to check: shut off all breakers but 11, see if it still heats. If so, it sure seems like it's only getting 120V from one breaker. If it doesn't, try turning on the other breakers one at a time to see what's going on. Commented May 2 at 4:17
  • 4
    Voltage detectors are flaky and weird. Don't check what it does to the voltage detector, check what it does to the heater. Commented May 2 at 6:03

1 Answer 1


Many older 240V devices only have two wires. Today they would have 3 with the 3rd one being a ground lead. There is no need for the NEUTRAL for things like your electric hot water heater and so only 2 wires, HOT1 and HOT2 (usually black and red) are used.

Not all 240V breakers have two reset handles. Some are designed that way but others have only a single. But the key difference is that it should have TWO HOT connections on it instead of just one like the 120V breakers have. Depending on the design of the panel, they are usually twice as wide so they can connect to both of the HOT planes in the panel.

  • 1
    Black and red cables are usually only used if it needs neutral. Most people will cheap out and use white for the second hot, use a /2 cable instead of a /3 cable. Conduits must use hot colours.
    – crip659
    Commented May 1 at 12:29
  • 3
    The OP's breaker is single-width :/ Commented May 2 at 0:26
  • 5
    single width, and it also has "1 pole" written on the label
    – Jasen
    Commented May 2 at 4:17
  • Since I moved in we have never used the heater. Also we’ve upgraded the panel bc the previous one was really old and potentially a fire hazard. I will try to unmount the heater and take voltage readings at the wires. Will try voltage between wire 1 and 2. Then voltage between 1 and ground(it it’s connected). Then voltage between 2 and ground. Does that sound correct?
    – milesmeow
    Commented May 2 at 14:30
  • @milesmeow: Yes, that will confirm whether you really have 240V or 120.
    – keshlam
    Commented Jun 1 at 15:38

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.