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Thread: Supplying 110 receptacles from 240v breaker?

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    DIY Member DVMSteve's Avatar
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    Default Supplying 110 receptacles from 240v breaker?

    Finished with the plumbing and framing, I've moved on to wiring for my basement remodel, and I have a question about wiring receptacles. There are already many on the basement walls, about 6' off the floor, some of which feed first floor receptacles. My original plan was to re-wire these, and feed all of the ones to the new bedrooms and play room. Then I had a thought...

    I now have a separate 15 amp circuit, 240v, wired with 12-2 w/ ground, which supplies a wall heater for the bathroom. Low amp draw with it wired to only 1000 watts. My wife didn't really want this, thinking that the boys would rarely use it. My thought was that I may be able to use this to feed all the new receptacles. I don't think I could do it with the 12-2 wire, no neutral. BUT... is it possible to use 12-3 instead? Then I think it could work this way:

    Using 12-3 w/ground: black and red hot from the 240v breaker, white to neutral bus, and ground to ground. At the heater switch box: red to red, black pigtails to black and then feeds receptacles downstream, as do white and ground.

    I'm pretty sure this would work fine, but I don't know if there are good reasons I shouldn't do it this way, both electrically and for code reasons. Also, if acceptable, is there any way to do it with 12-2? Any input would be appreciated.

    Thanks,
    Steve

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    Retired Defense Industry Engineer jadnashua's Avatar
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    IF the instructions for the heater call for it to be on a dedicated circuit, it's not allowed to share it with other things (this is often the case on that sort of item and is called out in the installation instructions). Keep in mind, things like wired heaters need to allow for derating, so that 1Kw is effectively quite a bit more, and thus, that load is already pushing the limits.

    It's not uncommon to use what is called a shared neutral to supply receptacles from a dual-pole breaker. Often, when this is done, they break the tab between the two sockets and feed the top and bottom with separate lines, this allows higher powered things to be installed (since it is two circuits). Because the phases are opposite, the neutral doesn't need to be twice the size since any current on one side through the neutral can't exceed the breaker's limit, and if there's an equal amount on the other side, the neutral has effectively zero current in it.

    You can't run a separate neutral - it must be within the jacket of the wire you're using, so you'd need 12/3. And, assuming you want to keep the heater...run a new circuit for the rest of the project. Keep in mind, the bathroom will require a dedicated 20A circuit for the receptacle there - it can't go anywhere else and must stay in the bathroom. It also requires a GFCI protection, whether via a receptacle or a CB (doesn't matter which).
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Member DVMSteve's Avatar
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    Thanks, Jim. The install manual for this unit says it doesn't need a dedicated circuit. "Power can be tapped from a nearby circuit depending on the heater wattage required and the amperage rating of the circuit. Heater can be converted to half-wattage to avoid overloading such circuits" Their recommendation is approx 10 w per sq. ft. This bathroom is about 85 sq ft, including the shower with it's glass door that will be closed. If I wire this heater to 1000 watts (factory as shipped it is 2000), it will pull 4.17 amps. Manual says 8.33 amps if I leave it at 2000watts.

    I do have a 20A GFCI protected dedicated circuit for the bathroom receptacles already. It looks from this that I can go ahead with a 12-3 wire according to my original post then; I'll use the existing 12-2 for a lighting circuit. I still have plenty of room left in the panels (I put in 2 200A panels when I wired the house originally).

    Have you dug out from the storm yet?

    Best wishes,
    Steve

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    Test, Don't Guess! cacher_chick's Avatar
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    You will need to pay attention to the more recent code changes, which most municipalities have picked up on. Living spaces (including finished basement areas) must have AFCI protection. Unfinished basement area receptacles must have GFCI protection.
    All of your new receptacles must be rated tamper-resistant.
    Last edited by cacher_chick; 02-11-2013 at 04:13 PM.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    The storm had some pretty distinct lines of demarcation...we got officially 'only' 19", and it wasn't too bad. Only a few miles closer to the coast, and higher areas, got hit much harder...being retired, I just looked at it and said 'glad I don't have to go out in this!'
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Member DVMSteve's Avatar
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    Weird; I typed a lengthy reply this morning, hit "Post", and then my iPad went kerflooey. Wouldn't navigate back to the website and kept giving me a "URL not found" or some such error message. Now from work a much shorter reply...

    GFCI and tamper proof, check. AFCI....oops. Thanks for the reminder. I'm sure the inspector would have found that, but good to fix this before he arrives!

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