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  1. #1
    Join Date
    Sep 2013
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    4

    Default Weird shared nuetral w/ double breaker

    I was in the process of installing a transfer switch that switches both hot a neutral wires on the circuit when I ran into a strange configuration. The circuit in question has a double pole 15 amp breaker with the white wire from the circuit going into one breaker and the black going into the other. My assumption was that these were two circuits with a shared neutral running back to box fron another circuit somewhere in the house. However, when I disconnect the black wire from the breaker and leave the white wire connected the circuit seems fine. When I disconnect the white wire leaving the black connected the circuit appears dead. I'm not sure what is going on and I'm not sure what the black wire is supplying when connected to the breaker as I can't find any outlets, lights, or appliances down when the black is connected. This begs the question, where is the power in the black wire going? Any help would be appreciated.

  2. #2
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,844

    Default Re: Weird shared nuetral w/ double breaker

    If it is on a double breaker it is a 240 Volt circuit with the black and white wires supplying a different legs.

    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  3. #3
    Join Date
    Sep 2013
    Posts
    4

    Default Re: Weird shared nuetral w/ double breaker

    This circuit appears to be two 120v circuits rather than 1 240 volt circuit and it must have a shared neutral somewhere but how can I find out which neutral is being used on the circuit? The black wire appears to go to another circuit but I cannot locate it.

  4. #4
    Join Date
    Jun 2007
    Location
    Fayette County, Ohio
    Posts
    5,844

    Default Re: Weird shared nuetral w/ double breaker

    If that is true then it is not to code and should be redone by a professional. Double breakers are never used in
    multi wire branch circuits, and the white is only used as a hot in a 240 volt circuit or a switch loop.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  5. #5
    Join Date
    Jan 2011
    Location
    Columbiana, Alabama
    Posts
    739

    Default Re: Weird shared nuetral w/ double breaker

    Some generators require both the hot and the neutral be switched by the transfer switch.

    Some just tie the neutrals together and transfer the hots.

    Some double pole breakers called "tandem" are just 120V to neutral on both screws (and 0 volts from screw to screw) because they are connected to the same stab in the panel.

    Multi-Wire Branch circuits (MWBC) measure 240V from screw to screw and share the same neutral. They measure 120V from any screw to neutral.

    Please provide more info.
    Good Luck from Columbiana, Alabama
    Maurice Turgeon, Hidden Content

  6. #6
    Join Date
    Aug 2011
    Location
    Northern Indiana
    Posts
    78

    Default Re: Weird shared nuetral w/ double breaker

    Quote Originally Posted by JLMCDANIEL View Post
    If that is true then it is not to code and should be redone by a professional. Double breakers are never used in
    multi wire branch circuits, and the white is only used as a hot in a 240 volt circuit or a switch loop.
    Jack
    Two pole breakers ARE used and on multiwire branch circuits, especially if handle ties are not present.

  7. #7
    Join Date
    Jan 2011
    Location
    Columbiana, Alabama
    Posts
    739

    Default Re: Weird shared nuetral w/ double breaker

    Quote Originally Posted by brrichter View Post
    Two pole breakers ARE used and on multiwire branch circuits, especially if handle ties are not present.
    True 2 p breakers are used on MWBC but only if they have a handle tie.

    However they don't have to have internal trip. Meaning someone could have two SP breakers, attach a handle tie between them and use them on a MWBC. Not a great idea, IMO.
    Good Luck from Columbiana, Alabama
    Maurice Turgeon, Hidden Content

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