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  1. #1
    Join Date
    Sep 2013
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    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
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    Fayette County, Ohio
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    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
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    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
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    Jun 2007
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    Fayette County, Ohio
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    5,775

    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
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    693

    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
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    65

    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
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    693

    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

  8. #8
    Join Date
    Aug 2011
    Location
    Northern Indiana
    Posts
    65

    Default Re: Weird shared nuetral w/ double breaker

    [QUOT=The Semi-Retired Electric;282318]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.[/QUOTE]

    Breakers with handle ties are not 2 pole circuit breakers. 2 pole (and 3pole) circuit breakers are manufactured with internal common trip unless otherwise labeled. You are correct that MWBC's can use handle ties or multi-pole breakers.

  9. #9
    Join Date
    Sep 2013
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    4

    Default Re: Weird shared nuetral w/ double breaker

    Upon further investigation and looking over my notes from years ago (been living here 28 years). I removed several circuits when I first moved in as the house had electric heat. I discovered then that there were two circuits installed that were using one of the neutrals from one of these circuits so I removed the hots but had to leave the neutral intact so the other circuits would continue to work. Later, when my kitchen was remodeled I added several new circuits for appliances, counter receptacles, recessed lighting, and under-cabinet lighting. In the process I also removed a circuit which was one leg of the double breaker which terminated with the black wire. SO, what I am left with is a single circuit where the neutral is no longer shared but the circuit is using a white wire from one wire bundle as the hot and another white wire in another bundle as a neutral. It looks weird but the only thing off is the color of the hot wire, which I have now marked black for the first three inches. Glad I kept notes.
    As for the relay switch, it switches both the hot and neutrals as the neutral and ground are bound at the generator and cannot be bound again at the panel.

  10. #10
    Join Date
    Jan 2011
    Location
    Columbiana, Alabama
    Posts
    693

    Default Re: Weird shared nuetral w/ double breaker

    Quote Originally Posted by brrichter View Post
    [QUOT=The Semi-Retired Electric;282318]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.
    Breakers with handle ties are not 2 pole circuit breakers. 2 pole (and 3pole) circuit breakers are manufactured with internal common trip unless otherwise labeled. You are correct that MWBC's can use handle ties or multi-pole breakers.[/QUOTE]

    Granted a small percentage of double or three pole breakers have only one trip handle.
    But, most have a handle for each "phase" and employ internal trip and the handles handles are always tied together.

    The internal trip ensures all the "phases" will open together but the tie handle may allow a "phase" remain closed.

    I don't understand what you mean "Breakers with handle ties are not 2 pole circuit breakers".
    Good Luck from Columbiana, Alabama
    Maurice Turgeon, Hidden Content

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