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Thread: Two GFCI Receptacles on 3-wire Circuit?

  1. #1
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    Default Two GFCI Receptacles on 3-wire Circuit?

    I'm armpit deep in a kitchen rennovation. I am planning to add a 20Amp-T-slot GFCI duplex receptacle on either side of the sink. I've run 12/3 to the first outlet, and 12/3 to the second outlet. I was planning feeding each GFCI from the different legs of the multiwire circuit.

    Homer has posted in another thread:

    "You can't protect both legs of a multiwire circuit with two GFCI receptacles.....however if you split the multiwire circuit into two circuits where the neutral is no longer shared, then you can protect those two circuits with one GFCI receptacle on each circuit. So, you can run one 3-wire multiwire circuit into the first box, and splice into two 12/2 or 14/2 cables so the neutral is no longer shared. These two circuits can then be protected by GFCI receptacles."

    I'm having trouble to conceptualize how this is different from a shared neutral situation. Isn't it still a shared neutral?
    "If you think education is expensive - try ignorance." (Bok's law)

    Steve
    IP

  2. #2

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    Doing it Homer's way means you are not sharing the neutral downstream of either device. You are feeding each device with it's own neutral. You are splitting the neutral before each GFCI (by using 12/2 not 12/3 as you said).
    IP

  3. #3
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    Here's an example setup that hopefully shows that the downstream neutrals are not shared.

    Remember, everything is powered somehow from a shared neutral or multiwire circuit. There's only 3 wires entering your home from the POCO transformer.

    Also, you could use a multiwire circuit to power alternate GFCI receptacles in a string. That is Blk & Wht, Red & Wht, Blk & Wht, etc. The thing to remember in this case is that you can't use the 'load' terminals of the GFCIs. You would need a GFCI in every location.

    Homer
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    Last edited by Homer; November 3rd, 2004 at 07:50 PM.
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  4. #4
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    I guess I wasn't entirely thinking clearly at 3am or so when I pulled through the 12/3 from 1st GFCI receptacle to the 2nd. The second leg would be carried by 12/2 just fine.

    Are you saying that if I pigtail the neutral to the first GFCI, I can keep the neutral going to the 2nd GFCI? Or are you saying that you must physically splice in a tiny length of 12/2 to join from the 3-wire feed to the first GFCI. There won't be any receptacles downstream of either receptacle.

    Sleep deprivation is like alcohol...neither one mixes well with planning out multiwire circuits

    Thanks for your help/patience.

    PS. Excellent sketches Homer
    "If you think education is expensive - try ignorance." (Bok's law)

    Steve
    IP

  5. #5
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    Great schematic Homer! The receptacles being placed in the schematic makes for a good understanding!
    Learning brings success. While you are waiting, I'm getting better!
    IP

  6. #6
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    Are you saying that if I pigtail the neutral to the first GFCI, I can keep the neutral going to the 2nd GFCI?
    Yes.

    Or are you saying that you must physically splice in a tiny length of 12/2 to join from the 3-wire feed to the first GFCI.
    No, you may wire one of the HOT wires of the 3-wire supply directly to the LINE side of the first GFCI receptacle.

    Here is a sketch of the alternate method that I mentioned also.

    Homer
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    Last edited by Homer; November 3rd, 2004 at 10:00 PM.
    IP

  7. #7
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    Ok, I can do this. Both diagrams make sense to me.

    I'm still struggling with the idea of "shared neutral". Are we talking about a situation where the neutral goes to the line terminal on the first GFCI, then goes from the load terminal on the first GFCI to the line terminal on the second GFCI without pigtails? 'Cause that just wouldn't work, right.

    I've got to get some sleep. Maybe tomorrow I will understand the "doesn't work" scenario.
    IP

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    Oops. The "unregistered" is me.
    "If you think education is expensive - try ignorance." (Bok's law)

    Steve
    IP

  9. #9
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    Homer if you have the time can you please post a diagram of the wiring method that will NOT work, such as where you said "You can't protect both legs of a multiwire circuit with two GFCI receptacles".
    Thanks.
    ________
    Last edited by jeff1; February 1st, 2012 at 08:25 AM.
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  10. #10
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    Quote Originally Posted by Guido
    Homer if you have the time can you please post a diagram of the wiring method that will NOT work, such as where you said "You can't protect both legs of a multiwire circuit with two GFCI receptacles".
    Thanks.
    Here is the classic example of an attempt to protect a split receptacle on a multiwire circuit by using 2 GFCI receptacles instead of a 2-pole GFCI breaker.

    Homer
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