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  1. #1
    Join Date
    Jun 2013
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    1

    Default Two Black and Two White wires for GFCI

    I recently purchased an older home and wanted to install GFCI outlets in the kitchen. When I opened up the outlet, there were four wires (two black and two white) in addition to the ground. I watched a few videos ****** about installing GFCI outlets, but they only gave guidance about doing it when there's one black, one white and the ground. Currently, the two-prong outlets have all four wires attached - the two black wrapped around screws on one side and the two white wrapped around screws on the other side. What do I do with these "extra" black and white wires on the GFCI outlets? Attach them somehow or tie them off? Also, the ground wire is attached to a screw in the rear of the outlet box. Is that "alright"? That is, can I leave it like that and the new GFCI outlet will be grounded. Thanks in advance.

  2. #2
    Join Date
    Sep 2012
    Location
    Boston
    Posts
    820

    Default Re: Two Black and Two White wires for GFCI

    the black wire that's live and the corresponding white one get attached to the bottom two screws on the GFCI, black to g-old and white to silver. the other white and black wires go to the top two screws and feed other outlets. the copper wire that's attached to the box should stay attached to the box and the other end of it will attach to the green screw on the GFCI outlet.

  3. #3
    Join Date
    Aug 2007
    Posts
    6,481

    Default Re: Two Black and Two White wires for GFCI

    Quote Originally Posted by MLB Construction View Post
    the black wire that's live and the corresponding white one get attached to the bottom two screws on the GFCI, black to g-old and white to silver. the other white and black wires go to the top two screws and feed other outlets. the copper wire that's attached to the box should stay attached to the box and the other end of it will attach to the green screw on the GFCI outlet.
    More simply, the GFCI terminals should be marked with "Line" and "Load". Your incoming hot wires connect to the "Line" terminals as described by MLB, the second set of wires connect to the "Load" terminals, ground, of course, goes to ground terminal, pigtail the two lines with a short wire to attach to the ground terminal of the GFCI.
    I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!

  4. #4
    Join Date
    Jan 2011
    Location
    Columbiana, Alabama
    Posts
    623

    Default Re: Two Black and Two White wires for GFCI

    Good answers guys. One SET of wires is the feed to the GFCI and the other (2nd set) can protect other outlets. Be careful to keep the black & white wires paired as they leave the cable, or the circuit may not work.

    In a kitchen countertop, the 2nd set probably feeds more countertop receptacles, per Code.

    However, there may be times when we would not want to protect downstream receptacles so, both pairs of wires should be landed on the "line" side of the GFCI.

    Those times could be when the downstream receptacles are located far away from the GFCI, in violation of Code. Then, if the GFCI tripped it could confuse the homeowner trying to restore power.

    And, long lengths of downstream wiring may add so much leakage that the GFCI might trip, without there actually being a ground fault problem.
    Good Luck from Columbiana, Alabama
    Maurice Turgeon, Hidden Content

  5. #5
    Join Date
    Sep 2012
    Location
    Boston
    Posts
    820

    Default Re: Two Black and Two White wires for GFCI

    thanks semi....you taught me something there

  6. #6
    Join Date
    Jan 2011
    Location
    Columbiana, Alabama
    Posts
    623

    Default Re: Two Black and Two White wires for GFCI

    Quote Originally Posted by MLB Construction View Post
    thanks semi....you taught me something there
    Yer welcome MLB, try to keep your powder dry up there
    Good Luck from Columbiana, Alabama
    Maurice Turgeon, Hidden Content

  7. #7
    Join Date
    Jul 2010
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    SoCal
    Posts
    5,081

    Default Re: Two Black and Two White wires for GFCI

    Semi,

    What does the code say about close downstream receptacle? how far?

  8. #8
    Join Date
    Jan 2011
    Location
    Columbiana, Alabama
    Posts
    623

    Default Re: Two Black and Two White wires for GFCI

    Hi dj, actually the Code doesn't say how far one can install a downstream receptacle from the GFCI, the closer the better.

    They just say something like it must be accessible. I've seen folks set one in the basement, near a panel, and it gets covered up with stuff. When it trips the HO has not idea how to restore power.

    Personally, if the downstream receptacle is longer than 50 ft away or in a damp/wet location I install a GFCI at that location and not try to protect anything downstream. I may install several GFCI's on a single circuit, if they're outside.

    Even new Romex will have more leakage than any other wire. And, shouldn't be run outside.
    Good Luck from Columbiana, Alabama
    Maurice Turgeon, Hidden Content

  9. #9
    Join Date
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    Default Re: Two Black and Two White wires for GFCI

    Thanks for the info !

  10. #10
    Join Date
    Jan 2011
    Location
    Columbiana, Alabama
    Posts
    623

    Default Re: Two Black and Two White wires for GFCI

    Quote Originally Posted by dj1 View Post
    Thanks for the info !
    Yer most welcome dj1, stay safe!
    Good Luck from Columbiana, Alabama
    Maurice Turgeon, Hidden Content

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