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shd106
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.

MLB Construction
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.

A. Spruce
Re: Two Black and Two White wires for GFCI
MLB Construction wrote:

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.

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.

MLB Construction
Re: Two Black and Two White wires for GFCI

thanks semi....you taught me something there

Re: Two Black and Two White wires for GFCI
MLB Construction wrote:

thanks semi....you taught me something there

Yer welcome MLB, try to keep your powder dry up there:)

dj1
Re: Two Black and Two White wires for GFCI

Semi,

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

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.

dj1
Re: Two Black and Two White wires for GFCI

Thanks for the info !

Re: Two Black and Two White wires for GFCI
dj1 wrote:

Thanks for the info !

Yer most welcome dj1, stay safe!

drewp
Re: Two Black and Two White wires for GFCI

Mr. Semi, In an outdoor location, with a long(er) run as you describe, you mention putting multiple GFI's in line. I'm assuming they would all run off of the line side of each other?

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