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GFCI on Multiwire Branch circuit

Posted by ardmi (My Page) on
Tue, Nov 19, 13 at 7:39

I have a GFCI on a multiwire branch circuit. In the box is a hot, neutral and ground going to the gfci. Off the load side of the GFCI is one (1) other outlet. The circuit does not extend past that outlet.

Is that correctly wired in regards to multi wire branch circuits?


Follow-Up Postings:

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RE: GFCI on Multiwire Branch circuit

Is it working correctly? Any problems evident? From your description, the installation is correct.


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RE: GFCI on Multiwire Branch circuit

All the GFCI needs is that the wires on the protected (load side) do not come into connection with any OTHER conductors. It doesn't care if it is fed from a MWBC. What you can't do is share the neutral on the protected side with something else (either the other side of the MWBC or even with another GFCI on the same circuit for that matter).


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RE: GFCI on Multiwire Branch circuit

Thank you, I knew there was an issue somewhere with MWBC and GFCI (and AFCI for that matter).... I was 99.9 percent positive though that wouldnt be an issue in this case.

Best regards.


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RE: GFCI on Multiwire Branch circuit

One other related question:

I know you have to pigtail the neutrals at the box where the MWBC is connected.

But If I replace an outlet elsewhere on either circuit, do I have to pigtail the neutrals?

Breaking the neutrals there would only kill the circuit, not turn it to 240v?


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RE: GFCI on Multiwire Branch circuit

In other words, my living room is one part of a MWBC. Each outlet is fed to each other using the 4 screws.

Does every outlet on a MWBC need to be pigtailed?


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RE: GFCI on Multiwire Branch circuit

If you have both hot wires and a single neutral present in a box, any receptacle present would need to have the neutral pigtailed. Once you split off the multiwire circuit and have separate neutrals for each hot circuit pigtailing isn't required.

Opening the single neutral on a multiwire circuit will definitely divide loads across 240 volts.


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RE: GFCI on Multiwire Branch circuit

Thank you for the explanation.

Is it considered bad practice to have an outlet prior to the split ??
(in same box with the shared neutrals and both hots)

Or is that standard?


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RE: GFCI on Multiwire Branch circuit

Not a problem. Let me rephrase that...normal outlets on the multi wire ahead of the split are not problems. Once it goes through the GFCI, it has to remain separate.

This post was edited by ronnatalie on Sat, Nov 23, 13 at 17:37


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