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So I just bought my first house and in lieu of changing loads of outlets in the kitchen for GFCI outlets I went with two 20A GFCI breakers. Upon going to install the breakers I found that the cable which feeds to my kitchen contains 2 hot conductors and 1 grounded ("neutral") conductor.

Is there any way I can connect both GFCI breakers to this cable? I tried splitting the neutral between both breakers and found that they both immediately trip.

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    You have a multiwire branch circuit. I think the only way to protect it with a GFCI is with a 2 pole GFCI breaker. As you discovered, trying to share the neutral across 2 GFCI's leads to nuisance tripping (which is a good thing since it'd be a safety hazard if one of the GFCI breakers tripped and the other didn't). There's some debate over the safety of Multiwire branch circuits in general. – Johnny Aug 12 '15 at 0:32
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You need to install a 20 ampere double pole GFCI breaker, instead of two single pole breakers.

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  • I see what you had said on a previous post regarding gfci outlets. So this should be possible with a two pole gfci breaker? What amperage should I use? Currently they are 2 separate 20 amp breakers. – Scott Aug 12 '15 at 1:21
  • @Scott 20 amperes. – Tester101 Aug 12 '15 at 1:34
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There isn't a way that you can use a GFCI breaker on this circuit.

The way a GFCI works, roughly speaking, is by measuring the current leaving on the hot wire and comparing it to the current returning on the neutral. The two currents should be identical – any difference is indicative of current "escaping" via a different ground path, possibly through a person.

The circuit you describe uses two out-of-phase (if they are wired correctly) hot wires that share a neutral. This configuration saves a bit on the cost of the wire, since you can run two circuits on three conductors instead of four, but it means that you loose the ability to use a GFCI on the circuit since the return current on the neutral will almost certainly not match the current on the hot wire(s).

Since you've been working on this circuit it would be a good idea to confirm that the two hot wires (the red and black ones) are indeed wired out of phase. They should be on adjacent poles in the breaker panel, or if they aren't for some reason make sure that they are on breakers that are out of phase (you can check this either by inspection or by measuring the voltage between the breakers, it should be around 240 Volts).

The safety concern with this type of circuit is that you potentially have two loads that, if the both failed, could expose you to 240 Volts between them.

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  • Thanks a ton! Since both of those breakers are right next to each other, would it be possible to use a dual pole gfci breaker to power this circuit? If so, what amperage? It is currently powered by two 20 amp breakers. Or is this a foolish idea and I need to just install the outlets? – Scott Aug 12 '15 at 1:15
  • You didn't mention what brand your panel is, but yes, 2 pole GFCI breakers are available. For example: homedepot.com/p/…. They aren't cheap, but that's a different issue. :-) – Craig Aug 13 '15 at 8:27

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