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I have two hot wires both supplying power to a single Gfci located in a bathroom. It is only two white two black and two neutral.

Only after investigating through a shock did I learn that it was powered by two separate breakers. I have found people speak about a red wire, but I do not have that. I thought it would be a simple 20 amp gfci to another new 20 amp Gfci.

Now it either trips one way immediately or other way does nothing by swapping load and line back and forth. I have to see what I lose by leaving off one set but did not know if there was something I'm missing that was ok 10 years ago and not now.

It is a trailer built in 1978 but gfci was installed 10 years ago after electrical fire in kitchen. All help would be greatly appreciated.

  • Do you know what else is controlled by each of the two breakers involved in this mess? – ThreePhaseEel May 30 at 3:47
  • With the limited information anything could be the problem, depending on the age of the install, it sound like a MWBC that has been code tor decades but when I was an appearance they just had to be on opposite legs only a few years later they had to have handle ties , same code today but many ahj or the county’s inspection required a dpdt breaker , having trouble with my connection so will just leave this – Ed Beal May 30 at 4:20
  • Having trouble with my connection but a multi wire branch circuit is one with 2 Hotts and 1 neutral with a common brea – Ed Beal May 30 at 4:24
  • Ok my connection sucks now but when I started the he 2. Lines had to be on l1 or l 2 today a double pole breaker or a handle tied breaker, hope this helps – Ed Beal May 30 at 4:28
  • Have you done any resent electrical work and back fed a wire? I have never herd of a gfci were tabs could be broken and have two feeds.Shut down each ,breaker one at a time and trace it out. – user101687 May 30 at 5:53
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NEVER "just try random things"

Why not? Think about it. You are trying things until when? Until it works. The problem is, there are lots of combinations that will work that will kill you.

No. Only do things based on knowledge and understanding. If you don't have enough, get more - either by reading more about electricity, or doing more testing, as needed.

The first rule of hooking up GFCIs

Hook up the LINE terminals ONLY. Fully test. When perfect, then hook up LOAD. And if hooking up LOAD results in a trip, then you know LINE is correct and so you know your problem is on the LOAD side.

The second rule of GFCIs is "Never use LOAD unless you know exactly what you're doing." Instead, pigtail all wires to LINE, or double-tap LINE if the GFCI supports it (most do). Most people have no earthly idea what LOAD actually does... They just know they have 2 extra wires, and look! Two extra screws under that warning tape I didn't read. Most GFCI trouble comes from people using LOAD thoughtlessly or by default.

Your particular situation

First, the thing about the red wire applies to circuits that are not like yours. Don't worry about that.

Yours is likely to be an "accidental ring circuit" (rings are a UK thing, not allowed anywhere else), where your circuit travels a big loop from the breaker through the house and back to the breaker, but in this case it's another breaker. This was a wiring mistake. Wiring layouts are supposed to be "tree style" and never loop back on each other.

If you are able to map this "ring", look for an appropriate place to break it, so it is once again two circuits. There may be an obvious place to do that once you get into it. You are likely to uncover an obvious wiring mistake, which you can then just fix. Or maybe two receptacles side by side in a double box (4 sockets) - wouldn't it be nice if they were served by separate circuits? Anyway, you break it there - take one hot-neutral pair and cap them off.

While you're doing this, be on the lookout for separation of hot and neutral. Neutrals must stay with their partner hot, and not cross over to the hots and neutrals of other circuits. That is because neutrals don't have fuses even though they can burn up just like any other wire! Their protection depends on being fed only by their partner hot. If you see anyplace the neutral isn't with the hot, get rid of it. It's unsafe by itself, and also won't feed properly off LOAD on a GFCI.

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