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Today I went to replace an old non-GFCI in my bathroom with a GFCI outlet. After completing all the connection, the outlet tripped immediately as soon as it was reset. I disconnected the load side, and the outlet operated normally. I did some continuity tests and found that the line and the load neutrals showed continuity when probed. I assume this is because neutral and ground have continuity somewhere on the load side, which obviously has to be fixed.

I then went downstream of the GFCI to the switch for the vanity lights (which shares a box with another light switch), and found that in addition to the other light switch, there was an additional daisy chain that appears to feed all other outlets and fixtures in the bedroom and adjacent hallway. When I disconnect those wires from the line and cap them off, the GFCI operates as normal, as do the two lights connected to the switches.

So I’ve narrowed it down very slightly, but it seems daunting to try to find the fault from this point forward. I assume I need to leave the chain of outlets disconnected from the line, then check for continuity from neutral to ground at each outlet and fixture until I find the one where it exists. Is this correct? If I knew the order of the connections, I could do a split-half search but since I don’t, I guess I’m just looking at each outlet (and potentially each light fixture or switch) one by one until I find the fault?

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  • There may be another option. If the LOAD side of the GFCI is only feeding receptacles that do not require GFCI protection under current code (e.g., bedrooms but no other bathroom or outdoor or garage, etc. receptacles) and the lights that are connected to LOAD do not require GFCI (i.e., they are not above tub or shower) then you could legally pigtail "load" and line together - i.e., not protect anything downstream. However, if there is anything that should (by code) be protected (e.g., other bathroom receptacles, lights above tub/shower, outdoor receptacles) then that's not an option. Jun 26, 2023 at 3:55
  • I thought about pigtailing the load side as there are no other outlets that need GFCI fed from the outlet near the sink. But don’t I still need to determine if there is a neutral-ground bond somewhere? Jun 26, 2023 at 4:27
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    In a perfect world, yes. Code says "neutral and ground should be separate" and it says "Bathroom receptacles need GFCI" but it doesn't say "thou shalt check your entire system for ground faults". In fact, if you go by current code you would actually have the bedroom receptacles on a different circuit altogether - bathroom receptacles can only be shared with other bathroom stuff (lights, fan, etc.) - but you are grandfathered in with the old setup. Jun 26, 2023 at 4:40
  • Are there switches in the same junction box as the GFCI? That can get complicated. Jun 26, 2023 at 6:29
  • They are not. The outlet by the sink (which will now be GFCI) is in a single gang box with nothing else. I can pigtail off the line to the switch, which is on the opposite wall. The only other electrical connection in the bathroom is the vanity fixture and aforementioned switch, plus a 3way switch for a light in the bedroom. Jun 26, 2023 at 6:38

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Probably not a neutral-ground bond but a neutral-neutral bond where one neutral is post-GFCI and the other is not (or is post a different GFCI). This is a problem because the return current splits between the return to GFCI and any other return and the GFCI sees a current imbalance.

If you have a separate circuit that does not originate with the GFCI, if must be isolated from the post GFCI circuit.

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  • I considered this possibility briefly, and it probably bears further testing. Any thoughts on how to try to find the rogue neutral? Jun 26, 2023 at 4:25
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    Agreed: a neutral loop is likely. @CharliePatton Turn off all your circuit breakers, except the one intended to power this GFCI, and disconnect all the neutrals at the breaker panel too. Connect the GFCI load side and confirm that the GFCI holds as expected. Re-connect neutrals at the panel until the GFCI trips; this will give an idea which other circuit is involved. Determine which outlets that circuit serves, and start making guesses as to where the two circuits' neutrals might meet in a junction box.
    – Greg Hill
    Jun 26, 2023 at 18:58

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