Bad breaker or ground fault?

hj said:

quote; The neutral is not shared.

Are you absolutely certain that there is NO OTHER circuit using the neutral wire? Does the neutral go DIRECTLY to the panel box so you can be sure of it.

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Unhook the neutral and hot (load side) from the GFCI breaker and measure the resistance (VOM and/or megger) between the neutral wire and the neutral bar -- it should be open.

In my limited experience with residential wiring (I am not a pro in that area), it's not uncommon for neutrals from different circuits to be intentionally tied together (obvious DIY hacks), but in that case, a GFCI breaker *should* always trip with a load on either circuit, and in theory possibly even without any load at all -- depending on the design of breaker.

I still think what you describe sounds like a flaky breaker. Probably a manufacturing defect...

As I mentioned before, this was an issue that I resolved some time ago. The reason for my post was to gain insight on how others would go about diagnosing such a problem.

It was a neutral to ground short, and while my ohmeter showed infinity, the megger did not.

I started at the panel and spit the circuit in half twice before being confident that it was in the lights. Unfortunately, I had to cut apart all 4 recessed cans to pinpoint the fault. The lights were split wired with 12-3 from 2 switches, and the short was located where the last recessed can junction box NM cable clamp was tightened on the cable.

After replacing the lights, I loaded the circuit over 20 amps and the GFCI breaker never as much as whimpered.

cacher_chick said:

The reason for my post was to gain insight on how others would go about diagnosing such a problem.

the megger did not.

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You answered your own question. This type problem is never easy to find