Breaker tripping inconsistently. PLEASE HELP!!!

[Little Bill]

A megger would be a more definitive test of the conductor insulation, etc., but you could also use a GFCI breaker to do some testing. This would be using 120V instead of say 500V, but it would still apply significantly more stress than a continuity test that only involves very low voltages.

A first test would be to connect only the hot of the circuit to the GFCI breaker output, but leaving the circuit neutral connected to the neutral bar. All loads should be disconnected. If the GFCI trips then that means there's leakage from the hot conductor to either the circuit neutral conductor or to ground.

If there's a trip during the first test, then a second test could be done to determine whether the leakage is going to neutral or to ground. For this test the circuit neutral would be connected to the GFCI load neutral terminal as is normally done. Then if the GFCI that was tripping on the first test now holds, that means the leakage is not from a ground fault but instead is caused by leakage between hot and neutral.

If tripping occurs in the tests above, then various parts of the circuit could be disconnected to isolate the problem area that causes it to trip.

I don't think a GFCI breaker will function, as far as the set/reset/test electronics is concerned, without the breaker neutral/pigtail connected. Now if the GFCI breaker had been installed and set, it may work, but I'm not sure it would set without the neutral from the breaker connected. I may be wrong about this.

Edit: I may have only assumed you meant to leave the pigtail disconnected. I read your post again and I don't see where you said that.

 

[synchro]

Edit: I may have only assumed you meant to leave the pigtail disconnected. I read your post again and I don't see where you said that.

Yes, I meant to leave the pigtail used to supply power to the breaker connected to the neutral bar. And a plug-on neutral type is also fine. But for the first test that I mentioned, the neutral conductor of the branch circuit would be connected to the neutral bar like with a standard breaker, but the hot conductor of the branch circuit would be connected to its proper load terminal on the GFCI breaker. The load neutral terminal on the output of the GFCI breaker would have nothing connected to it, just for this specific test. Therefore no current can flow through the load neutral terminal. But then if a current of 6mA or more is drawn by the branch circuit through the hot output terminal of the GFCI breaker it will trip. It wouldn't matter whether the leakage in the branch circuit is from hot to ground or from hot to neutral, it would still trip. But then connecting the GFCI breaker to the branch circuit in the normal manner in test 2 will determine whether this leakage in the branch circuit is flowing through its neutral conductor, or through the EGC. This is because a hot-to-neutral leakage current will not trip a GFCI breaker when both the hot and neutral load terminals are powering the branch circuit, because it would be indistinguishable from a proper load current. And so the first test is set up so that it can detect significant hot-to-neutral leakage.
If the GFCI trips in either test 1 or 2, there is a significant amount of leakage present. A megger can detect insulation defects before they reach that point.

 

[synchro]

Another thing is that in tests #1 and #2 II mentioned above, you could have a lamp. radio, etc. connected directly across the hot and neutral output terminals of the GFCI breaker to indicate whether the breaker has tripped or not. This load will draw equal currents through the hot and neutral output terminals of the breaker, and therefore will not affect either of the two tests. And in test #1, the branch circuit neutral would still be connected to the neutral bar.

 

[SparkyBirdman]

So the process would be, for example, if I wanted to check the cable between receptacle #2 and #3, to take out both receptacles so the only thing I'm testing is the cable itself?

And I'm not really worried about the light fixtures now because the breaker has been tripping with them disconnected anyways.

Using a dmm or fluke on continuity, have you checked the wires for shorts and ground faults? This is a faster, cheaper test than a megger and most of the time just as accurate for basic nm cable in a residential house.

Also, I didnt read in your tshooting if you disconnected the home run wire from the panel to its first device and see if the breaker still trips.

Maybe you did and I missed it.

Lastly, if your reading continuity L-N on the LOAD side of a switch, then you are reading through a bulb/ballast/driver

 

[kwired]

I don't think a GFCI breaker will function, as far as the set/reset/test electronics is concerned, without the breaker neutral/pigtail connected. Now if the GFCI breaker had been installed and set, it may work, but I'm not sure it would set without the neutral from the breaker connected. I may be wrong about this.

Edit: I may have only assumed you meant to leave the pigtail disconnected. I read your post again and I don't see where you said that.

I have played around with Square D 2 pole 50 amp GFCI's before and have come to conclusion that if you do not connect the neutral pigtail you lose GFCI function, but the breaker will still reset and presumably still will function fine as a thermal magnetic trip breaker. Also one of the ungrounded supply side terminals is powering the GFCI electronics and should you lose power on that particular pole you also lose GFCI function even though you could have a line to neutral load still operating on the other pole.