Breaker tripping inconsistently. PLEASE HELP!!!

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TJenks048 said:
... I can only think of 2 things: 1) it's a conductor that's between the panel and the last receptacle that is very slightly damaged somehow, and occasionally arcs or 2) the conductor from the panel to receptacle #2 runs through the crawlspace and might have a junction box that I'm unaware of and there is a loose connection or there is water in the junction box.
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Perhaps you could put an in-line slow blow 20A fuse in series with the hot wire in box #2 that's fed from the panel. Or if there's not enough room in box #2 with the GFCI receptacle, in box #3 instead. Then if the the breaker trips but the fuse doesn't blow, it's likely there's a short in the branch circuit upstream of the fuse location (which would be the conductor, etc. in the crawlspace if that conductor is fused in box #2).
 
petersonra said:
You should always have continuity between H and N unless you open the main coming into your house because it is seeing the transformer winding up on the pole outside which is a dead short to the DC resistance reading of your voltmeter..
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You won't show continuity checking hot to neutral along the branch circuit with the breaker off. You don't have to have the main off. Who would check continuity with a breaker on? You will however show some continuity if there is a load connected, such as a light bulb.
 
James L said:
But you mentioned a switch leg going back to the panel. Is that accurate?
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James, I think you misread what the OP said. He didn't say he had a switch leg going back to the panel. He said this is post #6...........

I should have continuity between hot and neutral on an open switch leg that isn't connected to anything that goes back to the panel?
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He was saying he shouldn't have continuity where he was checking because there was nothing running back to the panel from there. He was saying that as a question to Petersonra because he told him he would have continuity.
 
Little Bill said:
James, I think you misread what the OP said. He didn't say he had a switch leg going back to the panel. He said this is post #6...........



He was saying he shouldn't have continuity where he was checking because there was nothing running back to the panel from there. He was saying that as a question to Petersonra because he told him he would have continuity.
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Yes, I misread it. Even after your explanation 😑
 
One of the things I look for when breaker will hold for several days before it trips

Is abandoned cable leaving receptacle etc, often for old post light

Also rodents chewing romex, periodically see hot romex with insulation total gone in places, enough separation that maybe moisture causing trip
 
readydave8 said:
One of the things I look for when breaker will hold for several days before it trips

Is abandoned cable leaving receptacle etc, often for old post light

Also rodents chewing romex, periodically see hot romex with insulation total gone in places, enough separation that maybe moisture causing trip
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I've had every box apart and I haven't seen any abandoned cables,but thanks for the information
 
So I'm about to go into the crawlspace to see if there is any junction boxes or anything else.

If I don't find anything, on another forum a few people have told me to do megohm testing.

What do you all think?
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Breaker tripping inconsistently. PLEASE HELP!!!

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And if that sounds like a good route to go down, what about this meter? It is exceptionally cheaper than the flukes so I was wondering if it would be sufficient.
 
TJenks048 said:
So I'm about to go into the crawlspace to see if there is any junction boxes or anything else.

If I don't find anything, on another forum a few people have told me to do megohm testing.

What do you all think?
www.electriciantalk.com

Breaker tripping inconsistently. PLEASE HELP!!!

www.electriciantalk.com www.electriciantalk.com

And if that sounds like a good route to go down, what about this meter? It is exceptionally cheaper than the flukes so I was wondering if it would be sufficient.
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You should be careful using a Megger or similar device on installed wire. You need to be absolutely sure that no devices are plugged in anywhere, so you have to be positive that you have identified all of the receptacles. You'd need to (I think) jump out any light fixtures. I'm not sure I'd roll those dice.
 
gadfly56 said:
You should be careful using a Megger or similar device on installed wire. You need to be absolutely sure that no devices are plugged in anywhere, so you have to be positive that you have identified all of the receptacles. You'd need to (I think) jump out any light fixtures. I'm not sure I'd roll those dice.
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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.
 
gadfly56 said:
You should be careful using a Megger or similar device on installed wire. You need to be absolutely sure that no devices are plugged in anywhere, so you have to be positive that you have identified all of the receptacles. You'd need to (I think) jump out any light fixtures. I'm not sure I'd roll those dice.
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Yes you unplug in particular any electronics items that are potentially on same circuit being tested. Those tend to be the things that are most easily damaged by a high voltage test.

Before testing at a higher voltage is a good idea to take a reading at low test volts, if something tests low resistance that way you might still have something connected that you shouldn't be testing with the high voltage do not test hot to neutral, that will read through connected loads and is not necessarily indicative of fault conditions you should be testing to the EGC with these tests, but remember the neutral is bonded to the EGC back at the service so you must open the path back to eliminate that when doing your testing.

Make first high voltage test at lowest possible setting - this can vary depending on your equipment abilities. No point in throwing a 1000V test voltage for the first test on something that normally operates at 120 volts that increases chances of damaging anything you might have failed to take out of the circuit to be tested.
 
230114-1144 EST

Assuming the breaker is good, than a plain QO breaker will require substantial excess energy to trip. I have 40 to 50 of these breakers in my home. Over the last 55 years I have never had one trip from an unknown fault or randomly trip. And it takes a lot of energy to trip a QO, or any other good breaker.

I would first guess that a large over-current pulse is the cause. To test for this I would use a current probe and a single shot memory scope to look look for the transient. The first test would be near the breaker. Once I see the waveform of the overcorrect, then I may be able to guess what I am looking for.

Some normal loads may have moderately high starting currents. Thus, the trigger current may need to be set high. With a good scope you could use a mode where transients are stored and superimposed, this would allow you to work with a lower trigger threshold.

With a multichannel scope you could simultaneously look at current at different locations. With a single or two channel scope you could trigger from the main panel location, and look at the waveform in other areas.

There may be occurrences of the problem that do not trip the breaker.

.
 
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.
 
TJenks048:

I believe you have said the breaker is a plain ordinary QO breaker. These are a very rugged reliable breakers. In the past I have tested a QO 20 A with about 8000 amps DC. This was not a single test. The breaker was overloaded several times as I made timing measurements. The power source was about 6 six volt car batteries in series and some short welding cable. To trip a QO 20 A you need a considerable overload current, or the overload has last a long time to trip. I don't think you are looking for a small overload.

Current transformers placed at various points in your system and some means to record the result should allow you to narrow down the source of the problem. If there are multiple problem points, then it is more difficult and time consuming.

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Purchase a cheap megger, I bought one off of ebay when I was first starting out, it actually worked pretty well. This will find another insulation failure much better than the 3-9vdc your meter used to check resistance. Remove the gfci and any dimmer, usb outlet, etc before megging. You should see 20 megohms +.
 
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