Why the breaker trips

[kwired]

Will a standard clamp-on multimeter work to see a short? Like you'd see the buildup of amps before the breaker trips? I have never tried this.

Short circuit and ground faults generally are pretty rapid rise in current and unless there is too high of supply circuit impedance to limit the amount of current the OCPD often trips faster than many meters would be able to accurately display that current, though some might have a capture feature to show what the peak might have been after the fact. Even an analog meter you might see rapid rise but chances are that needle never reaches the actual peak before the OCPD opens the circuit as it would be too slow of a mechanical response to be able to do so.

 

[tortuga]

My diagnostic breaker for the mystery 'it trips randomly' is a 30ma GFPE breaker.
If I cant reproduce the problem while i am there I'll leave one of those and see if that trips.

 

[ptonsparky]

Sometimes you can hear the breaker trying to come out of the panel or feel it in your fingers as you switch it back on. Don't do it very often. Sometimes they quit tripping or do come out.
Spend the money get a decent meter(s). Learn how to use them. You need the tools to become proficient.

 

[jim dungar]

Like you'd see the buildup of amps before the breaker trips?

A short circuit gets to maximum value immediately, there is no build up.
Very few hand held meters can measure these currents. But, a meter with a Max Hold feature might capture a value well in excess of a full load (like motor inrush) which would indicate a potential problem.

 

[JoeNorm]

The reason I posted this is because I was brought out to job where the customer had a sporadically(but getting worse and worse over time) tripping Arc-fault breaker. It was a recently built, very high-end home. In that scenario I would have almost bet money that it was a faulty breaker, so I bought one to bring out and swap right off the bat. I did so but even the new one tripped. So then started the actual troubleshoot.

It took me a few hours but I was able to isolate it to one run of in-wall wiring that had somehow shorted. I disconnected that portion of wire from the circuit and all is well. I was happy to have found the problem but am always wondering how I could do it a little faster next time.

 

[hillbilly1]

A short neutral to ground will also trip them. Divide and conquer. Break the circuit in half, and go from there. Intermittent problems are the worst. Sometimes you can beat on the walls along the affected area to narrow it down.