Diagnosing an occasional AFCI breaker tripping.

[A.Adams]

I need help with knowing how to diagnose an arc fault issue. In particular, are there resistance measurements I can be marking to isolate the problem?

I’ve finished the rough in on a residential remodel job. It was such an extensive remodel with a lot of customization that it required about 85% total rewire. A new sub panel was installed (Leviton LP310-MB).

I energized two 20 amp circuits (AFCI+GFCI breakers) to give the other trades some power for tools and battery chargers. And I energized two 15 amp circuits (AFCI breakers) for temporary work lights. The fixtures I’m using are the temporary, hard wired sockets with an LED lamp screwed in.

Everything has worked flawlessly for a several weeks. The GC called me and said that one of the lighting circuits had an arc fault trip. I went out to the job site, reset the breaker and couldn’t get it to trip. On this circuit there is only one temporary light fixture. I left it on and headed out to another job. I swung back to that job site and the breaker had tripped again. I reset it, wiggled the wires in the switch box, went into the attic and wiggled several (but not all) nm cables that are on that circuit. I could not get it to trip. My assumption is that it’s not a screw in a wire from the drywall crew because it’s not tripping instantaneously. With only one LED lamp it certainly can’t be an overload.

The circuit feeds from the panel to a j-box in the attic. I disconnected all other branches that feed out of this j-box except for the the one that feeds into the box with the light switch. I’ll be heading back there to see how it’s faired overnight.

I’ve not yet replaced the breaker. I’ve heard about replacing the AFCI breaker with a GFCI breaker incase there is a low level leak to ground because a GFCI breaker will trip faster than the AFCI breaker. Since I finished the rough in there have been other changes to the scope that involved opening a portion of the roof and they had a rapid storm form and which dumped good amount of rain water in one section of the house. Could it be that a J-box has some moisture in it that is causing a low level fault to ground?

Are there measurements I can be making with my multimeter to help isolate where the issue may be? Any other tips?

Thanks for your help.


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[tthh]

You have a leg up on many who have investigated the same issue since you are familiar with the house. You did the right stuff to start off, I'd just repalce that breaker or swap it with the other one and see what happens. Could just be a bad breaker - there are some electronics inside and it is possible to be bad.

 

[kwired]

Possibly inductive kickback or other interference from certain power tools, even if not on same circuit as the lighting circuit?

I'd ditch the AFCI, not required while used as a temporary circuit, even if using permanent wiring as a temporary circuit.

 

[LarryFine]

Just yesterday I swapped two AFCI breakers because one was having issues with a refrigerator.

Doing this has resolved the issue just about every time I used it as a troubleshooting method.

 

[tthh]

I will say that one outlet at daughter's house will trip every time I used the chop saw when I fixed some exterior molding, but another circuit nearby does not -- GE panel, both with the AFCI breakers.

 

[A.Adams]

Possibly inductive kickback or other interference from certain power tools, even if not on same circuit as the lighting circuit?

I'd ditch the AFCI, not required while used as a temporary circuit, even if using permanent wiring as a temporary circuit.

The circuits that the power tools are on are AFCI/GFCI protected and they’ve not had any issues. The problem with ditching the AFCI breaker on this particular circuit for now is that it’s required in order to pass the final inspection. I’d just be pushing the problem down the road. And if there is an issue due to a mistake I made, I’d rather find it now before it costs a lot more to remedy it.


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[synchro]

I need help with knowing how to diagnose an arc fault issue. ...
I’ve heard about replacing the AFCI breaker with a GFCI breaker in case there is a low level leak to ground because a GFCI breaker will trip faster than the AFCI breaker. ...

You could also check for low level leakage from hot to neutral with a GFCI breaker by using the approach I described in an earlier thread at the posts linked below. You'd have to turn off the light switch or remove the bulb on the problem circuit so that there's no load current that would dominate any L-N leakage that might be present.

Breaker tripping inconsistently. PLEASE HELP!!!

... 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...

forums.mikeholt.com

Breaker tripping inconsistently. PLEASE HELP!!!

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...

forums.mikeholt.com

 

[ptonsparky]

I will say that one outlet at daughter's house will trip every time I used the chop saw when I fixed some exterior molding, but another circuit nearby does not -- GE panel, both with the AFCI breakers.

Swap the breakers and tell us if the problem moves with the breaker.

 

[suemarkp]

Does this brand of AFCI breaker have a diagnostic light that blinks telling you why it tripped? Swaping to GFCI may be the easiest thing to do since it may trip quicker if that is the problem. If it is a series or parallel arc causing the trip, that will be a fun one to find (or it could be a bad breaker so trying a different AFCI could also help). This will at least reduce the possibilities if you still end up pushing the problem down the road.

 

[mopowr steve]

If your using a pigtail socket, you may want to check to see if the wires have a bad solder joint to the shell or pin of the socket.
I run across it often enough, especially with well used ones.

 

[shortcircuit2]

If there are receptacles on the same lighting circuit...make sure when they were installed that the equipment ground has not rested against the neutral terminal on the device. With this, I have had AFCI trip when a load is put on the circuit.

 

[kwired]

The circuits that the power tools are on are AFCI/GFCI protected and they’ve not had any issues. The problem with ditching the AFCI breaker on this particular circuit for now is that it’s required in order to pass the final inspection. I’d just be pushing the problem down the road. And if there is an issue due to a mistake I made, I’d rather find it now before it costs a lot more to remedy it.


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Some items just don't play well with AFCI's or even GFCI's. Down the road you won't have power tools as the loads so you may not have much of an idea how well it will work down the road anyway.

AFCI is not needed during construction phase. It is up to you how much you want to possibly be chasing rabbits down the hole when loaded with something that won't be there after project completion.

As mentioned if this is a device that can tell you whether it tripped on AFCI, GFCI or thermal mag trip that can be a little helpful. GFCI function trips, I'd say meg the wiring, if it tests ok then it is the load that has problems or simply doesn't play well with the device.