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Discussion Starter · #1 ·
Question about troubleshooting an AFCI-protected circuit

In the spirit of full disclosure, I'm an apprentice doing this work for a family member. If this violates policy, please delete this.

Last night I was troubleshooting an AFCI circuit. HO reported that the breaker trips at random, that it went for about a year and a half without tripping, and then started again. Said he couldn't find a consistent pattern for when it trips.

The breaker was in a subpanel. Three homeruns were spliced together and pigtailed onto the breaker. After checking all the basics (screws on breaker/bus bar tight, etc), I found that the neutral pigtail was broken about 80% of the way through the wire and about to come off. Fixed it. Circuit still tripped in what appeared to be a random way.

Started the process of elimination by putting the homeruns on the breaker one at a time. Chased it down to a bathroom light/fan fixture. The tab that connects to the bottom of the bulb had a burn mark on it, as did the bottom of the bulb. I tried putting it on a different AFCI, and also on a regular breaker. It still tripped.

Disconnected the light portion of the fixture and put everything back on the original AFCI breaker, and it would not trip. HO says he wants to replace the socket in the fixture (I didn't have the part with me). I could not get the thing to trip without the light portion of the fixture in the circuit.

My questions:

Would the fact that the three homeruns were spliced together cause the breaker to trip when something other than that light is activated? Also, why would it go without tripping for 1.5 years, and then restart again?

Thanks in advance.
 

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Electrical Simpleton
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It may be possible that there was an arc signature that the breaker didn't like coming from the poor connection of the lamp to the socket. It could be intermittent with simple changes in temperature, humidity, etc...

I don't really see an issue with 3 home runs tied together and fed from the AFCI.

Pete
 

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Sounds like when they put a new lamp in,that started it up again,it may be that is the only problem.

Having 3 cables spliced together in the panel on to one AFCI breaker does not matter as long as all the splices are rock solid, and all the connections are tight it should be fine.

Such things like neutrals mixed together from different circuits in switch boxes will also cause tripping.


Ground wires touching the neutrals in any box will also cause tripping.

Loosely spliced splices caused by not twisting your splices together first and checking them to make sure they're good before putting on your wirenuts will cause tripping.

Connections to devises , check them and make sure that everything is tight before putting them in the box making sure the ground wire does not touch other wires or even the device it's self.
 

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Discussion Starter · #4 ·
Thanks, y'all. I still don't understand the randomness of the tripping. I will report back if the HO says it is still tripping.

I did check the splices in the subpanel. All were good. Also checked splices in other, close-by parts of the circuit. All good. HO had replaced the switch that fed the aforementioned light and had stuff like 2 wires under one screw, but I fixed that, and it also didn't seem to be a part of the problem.
 

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Just imagine the deadly fire the afci prevented by that slightly loose connection to a lamp in the fixture ..............................................................................................................................................Yup. :no:
 

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Discussion Starter · #6 ·
macmikeman said:
just imagine the deadly fire the afci prevented by that slightly loose connection to a lamp in the fixture ..............................................................................................................................................yup. :no:
omg i'm a hero.
 

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Discussion Starter · #10 ·
owl said:
I tried putting it on a different AFCI, and also on a regular breaker. It still tripped.
Yeah, see my original post.

Also, this was a GE panel with Siemens and Square D breakers in it. Not sure if that matters. According to the HO, everything else is working fine. I'm not sure how much of that breaker-must-match-panel stuff is legalese/an attempt to sell more breakers of one's own brand, or how much is a legit concern. Thoughts?
 

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Yeah, see my original post.

Also, this was a GE panel with Siemens and Square D breakers in it. Not sure if that matters. According to the HO, everything else is working fine. I'm not sure how much of that breaker-must-match-panel stuff is legalese/an attempt to sell more breakers of one's own brand, or how much is a legit concern. Thoughts?
I admit I missed that in your original post but if the regular circuit breaker opened as did the AFCI then you need to look a little deeper.

As far as using different manufacturers breakers in a certain panel that comes down to the listing (UL or some other NRTL) it will create a violation of 110.3(B). Is it an imminent hazard... most likely not but it isn't a good practice.

Pete
 
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Discussion Starter · #12 ·
Pete m. said:
I admit I missed that in your original post but if the regular circuit breaker opened as did the AFCI then you need to look a little deeper.
Yeah, and I don't understand the randomness of it. After disconnecting the fixture, I couldn't get it to trip again, so it was fine when I left. If it continues to trip, I will soon find out :D. Any other ideas about what could be happening are welcome.
 

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Discussion Starter · #14 ·
OK, so if it continues to trip, I should check boxes to make sure neutrals on this breaker aren't spliced with neutrals from some other breaker.
 

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OK, so if it continues to trip, I should check boxes to make sure neutrals on this breaker aren't spliced with neutrals from some other breaker.
Yes... and divide the circuit in half... see if problem is gone...

If gone.. divide next part of circuit in half and see if problem is gone...

You have to keep adding more onto to the circuit to see where it trips the AFCI...
 

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Yeah, if you've tripped several different breakers, including non-AFCIs, then you've got a legitimate fault that you need to find that is causing an overcurrent.

Time to break out the ammeter and the DMM and a megger if you've got one, and start dividing and conquering.

he/she is an apprentice.......doubt very much he/she will possess any of the proper knowledge to diagnose the problem much less own the equipment needed for it
 

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Sure doc, but being sent down arc fault road doesn't help matters.

There is no arc fault signature, it DOES NOT :censored: EXIST expect in the minds of predator manufacturers and the toadies they own parroting it

~CS~
 

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I attended a class on AFCIs a couple of months ago to get some continuing ed hours, I think it is Siemens that now sells an arc fault diagnostic tester that connects in between the AFCI and the load and aids in troubleshooting faults. I wasn't really interrested, I'll see if I kept the info. Supposed to work for all manufacturers equipment. This, or something similar will eventually be required by all who install AFCIs. The only two I ever installed were the blue handle Square D ones in my own house more than 5 years ago, just to try them out.
 

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I attended a class on AFCIs a couple of months ago to get some continuing ed hours, I think it is Siemens that now sells an arc fault diagnostic tester that connects in between the AFCI and the load and aids in troubleshooting faults. I wasn't really interrested, I'll see if I kept the info. Supposed to work for all manufacturers equipment. This, or something similar will eventually be required by all who install AFCIs. The only two I ever installed were the blue handle Square D ones in my own house more than 5 years ago, just to try them out.
The Siemens tool is the only such beast available and has been on the market for a few years.

I've had one for a year and I think I paid around $250 for it when I bought it.

Its an OK tool and has helped me find a couple of problems. Kind of quirky and you still have to have good troubleshooting skills to use it. It doesn't find the problem it just helps lead you to problem items.

Its definitely not foolproof.
 
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