# Question about AFCI troubleshooting



## owl (Oct 31, 2012)

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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## Pete m. (Nov 19, 2011)

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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## HARRY304E (Sep 15, 2010)

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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## owl (Oct 31, 2012)

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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## macmikeman (Jan 23, 2007)

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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## owl (Oct 31, 2012)

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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## owl (Oct 31, 2012)

Though to be fair, it did trip the normal breaker I threw on it as well.


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## 8V71 (Dec 23, 2011)

owl said:


> Though to be fair, it did trip the normal breaker I threw on it as well.


Well that changes everything.


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## Pete m. (Nov 19, 2011)

8V71 said:


> Well that changes everything.


I agree! 

Pete


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## owl (Oct 31, 2012)

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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## Pete m. (Nov 19, 2011)

owl said:


> 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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## owl (Oct 31, 2012)

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 . Any other ideas about what could be happening are welcome.


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## B4T (Feb 10, 2009)

You have to make sure your neutrals from the AFCI circuit are isolated from other neutrals that might be in the same box...


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## owl (Oct 31, 2012)

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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## B4T (Feb 10, 2009)

owl said:


> 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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## Big John (May 23, 2010)

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.


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## drspec (Sep 29, 2012)

Big John said:


> 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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## chicken steve (Mar 22, 2011)

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

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

~CS~


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## SteveBayshore (Apr 7, 2013)

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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## drspec (Sep 29, 2012)

SteveBayshore said:


> 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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## drspec (Sep 29, 2012)

chicken steve said:


> Sure doc, but being sent down arc fault road doesn't help matters.
> 
> There is no arc fault signature, it DOES NOT  EXIST expect in the minds of predator manufacturers and the toadies they own parroting it
> 
> ~CS~


Why would you expect it to help? And where did I imply it would?


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## chicken steve (Mar 22, 2011)

drspec said:


> Why would you expect it to help? And where did I imply it would?


It won't, and as far as your tester, you blew $250 on a fairytale to diagnose a fairytale....:thumbsup:~CS~


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## owl (Oct 31, 2012)

Hahaha, they sell a $250 product that enables you to deal with their other crappy product.


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## Bugz11B (May 12, 2013)

Just a question, was the bulb a CFL? I have found that a CFL that is about to burn out will trip arc faults, also having a forward phase (standard incandescent type) dimmer on a CFL can trip a arc fault breaker, lastly if the bulb wasnt screwed in tight there can be an arc causing burn marks that make nothing look like something and could also trip a arc fault.


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## owl (Oct 31, 2012)

Bugz11B said:


> Just a question, was the bulb a CFL? I have found that a CFL that is about to burn out will trip arc faults, also having a forward phase (standard incandescent type) dimmer on a CFL can trip a arc fault breaker, lastly if the bulb wasnt screwed in tight there can be an arc causing burn marks that make nothing look like something and could also trip a arc fault.


It was an incandescent bulb, and yes, there were burn marks on both the contact point of the bulb and the tab in the socket that touches the tip of the bulb. As I said, I disconnected the light portion of the fixture, and couldn't get the circuit to trip after that. Still, arcing at the bulb doesn't explain the randomness of the tripping, does it?


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## Dan Wheeler (Nov 22, 2013)

That's why when I wire or rewire a house, I don't add lights onto my arc fault. Only receptacles, only in bedrooms.

I have heard of times of lights causing arc fault issues.


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## macmikeman (Jan 23, 2007)

Dan Wheeler said:


> That's why when I wire or rewire a house, I don't add lights onto my arc fault. Only receptacles, only in bedrooms.
> 
> I have heard of times of lights causing arc fault issues.


If you did that in the last 7 or 8 years where I live, you wouldn't be able to pass an inspection. Lights, outlets, ac air handlers, smokes, anything 15 or 20 amp , 120 volts in the areas specified in the nec as requiring afci protection .


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## chicken steve (Mar 22, 2011)

Stuffing 30 in a 40 panel for over a decade here....... adds about $2000 to the ave house $$ .....one good power spike and most will be toast.....then all the calls come in, and we go out


~CS~


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## owl (Oct 31, 2012)

Also, as I said, it tripped a regular breaker. Would a bulb arcing trip a regular breaker?


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## Big John (May 23, 2010)

owl said:


> ...Would a bulb arcing trip a regular breaker?


 No. Like I said above, you've got a fault.


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## HARRY304E (Sep 15, 2010)

owl said:


> Also, as I said, it tripped a regular breaker. Would a bulb arcing trip a regular breaker?


No,because a regular breaker will only trip on overload,or a short circuit.

This is why they created the AFCI breakers to detect arcing,so if your lamp is loose in the socket and arcing the AFCI will pick it up and trip.


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## owl (Oct 31, 2012)

Thanks all. I appreciate the info.


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## don_resqcapt19 (Jul 18, 2010)

owl said:


> Also, as I said, it tripped a regular breaker. Would a bulb arcing trip a regular breaker?


If the bulb is still good, they it is very unlikely that the bulb could have caused a standard breaker to trip. If the bulb is burnt out, it is possible the that bulb could cause a standard breaker to trip. Sometimes when the filament burns open a small section drops across the internal wires that supply power and sometimes this can pull enough current to trip a standard breaker.


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## RIVETER (Sep 26, 2009)

owl said:


> 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.
> 
> ...


If the light bulb burned out after a year and a half and then another was put in loosely that could do it.


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## papaotis (Jun 8, 2013)

a bad connection at the base of the bulb can cause all kinds of weird chit. the fact that there were ARC marks proves there was a bad connection. very common in edison sockets. usually, all it takes to fix it is pulling the tab up from the bottom of the socket, unless it is fried:thumbup:


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