# Afci



## enosez (Apr 1, 2008)

Neutral wire is shorting to the bare ground, plastic box started melting. etc. NO FIRE THOUGH.
Homeowner plugged an extension cord into it last summer to run a 8500 btu A/C. Smelled something burning last year and stopped using the A/C. Waited until now to address the problem.
Outlet worked fine but found Neutral wire is shorting to the bare ground, plastic box started melting. etc. NO FIRE THOUGH.
Circuit is AFCI protected with A/L pigtailed to copper only on the hot and neutral. Pigtail was done with regular wirenuts and some nolux prior to us getting there.
What are your thoughts.


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## 480sparky (Sep 20, 2007)

If there's an AFCI breaker, it's defective. A neutral-to-ground short should cause it to trip.


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## BryanMD (Dec 31, 2007)

Who is the "genius" that installed an AFCI breaker onto a circuit fed with 35yo AL wiring?


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## 480sparky (Sep 20, 2007)

BryanMD said:


> Who is the "genius" that installed an AFCI breaker onto a circuit fed with 35yo AL wiring?


And the problem with that is.......?


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## BryanMD (Dec 31, 2007)

480sparky said:


> And the problem with that is.......?


the extra (uncalled for) expense, their sensitivity when installed in new construction without the issues related to AL, and without the issues related to 35 years of age, and MWBC's, and changes in the walls.

It is just asking for trouble that doesn't need to be asked for.


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## 480sparky (Sep 20, 2007)

I guess I was unaware AFCIs could sense the difference between copper and aluminum.


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## JohnJ0906 (Jan 22, 2007)

480sparky said:


> If there's an AFCI breaker, it's defective. A neutral-to-ground short should cause it to trip.


I agree.

I also agree it is more appropriate to install AFCI on something like this than new construction - assuming, of course, the AFCI works as it supposed to.


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## BryanMD (Dec 31, 2007)

JohnJ0906 said:


> I also agree it is more appropriate to install AFCI on something like this than new construction - assuming, of course, the AFCI works as it supposed to.


Hmmm 
I see your point. I suppose if you can isolate the circuit and know everything that is on it... but I still see it as the problem I described before.

I'm not the sort to back down from a fight... but I don't go looking for them either. Ya know?


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## electricista (Jan 11, 2009)

480sparky said:


> If there's an AFCI breaker, it's defective. A neutral-to-ground short should cause it to trip.





480sparky said:


> If there's an AFCI breaker, it's defective. A neutral-to-ground short should cause it to trip.


I don't believe a neutral to ground short will cause an AFCI to trip unless there is a load on the circuit. Please correct me if I am wrong.


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## 480sparky (Sep 20, 2007)

electricista said:


> I don't believe a neutral to ground short will cause an AFCI to trip unless there is a load on the circuit. Please correct me if I am wrong.


If I recollect rightly, AFCIs have some GFI protection built into them. Not the same as a 'normal' GFCI, but the same principal. A neutral-to-ground short will appear as a ground fault, and should trip the AFCI.

I've tripped AFCI's this way when there's no load on the breaker by accident by shorting neutral to ground. Next time I'm in a panel with an AFCI, I'll lift the ungrounded conductor and try it.


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## electricista (Jan 11, 2009)

480sparky said:


> If I recollect rightly, AFCIs have some GFI protection built into them. Not the same as a 'normal' GFCI, but the same principal. A neutral-to-ground short will appear as a ground fault, and should trip the AFCI.
> 
> I've tripped AFCI's this way when there's no load on the breaker by accident by shorting neutral to ground. Next time I'm in a panel with an AFCI, I'll lift the ungrounded conductor and try it.


I am sure AFCI have GFP in them and I think my recollection was wrong. I had a helper who hooked the ground on one recp. to the neutral screw and the neutral to the ground. Of course nothing happened until a load was plugged in. 

My apologies I believe I am incorrect. Oh well.


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## raider1 (Jan 22, 2007)

AFCI breakers incorporate GFPE protection that is set at typically between 30 and 50 milliamps. So for the GFPE protection to trip it must see an in balance between the neutral and the hot of 30 to 50 milliamps before the AFCI breaker will trip.

Chris


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## 480sparky (Sep 20, 2007)

OK, so as a simple experiment, I just put a SQ HO 15a AFCI breaker in my house panel (don't worry, it's a SQ D HO panel!)

For the record, I have a 4-wire feeding coming into my main panel as I have a disconnect outside the house.

I attached the breaker's white wire to the neutral bar, and nothing on the hot terminal.

I took a short wire and connected the branch circuit neutral terminal of the AFCI to the neutral bar, and nothing happened.

When I moved the wire over to the ground bar, the AFCI tripped. No load possible as there was no wire on the hot terminal of the breaker.



And in case you are wondering..... Yes, I was wearing my 35cal moon suit, using 1000v tools, and went down to city hall and got a permit.


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## raider1 (Jan 22, 2007)

Thats interesting Ken,

I would say that there must be some other function of the AFCI breaker causing the trip, the GFPE portion of the AFCI circuitry would require a load to monitor the imbalance before it would function.

Chris


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## electricista (Jan 11, 2009)

raider1 said:


> Thats interesting Ken,
> 
> I would say that there must be some other function of the AFCI breaker causing the trip, the GFPE portion of the AFCI circuitry would require a load to monitor the imbalance before it would function.
> 
> Chris


Chris, that was my initial thought also. I know that a GFCI does not need a load to trip the recep. or the breaker so I was thinking the AFCI with GFPE built in would not require the load. Hummm.


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## raider1 (Jan 22, 2007)

GFCI protection has a trip range of 4 to 6 milliamps whereas as GFPE protection has a trip range of 30 to 50 milliamps so it would take a much smaller load for a GFCI receptacle to trip than an AFCI breaker with GFPE protection.

Without a load how would either a GFCI receptacle or a AFCI breaker with GFPE protection be able to monitor an imbalance between the ungrounded and grounded conductor? An accidental neutral to ground connection down stream of the ground fault protection would act as a parallel path for neutral current which would cause the imbalance to show in the ground fault circuitry. Without current flow how would the parallel path be shown?

Chris


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## 480sparky (Sep 20, 2007)

To further this discussion and experiment, I took the GFI breaker that feeds my whirlypool and disconnected the branch circuit hot & neutral.

Repeating the same procedure I did with the AFCI breaker, I shorted the branch neutral terminal of the breaker to the neutral bar. It tripped.

Same thing when shorting to the ground bar. It trips.

No load as both the hot & neutral of the branch circuit were disconnected.


Hmmmmm.


















Thanks for getting me into my own panel. It allowed me to correct a wiring error (done by someone else) I had forgotten about. One ground wire was landed on the neutral bar. Tis now corrected.


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## Mike_586 (Mar 24, 2009)

Yeah that's a real pain in the butt to troubleshoot. If you try ohming things out, a grounded neutral is no different than a shared neutral, which means you either take all the neutrals off at the panel, or go running around opening every device on the circuit.

Here's a little more food for thought....

http://www.mikeholt.com/mojonewsarchive/AFCI-HTML/HTML/AFCITesterStory~20020826.htm

I've had arguments with guys at the last place I worked on how they tested AFCIs, it was (a pig tail on a plug with the neutral to ground) ridiculous. The thing is there's all sorts of confusion between AFCI indicators, testers, and weather the tester is actually testing the AFCI properties or if its just testing the GFP.


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## 480sparky (Sep 20, 2007)

Mike_586 said:


> ...........or go running around opening every device on the circuit....


If you know how to properly troubleshoot a circuit, you only need to remove about ¼ of the devices in the circuit.


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## Mike_586 (Mar 24, 2009)

Keep splitting it in half 

Must have had that last house I finished on my mind. It was, bar none, the worst wiring (someone else roughed it in) I've ever seen in new construction.


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## bobelectric (Feb 24, 2007)

480sparky said:


> OK, so as a simple experiment, I just put a SQ HO 15a AFCI breaker in my house panel (don't worry, it's a SQ D HO panel!)
> 
> For the record, I have a 4-wire feeding coming into my main panel as I have a disconnect outside the house.
> 
> ...


Your'e lucky you didn't get turned in.


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## 480sparky (Sep 20, 2007)

bobelectric said:


> Your'e lucky you didn't get turned in.


Yea. Intentially tripping AFCI breakers is addicting. I've been doing it ever since.

I need to join AA (AFCI Anonymous!) :laughing:


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## itsunclebill (Jan 16, 2007)

Give this a once over 

 http://www.rhtubs.com/GFCI/GFCI.htm


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## busymnky (Feb 16, 2009)

You always have to bring the circuits you work on up to current code, is it different other places? Most jurisdictions here will make you add smoke detection if anything of consequence (like service upgrade) is done.

Combination type AFI's detect and protect against "series" arcing(nuetral to ground). The branch/feeder AFI's do not , combination type wasn't required until 05:rockon:


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## 480sparky (Sep 20, 2007)

itsunclebill said:


> Give this a once over
> 
> http://www.rhtubs.com/GFCI/GFCI.htm


I don't see anything about AFCis there.:blink:


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## JohnJ0906 (Jan 22, 2007)

480sparky said:


> Yea. Intentially tripping AFCI breakers is addicting. I've been doing it ever since.
> 
> I need to join AA (AFCI Anonymous!) :laughing:


1st, you must admit your problem..... :laughing:


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## raider1 (Jan 22, 2007)

> Combination type AFI's detect and protect against "series" arcing(nuetral to ground).


Actually series arcing is between two points on the same wire, such as a loose terminal or wire nut. The neutral to ground connection you are talking about will trip the GFPE protection that is built into the AFCI device. Also the branch/feeder type of AFCI had the GFPE protection as part of their funtion.

Chris


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