enosez

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.

480sparky

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

__________________
In winter, why do we try to keep the house as warm as it was in summer when we complained about the heat?

BryanMD

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

__________________
November 2011: Relocated to Winston-Salem.
May have to change the username suffix.

480sparky

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

__________________
In winter, why do we try to keep the house as warm as it was in summer when we complained about the heat?

BryanMD

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.

__________________
November 2011: Relocated to Winston-Salem.
May have to change the username suffix.

480sparky

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

__________________
In winter, why do we try to keep the house as warm as it was in summer when we complained about the heat?

JohnJ0906

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.

__________________
John from Baltimore
"One day at a Time"
All responses based on the '08 NEC
It's not my fault, it's not my problem, I'm not your solution.

BryanMD

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?

__________________
November 2011: Relocated to Winston-Salem.
May have to change the username suffix.

electricista

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.

__________________
Alice

"I complained because I had no shoes until I saw a man who had no feet."

480sparky

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.

__________________
In winter, why do we try to keep the house as warm as it was in summer when we complained about the heat?

electricista

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.

__________________
Alice

"I complained because I had no shoes until I saw a man who had no feet."

raider1

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

480sparky

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.

__________________
In winter, why do we try to keep the house as warm as it was in summer when we complained about the heat?

raider1

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

electricista

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.

__________________
Alice

"I complained because I had no shoes until I saw a man who had no feet."

raider1

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

480sparky

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.

__________________
In winter, why do we try to keep the house as warm as it was in summer when we complained about the heat?

Mike_586

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.

480sparky

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

__________________
In winter, why do we try to keep the house as warm as it was in summer when we complained about the heat?

Mike_586

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.