AFCI Problem

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lbwireman

lbwireman

Senior Member
Location
Long Beach, CA
Hi All,
We just finished trimout on a 500 sq ft Bedrm/bathroom/wardrobe room addition for a customer. Our local AHJs previously went with a "soft" interpretation of NEC Art. 210.12 and only required that receptacle outlets in bdrms be AFCI protected. They have now switched to a "hard" interpretation, in accordance with the Art.100 definition of "outlet". We are now required to AFCI protect ALL outlets in the bedroom (including lighting). Problem: In this addition we put all outlets subject to this Art. on one circuit fed from an AFCI breaker in the main load center (new Murray 200A side by side combination panel). There is a ceilngfan w/ light kit receiving its 120V power through a hard wired SPST switch. The ceiling fan speed and light kit dimmer are controlled by a built-in remote receiver and a hand held remote controller. There are 4 incandescent can lights receiving their power through a switched dimmer. There is a flourescent ceiling luminaire in the wardrobe. The AFCI OC device remains set until a load is put on the circuit (energize any of the switches) at which time, the luminaire(s) will come on for about a half second then the AFCI trips. This also happens if an incandescent floor lamp is plugged into the first receptacle outlet in the circuit and turned on. Any thoughts? Thanks in advance.
Sean
 
Some switches and fixtures(fans) actually arc in operation, I would try changing switches to start. If dimmers are used, electronic is probobally the best way to go.
 
lbwireman said:
Our local AHJs previously went with a "soft" interpretation of NEC Art. 210.12 and only required that receptacle outlets in bdrms be AFCI protected. They have now switched to a "hard" interpretation, in accordance with the Art.100 definition of "outlet".
Click to expand...

In the 1999 NEC only the circuits supplying receptacle outlets where required to be GFCI protected, in the 2002 NEC and continuing into the 2005 NEC all circuits supplying bedroom outlets (per the definition) are required to be AFCI protected.

The AFCI OC device remains set until a load is put on the circuit (energize any of the switches) at which time, the luminaire(s) will come on for about a half second then the AFCI trips. This also happens if an incandescent floor lamp is plugged into the first receptacle outlet in the circuit and turned on. Any thoughts?
Click to expand...

Yeah.

1) You have some neutrals tied together from different circuits at a switch box or other j-box.

2) The neutral for the AFCI circuit is shorted to ground somewhere.
 
Also check for an inadvertant neutral to ground connection. AFCI breakers also have GFPE protection that trips at about 30 to 50 milliamps. If you have a neutral to ground connection then the ground wire will carry some of the grounded conductor current.

Chris
 
barbeer said:
Some switches and fixtures(fans) actually arc in operation, I would try changing switches to start. If dimmers are used, electronic is probably the best way to go.
Click to expand...

AFCIs contain a GFCI sensor as well as the Arc sensor.

It is IMO very likely the AFCI is tripping on current imbalance caused by a neutral that is tied into either another grounded or grounding conductor.
 
I have to agree with Iwire not just because he's usually right but also because I had a similar experience. I found that my helper (may God help him) somehow had the neutral and ground reversed on one receptacle. Everything was fine till you plugged something in or turned it on. Good luck-- It could be a bad AFCI but I am betting on the ground and neutral touching. Lets us know what you find.
 
OK. First thing is first. Go through the following 3 steps.
1. Loosen any tight staples in your wire. This seems to be a ongoing problem with some in the trade. Staples may be snug but not tight. Arc fault breakers cannot handle this type of pressure neither can GFCI breakers.
2. Make sure your grounding and grounded conductor or neutral wire are not touching each other not even a little bit.
3. Check your switches one by one to eliminate your steps.
 
Also check your wiring, the arc-fault is just doing what it's supposed to do.

You may have a staple that cut through or a nail in a wire, etc, but I don't disallow what the others are saying too.

I had an electrician by pass the arc-fault because it was "bad", when I made him go back and check it turns out his wiring was "bad".
 
Thanks for the feedback.

Thanks for the feedback.

We won't be back on that site until Fri. but I'm gonna print this thread out and give it to the journeyman & apprentice running that job. Bob and Chris, your suggestions re: a possible neutral/EG fault got my "troubleshooter's tuning fork" a' ringin' so I think I'm gonna go have a looksee myself as well. I'll definitely let you all know how it turns out. Thanks to all of you for the help.
Sean:grin:
 
You can lift the neutral and ground for that circuit at the panel and ohm them out to rule in or out a touching ground to neutral problem right quick.
 
Problem solved!

Problem solved!

To all who responded to my request for help, After disconnecting the grounded conductor and and the grounding conductor for the branch circuit in question, they were rung out (ohmed) and showed continuity between the two. It was then simply a matter of isolating the location of the fault along the cable. Staples were pulled, sheathing was inspected for penetrations and testing of each cable section between points of connection was conducted. The offending segment was identified, fault (contact between grounded and grounding conductors) was cleared. Problem solved. Apparently the insulation on the grounded conductor was inadequately applied during the manufacturing process and the flaw hidden from view by the NM sheath. Thank you, one and all, for your input. I am now considerably more informed re: the operation of AFCIs, and we would have spent a great deal more "head scratchin'" time without your contributions. I'll copy this to the Contractor Talk board as well, as several members there also offered their expertise. Once again, Thanks.
Sean:grin: :grin:
 
Good find.

I had a similar problem with a roll of #12 THHN. I was adding an outlet for someone and was using metal boxes and emt. The pipe run was less than two feet. When I turned the power back on the breaker went "pop". I checked to make sure I hadn't reversed the connections by accident and then turned it on again with the same results, checked to make sure nothing was touching. Finally pulled out the wire and it had a big nick in it and this was half way through the roll. Checked the roll and every few feet there was insulation missing off the wire. Don't know why I hadn't had a problem before.
 
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