AFCI troubleshooting suggestions

[ptonsparky]

I would like to discount over driven staples but on a walk thru prior to a rough in inspection, I spotted a damaged MC cable due to a misplaced whack. IDK who was responsible but the job foreman was pretty frustrated.

 

[goldstar]

I wouldn't totally rule out an over driven staple, but I still lean towards a neutral to EGC fault. Have you taken everything on that circuit apart, including switches, lights, junction boxes, etc? You can verify the fault by disconnecting EVERYTHING and at the panel, take the EGC and neutral off the bar. Then check for continuity between the EGC and neutral.

Thanks Bill. I've taken apart (2) 3-gang, (1) 2-gang switch box and a receptacle JB in order to find this problem. I narrowed it down to the 3-wire NM cable between both 3-way switches which led me to believe it's either an over-driven staple or possibly a sheet-rock screw that hit the cable. I did not take the recessed lights down. There was no EGC-N short in that wiring. The wiring that I could see exposed in the basement and the wiring to the new MBP was done neatly and with extreme care. I want to believe this was an inadvertent problem caused by a staple or a sheet-rock screw. It could have happened to any one of us and not necessarily a hack or an apprentice IMHO. Thanks for the reply and your insight.

 

[goldstar]

As you say it could be an over driven staple but it could be almost anything. If you can learn who did the work that can give a clue as to what you may find.

It's hard to believe that this renovation was done without permits but I found no inspection sticker on the MBP for the renovation or the service upgrade. So, I asked the HO to make an inquiry to the bldg dept. to find out why. At that point he will find out who the EC was and he can pursue it further if he wishes to.

 

[ramsy]

I did not take the recessed lights down. There was no EGC-N short in that wiring.

Do you mind sharing what instrument is telling you this ?

 

[goldstar]

Do you mind sharing what instrument is telling you this ?

For the entire circuit I initially used an Ohm meter. Once I established there was an EGC-N short I removed the circuit wiring in the breaker panel and used a "sounding" continuity tester that I made up years ago (everyone laughs at me when I make up my own stuff - like test equipment). That way I didn't have to keep going into the basement each time I split apart wiring. I narrowed it down to the 3-wire between the two 3-way switches and went no further. Once I remedied that situation, I put all the wiring back together in the JB's and re-connected the AFCI breaker.

I did make an assumption that it must have been an over-driven staple or a sheet-rock screw but I wasn't about to go tearing open walls and ceilings JUST to find the EXACT problem.

 

[bradleymattlin]

It has to be a staple. What else could it be? Whoever heard of an AFCI tripping for reasons that have nothing to do with the wiring in the house?

I have about two-three arc faults that will trip every time we get a bad storm.

 

[kwired]

It has to be a staple. What else could it be? Whoever heard of an AFCI tripping for reasons that have nothing to do with the wiring in the house?

I've been there when they tripped when POCO had a cycling of a recloser as well. Maybe back in about 2010 or so, but was in new house we were still working in. Power "blinked" which is not totally uncommon on rural systems, reclosers operate occasionally for many reasons when you have a system that covers such large area in the open wilderness. Several AFCI's in that house tripped at that time but not all of them. The ones that did trip was mostly ones that had active lighting loads at the time so I assumed loading had something to do with them tripping and maybe a transient voltage on the line was another factor?

 

[ActionDave]

My post was a sarcastic comment based on the well known fact that AFCI breakers trip for no good reason at all.

 

[kwired]

My post was a sarcastic comment based on the well known fact that AFCI breakers trip for no known good reason at all.

FIFY

Bet if FPE panels were still being sold in the US they could provide AFCI's that don't trip

 

[macmikeman]

After isolating it with an ohm counting meter , I would have removed wiring from both ends of the three wire cable mentioned and tested further with a megger. For at least a minute of time. And......... I would actually have used the Supco500 megger to be specific so I could show the dwelling owner the outcome of my test via the led display , which if bad/ damaged wire will result in a red led lighting up. Doing so removes any homeowner doubt about what you have found. Then I probably would have sold him on replacing the wiring run via probably some form of surface wiring method , of which there are a few varieties and ways to get er done. Either that or a wireless switching system. Either way I am of the opinion that it's best to be able to sell some solution since I am already there having taken up some of my time and travel.

 

[ramsy]

.. I would actually have used the Supco500 megger to be specific so I could show the dwelling owner the outcome of my test via the led display , which if bad/ damaged wire will result in a red led lighting up. Doing so removes any homeowner doubt about what you have found.

Did one like that this morning. Defective power strip would not have been found with a continuity meter.

Thanks for mentioning the Supco, will look into that model.

 

[ramsy]

I would actually have used the Supco500

Oops, Supco500 is 500 Volts only.

Good way to smoke 120 V appliances, lights, A/GFCI beakers, & devices.

..Then I probably would have sold him on replacing the wiring run via probably some form of surface wiring method

Yes, after smoking the 300v rated wire nuts, with 500 V tester, I could see a homeowner falling for remodel wiring.

If joe homeowner wants to keep existing GFCI devices and building wiring intact, the best way is to make sure no contractors touch your building with a "Megger tester".

 

[tortuga]

Oops, Supco500 is 500 Volts only.

A good description of a megger test is the one required for RV's in 551.60
I have often done a similar test to find and solve AFCI issues in dwellings.
You do of course remove anthing sensitive like a light fixture or a GFCI first.

 

[macmikeman]

Oops, Supco500 is 500 Volts only.

Good way to smoke 120 V appliances, lights, A/GFCI beakers, & devices.



Yes, after smoking the 300v rated wire nuts, with 500 V tester, I could see a homeowner falling for remodel wiring.

If joe homeowner wants to keep existing GFCI devices and building wiring intact, the best way is to make sure no contractors touch your building with a "Megger tester".

Did you not take note that I said after unhooking the cables from the 3 way and then test? Precisely because of the Led light.
Also, the Supco500 usually only outputs 400 volts on a good day, and wire nuts are no way getting smoked using this little mini megger. I doubt it even hurts if you were to sneak up and stick both prongs on some one else like a teenager prank , in the way we did in vocational school with a crank megger when the class teacher left the room ....

 

[ramsy]

A good description of a megger test is the one required for RV's in 551.60
I have often done a similar test to find and solve AFCI issues in dwellings.
You do of course remove anthing sensitive like a light fixture or a GFCI first.

Dwellings with cloth or rubber Type R insulation were made well into the 1960's, and never rated over 60 deg.C, much less for modern hi-pot testing per NEC 551.60.

Like bulls in a china shop, most contractors will destroy these buildings with Megger testers, then show property owners what lightning does when breakers blow immediately.

Many labor shops prefer remodel wiring when encountering hack jobs, Knob & Tube, or Aluminum, and are legally licensed to contract & advertise accordingly, with little incentive to disclose other listed means of repair for chump change, much less employ the labor skills to make such repairs.

 

[ramsy]

Did you not take note that I said after unhooking the cables from the 3 way and then test? Precisely because of the Led light.
Also, the Supco500 usually only outputs 400 volts on a good day, and wire nuts are no way getting smoked using this little mini megger. I doubt it even hurts if you were to sneak up and stick both prongs on some one else like a teenager prank , in the way we did in vocational school with a crank megger when the class teacher left the room ....

Except for European standards for insulation tests during domestic commissioning @ 500+ V for their 220 V systems (United Kingdom BS7671-2008 Appendix 13) US regulatory bodies may only defer to OEM instructions for proper application of tools & equipment. The Supco500 does include appliances among its undocumented list of applications, however, unclear if that is 240v and 120v appliances.

My solitary voice, buried in the middle of this long forum thread, won't add exceptions for cloth, rubber, or other fragile wiring, much less change the industry practice of Megger test procedures, especially when clients refusing to sign your remodel wiring contract, or attempt competitive bids, are left with blasted wire & bolted faults where an old, but working electrical service used to be.

 

[tortuga]

Like bulls in a china shop, most contractors will destroy these buildings with Megger testers

There has got to be a story behind that statement.

I have used Extech meggers, like I said with all devices removed, these are powered by AA batteries and basically work like a camera flash.

380260 - Autoranging Digital Megohmmeter | Extech Instruments

Autoranging Digital Megohmmeter. 1000V digital tester with large dual backlit display

www.extech.com

Just used it recently to find a intermittent fault in a undergound wire.

 

[macmikeman]

I find some answers sometimes here to be astounding. I'm going to call Supco up and ask how many buildings have burned down due to use of their low powered insulation testing device they sell................................ My feelings is it's going to be zero, and if I call em again in twenty years its still going to be zero. Most likely somebody else will have to make the third call twenty years after that....

 

[ramsy]

There has got to be a story behind that statement.

Standard breakers & fuses tolerate low level faults that will often trip an AFCI, GFCI, or Dual Function device.

Commercial and industrial electricians may not care about buildings riddled with low level faults, until someome complains about the electric bill.

I find some answers sometimes here to be astounding.

I'm sure ignoramuses on this forum, along with contractors in my area, still rip out AFCI's & Dual Function AFCI/GFCI's after inspection, by local AHJ's not yet convinced to amend them out.

For many years I was the only residential service guy on this forum that reported success with AFCI's, and my success did not subject existing buildings with old wire to Megger-testing voltages.

 

[macmikeman]

Standard breakers & fuses tolerate low level faults that will often trip an AFCI, GFCI, or Dual Function device.

Commercial and industrial electricians may not care about buildings riddled with low level faults, until someome complains about the electric bill.



I'm sure ignoramuses on this forum, along with contractors in my area, still rip out AFCI's & Dual Function AFCI/GFCI's after inspection, by local AHJ's not yet convinced to amend them out.

For many years I was the only residential service guy on this forum that reported success with AFCI's, and my success did not subject existing buildings with old wire to Megger-testing voltages.

Romex® Brand SIMpull® Type NM-B Cable

NMB 12/2 G 1000SpC​

Southwire #: 28828201

Nonmetallic-Sheathed Cable. 600 Volt. Copper Conductors. Color-Coded Jacket. SIMpull® Jacket Designed for Easier Pulling.​