AFCI Tripping

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RJB100

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I have a friend who's AFCI trips. She had someone change it out thinking it was defective. However it still trips. Not all the time though just when she gets home from work and it is tripped. I checked all of the connections and devices and they all look good. Nice and solid. What is odd though that the only thing plugged in on that AFCI circuit is the alarm clock which is plugged into a power strip. When she is at work is when it trips. Right now I have swapped that room with another to see if it trips or not trying process of elimination. Any ideas!
 
iwire

iwire

Moderator
Staff member
Location
Massachusetts
At the panel lift the white, bare and black. Use a meter and make sure there is absolutely no continuity between white and bare.

If the bare ground is touching the neutral anywhere in the circuit it can trip the AFCI.
 
brantmacga

brantmacga

Señor Member
Location
Georgia
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Former Child
i've had this happen where when pushing the receptacle back into the box, sometimes the ground can get pushed next to the neutral screw. i had one do it they other day; the ground wire visibly appeared to be making no contact, but when i pushed back away from the screw, the tripping stopped. this was a similar situation where it wasn't an instantaneous trip. it would hold anywhere from 5 min. to 5 hrs. before tripping.
 
480sparky

480sparky

Senior Member
Location
Iowegia
Sometimes the drywalls will nick the insulation on a wire (huh, imagine that!), and that could be shorting to ground as well.
 
mdshunk

mdshunk

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Location
Right here.
RJB100 said:
I'll try it! Thank you
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Since it's not an immediate trip, nothing may show on your ohm meter. I generally root out these intermittantly tripping AFCI's with a megger. It's generally come down to an isolated section of cable within the wall or ceiling that megger's bad. I've never removed any to see what the scoop was, since that would do damage just to satisfy a curiosity, but I blamed it in my mind on an overdriven staple. A few times it was an exterior receptacle jumped off an AFCI circuit that had drawn damp or had insect nesting material in the receptacle box.
 
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Jack Maynard

Member
Location
Portland, Oregon
mdshunk said:
... It's generally come down to an isolated section of cable within the wall or ceiling that megger's bad. I've never removed any to see what the scoop was, since that would do damage just to satisfy a curiosity, but I blamed it in my mind on an overdriven staple. ...
Click to expand...

So how have you fixed it if you don't open the wall? Take that circuit off the AFCI? Fish a new cable from above or below?

I've had plenty of afci trips, and it has always come down to the neutral/ground contact in a recep box. The classic case is when plug checking a just-trimmed AFCI circuit, the breaker holds while chekcing plugs, but trips just as soon as a light is turned on. I chalk it up to the afci only tripping when there is enough current that the neut/ground short can be seen at the breaker, much the way a gfci acts under the same circumstances. Funny that the small current drawn by a plug checker will not trip the afci in this case.

Wasn't it squareD homeline afci's that were recalled two years ago because of false/nusance trips? My shop mostly installls CH BR panels and their afci's seem pretty solid. And two-poles are now available for retrofitting in multiwire brance circuits feeding bedrooms. Not cheap though.
 
mdshunk

mdshunk

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Jack Maynard said:
So how have you fixed it if you don't open the wall? Take that circuit off the AFCI? Fish a new cable from above or below?
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By any means necessary.

The neutral touching ground is an easy one to troubleshoot, since they generally happen right away. It's the intermittant one's that require you to break out a megger. I'm telling you, when we start putting AFCI's everywhere in '08, guys that think I'm goofy for preaching about meggers are going to be thanking me. You know, in the UK, the actually have to have the wiring in buildings completely megger checked on a regular basis, per government requirements? The test periods are -

A domestic (house) every ten years
This varies with a rented property to a test being done on every tenancy change.

industrial/commercial every five years

Bars and clubs every year

Temporary structures ( site huts on building sites ) Every three months
 
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wptski

Senior Member
Location
Warren, MI
mdshunk:

Yes, in the UK, etc. they used something like the Fluke 1653 loop tester which isn't sold in the USA.

If you were to meggar a circuit with a AFCI tripping problem, what value would you consider to be a problem?
 
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tom baker

tom baker

First Chief Moderator
Staff member
Location
Bremerton, Washington
If an AFCI is tripping due to a neutral to ground, then the AFCI will trip at 50 mA.
For an insulation test, when new I would expect around 10 to 50 megs at the 500 volt scale. I've seen submersible pumps meg at 1000 with 300 ft of cable.
Of course with nothing plugged in or turned on...
 
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wptski

Senior Member
Location
Warren, MI
mdshunk said:
Anything under 20 meg at 500 volts I will condemn. I'd like to see infinity.
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I did two circuits that I could easily unplug everything and the lowest reading was 168M@500V. Infinity on a meggar or insulation tester, really??
 
M

masterelect1

Senior Member
Location
Baltimore
mdshunk said:
Anything under 20 meg at 500 volts I will condemn. I'd like to see infinity.
Click to expand...


Re: Infinity- there is no such thing: only an instrument which does not scale high enough to read the actual value- in this case, resistance. What is actually being read is a value which is above the meggers capability.

I know from your your past posts that you use/understand meggers quite well- just trying to eliminate confusion for some on here not quite up to par on megger usage. I have found since I began inspecting that many in the construction field have lots of misconceptions regarding the use of a megger as a troubleshooting tool. Not meant to be a p---ing contest
 
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mdshunk

mdshunk

Senior Member
Location
Right here.
cschmid said:
Marc you are good advertiser some megger company should give you a new one for your promotion of them...any salesmen out there can you hook up marc...
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:grin:
Naw, I have some nice Meggers. What I really need is a new DLRO. The one I use is from the 60's. Maybe I should figure out a way to work in DLRO's in my next couple hundred posts? :wink:
 
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