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Discussion Starter · #1 ·
Had a call back involving an AFCI tripping, not much to do except replace it. Read up on the matter and was surprised to read that there really is no standard for AFCIs, although they are required. I guess both Fox and Ideal make a tester for them -- Fox's is cheaper, but what I really would like to find is a tester that can test the problem branch circuit to determine if there really is an arc fault or if there is a "noisy" device causing the tripping.

As I replaced the breaker (forty dollars a pop and twenty-five dollars worth of gas) I suddenly felt very vulnerable. With everything on, current read 8.8 amps, but what now? Replace the AFCI with a regular breaker? No way. Keep replacing breakers (at forty dollars a pop) until I get one that works? Or doesn't?

House catches fire, AFCI in the panel, I did what I could, right? House catches fire and no AFCI in the panel, bring a lot of money to court, huh?

Does anybody know of a branch circuit tester that might be able to detect arc-fault type problems in circuits?
 

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Does anybody know of a branch circuit tester that might be able to detect arc-fault type problems in circuits?
Yea. They're called AFCI breakers. :laughing: You might be able to narrow down a possible arc with a megger.

And to my knowledge, no portable tester exists for AFCIs.
 

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I do not know of device to test the arc fault, but I have found that even over tightening the screw in the back holding the wire in place (I have no idea what its called, or just cant think of it right now) can cause the arc fault to trip. When we have a problem we have a standard trouble light on a short cord that we just start plugging into the devices on that circuit until we trip the breaker, once we find it often the repair is just loosening the screw in the back of the box a couple turns.

I have not personally ran into an arc fault problem that could not be resolved by loosening the connection in the back of the box yet, so my help may be limited.
 

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Megger the circuit.
If the box clamp (?) is to tight you have damaged the conductor and you need to do more than loosen the screw. (If we are discussing the box clamp.)
 

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Megger the circuit.
If the box clamp (?) is to tight you have damaged the conductor and you need to do more than loosen the screw. (If we are discussing the box clamp.
ya the box clamp.
with the AFCI the box clamp can be tight enough to trip the breaker even though the wire is not damaged.
 

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I do not know of device to test the arc fault, but I have found that even over tightening the screw in the back holding the wire in place (I have no idea what its called, or just cant think of it right now) can cause the arc fault to trip. ......
The terminal?
 

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ya the box clamp.
with the AFCI the box clamp can be tight enough to trip the breaker even though the wire is not damaged.
I don't see how the clamp being so tight it could trip the AFCI hasn't already damaged the wire insulation. I would megger it and see what happens from there.
 

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I don't see how the clamp being so tight it could trip the AFCI hasn't already damaged the wire insulation. I would megger it and see what happens from there.
I agree. Simply loosening the clamp is only a band aid. The underlying problem is still there.
 

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You have had to damage the insulation, Loosening the clamp takes away the ground connection (the arc location). BUT the insulation is damaged.
 

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If you want you can check the insulation. I am just passing my experiance on, and i have seen this many times, esspecially when using your drill to tighten the clamp.

EDIT, I am also assuming this arch fault problem is with lumex (romex?) and not bx. But while I havent really used lumex in a while I do remember the arch fault problem being the clamp was too tight, and there was no damage to the insulation.
 

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Discussion Starter · #12 ·
Very interesting! So, problems with AFCIs have been helped by loosening the box clamps? Good to know.

As I wrote, Fox and Ideal both make portable testers for the breakers themselves, but I know of nothing that can test the branch circuit to determine if there really is a problem. I hate to trroubleshoot by "Easter Egging," but I guess that's all one can do.

I'm interested in the use of the megger, although I can't make the idea work in theory. Of course, AFCIs don't work as I assumed they did. Seems sort of flaky, the theory of operation I read. Seems like they would operate by detecting the high frequency generated by arcing, but they (apparently) operate by detecting a voltage signature peculiar to arcing. In theory, I cannot imagine a voltage signature for arcing that couldn't be produced by certain loads.

Thanks for the responses. Be careful out there.
 

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Murray had an afci recall on 20 amp afci's a few months back from what I was told. What brand did you say your was.
 

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Jeff:

What causes an "arc" between conductors, typically a breakdown in insulation be it, air, porcelain, glastic, or thermoplastic. Whenever there is a breakdown of the insulation the breakdown MUST be addressed. Now loosening the clamp might be a short term repair, but in the long run the insulation was damaged and this issue will pop it's head again.

By loosening the clamp you have moved the conductors apart, but the damaged was done.
 

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Jeff:

What causes an "arc" between conductors, typically a breakdown in insulation be it, air, porcelain, glastic, or thermoplastic. Whenever there is a breakdown of the insulation the breakdown MUST be addressed. Now loosening the clamp might be a short term repair, but in the long run the insulation was damaged and this issue will pop it's head again.

By loosening the clamp you have moved the conductors apart, but the damaged was done.
I have looked at the insulation before and there was no visible damage at all.
AFCIs are VERY sensitive, just squishing the insulation can make it thin enough that a TINY amount of current will pass between the conductors and thus trip the AFCI, if the clamp was tight enough that the insulation was broken and the conductor was actually touching the box it would trip a normal breaker even.
Insulation is flexible, and pliable, and while the clamp may slightly deform it, it will go back to how it was once the presure it released, or at least back enough for it to not matter.
 

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I have looked at the insulation before and there was no visible damage at all.
AFCIs are VERY sensitive, just squishing the insulation can make it thin enough that a TINY amount of current will pass between the conductors and thus trip the AFCI, if the clamp was tight enough that the insulation was broken and the conductor was actually touching the box it would trip a normal breaker even.
Insulation is flexible, and pliable, and while the clamp may slightly deform it, it will go back to how it was once the presure it released, or at least back enough for it to not matter.
AFCIs have GFCI protection built in - not Class A (5 ma) but something more like 30 ma.
120v/.030a = 4000 ohms
120v/ 20a = 6 ohms
It takes less damage to insulation to cause an AFCI to trip from a ground fault than a standard breaker.
 

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AFCIs have GFCI protection built in - not Class A (5 ma) but something more like 30 ma.
120v/.030a = 4000 ohms
120v/ 20a = 6 ohms
It takes less damage to insulation to cause an AFCI to trip from a ground fault than a standard breaker.
Yes, I meant if the insulation was broken, as in visually exposing the bare wire.

Not all AFCI's are listed as GFCI as well. I have never actually seen a dual listed one, but I have heard of them.


I thought a GFCI was 6mA? not that 1mA is really all that much.
But ya the hearsay about the dual listed was something about the GFCI being 30mA and not the standard 6mA
 

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A standard AFCI has built in GFCI protection, just not at the class A level. A standard AFCI is NOT the same as a GFCI/AFCI combination breaker. (Which does have the 5 ma setting).
 

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Discussion Starter · #19 ·
I suppose a too tight clamp could change the inherent capacitance between the conductors and cause the appearance of leakage (called a parallel arc, I think.)

Reading the responses, I wonder if AFCIs might have the same aversion to shared neutrals as GFCIs.

Hmmmm.
 

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Reading the responses, I wonder if AFCIs might have the same aversion to shared neutrals as GFCIs.

Hmmmm.
If you mean shared neutrals as in MWBCs, they sure do. As well as downstream EGC/neutral contact.
 
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