Arc Fault nuisance tripping

[John Leiby]

I have a 20 amp arc fault breaker that trips in the middle of the night. The home owner has 4 night lights in this room. It does not trip every night. We removed a surge protector and a battery backup that was in the room also. Breaker has been replaced several times, all outlets were inspected and all wiring was inspected with no problems found. Cutler Hammer acknowledged that they were having issues with breakers tripping with surge protectors and sent us new breakers. Problem is still occuring.

 

[bphgravity]

If more than one breaker fails on the same circuit, it is more likely there is something downstream of the breaker that is not electrically compatible with an AFCI or you do indeed have a wiring problem.

Check for points where grounded and grounding conductors may be making contact. Remove all loads with high inrush currentor or with Non-Sinusoidal Waveforms. Disconnect nearby circuits to see if "Cross Talk" is occuring between the adjacent circuits.

Good Luck!

 

[mdshunk]

At the risk of beating a dead horse, I still must ask... have you megger'd the circuit?

 

[ty]

Cutler Hammer acknowledged that they were having issues with breakers tripping with surge protectors and sent us new breakers.

Wow!
We are CH installer and have never heard of this issue.
Did CH send you new breakers, or did the supplier give them to you?

Turn all switches 'off', unplug everything, disconnect breaker, test continuity from white to ground. Start troubleshooting from there.

I purdy much agree with Bryan.

 

[Bmadmax40]

Exactly...
I don't think that u have to meg the circuit to find a fault. Arcfault breakers are like GFI's in the sense that a small groundfault from either hot or neutral may SOMETIMES trip the brkr. If u changed the breaker and the problem still there, it was pointless to do so. Just Ohm the circuit. The arcfault brkrs are reliable (as GFI's) when INSTALLED properly. They are sensitive to ground fault.

 

[mdshunk]

Exactly...
I don't think that u have to meg the circuit to find a fault.

Such a silly man! :roll:

I've lost count of the number of nuisance tripping AFCI circuits that I've troubleshot with a megger that other contractors gave up on or couldn't figure out. If the problem will show up on an ohm meter, the AFCI will normally trip as soon as you try to reset it. For intermittant tripping, you need to use a megger. Same with GFCI's.

 

[augie47]

afci

afci

my experience has been the same as marc's. sometimes the ole megger pays for itself, of course, if the megger shows falult, the fun has just begun.

 

[mdshunk]

my experience has been the same as marc's. sometimes the ole megger pays for itself, of course, if the megger shows falult, the fun has just begun.

Thank you for that.

Sometimes I feel like the lone drummer for the Megger tribe. I can't even begin to tell you what a valuable troubleshooting tool it has been for me over the years. For as little as 100-150 bucks, every contractor and every service truck should have one. It's a no-brainer, in my opinion. It's just a freaking ohm meter that puts a little "juice" to the conductors to make hard problems declare themselves more clearly.

 

[brantmacga]

shunk, can you recommend a good $150 megger? thanks.

 

[mdshunk]

shunk, can you recommend a good $150 megger? thanks.

Sure can... Either the Extech 403360 or the Supco M-500 are both excellent choices for troubleshooting type meggers.

The Extech is digital, and the Supco uses "idoit lights". Throw away your old hand-crank meggers.

 

[brantmacga]

ok thanks.

Throw away your old hand-crank meggers.

next you'll tell me to get rid of my hand-crank wall phone. and you say silly man.

 

[LarryFine]

I've lost count of the number of nuisance tripping AFCI circuits that I've troubleshot with a megger that other contractors gave up on or couldn't figure out. If the problem will show up on an ohm meter, the AFCI will normally trip as soon as you try to reset it. For intermittant tripping, you need to use a megger. Same with GFCI's.

Marc, how does the problem manifest itself, and what do you find to end up being the problem?

 

[mdshunk]

Marc, how does the problem manifest itself, and what do you find to end up being the problem?

One of everything.

On AFCI circuits, I mostly find a section cable inside a wall that is faulty. Just figure out a way to refeed a new piece from "A" to "B" and the problem is solved. I have no idea what might be wrong with these isolated pieces, since people obviously don't want you tearing the walls apart. They are just abandoned in place. Naturally, I find a good many "leaky" appliances. That's a tough thing to explain to a customer, since they're quick to tell you that it works just fine on a non-GFCI or non-AFCI circuit. The megger doesn't lie, however.... the equipment leaks hot to ground or neutral to ground. Some people blame some paddle fans and some vacuum sweepers for tripping AFCI's for no good reason, but if you megger this equipment hot to ground or neutral to ground it's for a reason. The equipment is faulty. Right now, many Genie garage door openers and many furnace UV lamps will trips GFCI's and AFCI's right out of the box. I'm finding over 100ma leakage in these two items.

 

[Pierre C Belarge]

I agree with Marc that the megger is not used as much as it can be in the work we perform.

One thing to remember about Arc Fault CBs is that the GFCI portion of the CB is usually set at 20 - 40 miliamps. Sometimes the CB at those levels will not trip on GFCI until some kind of load is applied. That load may not be applied as part of the circuit that is initially turned on. This could be such as a branch circuit energized and maybe a light or other load is not turned on until later, or someone plugs something into the receptacle at a later date.

 

[martymacman]

megger

megger

please explain how to troublshoot with the megger

 

[don_resqcapt19]

Bryan,

If more than one breaker fails on the same circuit, it is more likely there is something downstream of the breaker that is not electrically compatible with an AFCI or you do indeed have a wiring problem.

How much worse is this problem going to get when we have to start using the combination type AFCIs on 1/1/08? Remember that the branch circuit/feeder AFCIs don't look at the arc unless the current exceeds 75 amps, the combination type looks when the current exceeds 5 amps.
Don

 

[cowboyjwc]

You can check continutity from neutral to ground until the cows come home and still miss the problem. An arc-fault is designed to find just that an arc. it could be line to neutral, line to ground, neutral to ground, line to line (including a cut hot that is arcing end to end).

I've never been much for using a megger, but I think Marc has the right idea.

Guys just have to be more careful how they handle their MC cable, can't just be throwing it around and dragging it all over and be careful how you staple it and use lots and lots of nail plates.

 

[Terrynistler]

Damn the hit cycles on those two items went up 50% in the last 30 minutes

 

[don_resqcapt19]

John,

You can check continutity from neutral to ground until the cows come home and still miss the problem. An arc-fault is designed to find just that an arc.

That is not correct...all AFCIs have built in ground fault protection set at about 30mA. The most common installation problem that causes an AFCI trip is a neutral to ground short.
Don

 

[cowboyjwc]

Don,

I thought that someone said that an arc-fault worked like a Gfci and that is not true and I said ground to neutral, but before when you got a cut hot wire all that would happen is you had no power to one or more receptecales I don't believe that this would cause a GFI to trip.

My point was that a wiggy and a continuity tester is not all that you need and I think that Marc has the right idea about using a meggar.

A GFCI will de-energize a circuit or portion thereof wihin an established period of time when a current to ground exceeds the values established for a class A device (4mA-6mA)

An AFCI provides protection from the effects of arc faults by recognizing characteristics unique to arcing and by functioning to de-energize the circuit when an arc fault is detected.

Actually you could have a hot to nail arc and you're not going to find that with a continuity tester.