Bad batch of breakers?

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rob42

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Ran into a situation I haven't seen before. New kitchen sub panel setup with both AFCI-only and AFCI+GFCI combo breakers. The AFCI-only circuits have GFCI at the receptacle.

When an appliance with a universal motor is used AFCI-only breakers nuisance trip with an arc fault, but combo breakers don't. Swapping breakers around temporarily confirms it's the breaker.

Possible I have a bad batch of breakers? Can't imagine why the combos would be less likely to trip for an arc fault.

(Breakers are Murray MP-AT2/GAT2).
 
I've heard from local electricians that arc-fault breakers don't play nice with GFCI outlets (receptacles). I am mostly seeing everything protected at the panel with either AFCI breakers, GFCI breakers, or Dual Function AFCI/GFCI breakers.
 
Since you say it is specifically an arc fault trip, you must have confirmed that using the breaker diagnostic code.
With only a normal current (but greater than 7Amp!) drawn, it would have to be a series arc signature. I cannot think of anything that the GFCI could do to influence the signature of the brushes in the universal motor, but maybe I just do not have enough information.
The AFCI-only breakers will contain different firmware and maybe different hardware from the dual function (combo just means series and parallel arc) breakers. That could make all the difference.
Do the AFCI-only breakers trip on a universal motor and 7A load even when there is not a receptacle GFCI in the picture?
 
Joe.B said:
I've heard from local electricians that arc-fault breakers don't play nice with GFCI outlets (receptacles). I am mostly seeing everything protected at the panel with either AFCI breakers, GFCI breakers, or Dual Function AFCI/GFCI breakers.
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Are they using the cheapest GFCI receptacles they can find? those don't always play well with a lot of things that put "noise" on the lines, as well. And many AFCI's don't play well with a lot of things that have nothing wrong with them, even if on the supply side of the AFCI at times.
 
kwired said:
Are they using the cheapest GFCI receptacles they can find? those don't always play well with a lot of things that put "noise" on the lines, as well. And many AFCI's don't play well with a lot of things that have nothing wrong with them, even if on the supply side of the AFCI at times.
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I am also skeptical of the AFCI don't play well with GFCI claim. It seems to be a common urban legend
 
electrofelon said:
I am also skeptical of the AFCI don't play well with GFCI claim. It seems to be a common urban legend
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There are no major brand name GFCI's that should interfere with other components. There are other components that create problems, particularly when it comes to inductive kickback or RF interference, for even some the better GFCI's that are made though.
 
electrofelon said:
I am also skeptical of the AFCI don't play well with GFCI claim. It seems to be a common urban legend
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Agreed, it's likely a user error or cheap products. But, that is what I've heard from more than one electrician, so there may be a grain of truth there. I only shared for discussion sake. Other electricians I've talked to are unwilling to use the breaker to provide GFCI because they want the reset button at the outlet, not in a panel somewhere. I get that too.

Just because I posted it doesn't mean I believe it ;)
 
I wonder if the contacts opening in a GFI receptacle tripped under load could cause a AFCI to trip. Especially if the GFI was old or in poor condition.
 
About the only thing I can think of that would be problematic with GFCI receptacles and AFCI breakers might be if the afci is older and still has ground fault component that might trip if MOV’s in the GFCI receptacle are clamping a spike to ground.
 
Todd0x1 said:
I wonder if the contacts opening in a GFI receptacle tripped under load could cause a AFCI to trip. Especially if the GFI was old or in poor condition.
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What about other switching in a AFCI protected circuit?

Can't say I know much at all about exactly how AFCI's work, but you would think they need to be able to ovelood arcing from normal switching for a few cycles or you wouldn't be able to switch any loads without tripping issues.
 
mopowr steve said:
About the only thing I can think of that would be problematic with GFCI receptacles and AFCI breakers might be if the afci is older and still has ground fault component that might trip if MOV’s in the GFCI receptacle are clamping a spike to ground.
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I didn't know GFCI receptacles had MOVs in them. Never heard of one that had surge suppression.
 
rob42 said:
New kitchen sub panel setup with both AFCI-only and AFCI+GFCI combo breakers. The AFCI-only circuits have GFCI at the receptacle.

When an appliance with a universal motor is used AFCI-only breakers nuisance trip with an arc fault, but combo breakers don't. Swapping breakers around temporarily confirms it's the breaker.
Click to expand...

To me this statement would indicate that the AFCI-only breakers are tripping with both regular receptacles and GFCI receptacles. If so then it would seem that the GFCI receptacles are not responsible for the tripping.
It would be good for the OP to clarify this in order to get the best guidance from the forum.
 
Thanks for the replies all, this was very helpful.

As suggested, I temporarily swapped the GFCI outlets for regular ones, but the tripping still occurred. Bought a set of brand new AFCI breakers and this has fixed the issue.

The Murray MP-AT2s that were installed were "new" but discontinued, so the replacement was the equivalent Siemens part (QAF2). Perhaps the firmware in the older Murrays is overly sensitive?

Guess I did have a bad batch of breakers after all 😁
 
kwired said:
I doubt they are significant surge protection for the sake of user items, but could see them having MOV's on the GFCI logic board just for some protection for the board.
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Iirc, I found this out once when I had a call that a GFCI receptacle started chattering when a wall fan control on the same circuit was switched to different speeds. I think that was when I took the GFCI apart and found a set of mov’s on the line side that I thought to be bad. Changed the GFCI receptacle and all was good again.
 
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