Not Sold on AFCI's

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A/A Fuel GTX

A/A Fuel GTX

Senior Member
Location
WI & AZ
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Electrician
I'm having some troublesome, random breaker trips that have no rhyme or reason. The house in particular is mine and I wired it myself. It is less than a year old and per code, I used AFCI's as required. So far, three of the circuits have had tripping issues that mysteriously come out of nowhere and seem to be fine after several trips and resets. I'm wondering if these breakers have break in period and the excersizing of the breaker during the resetting ritual is clearing the seemingly erroneous faults. FWIW, these are Cutler Hammer CH's. Anyone else having these issues?
 
A/A Fuel GTX said:
So far, three of the circuits have had tripping issues that mysteriously come out of nowhere
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I've encountered problems with vacuum cleaners tripping AFCIs. It would probably help if you stated what you have plugged into those receptacles when the AFCIs trip.
 
Jon456 said:
I've encountered problems with vacuum cleaners tripping AFCIs. It would probably help if you stated what you have plugged into those receptacles when the AFCIs trip.
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There is nothing I can pinpoint as to the reason. Sometimes it's just turning on a light fixture and sometimes there is no event at all proceeding the trip.
 
I have had trouble with GE and SQd brands . In particular tripping when electronics are involved- flat screen tv's, soft start tools, fancy vacuums and the like. Problems with the SQd breakers went away when the carpenters were done working. Problems with the GE breakers did not show up until eight months later.

Contacted GE and they sent me some new, improved breakers better breakers that have not caused problems so far.
 
Well. if the nusiance tripping continues, I'm going back to non AFCI's. It's my place and I'm fine with that. I think this whole concept was rammed down our throats with not nearly enough justification.
 
I think the trouble has come about with the new combo AFCI's. I have the old style in my house and don't have any trouble. I was an AFCI defender for a long time. I would go out and trouble shoot AFCI problems and fix them all the time. It was always a problem with the circuit, not the breakers. Then the combo styles came out and they would trip on a circuit that I knew was good. I am now an confirmed "AFCI HATER".
 
I wired two bedroom circuits last year on AFCI's. After a year one of them tripped and could not be reset. I swapped the two circuits and both held. I did not think that would work and am amazed and baffled as to why it did.
 
Surge protectors by design will shunt surges to ground.

Since AFCI breakers contain GFEP such shunting by those power strips can cause nuisance tripping during surge events.
 
kbsparky said:
Surge protectors by design will shunt surges to ground.

Since AFCI breakers contain GFEP such shunting by those power strips can cause nuisance tripping during surge events.
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Did you know that most if not all AFCI & GFCI devices contain a surge protection device inside as part of their design?
 
ELA said:
Did you know that most if not all AFCI & GFCI devices contain a surge protection device inside as part of their design?
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Moot point. Since that internal surge device is designed to only protect the guts of AFCI/GFCI unit?

IF you plug in your surge power strip for your computer or other electronics, it will still shunt surge events, and the AFCI/GFCI device can trip out when that happens....
 
What is your point then? That Surge protectors cannot be used on circuits with AFCIs or GFCI's? Like that is going to happen.

AFCI's and GFCI's are specifically designed to withstand transient events to a certain level. If the transient is severe enough (beyond design level) it can become be the direct cause of the electronic devices tripping.
An AFCI is way more likely to trip due to the transient itself than due to shunted current through the protection device. Thus exactly why it is not a moot point.
 
A/A Fuel GTX said:
I think this whole concept was rammed down our throats with not nearly enough justification.
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I'm with you on this 100%.

I've had numerous CH-tan handle AFCI's installed and haven't had a specific problem. However, having said that I would suspect that any device that would cause the slightest arc would set them off. The last residential job that I had the tile guy, using the tile saw, was able to make the tile cut but as soon as he released the trigger the AFCI would trip. Same was true for the carpenter and the trim saw.
 
goldstar said:
I'm with you on this 100%.

I've had numerous CH-tan handle AFCI's installed and haven't had a specific problem. However, having said that I would suspect that any device that would cause the slightest arc would set them off. The last residential job that I had the tile guy, using the tile saw, was able to make the tile cut but as soon as he released the trigger the AFCI would trip. Same was true for the carpenter and the trim saw.
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Those cases likely tripping because of some inductive kick back related issues.

My understanding at one time was that the AFCI component is a processor that evaluates the current wave form. It is basically programmed to accept specific current waveform patterns. Any waveform pattern not in the list of acceptable patterns is reason to assume a fault and operate trip mechanism. This would make sense that some "normal" loads may present a waveform that the designers did not include in the database of recognized acceptable waveforms. If that is truly the way these work then I see the possible need to be able to field program "acceptable" wave forms when they are encountered.
 
kwired said:
Those cases likely tripping because of some inductive kick back related issues.

My understanding at one time was that the AFCI component is a processor that evaluates the current wave form. It is basically programmed to accept specific current waveform patterns. Any waveform pattern not in the list of acceptable patterns is reason to assume a fault and operate trip mechanism. .
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While that is the intuitive expectation it is a much more complicated and expensive method than what is actually used.

http://forums.mikeholt.com/showthread.php?t=111163&highlight=AFCI
 
ELA said:
What is your point then? That Surge protectors cannot be used on circuits with AFCIs or GFCI's? Like that is going to happen....
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That's exactly the point. The codes have become so filled with these types of requirements, that nuisance tripping is now more prevalent than ever.

AFCI's and GFCI's are specifically designed to withstand transient events to a certain level. If the transient is severe enough (beyond design level) it can become be the direct cause of the electronic devices tripping.
An AFCI is way more likely to trip due to the transient itself than due to shunted current through the protection device. Thus exactly why it is not a moot point.
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I respectfully disagree here. While the AFCI and GFCI units may have some internal circuitry for its own transient protection, I don't believe that protection extends to the rest of the circuits.

I have had cases where nuisance tripping was reported, and the ONLY thing we did to eliminate it was to remove the surge-power strip from the circuit. Once a non-surge strip was used, the nuisance tripping stopped.

Maybe it was an overly sensitive surge strip? Or that particular house was connected to part of the grid that experiences more surge events? I don't know.

goldstar said:
I'm with you on this 100%.

I've had numerous CH-tan handle AFCI's installed and haven't had a specific problem. However, having said that I would suspect that any device that would cause the slightest arc would set them off. The last residential job that I had the tile guy, using the tile saw, was able to make the tile cut but as soon as he released the trigger the AFCI would trip. Same was true for the carpenter and the trim saw.
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This is due to the electric brake built-in to those type of saws. Basically, when the trigger is released, the saw is slammed into "reverse" for a split-second, significantly slowing down the blade speed. This action is interpreted by the ACFI device as an undesirable arcing condition that causes it to trip out.

IF the carpenter or tile guy were to unplug the saw instead of releasing the trigger, I'd be willing to bet a dollar to a donut that the AFCI breaker would not trip, since the reversing action would be prevented.
 
kbsparky said:
I respectfully disagree here.

I have had cases where nuisance tripping was reported, and the ONLY thing we did to eliminate it was to remove the surge-power strip from the circuit. Once a non-surge strip was used, the nuisance tripping stopped.

Maybe it was an overly sensitive surge strip? Or that particular house was connected to part of the grid that experiences more surge events? I don't know.
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So you removed a surge strip and you did not get a call back. As you stated you really do not know why that fixed the issue. ( or if it did?)
It could be possible that the surge strip was defective and the MOVs or internal capacitor (EMI filter) in it were leaky or the device had some other defect.

My point its that it was not the action of a "normally operating surge strip" suppressing a transient that caused the trip.

Suppose you have a surge strip downstream of an AFCI and a device plugged into it generates a transient. What is the current path?
The current path is from the inductive load through the Surge strip MOV and returning back to the load that generated the transient. The AFCI is not part of that current path!

When you have a large transient that is not suppressed by a Surge Strip or MOV/EMI filter it is possible for that transient ( high frequency dV/dt) to directly upset an AFCI. The reason has nothing to do with arc detection or GF protection. High dV/dt events are directly coupled into the microcontroller or other internal circuitry that cause the device to operate in a mode outside of its normal operating range ( nuisance trip).

I used to perform EMI/EMC testing on electronic equipment using EFT (Electrical Fast Transient) generators to assure that the equipment met minimum EMC standards. At a high enough test level any piece of electronics can be corrupted into operating outside of its normal operation.
 
ELA said:
While that is the intuitive expectation it is a much more complicated and expensive method than what is actually used.

http://forums.mikeholt.com/showthread.php?t=111163&highlight=AFCI
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I didn't see anything in that thread the tells us what the microprocessor actually analyzes, I mean yes it looks at the load current, but how do we know what it is looking for when it looks at the load current to determine whether or not it is time for it to trip?
 
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