AFCI and tools

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Old 04-08-15, 04:40 PM
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AFCI and tools

Anyone experience problems while using tools on an afci circuit? I've been on an install for the last 1 1/2 weeks and anytime we use the jigsaw on an afci circuit, it tends to trip. It seems to happen if I pull the trigger on slowly.
 
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Old 04-08-15, 04:54 PM
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No experience but most corded hand tools use universal motors and with a bit of brush wear they can spark excessively at the commutator. This MAY be interpreted by the AFCI as an arc fault.
 
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Old 04-08-15, 07:04 PM
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Yep, what Furd said.

Some vacuum cleaners used to be notorious for tripping earlier AFCI breakers as well as the power tools mentioned. The later combination type AFCI breakers don't seem to be quite as susceptible to nuisance tripping.
 
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Old 04-08-15, 07:18 PM
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Has this circuit always had an AFCI breaker installed on it?
 
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Old 04-08-15, 08:22 PM
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IMO, if a device is causing either AFCI or GFCI to trip, it's defective (either by age or design) and needs a quality replacement. Every outlet in my house is protected by both CAFCI breakers and GFCI outlets. No nuisance tripping; even with many of the classic "trouble" devices.
 
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Old 04-09-15, 01:29 PM
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I have a cheap power miter saw that reliably trips AFCI breakers, it could essentially be used as an AFCI tester. Works fine on GFCI though.
 
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Old 04-09-15, 04:32 PM
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Has this circuit always had an AFCI breaker installed on it?
I assume so. The building was completed in 2008.

IMO, if a device is causing either AFCI or GFCI to trip, it's defective (either by age or design) and needs a quality replacement.
That's a bit extreme. This is a Bosch jigsaw. A very good tool with a very long life expectancy. It all depends on how the trigger is pulled.
 
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Old 04-10-15, 07:43 AM
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I agree that if it trips a GFCI, the tool is a hazard and should be fixed or replaced. Tripping an AFCI is not necessarily a safety problem with the tool. With your jigsaw it's almost certain that the variable speed drive circuit in the trigger mechanism is creating a waveform that appears to the AFCI like an arc. I really don't think it's a safety problem, but just inconvenient.
 
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Old 04-10-15, 01:11 PM
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Yes, AFCI can be fooled. My point is, why put up with the nuance tripping, when a replacement model (with a better design) will probably avoid the hassle. GFCI and AFCI will only expand in usage, so why bother with equipment that is incompatible with them in some way.

BTW, you can add a filter inline to the tool causing the issue (search for AFCI FILTER) but I hate the idea. I'd much rather throw away poorly designed equipment. Then again, just adding filtration is perhaps what many of the tools are doing already. Sure hope not, as that essentially disables the AFCI protection.
 
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Old 04-10-15, 02:35 PM
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Is it an Eaton AFCI? Most early one's have big EMI false trip issues. Eaton has been working on a new version which I believe is now available.

Also, the later AFCI's are combination triggered; meaning since 2008 they added series arc detection. If your load is >5Amps and has a waveform like an arc, the breaker will trip. I can imagine that a slowly starting motor could make a combination rated AFCI trip out.
 
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Old 04-10-15, 06:33 PM
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It's Square D.

My point is, why put up with the nuance tripping, when a replacement model (with a better design) will probably avoid the hassle.
Who has the better design? And is it worth throwing a $150 tool into the garbage?

Didn't find anything useful searching "afci filter".
 
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Old 04-11-15, 07:38 AM
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The problem is that the tool motor controller is designed to chop the input voltage into pulses, which at low motor speed, will be high current, narrow width bursts of power. The AFCI is designed (by law) to kill the circuit if it sees high current intermittent pulses in the load circuit, thinking they are series arcs So, the system is designed to be not compatible.

If this is a academic exercise, you could try a series inductor with the tool. That will tend to smooth out the current waveform. Maybe one of the larger sized Corcom ac input filters would work. Measuring the current waveform of the tool with a CT and an oscilloscope would be revealing.
 
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