ECN Electrical Forum
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I just inspected a job yesterday and I asked the homeowner if everything was working OK. She said no, there were a few circuits that kept tripping. I asked a few questions and it seems the vacuum cleaner plugged into certain circuits would trip the AFCI. She wanted to know what she could do about it. First thing I suggested was to try the vacuum in a different circuit, and to try a different vacuum ( or dust buster/handheld, etc)in the same outlet and see if the breker trips. She said the EC who just got done wiring her new reno work said that it was the AFCI's fault. She asked me if that was true, and all I can say to her was that I have heard of such problems, but I haven't seen or heard of any cures yet. I didn't know if it was an appliance problem or a wiring problem.

I think "IF" is the second biggest word in the English language.

The 'authorities' assert point-blank that there has never been a documented instance of a properly functioning, listed appliance falsly tripping an AFCI. Look carefully at that statement, and there are plenty of "ifs" lurking within.

"Listed" rules out the very large number of things we use that are not listed, and are not required to be listed. That's the first hurdle- especially if your 'appliance' is some trendy European or commercial gizmo.

That in turn implys following the manufacturers' instructions. This can get interesting, as many appliances have instructions that some will assert are in conflict with the NEC. For example, refrigerators that say NOT to use on a GFCI circuit.

"Properly functioning" refers to TODAY'S standard, which was likely revised quite recently to accomodate the GFCI and AFCI problems. That expensive, top-quality Swedish vacuum of yours - the one you get as a wedding gift 30 years ago - wasn't made to these standards ... so POP goes the breaker.

Naturally, the 'experts' will then assert that it's your fault you didn't replace all your stuff with new when they changed their standards.

Harold:
From your comments..."She said the EC who just got done wiring her new reno work said that it was the AFCI's fault. She asked me if that was true, and all I can say to her was that I have heard of such problems, but I haven't seen or heard of any cures yet. I didn't know if it was an appliance problem or a wiring problem."

The ECs comment that it is the fault of the AFCI is (IMHO) a not correct. He should have explained the function of AF and then proceeded try another appliance in the tripping circuit(s), as you mentioned.

A recent new SFD had two (2) tripped AFCIs when I walked to the panel. One reset, one immediatley tripped. The trim carpenter had a small miter saw that tripped the one I reset. It worked fine in a countertop 20 amp GFI outlet. Plug the same saw into an AFCI outlet...trip. The second circuit that immediatley tripped had a wayward nail thru the NM, HG&N straight thru.

There have been a few others (AFCI) issues, bad splices, bad AFCI cb, & the fateful...MWBC! We all learn by experience!