Does an AFCI breaker protect the downstream/ load side wiring from a GFCI receptacle that has been installed

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billynstar

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I was having an AFCI breaker trip every time the Carpenter used the table saw on the job site if I used a GFCI cord set from the receptacle to an extension cord the saw no longer affected the breaker this leads me to believe that possibly when you wire a kitchen circuit 20 amp AFCI and go and install the first GFCI receptacle is the downstream protected by AFCI
 
First off, an AFCI breaker protects nothing. About all they are good for is nuisance tripping which is what you are describing. If I am reading your post correctly (which is difficult without sentences and punctuation), my theory is that the saw brushes create arc noise that the AFCI breaker thinks is an actual arc signature and trips. (This also happens all too frequently with vacuum cleaners and other equipment also.) My theory goes on to suggest that when you put a GFCI between the saw and AFCI protected receptacle, the inductance of the sensing coil within the GFCI filters out the arc noise enough so that the AFCI breaker doesn't respond- at least in this particular instance.

So, to answer your question, the downstream receptacles fed through a GFCI receptacle fed from an AFCI breaker are protected about as much as AFCI are capable of... which has never been proven.

-Hal
 
Hal's theory in post 3 was my first thought.

Another possibility is that the original extension cord plug prongs were loose in the socket, and that there was actual arcing at the contact point. In this scenario, the AFCI was correctly sensing this arcing. When the GFCI cord was added, it changed the plug/socket pairing and actually removed a point of arcing.

Another user has reported that tightening the screw connections to receptacles often resolved apparent nuisance tripping, suggesting that those trip events were caused by actual loose connections.

I am skeptical of the value if AFCI devices, but don't think there is enough information to categorically say that all trip events where the circuit seems to work fine are nuisance trips.

It is plausible that sometimes these trips are caused by 'subclinical' arcing, real arcing caused by loose connections which is minor enough that it doesn't get noticed without the AFCI.
 
Motors with brushes don't trip AFCIs. I've run all kinds of tools with lousy commutators and brushes on all the brands and never a trip. Arcs don't trip AFCIs, there is no way they can at 120V given the design criteria of the breakers.

I have consistently tripped AFCIs using tools that have soft starts. I'm sure it's the electronics in the power supplies. Electronic loads trip AFCIs. That's why LED lights, vacuum cleaners, new refrigerators, late model power tools, and all that stuff nuisance trip them; it's the power supplies. I posted an article from Electrical Contractor a few years ago where a rep from one of the manufacturers said it, and I had a guy from GE tell me the same thing.
 
ActionDave said:
Motors with brushes don't trip AFCIs. I've run all kinds of tools with lousy commutators and brushes on all the brands and never a trip. Arcs don't trip AFCIs, there is no way they can at 120V given the design criteria of the breakers.

I have consistently tripped AFCIs using tools that have soft starts. I'm sure it's the electronics in the power supplies. Electronic loads trip AFCIs. That's why LED lights, vacuum cleaners, new refrigerators, late model power tools, and all that stuff nuisance trip them; it's the power supplies. I posted an article from Electrical Contractor a few years ago where a rep from one of the manufacturers said it, and I had a guy from GE tell me the same thing.
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Your AFCIs weren't working then. Vacuums consistently tripped the first ones. Wife bought new vacuums and tripping quit. Brushed motors on the originals.
 
ActionDave said:
No. They didn't work because AFCIs don't work. Whatever was in that vacuum that tripped the breaker it wasn't the motor, no more than there were arcs in big screen TVs or T8 fluorescent lights in the past that made them trip.
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I will agree that saying an AFCI works is a stretch. I should have just said mine tripped and the solution was replacing the vacuums.

ETA: I had Customers with the same issue and solution.
 
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