ECN Forum Forums Code Related Discussion NEC & other Code issues arc-fault circuit interrupters

The AFCI looks at waveform distortion that is cause by the arc.
Don(resqcapt19)

For a series arc the waveform will be what the equipment completing the circuit from the receptacle allows. Current in a series circuit is the same at all points. If an arcing connection is in the branch circuit portion the current will still need to pass through the extended part of the circuit from the receptacle. Would the waveform be distorted the same whether the arc is in the equipment or the branch circuit wiring? It is the same current.

The AFCI is not looking at a waveform like we would see it on an O-scope. It needs some criteria to determine that an arc is present. If it is counting the jagged edges of the wave it is counting more peaks than would be present in 60 cycle. That is why I think it would be looking for a higher frequency than 60 HZ. I know it is looking at the waveform for an abnormality. I am guessing at how it determines the wave is not clean and is not going to trigger erroneously on harmonic loads. Do you have more information on exactly how this is done?

Bill's first link explains series/parrallell arcing....has some waveforms...

Bill's second link shows a pictoral , ends in a microprocessor...

not that i understand it all, but pix's help !



[This message has been edited by sparky (edited 05-07-2001).]

Thanks, Sparky, for referring to the links. I had thought they were some links I had already read. The one at http://www.zlan.com/arc.htm mentions "ability to detect the distinctive difference between normal current and intermittent arc current" so it must be the sputtering nature of the current instead of the jagged wave signature. It looks like the current is at zero longer in an arc than in normal current so a fast switch could be the detection device for the input to the processor.

This is more complex than the GFI pix, i can view them and grasp how the mechanism works, these AFCI's have more 'guts' to them..

Yes, AFCIs have a microprocessor (computer) in their guts.

Okay. Somehow until now I had missed your response to me.


>>Integral OPD on each device?
>As long as the circuit is protected as per Code, this would be unnecessary.

>Great Idea! for those above 1440W...
Cool.


>Mogul base for 75W and up? Or similar? Not a bad idea either.
I see we agree on a lot of things...


>>Metal conduit or armor everywhere above ground?
>Or sched. 80 PVC (assuming outdoors)
That would be a lot of cutting and bending or gluing... Call a plumber!

How much will they cost?

Previously I posted: http://www.ourhouse.com/cgi-bin/prod_index.jsp?catOID=-97286&page_name=prod_index

I note that the price appears to have been increased a couple of bucks since I posted that. Perhaps they are planning on offering a larger discount soon. Today's price is $40.58.

Is there a tester, like a GFI tester that anyone has seen for an AFCI???

Two wires and a steady hand?

Just Kidding...