[Shop-talk] Question about: Arc-Fault Circuit Interrupters Spark Controversy

[Randall]

>     Anyone else have any experience you'd like to share?

I don't.  But as an almost-EE, I do have a question.  They taught us at
Purdue that an electrical arc is a sort of plasma, with a very low
resistance (lower than copper as I recall).  So how exactly does one get an
arc to ground that will not trip a GFCI ?

I can see where a GFCI or a standard breaker would not be able to detect an
in-line arc, like might be created by a bad contact or a broken conductor.
But how often is that really a problem ?  Seems to me that it would fairly
quickly burn the wire back (ever tried welding with a pure copper electrode
?) until the arc went out ...

I'd be a lot more convinced if someone could point to an actual fire that
could have been prevented by an AFCI, but not a GFCI.  Or even explain how
an AFCI distinguishes between an intentional arc (eg brush sparks on a
universal motor) and an accidental one.  From the comments presented, it
appears that they can't reliably tell the difference.

Randall 
(Tedious but unavoidable disclaimer follows) 






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