On Monday, February 22, 2016 at 12:15:58 PM UTC-6, Texas Kingsnake wrote:
Gentlemen and women:

I am not sure if you all remember, but I had the circuit breaker panel with
the bad aluminum feeder cable that was shooting sparks.

We finally put the new panel in yesterday -- by *we* I mean *I* stood around
while my electrician buddy did the work. We used 6 AFCI's in the panel for
the bedroom and kitchen circuits. When it came time to power the panel back
up, AFCI breaker number 6 refused to latch.

Here is the big question: How do you locate the arc fault that's tripping
the breaker? In this old house the wire is buried deep in plaster walls and
routed from the basement up to the attic and back down again, FWIW, it's not
K&T, just old cloth-covered wiring from the 40's. My buddy had a word for
it I had never heard before -- ragwire.

TKS

Have you checked to see if it could be a defective table lamp, light fixture or appliance. Some items that you may think that would never cause a problem are doorbell circuits or a clock radio. An engineer friend who worked for the power company communications division would often track down RFI caused by doorbell transformers which were sizzling/arcing but not drawing enough current to burn up or trip a standard breaker. You may have a light left on in an attic or basement/crawlspace that has a burned center contact or rivet at the bottom of the socket shell that is arcing. I've seen all sorts of weird crap cause problems in electrical and electronic circuits and only discovered them by eliminating every possible cause. ^_^

[8~{} Uncle Arc Monster