AFCI....yet again.

[Cow]

Went on a service call more than a month ago for a tripping AFCI. Following Marc's advice I got out the megger. I unplugged all appliances and shut off the lights. It megged OK, I even took all the devices out real quick to take a peek and they looked fine. Not knowing the failure rate for Siemens AFCI breakers, I thought maybe it really could be an overly sensitive breaker, so I changed it.

Fast forward to a week ago. Tripped again for the first time since the new breaker was installed and it hasn't tripped since. Story was, she went to turn on her bath lights(which share that same circuit)and it went "pop" and everything went out. In hindsight, it was my fault I never megged past the switches on the first service call. Opened all boxes, fixtures, etc in bathroom and megged it all. Switches, wires and the fixture. Everything checked out, am I missing something? Two of the six bulbs were blown in her bar light, but didn't know if that could cause it?

I hate not being able to tell the customer I don't know what the problem is. How frustrating! I asked her to check the breaker for the yellow indicator if it trips again, at least then I'll know if it's an overload/short or an arc fault.

 

[mdshunk]

Yeah, you really need to meg from the panel in cases like this. Don't take stuff apart. Just unplug everything and unscrew the lamps. Turn the switches on.

Can you describe how you did your megger checks?

 

[Buck Parrish]

Yeah their great arent they. The only ones I like are the ones some body else installs. Then I can charge by the hour to fix it.

 

[Cow]

Yeah, you really need to meg from the panel in cases like this. Don't take stuff apart. Just unplug everything and unscrew the lamps. Turn the switches on.

Can you describe how you did your megger checks?

First service call:

Disconnected all the wires at the panel. Unplugged all appliances and shut all the switches off. Also, I think I pulled all devices out prior to testing. Megged it at 50v first, it registered zero. Come to find out smokes were on that circuit also, so I disconnected them. I megged the entire circuit at 100v(which may have not been enough voltage looking back at it now) and it megged at 110 megs, I believe that's full scale on a Fluke 1507 at that voltage. I did not meg past the switches.

Second service call:

Only megged in the bathroom this time but still that same circuit. First, I pulled everything apart and looked for cuts, nicks, wires touching, etc. Didn't find anything. Completely seperated all wires and megged everything including the fixture and switches this time at 250v, read full scale(220 megs).

I realize I have made a few troubleshooting errors in that I shouldn't have pulled the devices on the first service call and I should of just yanked the bulbs so I could of megged through the switches.

Thanks for the help.

Yeah their great arent they. The only ones I like are the ones some body else installs. Then I can charge by the hour to fix it.

We did not wire this house, our particular shop doesn't really do new residential construction. Only small remodels and service calls. This is my first AFCI trouble call. I feel guilty for charging her, I've done nothing more than change a breaker and tell her I don't know what's wrong. I have a feeling she'll refuse to pay....

 

[bobbyho]

Any chance of a neutral touching a ground in the circuit? Found this once the hard way, second time it happened found it within 5 minutes. Kind of a geek but that is one more reason I tape (and always have) all my devices before I put them in the boxes.

 

[ceb58]

You may have answered your own question. You stated she turned on the bath light and it "popped". And you found two lamps burned out. A lamp could have went out causing a arc which the breaker picked up on. On a side note I turned on the vanity lights in my bath with cfl's one of the lamps blew triping a standard 20 amp breaker. The point being is some times all of the complaints about nuisance tripping becomes ingrained and we overlook the fact the breaker is just doing it job.