Shouldn't the breaker trip?

[David Block]

I was getting into an attic space today. I opened the hatch and moved it to the side when all of a sudden, arcing and sparks flew. After I caught my breathe, looked and saw some abandoned live wires just hanging near the attic access panel. I was sure the whole arcing ordeal would have tripped the breaker at the panel but the wires were still live. I've had similar mishaps at my own home (you know, those whooops kinda moments) and the breaker would trip in the panel. Am I wrong in my thinking that the circuit breaker should have tripped?

[Rick Hurst]

There shouldn't be any wiring near the attic access panel to begin with. I've noticed more of this problem lately than in the past. Electricians are not bundling the wiring away from the atttic access.

From the 03 IRC.

E3702.2.1 Across structural members.
Where run across the top of floor joists, or run within 7 feet (2134 mm) of floor or floor joists across the face of rafters or studding, in attics and roof spaces that are provided with access, the cable shall be protected by substantial guard strips that are at least as high as the cable. Where such spaces are not provided with access by permanent stairs or ladders, protection shall only be required within 6 feet (1829 mm) of the nearest edge of the attic entrance.

[Scott Patterson]

I was getting into an attic space today. I opened the hatch and moved it to the side when all of a sudden, arcing and sparks flew. After I caught my breathe, looked and saw some abandoned live wires just hanging near the attic access panel. I was sure the whole arcing ordeal would have tripped the breaker at the panel but the wires were still live. I've had similar mishaps at my own home (you know, those whooops kinda moments) and the breaker would trip in the panel. Am I wrong in my thinking that the circuit breaker should have tripped?

Sometimes it won't trip a breaker. One of the reasons for AFCI breakers being required.

Yep, it's moments like that when you wish you had a pair of Depends on! :D

[John Steinke]

Only one thing will trip a breaker, or blow a fuse: more amps flowing through than are intended.

Visit a welding shop; you'd be amazed at just how much welding is done with less than 20 amps.

Ditto electrical injuries; a 'typical' breaker can easily electrocute 200 people, at the same time, without tripping.

As for the arc fault breakers .... the 'combination' types have yet to be seen, and the ones we've been using will not respond to a 'series' arc.

All these "safety" things are nice ... just don't bet your life on them.

[Jerry Peck]

The correct answer to "Am I wrong in my thinking that the circuit breaker should have tripped?" is "sometimes, maybe".

*IF* the arc is large enough for long enough, yes.

*IF* the arc is not large enough for long enough, no.

Most of us (especially electricians, I'm sure John has done this too) intentionally (and unintentionally) tripped breakers by either: a) sticking one of our screw drivers across the connections, leaving a melted out area in the screw driver shaft; b) touched two wires together to make sure they were not live (or, if live, that the breaker trips - which required touching them together a couple of more times to make sure they were no longer liver after the first arcing or two). :cool:

Yeah, yeah, I know, we are never supposed to admit we do/did those things. :D

[David Block]

Yeah, that makes sense. One of the times I tripped the breaker at my own home, I chose to cross the wires rather than go all the way down into the basement to trip the breaker. Yes, the wires did melt together and yes that is kinds dumb to do but it saved me from getting off a ladder and going inside. When I brushed across the wires in the attic space, the hot wire did have a burned area but it didn't arc very long so it makes sense that the breaker didn't trip. My clients and the agent were a little concerned when the heard loud pop and heard me jump. They were more concerned that the breaker did not trip in the panel rather than the fact that they had live exposed wires right next to the attic access panel. Go figure. It turned out the current owner was attempting to install a whole house fan before he fell through the ceiling. After that ordeal he decided to stay out of the attic space so he just left the live wires for me to find. Thanks alot buddy! As always, I appreciate the feedback.

[John Steinke]

Actually, I've never deliberately tripped a breaker by creating a fault. I do that far too often, and have sacrificed far too many tools to the tool gods, purely by accident!

That kind of highlights one of the hazards of electric work ... you do your best to work 'cold,' you check and meter ... and sometimes you still get surprised.

Nor can you count on your ability to judge the size of an arc. Some massive, fiery arcs will fail to trip the breaker ... while a tiny 'crackle' will cascade through several panels!

All you can do is LOTO, check, check again, proceed as though it were live anyway, and pray.

[Jerry Peck]

Actually, I've never deliberately tripped a breaker by creating a fault.

Never?

Really ... never? ;)


I do that far too often, and have sacrificed far too many tools to the tool gods, purely by accident!

Yeah, that happens to all of us.