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gone_fishing 12-30-2008 06:54 PM

Scary day...is my electrical box ok?
 
I am renovating my garage to create 1/2 as an office and 1/2 as a workshop/garage. The house's wiring was running on the outside of the drywall so I can rerouting. I turned off the power at the box and was removing one wire at a time. One of the wires hit the hot main and made a pop sound. It didn't blow anything out or shock me. I now have all of the wiring rerun and fixed but the incident worries me. My neighbor is a union electrician and is coming down this weekend. I will have him look at it but just from the story do you guys think all is well?

jamiedolan 12-30-2008 07:22 PM

Quote:

Originally Posted by gone_fishing (Post 204539)
I am renovating my garage to create 1/2 as an office and 1/2 as a workshop/garage. The house's wiring was running on the outside of the drywall so I can rerouting. I turned off the power at the box and was removing one wire at a time. One of the wires hit the hot main and made a pop sound. It didn't blow anything out or shock me. I now have all of the wiring rerun and fixed but the incident worries me. My neighbor is a union electrician and is coming down this weekend. I will have him look at it but just from the story do you guys think all is well?

Are you saying in your panel, a bare wire made contact with a exposed portion of a un-fused service conductor (where the power comes in before the main breaker)?

Why is there an exposed area on your service conductor? Or did you somehow make contact with the terminal?

Jamie

gone_fishing 12-30-2008 07:39 PM

Jamie, There are two big (@1") wires that come into the box. They come in the bottom and curve around to the main breaker. I believe the outside of an unattached wire hit the point of connection that was hot. The wire that hit it had the insulation on it so I think the pop I heard was the electricity hitting the rubber. There is some black stuff on the inside of the box at that spot. All is running well in house right now.

Gigs 12-30-2008 08:00 PM

The pop you heard was an arc. It's hard to say what the damage might be since this was an unprotected wire. There could definitely be overcurrent damage in the branch conductor that you shorted to the service mains.

Try to identify which wire touched. It should have been burned on the end the same as the black flash formed on the service conductor terminal.

I would inspect the wire carefully that touched, and any devices connected to it. Most likely it didn't get a massive amount of current since you didn't mention the wire melting or anything, but there still could be latent damage.

I never understood why electrical boxes don't have some kind of cap over the service conductor terminals to prevent this sort of thing.

ACB Electric 12-30-2008 08:01 PM

did ya buy a lottery ticket directly after that happened? cause you got lucky thereif you did short something accross a main to ground before the main breaker,,, wow thats alot of power unfused, could have been alot bigger bang with flying molten metal. hopefully there is no real damage to the main cable, thats allways a tricky area to work in, whenever I have to work around live exposed parts like that I would try to cover the parts even with a peice of carboard to protect against a little slip like that, (then remove when done)

jamiedolan 12-30-2008 08:04 PM

Quote:

Originally Posted by gone_fishing (Post 204557)
Jamie, There are two big (@1") wires that come into the box. They come in the bottom and curve around to the main breaker. I believe the outside of an unattached wire hit the point of connection that was hot. The wire that hit it had the insulation on it so I think the pop I heard was the electricity hitting the rubber. There is some black stuff on the inside of the box at that spot. All is running well in house right now.

Somewhere metal hit metal that caused a fault, maybe just at the end of the wire. These are unfused wire at this point and have virtually no protection. My point is what happened could have been very bad and could have seriously injured or killed you.

It would be good to have your setup looked over by an electrician at this point to ensure there is no damage to the service conductors.

Jamie

gone_fishing 12-30-2008 08:09 PM

Yes, I realize I got very, very lucky. Thanks for the feedback guys. I will have my neighbor take a look asap. Would not have been good for a guy in the industrial safety industry to get hurt!

Gigs 12-30-2008 08:13 PM

Quote:

Originally Posted by gone_fishing (Post 204573)
Yes, I realize I got very, very lucky. Thanks for the feedback guys. I will have my neighbor take a look asap. Would not have been good for a guy in the industrial safety industry to get hurt!

Next time wear arc flash PPE. :P

AllanJ 12-30-2008 08:31 PM

Do you remember which small wire hit the large feed wire? If so, put a colored ribbon around it so your electrician friend can quickly identify which branch circuit was involved and do further tests.

If the pop was not very loud and you did not see a really bright spark and also the contact was made for only a moment, chances are nothing was damaged.

And, if the small wire that made the contact was black or red (not a neutral or ground) most likely the arc was due to electricity trying to power lights and appliances on that circuit normally, not a short circuit.

gone_fishing 12-30-2008 08:50 PM

Allan, the wire that hit the juice was not connected to anything. I had already disconnected from the terminal and had cut it just above the box. I am still very lucky!

InPhase277 12-30-2008 09:42 PM

Quote:

Originally Posted by AllanJ (Post 204590)

And, if the small wire that made the contact was black or red (not a neutral or ground) most likely the arc was due to electricity trying to power lights and appliances on that circuit normally, not a short circuit.

Bingo! I was about to write the same thing when I read this. My first thought is that it was the small arc caused by powering a load.

Amigo, you are quite lucky as this could have been a much worse situation. Think 2500 degree copper liquid in your eyes! You HAVE TO BE MORE ATTENTIVE, and watch where the ends of those wires are! Tape them up, or stay out of the live panel.


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