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Dave Marshall

Mon Mar 31 2008, 02:23AM

Registered Member #16 Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554

I was working with my variac today and accidentally shorted an AC power cord to my grounded saw table. You can guess what happened next, everything went dead.

I wandered over to the fuse box to reset the 30A breaker, and realized it wasn't blown (I didn't know which switch it was at first, it took almost an hour to find it by process of elimination). There are three outlets, a light, and the garage door opener without power, but the breaker never blew. I reset it several times, and still nothing. I have to assume that the breaker switch itself suffered a mechanical failure, and it needs replacing.

Trouble is, I've never done it before. I can't even figure out how I'd get the switch out of the box. I took a couple photos in hopes that some of you who've dabbled in home wiring can keep me from barbecuing myself in spectacular fashion.

Dave

Nik

Mon Mar 31 2008, 02:55AM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

Those look like stablocks which are easy to work with. Make sure the breaker is actually off and remove the wire from under the screw. The breaker should pivot away from the center of the panel and pull out. If you bring the breaker to a hardware store or electrical supplier they should have a replacement for you.

*edit*
BTW For the love of god do not touch the buss bar. The 120v buss has enough surface area to make the resistance of your skin well below what is needed to kill you.

ArcLight

Mon Mar 31 2008, 02:59AM

Registered Member #341 Joined: Thu Mar 23 2006, 07:41PM
Location: Northern Illinois, USA
Posts: 69

I'm not sure that I can draw you the proper mental image, but I won't let that stop me. The breaker is in the box with only friction. Your photos show the alternating fingers from left and right, the breaker grasps those fingers with it's own copper fingers. Just gently pry the breaker outward from the centerline of the box and it will let go of the bus bar. On the other end of the breaker (the outside edge of the box) it is only a claw that will let go of the breaker once it is uncoupled from the bus bar. Now the breaker is free of the box and only attached to it's wire. Unscrew the clamp and replace breaker in reverse order.

Regards, ArcLight

...

Mon Mar 31 2008, 03:14AM

Registered Member #56 Joined: Thu Feb 09 2006, 05:02AM
Location: Southern Califorina, USA
Posts: 2445

Of course the first thing to do would be to put a voltmeter from the breaker to nuetral to make sure it is indeed the breaker that is dead, and not a piece of wire connected downstream.

Then turn off the main breaker (some older houses will have a large set of fuseblocks outside that you can pull out, or else flip that big hunking breaker at the top of the panel)

Then you can remove the wire, and then the breaker, as noted you just pry it out (poping the side closer to the middle out first).

Also, for a 30a breaker you need at least #10 wire, and it looks like you only have #14 or #12 in that picture. (It should say on the wire somewhere 12awg 10awg etc) If that is the case, you should make them sell you a 20a breaker as to avoid melting the wire in your walls

BTW, in the future if a breaker is actually blown the switch will be in the middle, not on the on or off side. You can spot of of these because its switch won'y line up with the ones above/below it. To reset it you have to turn it off first, then you can turn it back on.

Dave Marshall

Mon Mar 31 2008, 03:46AM

Registered Member #16 Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554

Well, I can say that the the breaker wasn't in the center position. It was still on when I checked it. I will definitely investigate further to make sure its the breaker and not something down stream. I can follow the wire all the way back to the box though, and everything looks kosher.

Dave

Backyard Skunkworks

Mon Mar 31 2008, 04:17AM

Registered Member #1262 Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451

I'll bet the contacts in that breaker welded themselves as soon as the flat short happened, after all you can get at least a couple hundred amps from a flat short in a wall socket. That likely melted something very quickly. Breakers are designed to trip when you try and plug like five microwaves into a couple outlets, I'd bet they are pretty useless for tripping when you are dealing with a flat short.

Ultra7

Mon Mar 31 2008, 04:27AM

Registered Member #1157 Joined: Thu Dec 06 2007, 12:11PM
Location: Houston, TX
Posts: 307

As odd as it sounds. . .
Is there a GFCI outlet connected to that particular circuit?
The outlet I use in my garage is mysteriously hooked to the GFCI outlet in my Master Bedroom, and any time I overvolt or short anything, I have to run to my bedroom and hit the reset button on the GFCI.

The GFCI trips and my breaker outside stays hot.

Dave Marshall

Mon Mar 31 2008, 04:41AM

Registered Member #16 Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554

You aren't the only one to suggest it Ultra7.

Here's the present situation. I pulled the breaker and tested it. Its fine and functioning properly. I left it uninstalled (presumably killing that circuit), tested the outlet, which was dead, and pulled it out of the wall.

At this point, I got the crap knocked out of me.

Apparently the ground wire is floating at 120v. It was not as strong a shock as I'd expect from an outlet (I've gotten a couple before), but it was enough to get my attention. I apparently have a ground fault somewhere on that circuit. The two terminals on the socket show zero volts in reference to each other, but BOTH show 120v when referenced to ground.

The interesting bit is, there are only two GFCI outlets in the entire house, and they're on seperate circuits on the opposite end of the house. I'm really at a loss as to where the fault could be, but tomorrow I'll start pulling and testing outlets and such.

Worst case, I guess I'll get an electrician on the phone and call up the insurance company. They can either shell out the money now to pay the electrician, or pay for the house fire in a couple days.

I did manage to eliminate the voltage on the ground wire by throwing the other breaker for the garage (the ACTUAL breaker for the garage, my suspected bad breaker apparently doesn't do anything. It isn't tied to the bad circuit at all).

Anyway, I'll keep this thread updated to document my saga.

Dave

Nik

Mon Mar 31 2008, 12:07PM

Registered Member #53 Joined: Thu Feb 09 2006, 04:31AM
Location: Ontario, Canada
Posts: 638

If some previous owner has done some of their own handy work in your house 120 on the ground might not be as strange as you think. I often find people tie the ground and neutral together on plugs (I'm not sure why because its done in the panel) and even more often I find people who swap the hot and neutral when they hook up plugs. So if some one has done both of those (which is likely) in other plugs on that circuit or a circuit that shares a gnd/neutral with the one that zapped you it would explain your 120v gnd wire.

HV Enthusiast

Mon Mar 31 2008, 01:00PM

Registered Member #15 Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068

wrote ...

Apparently the ground wire is floating at 120v. It was not as strong a shock as I'd expect from an outlet (I've gotten a couple before), but it was enough to get my attention. I apparently have a ground fault somewhere on that circuit. The two terminals on the socket show zero volts in reference to each other, but BOTH show 120v when referenced to ground.

I was going to say that before, but by just looking at the photos of the bottom of the fuse box you have above, it looks suspiciously "empty." You should have lots more neutral / ground wires, and buses in their, unless they are all crammed near the top.

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