Odd condition in fuse block

**Jack Feldmann** · 07-09-2008, 02:01 PM

I was checking a fuse panel today and found an odd condition. When I put my wiggy between the threaded part of the fuse block and a ground I got 120V. Got the same 120V between ground and the bottom of the fuse block. No other fuse block in the panel did the same.

Nothing was connected to this block by the way.

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**Gunnar Alquist** · 07-09-2008, 02:34 PM

Jack,

Sounds (weird thing to say when I didn't actually hear you say anything) to me like voltage is "backfeeding" into the panel from somewhere else. Did you remove the fuse to check that socket or was there no fuse in place?

**Jerry Peck** · 07-09-2008, 02:59 PM

Could be two things.

First, that could be shorting out. Was it being used or was it already empty (no fuse in it)?

It could also be that there was a multi-wire circuit or voltage back feeding as Gunnar stated.

The center is hot - connected to hot.

The shell is hot - connected to hot through the fuse.

The wire coming off the shell is hot - when the fuse is installed.

That wire could be getting voltage from something else, which in turn is showing up as the fuse shell being hot.

If that voltage were on the same phase leg, it would not cause a problem, if on another phase leg, it would short out and blow fuses.

It is quite possible that, at some point in time, some wires were interconnected and two circuits from two fuses got tied together somewhere.

**Jack Feldmann** · 07-09-2008, 03:12 PM

fuse was not in, and there isn't a wire connected to the fuse anyway.

**Jerry Peck** · 07-09-2008, 03:39 PM

Originally Posted by Jack Feldmann

fuse was not in, and there isn't a wire connected to the fuse anyway.

If there is no wire connected to that fuse's terminal, then the fuse holder must be shorted out in some manner.

**Jack Feldmann** · 07-09-2008, 05:04 PM

I kinda thought that, just wasn't sure the mechanics of HOW?

**Gunnar Alquist** · 07-09-2008, 05:09 PM

Originally Posted by Jerry Peck

If there is no wire connected to that fuse's terminal, then the fuse holder must be shorted out in some manner.

Probably why there is no fuse in it.

**Jerry Peck** · 07-09-2008, 06:27 PM

Jack,

There is usually an insulating washer/bushing under the center contact between it and the shell.It does not take much contamination to cause electrical leakage, which, over time, leaves an arc track. Also, like everything, those insulators age and deteriorate.

Also, sometimes I've seen where the center contact comes in contact with the shell where the center contact penetrates the shell - where the slot in your photo is.

If you zoom in on your photo, there is little to no space between the top of that center contact and the shell, right were the dark area is. I just zoomed in while typing this and even at 400 times zoom, the two pieces look like they are touching.

**Jack Feldmann** · 07-09-2008, 06:58 PM

At 400X I guess my finger tip looks pretty cracked.

Thanks for the responses. I talked to my client this evening, and the first thing on his plan is to replace all the panels and clean it up a bit. There were several ungrounded outlets, and he needs some dedicated circuits. He is planning on a lot of wiring anyway.

We just see strange stuff sometimes, and about when we think we have seen most of it..................

Thanks again. I really appreciate the answers.