I'm so stupid... Was: Head Cleaners

From: Rob O'Donnell <classiccmp.org_at_irrelevant.fsnet.co.uk>
Date: Thu Jul 1 17:49:22 2004

At 16:38 01/07/2004, you wrote:

>On Thu, 01 Jul 2004 07:04:45 -0400
>"Joe R." <rigdonj_at_cfl.rr.com> wrote:
>
> > He merely said "let that be a lesson, allways check the breakers
> > yourself". I've never frogotten that!
>.... and after checking the breaker, get out a volt meter to check if it
>was the right breaker...
>
>An other story: A colleague was screwing in a new "DIAZED" fuse into a
>breaker panel. BANG! Parts of the fuse flew acros the workshop, a cloud
>of smoke came out of the panel and all lights where out. We had to
>replace two big 63 A "NH" fuses that where in front of that breaker
>panel. "NH" fuses need a _lot_ overcurrent to blow that fast. At close
>inspection of the breaker panel we saw traces of a wire that had
>shortend two of the three phases (400 V) and ground. The wire was
>vaporized.
>--


Talking of fuse boxes, at my last place of employment, we had a strange
happening... somebody turned on an electric fan heater at the same time
the kettle was on, and a seemingly random selection of sockets scattered
over half the building all suddenly powered down.

On investigation I discovered the following:
- the building, in which we occupied the first floor (second floor, to our
American readers) and where the ground floor (first floor) was empty, had
obviously been one set of offices at some point, not two.
- there was only one electricity supply to the whole building, one meter,
and one main breaker.
- the building had been extended and patched and adjusted multiple times,
and the electrics in each section had been installed by taking hefty cables
out to remote fuseboxes.
- there were circuits for machinery and underfloor heating that didn't
exist any more, but were still all connected up, just switched off.
- as and when more sockets, lighting, etc, was required, they seemed to
just ran cables from anywhere they felt like.

I found fuseboxes in at least five different locations, and adjacent
sockets in the same room could come from two or three of them!!

And the reason why something blew when the kettle was turned on?

A large selection of our sockets and lighting, was fed by a fusebox in an
empty office downstairs. This box was fed by a hefty cable and a 60A
switch from where the power came into the building. This switch was OFF.

However power to the circuit was supplied instead, god knows why, by a
short piece of what looked like 1.5mm2 lighting cable linking the output
from that hefty switch to a 30A ring-main circuit on an adjacent panel, via
a separate 13A fuse !

First time this happened, someone just replaced the 13A fuse.

The second time it happened, I went to check that fuse, and noticed that
this short length of cable was distinctly hot ! If it was 1.5mm cable, it
would be rated for, maybe 5A? With presumably over 13A current going down
it. If it wasn't for that extra fuse, the place could have gone up in smoke!

Now, given we had three phase into the building, and at that point I had no
idea if each end of this mad bit of cable was even on the same phase, I was
a little hesitant to just throw the big 60A switch instead.

The boss finally got an electrician in to sort out it out, some weeks later..

(Not that I couldn't have done it, but he never did value the skills his
staff had...)
Received on Thu Jul 01 2004 - 17:49:22 BST