Don Pearce spake thus:

On Tue, 18 Apr 2006 23:32:56 -0700, David Nebenzahl
wrote:

Eiron spake thus:

David Nebenzahl wrote:

mc spake thus:

I gather that you are in the UK (hence "ring" wiring structure, which
I like, instead of the American daisychain) and that everything is
in the same room. It should work fine.

So how does house wiring work in the UK? Is there more than one
grounding ("earthing") point? And how is this better?

(Here, the Merkin practice is to ground the "service panel"--the box
where the big wires come into the house--to a single ground rod, with
everything running downstream from that.)

By the way, this brings up a strange experience I had recently doing
some wiring. I was working for a guy who owns two houses right next to
each other, and he wanted to run a cable TV connection from one house
to the other. I was about to connect the cable in the attic of the
house that was the source of the signal when I got a little tingle.
After grabbing a VOM, it turned out that there was about a 20 volt
difference between the two cable grounds.

Mc doesn't understand ground loops. You can get them between two boxes
plugged into the same double socket.

Your tingle was because your equipment is not grounded, and is perfectly
normal.

No, my tingle was because I was holding two cables strung between two
different houses, each grounded at its end. Doesn't seem normal at all
to me.

Most likely the two houses weren't on the same phase of the three
phase supply to the street. Their two grounds could have been doing
very different things voltage-wise. You should always have an
isolation transformer in a connection like this.

I seriously doubt that, because then the potential would have been more
like 120 volts, right? I think that's grasping at straws: so far as I
know, PG&E (local electricity dealer) doesn't even supply 3-phase to
residential customers. In fact, not even in come commercial districts. I
owned a small business in Berkeley (print shop) until last year, and I
remember the previous owner telling me about all the headaches he had in
having PG&E put in a 3-phase converter (in an underground vault below
the sidewalk outside). So I know that utility lines don't usually carry
3-phase power, except to large industrial customers.


--
Pierre, mon ami. Jetez encore un Scientologiste
dans le baquet d'acide.

- from a posting in alt.religion.scientology titled
"France recommends dissolving Scientologists"