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.

d

--
Pearce Consulting
http://www.pearce.uk.com