On Mon, 30 Jan 2012 08:25:23 +0000, "J. P. Gilliver (John)"
wrote:

In message , Don Pearce
writes:
On Sun, 29 Jan 2012 20:48:39 +0000, "J. P. Gilliver (John)"
wrote:

(I am not on either side in the argument between Jerry and others: I
live in UK, but still find ring mains odd.)

Why do you find ring mains odd? Once you have daisy chained all the
sockets it is an extremely sensible idea to complete the loop back to

If you happen to have laid them out in a ring manner anyway, yes.

the distribution board. For the cost of a few feet of cable, you have
halved both the effective resistance of the mains and the distance to
the furthest socket. I can't imagine a single reason not to do it.

d

I can see the halving of the resistance (well, at the most remote point
anyway), but not the halving of the distance.


For the most remote socket, the distance can be reduced to almost zero
by completing the loop (assuming the run goes around the house and
almost back again. For any socket beyond half distance, the run is
reduced. Half was just an estimate.

I think maintenance (I mean when modifying, not just general wear and
tear): most extras added to ring mains are spurs. (Also, instinctively,
it's easier to know when one is isolated with a spur, though that
shouldn't be done that way.)

Spurs are allowed on a ring main, but to a single point only (which
can of course be a double socket).

d