In article ,
NT writes:
On Oct 19, 1:21*pm, Jim wrote:

We've got a similar problem in that we have solid floors downstairs so
all of the ring mains will need to run in the suspended ceilings. The
trouble being that there is a 50m cable length limit on the ring main,
and you use up about 4.5m each socket coming down from the ceiling then
back up.

Unfortunately the windows come too low down on the wall to run across
underneath them, and there are doors/chimney breasts to get in the way
as well.

I was thinking it might be possible to run a thick cable out to some
kind of junction box, then spurs out to each socket rather than a ring -
I don't know if that's allowed under the wiring regs?
It sounds like a sensible approach, as long as you treat the circuit
as a radial. You cant treat it as a ring because you'd have more spurs
than socktes in the ring.

That's a guideline only, and not part of the regs.
It comes about because rings normally start with no spurs,
and have spurs added as later additions. When you reach the
point where there is more addition than original, the original
installation clearly no longer meets current requirements.

In the case of designing a system to be laid out that way
from the start, this concern would not apply.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]