In message ,
Andy Wade wrote:

Martin Angove wrote:

If the shower has been there some time, chances are that it will be
wired in 6mm2 T&E (this stuff is about half an inch wide altogether)
[...]

[...] one you can afford so you should also be factoring in the cost of
running a new length of 10mm2 cable (it's about an inch wide:

Your suggestion that 10 mm^2 cable is about twice the width of 6 mm^2
didn't quite ring true. According to the Pirelli data sheet 6 mm^2 T&E
is approx. 13.1mm wide and 10 mm^2 is approx. 16.8 mm wide - so "just
over half an inch" and "getting on for eleven-sixteenths of an inch" is
nearer the mark.

Ok, you win. I have actually been using the Pirelli stuff this weekend,
though I haven't gone so far as to measure it :-) Having said that, if
it were one of those nothing-to-compare-against, instant-guesstimate
things, I would probably look and say "half inch" or "inch". In the OP's
case all he needs to do is to say "is it a half inch, or significantly
bigger?"

Just thought... 4mm2 cable isn't *that* much smaller than 6, but then
you wouldn't find a... erm... would you? ;-)


While you're at it, you need to think about the shower disconnection
times and whether or not an RCD is required for it. This will largely
depend on the type of earthing your system has and the length of cable
from CU to shower.

And on the type of overcurrent protective device. For a 45A shower
circuit the maximum voltage-drop limited circuit length is 49 m. With a
PME supply there is no need for an RCD with any device type (other than
Type C or old Type 3 MCBs on circuits longer than 23 m - but these
device types aren't appropriate for a shower in any case).


Yes, and we're probably getting way out of the OP's depth by now. I
assumed he had MCBs when he was asking about sizing the shower by "the
rating of the circuit breaker"... but I do tend to assume things which
aren't necessarily the case.

49m is a heck of a long way (come to that, 35m is a fair old distance
too), especially since 10mm2 cable gets extremely unweildy if you have
to manhandle anything more than a 25m drum!

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... Doing my part to preserve order in the universe