In message ,
(Swampie) wrote:

I've been thinking about cavity wall insulation

[...]


Currently the whole side-wall [...] cavity is
open into the loft (at least, the shower cable from the CU runs
up the cavity and into the loft so I assume it's open).

[...]

Are there any implications with doing this?


Forgetting ventillation and insulation, about which I know little, you
may need to check the rating of your shower power cable if you are about
to surround it with insulation.

I have just done some work in a house with a similar situation. The
8.5kW shower is currently wired in 6mm2 cable which runs up an empty
cavity, across the tops of joists in the attic and down into the (switch
and) shower.

8.5kW at 240V is about 35.5A and given that the cable is
well-ventilated, the regulations say that it will carry 47A. This is
fine, but if the wall were insulated or the cable was enclosed in
insulation in the loft it would have to be derated to 35A which is one
of those situations where you say "it'll *probably* be ok, but..."

If you happen to have a 9.5kW shower (39.5A) then this derating should
prompt you to uprate the cable. The next size up is 10mm2 which is a
*pig* to work with.

Just a thought.

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... If flies couldn't fly, would they be called walks?