On Tue, 17 Apr 2007 21:22:51 +0100, Owain
wrote:

DaveH wrote:
Anyone advise what size of cable is required for a sub-main going to a
granny annexe? The Annexe/flat has an 8kw electric shower, a 4.5kw
cooker and the usual aray of kitchen appliances. Will 10mm² twin-core
and earth be adequate? It'll need it to pass the part-p certification
periodic test.

There's no such thing as a Part-P periodic test. You'll need either a
Design, Installation and Inspection and Testing Certificate, or a Minor
Works Certificate, OR a building control application to the local council.

And what size of main fuse is suitable for this sub-main?

If it's a bedsit type annex, integral to the house, with gas or other
non-electric heating, I'd suggest a 60A supply using 16mm.

For anything larger or if electric heating, treat as a separate dwelling
and provide 100A using 25mm. If the annex might ever be used separately
(rented out) then it might be worth biting the bullet and getting a new
supply from the street mains.

Seems worth thinking about.

Be aware that T&E may not be acceptable with its reduced earth conductor
size, and submains are often done in MICC or armoured.

OK, many thanks.

DaveH