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.
And what size of main fuse is suitable for this sub-main?
Thank you,
DaveH
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.
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.
Be aware that T&E may not be acceptable with its reduced earth conductor size, and submains are often done in MICC or armoured.
Owain
On Tue, 17 Apr 2007 17:40:55 +0100, DaveH mused:
The size on the cable depends on the length, installation method, load etc... You have only given part of the information.
Part p isn't a periodic test. Who is doing the commisioning and certification of the installation?
10mm does sound small though, I wouldn't use it as a submain for a flat with electric cooking and heating.16mm T&E with a seperate 10mm earth seems normal in new build flats around here.
Adam
The length of the sub-main cable will be 8 mtrs.
Haven't decided yet.
The flat would not normally have any electric room heating as it has central heating.
DaveH
Seems worth thinking about.
OK, many thanks.
DaveH
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