SWA to submain and NSH

[BasiLR88]

Hi guys,
Can I ask you a DIY question?

I'm refurbing a detached garage and adding a garden building. Garage currently has a submain supplied by 10mm T&E on catenary from the house. I want to replace this with buried cable from house to garage submain, and from garage submain to garden building. Garden building is 10m from house, with garage between the two. It would be useful if I could lay the cable while I'm doing groundworks, then I'll get a pro for the installation.

Our house is heated by NSH on E7 so I would like to extend this to the garden building and the garage. Question is, do I need to run TWO cables from the CU in the house - one for daytime and one for E7? Embarrassed that I don't know this but I don't.

Also, any thoughts on size of SWA? It will need to supply lighting and sockets for six small rooms, plus 5 x 2kW NSH, plus one on-demand bathroom heater (1kW). Water will be heated by LPG.

Thanks for reading this far - advice appreciated!

 

[timhoward]

Without specific information I could only a give belt and braces ‘cover all bases
answer which will definitely be costing you considerably more.
My advice is pay for a sparks to spend an hour there. They will look at the earthing type, measure the external impedance (distance from substation), work out the max demand, select a protective device, consider bonding requirements the far end and volt drop, look at the metering arrangements, and then select how many cores are needed and cable size.

If you look at the price difference between 10sq mm 3 core SWA per m, and 25 sq mm 4 core, you will see that an hour of sparks time is well worth it! They will be pleased at being consulted before a cable is buried too.