SWA size, what do you think

[Spoon242]

Hey guys,

I am after some fast advice for an installation.

I need to supply a new single phase CU in a building with 2x 20A radial sockets, 2x6A lights and room for some extra capacity. The new CU is approx 12M away from the supply board where it enters the building and it will be run under the floor for half of the run, on the sub soil and then in to metal trunking for the remainder to the new board, being shared with 7 additional cable including a 16mm SWA, a couple of 10mm T&E, 2.5mm T&E and 4.0mm T&E's.
The building is not occupied at night at all as its a school but they probably wont switch things off, tut tut.

I was looking in the big green book on Page 338 at REF method D and was considering a 2 core cable single phase @ 16mm which says 78A but really should I go for 25mm to get to 99A?

 

[telectrix]

i'd go with the 16mm on a 63A OCPD.

 

[Spoon242]

I just spotted a 12kw electric boiler also, Bah!

 

[specs]

25mm,who knows what is going to happen 6months down the line.

 

[telectrix]

oops. can't you test it and condemn it?

 

[KAS1]

I think I'd do the calculations and post up on here and see if anyone agrees

 

[Spoon242]

oops. can't you test it and condemn it?

Haha, Tele, they are installing the 12kw next week

 

[telectrix]

yeah, school. taxpayer foots the bill.

 

[ackbarthestar]

I assume the SWA has been dogged in already, if not and you are still contemplating your navel.
What do your diversity calculations predict?