sub main 60m away from house, pv system to get installed on sub main roof

stubo300 · Mar 11, 2011

we have been asked to quote for a 3.80kw pv system on a roof which is 60m away from the main distribution board, there is a sub main in the building where they want the pv system installed which has a few spare way on it, this submain is fed by a 16mm 3 core swa,

do i need to take the pv supply all the way back to house or can i install it to the sub main, would that work,

please help

edexlab · Mar 12, 2011

I think you'll need to look at a new cable run
reccommended volt drop for AC side of pv is 1%
regs recognise this may be costly and will permit within BS 7671 limits.
In theory the submain will have to carry the extra 3.8kw
and should be sized appropriately anyway and comply with the 1% Vd .
on the PV jobs we've done with the longest run being 65mtrs it was easier to install the cable than to try and work out the load/diversity/also PIR of circuits on the submains, especially as this takes time and you 're just quoting for work, or the submains in question were too small for they're intended loads ,even with diversity applied!

stubo300 · Mar 12, 2011

thanks for that reply i think i will be better to run a new cable i then. the only thing is at the main consumer board there is no spare ways, so can i install a new small consumer board next to the main consumer board, will that work

BruceB · Mar 14, 2011

Ther was a very similar question on the IET forum over the weekend and the answer from someone whose professional job is designing all sorts of installations was that in principle it is OK to connect at the end of a sub-main. The PV needs its own circuit after the sub-DB of course.
IET Forums - Connecting Solar PV
Regards
Bruce