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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Electrical Questions >> power supply to outbuilding https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1328270818 Message started by Natedog on Feb 3^rd, 2012, 12:06pm

Title: power supply to outbuilding
Post by Natedog on Feb 3^rd, 2012, 12:06pm

i've got shed/workshop that it would be useful to have power in, as it is a bit antisocial to start up the generator if i want to be working in there late in the evening.

the workshop is about 50m from the house, or 65m from the CU, depending on how you would need to look at it.

it's only going to be supplying a single striplight and a single double socket, so i'm guessing the cable doesn't need to be any bigger than 2.5mm?

does this have to be armoured cable, or is it acceptable to run "normal" t+e inside a conduit of some kind? years ago in a previous house the sparky ran t+e inside blue mdpe when running a supply to my garage

for a small load such as this, would it be acceptable to put a fused spur from one of the sockets at the back of the house, or would it need to be supplied separate to the main house electrics?

just trying to work out if i'm likely to be able to afford it before i speak to the sparks

Title: Re: power supply to outbuilding
Post by Lectrician on Feb 3^rd, 2012, 5:57pm

You cannot use Twin and Earth in conduit - while this was once permissible, it no longer is.

SWA is the easiest way to comply.

Even at just 13amp (from a fused spur), 2.5mm is just a tad to small - 4mm would be OK, but larger preferred.

For a 20amp supply from your CU, you would need to up it to 6mm.

These figures assume no huge lengths within the outbuilding.

You would be far better budgeting for a larger cable - 10mm SWA, and a 32amp breaker. You are pretty well covered then.

13amps from a fused spur may be OK if you only use the odd power tool and a light.

Title: Re: power supply to outbuilding
Post by scotspark on Feb 3^rd, 2012, 6:03pm

to be honest for the extra cost i would stick a 6mm 3 core swa back to the board on a 20A mcb at the minimum in.

the work is in the trenching.

Title: Re: power supply to outbuilding
Post by Natedog on Feb 4^th, 2012, 4:31pm

scotspark wrote on Feb 3^rd, 2012, 6:03pm:

the work is in the trenching.

i was thinking hire a minidigger. don't fancy digging a 65m trench by hand ;D

Title: Re: power supply to outbuilding
Post by CWatters on Feb 5^th, 2012, 10:06am

I did something similar. Found this helpful...

http://www.google.co.uk/url?sa=t&rct=j&q=electrical%20supply%20to%20outbuilding&source=web&cd=1&sqi=2&ved=0CE4QFjAA&url=http%3A%2F%2Felectrical.theiet.org%2Fwiring-matters%2F16%2Felect-inst-outdoors.cfm%3Ftype%3Dpdf&ei=QFQuT_6UOqaR0AXd9pGtCA&usg=AFQjCNHdTWfigRIv_mVA-SEjvMCbiYcuAw

Title: Re: power supply to outbuilding
Post by baz on Feb 5^th, 2012, 11:23pm

That old Wiring Matters article is quite good and mostly is still relavent. But it should be remembered that it was written under 16th edition Regs. One or two things have changed since then.