Wiring for a garden workshop

[johno]

I have a shed at the end of the garden that I want to use as a small craft workshop, problem is there is no power at the moment. I can take power from an upstairs bedroom as a spur and run it down the wall etc in conduit, a run of about 10m or I can connect direct to the board, but this involves a run of nearer 35m again along a garden wall in conduit. I cannot access a powerpoint nearer downstairs as this would involve concrete floors and a nicely decorated new kitchen! I am looking at one florry strip and two double sockets, for a small bandsaw, bench sander, radio, Dremel etc nothing heavy duty. Any suggestions etc? Thanks John

[Christian McArdle]

Rather than running cable in conduit, run SWA/XLPE armoured cable. This can be clipped directly to the wall (or buried underground), although there's no harm in sticking it in conduit as well if you want straighter runs or a different colour. Buy 3 core cable if you want to export the house earth (the armour isn't as reliable as a copper core), or 2 core cable and an earth rod if you want TT earthing. If the shed is distant from the house, or the house itself is TT earthed, then local (to the shed) TT earthing is appropriate.

I would run directly to the consumer unit, rather than spur off the upstairs socket, despite the extra distance. Running an entire shed off a ring could easily unbalance it, and it would have to be run off a 13A fused spur, which could be quite limiting, especially if you are running a heater in winter.

Christian.

[johno]

Thanks Chrstian, thats a great help, yes the armoured cable makes sense. Now all I need to do is measure up and find out how much it will cost!! Cheers John

[jcurthoys]

Get a garage consumer unit from Screwfix for £26 or so - this wil seperate the lights/sockets and has another RCD since it is a way fro the house. They also do earth rods and armoured cable. Use 4mm and g straight to the house consumer unit with it's own fuse on the socke side....

J

-- jcurthoys

[Dark Angel]

Should someone not point out at this juncture that installing power in the garden shed will undoubtedly require testing by the local council prior to being finally wired up?

[John Rumm]

You will want a RCD for the socket circuit in the outbuilding, but you probably don't for the lights. Hence a small CU with a plain incomer switch and then a RCBO for the power circuit may be a better bet.

To correctly address the issue of earthing we need to know what type of earthing install the OP already has in the house. If for example it is TT then he will need a RCD at the head end of the cable as well. Since this will have a downstream RCBO then it will need to be a time delayed type to make sure it does not trip and loose the lights due to a fault on the power circuit in the outbuilding.

Altenativly if the house in a TN-C-S install you can probably do without the head end RCD but you alnmost certainly won't want to export the house earth to the outbuilding, hence he will need to make that a TT install.

[Christian McArdle]

A 35m run would be better off with 6mm, to leave some voltage drop available within the shed installation, especially if designing for a 32A circuit, which might be an idea if heating might be required in the workshop.

Christian.

[mungoh]

And if the day ever comes that the shed gets elevated to an auxiliary food store (i.e. add a freezer) then provision of a third power circuit which is not on the RCD might be viewed as a useful contingency. Not relevant for present circumstances of course but I like to think ahead.

HTH

Mungo

[johno]

Thanks for all the comments and sound advice, as it now happens a new neighbour that I have not previously spoken to turns out to be an Electrician. He will be doing the work in return for me re upholstering his three piece suite, job done and all happy campers!! Thanks again John