outside power

[Chris]

My dad wants a light and a socket in his shed (12m from the house), so I am tasked with the job of making it so.

On the inside of the wall of the house nearest the shed there is a socket inside, so my plan was to drill a hole through to the outside, and run a spur off that ring main.

My Dad is a bit of a "it'll be alright" merchant, and seems happy with burying some 2.5 T&E in 20mm plastic conduit under about 3" of gravel. I, on the other hand would rather do it thus :

- hole through house wall into metal conduit box

- 12m of 2,5mm SWA to the shed, where the SWA will come up through the floor.

- Into an RCD, them from there into the 2G socket.

- Lights to run off a switched fused spur.

This seems about right to me, any comments.

The next thing is the issue of earthing, as all the SWA I seem to find is

2-core. and as SWA glands have earth tags, it seems the steel wire is suitable.

On this basis, should I attach the metal conduit box on the house into the ring main earth so that the box is earthed, and then rely on the metal gland screwing into the conduit box as making sufficient contact?

It seems that 2.5mm SWA is ~£1/m + VAT and that gland packs are about £3+VAT. It's hardly expensive to do it properly

All suggestions welcome.

Cheers Chris

[zikkimalambo]

This has been covered a number of times (by people with much more knowledge than me!) If you do a google groups search for

+uk.d-i-y +shed +earth rod

You should get all the info you require (and then some!)

Regards

Zikki

[gort]

Go to your local electrical wholesaler, they will stock all the cores you could ever need. might find they are a bit cheaper than B&Q etc.

Dave

[David Hansen]

On Fri, 5 May 2006 13:26:57 +0100 someone who may be "Chris" wrote this:-

Look harder, one can get SWA cable with hundreds of cores (for telecommunications) and up to at least four cores (probably more) for low voltage (mains) wiring.

The main earth terminal of many buildings is provided from the steel armouring of the supply cable. It is in the building I'm writing this posting in.

The best way of doing it is to use the earth tag and connect the supply earth to that. Joints, especially outside, are not particularly reliable.

Note that the box needs to be weatherproof, if it is external. There is much to be said for making joints in the warm and dry inside the building by putting the box inside and leading the SWA cable to it through the wall.

However, earthing is more complicated than it seems for such installations. All this has been covered here several times in the past few months and I'm sure you can use a search engine just as well as I can.

[Andy Wade]

This may help:

This needs to be a fused spur, so you'll need to install a fused connection unit in the house, near the exit point.

A waterproof (IP66) plastic box would be a better bet.

No RCD required if there's already (a 30 mA) one protecting the house ring circuit. A further option is to use an "RCD spur" unit at the house end.

OK.

450 mm is the usually recommended burial depth for SWA in such circumstances, not 3"! 2.5 mm^2 seems a bit skimpy. 4 mm^2 SWA costs not a lot more and will keep the voltage drop down.

Use the 'banjo' tags provided in the gland kit if necessary. When terminating the SWA to a metal box use the earth terminal of the box. Always be sure that the gland nuts are tight.

Quite.

You are aware that this work is notifiable under Part P?