Underground cable

[sandy_v]

We're planning to run an underground cable (under the grass) to a shed. I've read that you can thread it through a drainpipe etc to protect it. Is this a good idea? Doesn't it fill up with water?

[pigletwillie]

The only cable suitable is steel wire armoured (swa)and this will need burying 18` below any cultivated areas and at a suitable depth in non cultivated areas.

It will not require putting in a pipe.

[peter]

Piglet, unless the EU have been on the case I assume you meant 18" not 18' as that would be one heck of a trench.

On a more serious note, is it not the case now that all external (and internal) home wiring now has to be done by a certified electrician?

[pigletwillie]

Your right on both counts Peter. Typing is not my best forte.

[Tigger]

Typing must be difficult when you have trotters.

[sandy v]

Yes, I read the other thread about electrical wireing requirements and new rules. This is only going to be an extension, i.e. plug in at the house end, but it's quite a long way, and we don't want it flopping about in the air.

[richard p]

when the electricity board installed our underground supply the installation team asked if we could supply a suitable length of plastic mains water pipe to thread their armoured cable through to give additional protection in our layered limestone. The installation team were also on call to repair faults on underground supplies so presumably knew that stones could penatrate armoured cable. we also ensured that several layers of flat stones were laid on top of the cable before the trench was backfilled.

[pigletwillie]

Stone is a killer for undergroung cables. Any cables in trenches should be laid on a bed of sand and covered with the same unless protected like you say by a pipe.

All the cables from my house to the workshop run inside a soil pipe buried by a jcb when we had our extension built. A bonus being that we could pull in other cables (telephone, burglar)at a later date very easily.

[TimMead]

There are a couple of issues here. Number 1 is the point raised earlier in the thread about this now being the exclusive preserve of registered electricians. There's no get out clause for outside wiring for sheds etc like there is for inside stuff. (inside you can get it inspected by a registered electrician afterwards if you can find one willing to do it!)
You may just about get away with regarding it as a temporary extension cable, but you'd be wise to tuck it out of sight if you try to sell the house !

Number 2 is the minimum distance required between mains power and telephone equipment, which I believe is two feet ?

I'd certainly recommend SWA cable, as you really don't want to be chopping into this puppy as you dig the veg patch ! A water pipe will offer some protection, but not enough. I'd recommend going overhead with a catenary as it's generally less effort. Straining wire, tape and tie wraps are cheaper than armoured cable too !

Tim

[richard p]

another point with buried cables (or pipes ), u can get a 4inch wide flimsy plastic marker tape to bury a few inches above the cable, so if you're digging a hole in ten years time and find the tape u know the cable is a few inches below.