Swa, sub main electrical connection outbuilding

28 Jul 2015
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United Kingdom
Wondering if I could get some advice from you sparky’s please.

House consumer unit connects to another consumer unit for the kitchen.

Kitchen sub consumer has electric oven, induction hob, hood, lights and sockets connected. The connection for this secondary consumer unit is 16mm 3 core armoured cable to house one.

I would like to update outbuilding which is currently on the old style consumer unit linked to kitchen consumer via twin and earth ‘externally’ clipped. (Bodge!)

Could the same system be applied for the outbuilding consumer unit? Ie another 16mm armoured buried?
It’s an 18m run from kitchen to outbuilding, I will be using power tools and might consider a welder at some time.

I would like to prep for digging to save some time and money and may buy the cable beforehand.

Thanks in advance.
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The enterprise that you plan requires notification to the local authority. You need to raise a building notice With LABC before you start work. And pay their exorbitant fee. They will expect you to be fully conversant with and be able to design, install and test the installation up BS7671. And certify it. Got the nouse and The required calibrated test equipment for all that?

the better route is to engage a registered electrician now. Most will be delighted for you to do the hard work for them.

if you are desperate to Dig your trench, go ahead and put some of this in it.
You or the Electrician can pull in the SWA that he/she calculates that you need. don’t buy it without advice, it’s not usually A returnable item.
Thanks for that, I don't intend doing the work myself, (other than digging) was merely asking if the method was OK, as I've had conflicting advice on exporting the earth.

Previous electrician suggested it, although I won't be using again as his work wasn't that neat.

Out of curiosity why would I need trunking for armoured cable? or is it just to facilitate doing the job.

Exporting the earth depends on many details. The main one will be if there are any extraneous conductive parts in the outbuilding. Typically water or mains supply in metal pipe, the building itself being made of metal, and other concerns.

Generally the earth can be exported but it needs an expert assessment.

Conduit not necessary for SWA. It can be buried in the ground, the suggestion was that you must the conduit in the ground, then your qualified, registered electrician can calculate what size SWA is needed.
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