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What regulations (if any) do I need to follow if wiring a 12 V system (in the UK)?

I was planning to wire up a garden shed / summer house to the 220 V mains. I'm confident I could wire it safely and sensibly, but not being up-to-date on UK wiring regs I'm not sure I wouldn't miss something that might upset a bureaucrat should it ever come to be inspected.

To avoid this I'm thinking of installing a 12 V system instead (100 W solar panel, plus old truck battery). It's only a shed, so realistically the most I need is power for lights, a laptop, mobile phone charger, maybe a couple of cooling fans for the warmer days, and perhaps a drinks cooler.

If I went down this route, are there any UK regs I'd need to follow?

I'm an electrical engineer, I'm happy with the technical (and safety) side of the work, just looking for the regulatory side of the problem. As far as I can tell, boaters and caravaners have to obey boating and caravaning regulations for the wiring. I can't find any general 12 V wiring regs.

ocrdu
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ConanTheGerbil
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  • Good question. I'm not aware of any. Maybe ask the campervan/mobile home or boat forums for recommended practice. Even connectors aren't well established. (I use XLRs on my boat, rated for 15A. Above that, search Anderson connectors. Breakers per circuit, and a "battery isolator" right next to the battery. –  May 21 '20 at 09:57
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    As far as I know, UK Building Regs don't cover outbuildings such as sheds and garages and Wirings Regs only cover the need for separation between low voltage circuits and mains, so neither will be an issue. Probably best to check on the Home Improvement stack exchange, they will probably know more – Finbarr May 21 '20 at 10:05
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    However, I think you're asking a great deal from your solar panel. You won't average more than about 400Wh a day from it. – Finbarr May 21 '20 at 10:07
  • @finbarr - I typically use the summerhouse a few hours a day at the weekend. after a week in the sunshine I would expect the battery to be close to full – ConanTheGerbil May 21 '20 at 10:13
  • You need to do a calculation - expected energy available from your panel over a week versus expected energy required by that list of devices over a week. If the latter is greater the battery will get depleted. And you need to ensure it has enough capacity to get you from sundown to sunrise. Bear in mind that during daylight the panel will need to be able to supply all the load as well as recharge the battery. – Finbarr May 21 '20 at 11:05

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Legally, Building Regulations Part P in most of the UK. Be aware that the regulations are different in each part of the UK (England, Scotland, Wales and NI).

In terms of standards, BS7671 18th Edition, IEE Wiring regulations. That's not law, but it is the British Standard. BS7671 is a massive document.

Simon B
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    This is true but not very helpful - which bits of these giant standards apply to 12V? – pjc50 May 21 '20 at 10:33
  • It doesn't. What it does cover is HOW you create the 12V. What is applicable is (2014/35/EU)  which is the LVD and since 12V < 50V you are fine. Just keep an eye on how you derive 12V –  Apr 16 '21 at 07:09