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Garden kitchen and bar wiring advice

Postby Doherto » Mon Jul 20, 2020 3:07 pm

Hi, I have not used this forum for some while but it was great when I did so hopefully someone can advise me on this next project. I am a retired ex electrical engineer, but not a qualified home electrics engineer. So, I am hoping, with some advise, to run all the cables for my project, which is not built yet, and then get them connected and certified by a registered engineer. So, my CU is at the front of the house, with spare capacity, and my thoughts were to run a suitably sized cable through the house to the rear and install a slave CU internally on the rear wall, a distance of 11 metres. Then I need to run suitable cables underground to the garden kitchen/bar area and I would like to run power to the garden shed. The kitchen, 25 metres from the house, will need three double sockets and some lighting, just for light use (fridges etc no cooker). The shed, 15 metres from the house, just a double socket. So my questions are 1) what size cable do I need to run through the house. 2) Can I run cables in plastic conduit underground or do they need to be armoured. 3) Can a 2.5mm twin and earth ring be sufficient for the Kitchen/bar over that distance. 4) Will a 1.5mm twin and earth ring be ok for lights over that distance. 5) Do I need a 2.5mm twin and earth ring for one plug in the shed or can that be a spur from the CU. ( The shed is in a separate part of the garden so cannot be part of the ring for the kitchen/bar) A lot of questions I know but hopefully someone with more knowledge than me can provide some guidance. Thank you in anticipation. Tony.


Simply Build It

Postby Mr White » Mon Jul 20, 2020 7:09 pm

Since you were here last things have changed. You should get a qualified electrician to come to your place and discuss with him/her what you wish to do, the reason is that it is him/her who has to sign the job off, not me or any one else sitting at a keyboard.
By visiting site they will also have a better understanding of the job.

Anyone can only go by what anyone else types, and already you have made a few simple mistakes, which I am sure a site visit would soon correct.

Yes, it is frustrating you being an ex retired electrical engineer, and me having to tell you that you can not do the job without guidance, but sadly in this blame / claim culture (and Part P) that is how it must be.

We do have a retired electrical engineer on this forum, and even he admits to making mistakes, and as such will not give specific assistance. He will give opinions though.
Mr White
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Postby ericmark » Fri Jul 24, 2020 8:34 am

Depends where you live, here in Wales garden and kitchen are special areas so need notifying, but not the same in England.

When is a consumer unit not a consumer unit? If you read BS7671 you get different results to building regulations, as with most laws the original is not well written, and case law will over time clarify what is required. However I don't want to fight a test case, and I am sure your the same.

So a circuit is all after the overload device, so fitting a FCU produces a new circuit, however it seems the scheme providers do not class that as a new circuit, only new connections to the CU is considered as a new circuit, however clearly a mini consumer unit (CU) with one MCB is in real terms the same as a fused connection unit (FCU) but it seems they are notifiable.

You still can DIY officially, you can notify the LABC your going to do some work, pay their fee, and still DIY.

However back in 2004 I tried it, it seems they must satisfy themselves that you have the skill, and they can appoint a third party tester that you pay for, so in Wales your looking at around £150 fee even for the smallest job, they did in the end allow me to do the whole job, both my son and I are electricians, he was doing the talking, and he pointed out he had inspection and testing as as it was then 16th Edition, but LABC inspector was not budging, then my son said "OK then, but the inspector must be higher qualified than us, my dad has a degree in electrical engineering." Only then did he back down and allow us to do the job. Lucky the work was to accommodate my mothers disability so no charge.

I think the ceiling for when the charge hits next bracket is £2000, and that is a lot of electrical work, and of course you can't sneak some items in which require planning permission, the building inspector is there on site, we did not realise you needed planning permission to turn a pantry and coal house into a wet room, we do now.

So if the LABC is aware, you can't sneak anything past him, so if the kitchen has planning permission then the electrics must also tick all the boxes. There have been many things in the past where the LABC has assumed your using a scheme member electrician, it seems it is one little tick box on the application, and after completing the work, you ask for the completion certificate and the LABC inspector asks for the compliance certificate first.

From your post I would assume you were not an electrician, a ring final is only used with 13 amp sockets, no where else do you use a ring final, the calculations for the ring final are complex, I use a java script program to work it out, to be within the volt drop normally maximum cable in a 32A ring final is 106 meters, the formula is in BS7671 it uses square roots to work out the correction factor, and the design current is not the same as maximum current, for volt drop taken at 26 amp not 32 amp, with the java script program I could work it out, but not easy.

I am only qualified to 17th Edition, we are now on 18th, and I know fire regulations has muddied the water a bit, well a lot, plastic RAW plugs are things of the past. We have returned to metal clips.
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