Cabling for outside lighting query

25 Nov 2020
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United Kingdom
I have a quick question, I am getting my rendering done on my extension and wanted to clarify I can do what I think I can do for the outside lighting. The fuse board location is on the first floor as shown on the drawn picture. I have four post lights that I want to position as shown by the little circles on the pic.

Would it be feasible to run a cable down the inside of the unused chimney breast as it’s right next to the fuse board to bring it down to ground level and outside the house and run cables to the positions of the outside lights. I am just wanting to clarify this is possible so I can go ahead and get the rendering done. As the driveway and patio are yet to be done, all cables could be buried then. I have posted a pic of the post light spec I have, no switches needed as operated via app. Also what cable would I need to run in? Assume armoured cable…

Thanks in advance.


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In the main if you still have a fuse board then you will need that changing first to a consumer unit. New circuits need notifying, and an electrician will not want to notify other peoples work, and using the LABC can be expensive, so in the main you need to approach an electrician first, so he tells you what you can do for him.

You can of course ignore all regulations and laws, but it would be pointless asking the question if that was what you intend to do.

Largest problem with outside lights is water ingress and this tripping the RCD, and you need to consider if this happens what you loose. In my house I have a modern consumer unit with all RCBO's which are MCB and RCD combined, so any circuit with a problem does not affect another. But may homes have been wired on the cheap with one RCD supplying many circuits, and although the MCB switches off the line, the neutral is still connected, so water can cause RCD to trip even with circuit switched off.

With outside lights it is common for an isolator to be fitted in doors, which will turn off both lives, i.e. line and neutral, in some cases using a fused connection unit (FCU) which may include a double pole switch and a RCD, the latter could be 10 mA so outside lights will disconnect before the earth leakage reaches a point which will trip other items in doors.

I do like the idea of using smart bulbs, no point lighting the way for intruders, let them trip over, lights are for you, and dusk to dawn and timed switching also possible. But in the main smart bulbs will default on, so after a brown out or power cut likely they will light, so you do want some method of isolating.
Thanks for your reply, I think I have accidentally confused the issue. I have had a complete rewire so I already have a new consumer unit in place so all good there. I don’t intend on actually installing them myself, I’m just thinking of running in suitable cable to save a bit of money by getting someone else to do it and more often than not, people want to do it the quick way and I really want to hide the cabling as much as poss.

Anyway, the main reason for my question was initially I was thinking I could take the power from a socket but that would mean running cable down from that which is on the rear of the extension. The extension needs rendering so if cable had to be run in, I wanted to do it before the rendering. However this solution doesn’t really help with the ones I want to go at the front of the existing house.

I thought if I ran a new cable from the CU, this would be the more correct way to do it, cables could then be concealed when driveway and patio was done. I also didn’t consider what you mentioned about potential water ingress. Good point, I had an issue with this with an old fuse board in the garage at my old house. Rain was getting in somewhere and that was then tripping the rcd’s in the house. I had to switch the old fuseboard off in the end and just switch it on when I needed to use it.

Hope this makes more sense now!

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