Hey friends,

I have a few small updates this week which you'll find below the main feature - how I (we) wired my downlights that I documented installing last week. Now I might just be able to fumble my way through explaining this but why not hear it from the horse's mouth - my buddy Steve.

In Troy McClure fashion, you may remember him from such classics as Plasterboarding and Wall Insulation. Electrics are a serious matter so is he to be trusted? Well, there's a disclaimer later on but he has a degree in Information Systems Engineering from Imperial College as well as having worked in a Power Station for National Power, and has recently completed the TradeSkills4u Domestic Electrician's course. Without trying to blow too much smoke up his behind, he's one of the smartest people I know and can seemingly turn his hand to anything and pick it up quickly. Simultaneously impressive and annoying, but I trust him completely with this stuff.

⚡ Wiring My Downlights

Hi all, I’m Steve and a friend of Ali's. We get together now and then, to help each other out with our various DIY adventures. Ali helped me out with some plasterboarding of an acoustic ceiling for my office last year, and I’ve more recently been helping him out with installation of his downlights. We have many times discussed whether it is right to discuss electrics in Ali's newsletters and videos, given the inherent dangers. I hope that we have got it right in this newsletter, by explaining some choices we made, as well as where you can get more information and skills. Let us know what you think. If the response is positive, maybe we'll do a series of videos too!

Downlights

I have previously installed all sorts of downlights, but my current preference is standard GU10 light fittings, where you can install bulbs from any supplier, whether those bulbs are ‘dumb’ filament bulbs, LED bulbs, dimmable LED bulbs or even full-on smart bulbs such as Philips hue.

I suggested the Aurora EN-DLM981X fittings. These fittings are good for a number of reasons:

1. They are fire rated, which is important if you are going to be cutting holes in your ceiling and there are rooms above. The hole you cut is an opportunity for a ground floor fire to make its way through to upstairs bedrooms more quickly. Fire rated downlights are tested to make sure that they don’t give any flames an easy job. Not a ‘nice to have' this one – it’s a requirement of the regs.
2. Ali mentioned he might insulate the floor/ceiling with rockwool. These lights are rated to not burst into flames with up to 300mm of insulation over them. To be fair, from what I have seen of the existing wiring in Ali's house, I think his new downlights will be the last thing to spontaneously combust!
3. The bezels are removable and are supplied separately. This means you can decorate and then slap the bezels on afterwards. If later on you fancy some bling, you can swap your matt white bezels for chrome ones! Don’t do what I do and forget to order the bezels alongside the downlights. I've done this twice now!
4. The terminals blocks on these lights are fairly nice to work with. So long as you have at least three hands.
5. And last but not least, the spring loaded clips that hold the fitting flush with the ceiling actually work. I can’t bloody stand downlights hanging out of the ceiling because of crap retaining springs. You can spend ages doing a really neat job of the wiring in the ceiling, but all anyone sees is your wonky lights if the springs don’t do their job.

Junction Box

We were going to be replacing a light fitting that was fed from (what I thought was going to be) a ceiling rose. It turned out there was no rose at all and just a couple of random bits of terminal block floating about inside the fluorescent light fitting - nice. Anyway, we would be pulling this wiring up into the ceiling (as there would be no rose and we weren’t going to leave the choc block poking through the ceiling as decoration or dinner party talking point) and so we’d need a junction box from which to power the downlights. Since the JB would no longer be accessible, once the floor is back down, we needed to use an MF or 'Maintenance Free' junction box. Again, it’s not just a nice to have, it’s part of the regs. Picture the next owner of your house tearing out his ceiling, (plasterboard landing in his tea mug), trying to work out where the loose connection is that's stopping his lights from working. MF junction boxes are made to standards which makes them very unlikely to fail compared with a standard box with screw terminals. If you are too tight to spring the extra £1 for the MF junction box, another solution (better really, if doable in your situation) is to move any junction box so that it is accessible through one of the downlight holes and may be pulled down out of the ceiling for any maintenance required.

Cable

The cable that we settled on for wiring the downlights was 1mm2 twin and earth cable. These have a brown cable (live), a blue cable (neutral) and a bare earth wire in between. It's aptly named. This cable would be ‘clipped direct’ to the centre of the floor joists which allows heat to dissipate into the joist. Mounted in this manner, 1mm2 T&E has a current rating of 16 Amps. Given that we were powering 4 x 8 Watt downlights, our current carrying requirements were going to be 4 x 8W / 240V = only 0.14 Amps. Might just be ok! In fact, taking into account the cable alone, you could in theory use this gauge of cable for 480 x 8 Watt bulbs! If the cable were bunched with several other cables or covered with fibre glass insulation, then this would derate the cable. But even if totally surrounded by insulation, this would only halve the current carrying capacity, meaning the cable could safely cope with 240 downlights, so I think we’ll be ok! Refer to the IET On-Site guide for how to work out safe cable current carrying capacity.

Installation

I lent Alistair my hole saw and dust collector, so he could make all the noise and dust before I turned up. Plus unlike me, he’s plenty tall enough to drill holes in the ceiling without a ladder. This also makes him a very good ceiling plasterboard prop by the way 😉.

We turned off the electrics at the main isolator in the consumer unit before any work commenced. We used a Voltage Tester to check the circuit was dead after isolating. We also used a proving unit to prove that the Voltage Tester was working correctly prior to these in-circuit tests – this ‘proves’ that your test tool actually works. If you think you’re isolated, but you’re not and your test tool is just broken, that is a deadly situation – this is why it is important to ‘prove’ your tool before testing the circuit. All screwdrivers and pliers used were VDE. These are basically tools that are insulated for as much of length as is possible, as well having finger guards to prevent your fingers from slipping off the handles and onto the pointy ends. I recently bought a special set of 'Jokari' wire strippers and they are great for speedily stripping twin and earth cable, so I brought those along too - any tool that minimises wiring time and maximises tea drinking time is alright in my book.

We found that there was already a series of holes drilled through all the floor joists. These holes were already used to bring the ring final to the power sockets in the room. The holes were plenty big enough, so we used them to route the downlight cables across the joists, without further weakening the floor joists with more holes.

The cables between the downlights were joined in a ‘daisy chain’ layout, with the power from the JB rose replacement being fed into one end of the chain (it doesn't matter which - in this case the bottom-right downlight). The reason to do this is so that each downlight terminal block has at most two cables entering it, with the end downlight just having a single cable entering the block (bottom-left downlight). If you tried to fan all cables out from a central point (in a kind of star configuration), you'd have a shit load of cables all coming back to one point, and that's always a nightmare to deal with.

The cables were clipped to the centre of the joists. This keeps them as far as possible from any intrusions from above or below – think floorboard nails or perhaps a door stop screwed into the floor from above. You never know when someone is going to put an extra screw in the floor to stop that squeaking floorboard! Best not to leave the wires resting on the plasterboard ceiling either – it’s asking for trouble down the road. I think it's fair to say that the existing wiring in Ali's house was pretty grim (nothing to do with him btw), but regardless of this, anything we added or altered, we were going to do properly.

The JB was left loose, rather than mounted on the joist. This is because Ali is going to move the light switch in the room (using the existing cable) and he wanted more slack to be available by moving the JB away from the centre of the room and towards the wall with the switch on. Screw it down to a joist once you’re done mate! Our new cabling is that to the right, tacked to the joist. The cabling laying on the ceiling is the original wiring.

You will notice that there is slack on the wires within the JB and this is deliberate. Note also that all bare earth wires from the twin and earth cables have been sleeved with yellow/green sleeving. Another common sense detail that must be done.

Whilst it would look neater to have dead straight wires from strain relief to terminal, this makes it much harder to check that each connection is fully seated in the terminal and then give each one a tug, to make sure the connection is sound. Plus there’s enough slack there to cut, strip and remake any connection, should one of the cores snap where it has been stripped for any reason. I.e. If we had nicked the conductor when stripping, future movements could cause the conductor to fatigue around the nick and this is where it will break. 

Another point to mention about the JB were the cable clamps. Due to the smallish size of the cables we were terminating, it was necessary to invert the cable clamps in order to get any clamping force on the sleeve. The moulding of the clamps is such that it can cope with a wider variety of cable shapes and sizes this way.

Where the cabling comes away from the joist and into the downlight, the cables have been taped together. This makes it easier to strip the pair of cables to the same length and holds them together whilst making the connections inside the downlight terminal block. The swept bend in the cable gives slack, so that in the future, the downlight may be pulled down out of the ceiling for maintenance, without a lack of cable preventing this.

A little trick here: When you are clipping your cables to the joists, try to get them the same ‘way up’ I.e. both cables with either blue or brown uppermost. Then, when you come to tape the cables together and strip the ends, you will have parallel pairs of matching colours, rather than having to twist the cable around, so that both ‘blues’ are one side and both ‘browns’ the other. If I’ve explained this badly, just ignore it, wire your first light and have that ‘oh shit yeah’ moment… or not – it’s 50/50 either way!

This image below shows the inside of a downlight terminal block. Each connection can take two conductors, not more. Again, this is why the lights are wired in a daisy chain configuration - 1 cable in, 1 cable out.

Disclaimer

With electrics, there is always the risk of electrocuting yourself or others, as well as causing a fire. You should only attempt electrics if you are both competent and confident that you can carry out the work to a sufficient standard. As a bare minimum, I recommend buying:

1. The On-Site Guide for the IET Wiring Regulations and 
2. The Electrician’s Guide to the Building Regulations. 

These handy spiral bound books gives you a wealth of information on the regulations, such as IP rating, how to select cable sizes, how to decide where to drill floor joists for cabling etc. These are great books to refer to. It is good to know what you don’t know, as well as what you are and are not allowed to do. You can then make an informed decision about whether you want to DIY it or not.

The choices that Ali and I made with regard to his downlight installation were specific to his application and may not be appropriate for yours. If in any doubt at all, consult a qualified electrician.

And finally, thank you Alistair for the very complementary introduction (but bloody hell, talk about setting someone up for a fall!). This does however allow me to make a point that I feel is very important. Whilst my favourite book when I was 5 years old was Ladybird's 'Magnets Bulbs and Batteries' (yes, I was a very strange kid); whilst I worked in a power station; whilst I have a degree that covers electrical laws, this does not make me an electrician. No matter how clever you might be, unless you've read and digested BS7671 (or preferably have been taught and tested on an electrician's course), there will be stuff that you do not know that you do need to know. I learnt something on each day of the 18 day course and exams that I took and really enjoyed the whole process. Whatever an electrician might say, the course is not that hard. The tutors described it as 'about GCSE level', which I think is fair, so pretty much anyone could pass it if they wanted to. But even if something is straightforward, it can still be essential. You owe it to yourself, your family and the people who own your house after you to do this kind of stuff right. So please do the responsible thing.

👨‍👩‍👦 Life

• The new his-and-hers desk is up and running but there's still a piece I'm waiting on so I'll tell you all about it a future edition but I've definitely picked up some brownie points:

• The boy turned 1 year old this week. How time does fly. Looking back over the past year, there's no doubt about it, parenthood is bloody hard work but it's also brilliant and he's such a charming addition to, well, life. We consider ourselves lucky to have both been home with him during his first year which leads me to my third piece of news...

• Along with full remote working and a 4-day week (I'm sure I've mentioned this before) Abi did indeed score a pay rise and a promotion, which is amazing particularly coming off the back of a year's maternity leave. I'm very proud of her. To make this a vaguely useful anecdote, here's a good podcast on asking for a pay rise. The upshot is more funds to get on with the house and being sensible, throwing a bit more into pensions and ISAs.

👋

Hit "reply" if you've got any comments on this week's newsletter – otherwise I'll see you next time. Have an epic week :)

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P.p.s. You can find all previous newsletters here.