Double-Insulated (or not) downlights - Ping Adam

[Roger Mills]

Following on from my earlier thread about converting halogen downlights to LED, I have made *some* progress.

The upstairs office had 6 of these

each with a 35w

12v MR16 halogen bulb - powered by 2 electronic transformers (3 per transformer) - all installed by me about 20 years ago.

Because they had been wired for low voltage bulbs, the wiring was L&N only, with no provision for an earth. Because they go through the ceiling into the roof space, I wanted to be able to cover them with insulation, which had not previously been possible.

In the end, I removed the transformers and replaced the whole lamps with with these mains powered double insulated fire rated lamps

 each with a 5w GU10 LED bulb. This solved the "no-earth" problem, and enabled me to cover them with thermal insulation.

I now want to do the lounge - which is where I'm looking for some advice. There is no issue with thermal insulation here.

The lounge is L-shaped and currently has 3 groups of 4 downlights of the same type as were in the upstairs office. Each of these has a 50w 12v MR16 halogen bulb. Each group of 4 is powered by an electronic transformer. As with the office there are no earth conductors.

The easiest and cheapest solution would be to get rid of the transformers, and replace the 12v MR16 bulbs with 240v GU10 LEDs. These are dimensionally compatible, and it would only be necessary to replace the bulb connectors and their wiring. [See

which shows the existing bulb and connector at the bottom and the proposed bulb and connector at the top]

However, these lamps were designed for low voltage bulbs, and have no provision for an earth - even if I could provide one. They obviously don't display any double insulated logos! Having said that, it seems to me that there is a vanishing small danger of the metal bits ever becoming live, since the wires enter through a big open space - see

[The wires in the new double-insulated lamps are mush closer to the metal parts!]

If I were to do this: a) Would I be in contravention of the currents regs? b) Assuming yes, would I have been in contravention of the regs 20 years ago if I had converted the lamps to GU10s at that time? [The conductors are red and black!] c) Regardless of the regs, would it be fundamentally unsafe? If so, why? d) If my house were subject to an electrical safety inspection, how likely is it that this would be picked up? [11th Commandment - Be thou not found out!]

I would very much appreciate your thoughts!

[Brian Gaff]

All I'd say is what happens if a lamp feels short circuit. Brian

[ARW]

Couple of questions before I answer.

Are the existing lights a kit that came with one transformer per so many lights and were plug and play ir did you choose to install two core flex?

On photo DL3 should the cap on the cover over the strip connector have a screw thought the strip connector onto the metal lamp support bracket?

[Animal]

the resulting fittings need to be either earthed or double insulated. I can't see whether they'd meet the latter.

earthed lighting circuits were required some time in the 1960s, and I think about 1970 for earthed metal fittings IIRC.

If insulation fails & mains touches case, an unearthed case will happily sit there live until someone touches it. If you have an RCD that improves things, it would probably trip on touch. But not in every case.

it would, it's standard stuff.

There are plenty of house wiring items that don't meet current standards. There are plenty of countries where earthing metal lights is not the norm. Legally you're required to comply when doing work.

[Roger Mills]

No, I bought the lamps and transformers separately - but both from Screwfix. I used one 210w transformer per 4 x 50w bulbs and one 150w transformer per 3 x 35w bulbs. The transformers are double insulated, and have no provision for an earth on either the input or output. In the case of the lounge lights, with groups of 4 x 50w, the output from each transformer is taken to a circular junction box - which has 4 outputs - one to each lamp. The cable is actually T&E, but the earths are not connected in the junction boxes, and the junction boxes are inaccessible. [They were put in while the ceiling was down when the house was being extended.]

No, the cover has a central plastic spike which goes through the hole in the middle of the choccy block, and (just) into the hole in the metal strip. See:

The covers tend to fall off over time, so I have put cable ties around all those which are still installed.

[Roger Mills]

Any comments, Adam?

[ARW]

Yes - for some reason your fist reply only came through this morning!

I would be temped to buy an LED driver and swap the transformer and use LED MR 16 lamps.

Using the T&E without using the earth (for mains voltage) is a contravention of the regs (and was 20 years ago) and I would spot that that on an EICR.

Cheers

[Roger Mills]

Thanks Adam - that makes sense!

Is there any problem with what I've done in the upstairs office - with fire rated double insulated lamps without the earths connected?

[ARW]

It would be coded as no earth on that section of the lighting circuit.

C2 if the circuit is not RCD protected C3 if the circuit is RCD protected

[Roger Mills]

But does that still apply when the lights are double insulated - and sold as being suitable for circuits with no earth connections?

Is what it says here

cobblers? If so, I've been taken for a ride!

[ARW]

Yes. I have not got a copy of the regs on me but there is a reg that states there must be a earth at every point with small disclaimers for pendant drops etc.

Actually I have the 1970 14th edition and section D6 says "At every lighting point an earthing terminal shall be provided and connected to the earth-continuity conductor of the final sub-circuit."

You have not been taken for a ride as the class II lights do not need an earth. However the unearth T&E cables will be flagged up on an EICR which is why I suggested 12V LED as they do not require the earth.

Cheers

Adam

[Roger Mills]

Thanks. However, I've now found that, with a bit of re-jigging, I *can* get at the junction boxes which feed the lights. The inputs into those boxes *do* have a working earth so, by shortening the cables a bit and re-wiring the boxes, I *can* provide an earth to each lighting point. I've already done that in the lounge, which leads to the next question. [I want to stick with mains GU10's because I've already bought a lot of bulbs] Question: the existing eyeball lights were designed for 12v, with no provision for an earth. When using them with mains GU10's, is it acceptable to crimp an eyelet onto the earth wire and pop rivet it into the L-shaped metal strip which holds the connector block.

As far as the upstairs office is concerned, I can provide an earth to each of the double insulated lights if I grovel in the attic again. Although these have "provision for an earth", the earth terminal is not electrically connected to anything, and is just somewhere to park the earth. Is it really worth the trouble of providing an earth which will never be used?