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
https://app.box.com/s/47h86r5d67p79gfhmrxa1razhp1yxrjk, 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
https://www.lightahome.net/240v-premium-fire-rated-led-downlight-tilt-no-bulb-double-insulated-1173244-p.asp,
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
https://app.box.com/s/p3o0kfqvocgmiestmta142afi6bpex4h 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
https://app.box.com/s/eiyv4tfut1utvcqc9pxmafu62l19yyji [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!
--
Cheers,
Roger

[Brian Gaff]

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

--

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[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.

> 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!]

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

> c) Regardless of the regs, would it be fundamentally unsafe? If so, why?

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.

> 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!]

it would, it's standard stuff.

> I would very much appreciate your thoughts!

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]

> lights and were plug and play or did you choose to install two core flex?
>
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.]

>
> 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?
>

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:
https://app.box.com/s/cqhard7fg45ysxbqx6i9bihj8tz4qcjx

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

--
Cheers,
Roger

[Roger Mills]

Any comments, Adam?

--
Cheers,
Roger

[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]

On 20/09/2022 18:18, ARW wrote:

>
> 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
>
>
>

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?

--
Cheers,
Roger

[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
https://www.lightahome.net/double-insulated-recessed-downlights-39-c.asp
cobblers? If so, I've been taken for a ride!
--
Cheers,
Roger

[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?
--
Cheers,
Roger