Question for any electricians

divuk83 · 20 Oct 2015 at 23:48

Here goes.......

The bathroom (in the extension built in 2000) currently has 4x MR16 50 watt Halogen downlights (none of which are ip rated, even the one over the shower). The plan is to switch them to GU10 LED's by replacing the fittings and the one of the shower with a proper sealed, ip rated unit. Currently each MR16 has it's own individual 240-12v transformer, the 240v input is two core (no earth cable) though the wall switch is earthed and presumably the junction boxes in the loft the feed the downlights are earthed too. The plan is to snip off the 240v feed as it enters the transformer and then wire up my new GU10 fittings to the 2 core 240v feed. The IP rated light doesn't even have an earth, and says not to earth it in the instructions. The 3x non shower rated have an earth terminal but I have no earth to connect to it, as the cable on a GU10 fitting is double insulated where it passes through the fitting, does it need an earth? Plus the fitting if more of a bulb holder than a part of the light? Googling gives me differing opinions on this and makes me more confused than when I started!

Thanks in advance.

Dave

C.R.A.Z.Y · 21 Oct 2015 at 00:05

Any exposed metalwork or chromed fixtures should be earthed for good measure.

Why not simply replace with 12v MR16 LED bulbs, one big problem with GU10 LED bulbs is the fact the transformer is crammed inside the little light bulb adding more heat into the device and reducing reliability! Also you wouldn't need to worry about ip rated light as it would only be supplied with 12v (just place the transformers in safe zones and run extra cable to lights on the ultra low voltage side if needed)

It would be a complete waste to chuck the transformers if they are still working, also bare in mind they will be rated at silly watt/amps (to drive 30-50W incandescent bulbs) so running some low power LED's off them will be a walk in the park!
Admittedly it would probably be slightly less efficient but only by a watt or less overall and tbh I think you'd negate that with it being a more reliable setup!!

Well thats what I would do and I'm a qualified electrician.

divuk83 · 21 Oct 2015 at 00:26

Thanks for the reply.

The transformers are rated 20-50 watt and there is one on each MR16 fitting, I don't really want to buy 4x new transformers as well as 4 LED MR16's. I have tested if they will power a 4 watt LED and they don't work properly, buzzing and flickering.

GU10 seemed like the more sensible and cheaper option to save buying transformers? I have a new (to me) house full of 50 watt MR16's that must be costing me a fortune to run!

Dave

HardwareGeek · 21 Oct 2015 at 01:07

Getting MR16 LED replacement bulbs it a bit hit and miss whether they will work properly with whatever existing transformers you have - have seen them flicker or have weird level of brightness or even melt the tranny before

If no earth in the wiring to each downlight what type of cable is it? is earth just cut back as it wasn't being used and you could just strip the cable back a bit more to get an earth - assuming they connected it at the jb?

would need to test that is it actually connected - if not connected chances are you may be able to fish the jb out of one of the downlight holes and connect it up - if no earth in the cable you can tie onto the old cable and pull new though that has an earth from hole with jb to each downlight hole or if top floor access via the loft

What about just using all ip rated fittings if they dont require an earth to avoid the issue?

Or just buy purpose designed LED fittings? afaik most if not all the LED downlights i have seen are IP65

Ps. They do sell GU10 LED bulb and fitting together as a package - so if installed correctly shouldn't be a overheating problem that you may get with retrofitting an LED bulb into an existing old GU10 fitting etc - although a decent brand LED bulb should be well designed to dissipate the heat might have a heatsink/fins of the back of the bulb

divuk83 · 21 Oct 2015 at 02:38

I was disappointed to find out they were all 12v mr16's, I have another 10 downstairs in the kitchen to sort as well, all with individual transformers that won't power the low LED load.

The cable is 0.75mm 2 core. Loft access will be very tricky as it's under the very low roof end and access to that end is very narrow as it's blocked by the joists. I have seen a jb through the downlight holes, that might be worth investigating if there is an earth then I could switch the 2 core for t&e. If not fire rated/ip rated which don't require an earth is an option, though they require slightly larger holes so I would have to cut another 5mm of ceiling out in each hole!

Cheers

Dave

a1ex2001 · 21 Oct 2015 at 09:30

Have you considered buying a single transformer and running multiple lights off it 12v systems are a nice comfort blanket in a bathroom.

divuk83 · 23 Oct 2015 at 20:22

Thanks for your advice. I have bought 1x 240volt ip65 gu10 for over the shower, which is double insulated so does not need an earth. For the other 3 bathroom lights and the 10 kitchen lights (which are identical fittings) I have gone for some integrated led fittings (8.5 watt, 60 degree beam in warm white) http://www.collingwoodlighting.com/en/products/downlights-halers-range/item/h2-pro-550-uk . Not cheap, but solves my lack of earthing issues, plus they come very highly recommended from the trade place I bought them and my workplace who use 100's of them! 7 Year warranty too.

Thanks again for your advice, I think my bad feeling of metal fitting with an earth terminal and nothing to earth it to was justified and this is a better solution. Plus I'm going from 700watts of lighting (just in the kitchen and bathroom) to 115watts so should notice a saving on my electric!

Dave