DIY Doctor

Replacing bathroom downlights but only LED replacement available?

Postby AnthonyCla » Mon Jun 29, 2020 10:49 am

Hi, wondering if anyone can point me in the right direction please.

I'm trying to replace a halogen downlight in the bathroom. It seems that only the LED type exists now.

I have attached a few pics of the current light and fittings.

The electronic converter states that it is for halogen lamps only. Question: If I purchase the new LED lamp, is there a special converter for those or would it be a case of removing the converter and wiring directly to the mains?

The particular one I'm looking at is: https://www.screwfix.com/p/robus-fixed-downlight-polished-chrome-240v/22455#product_additional_details_container

Thanks, Anthony
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Postby Mr White » Mon Jun 29, 2020 5:39 pm

What you have got is 12v halogen mr16 lamps and an "electronic transformer"
What you are intending to buy is a fitting for a mains GU10 lamp.

You can bin your "electronic transformer"
You will also have to buy a GU10 LED lamp as they are not included.
You will also save electricity.
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Postby ericmark » Mon Jun 29, 2020 9:30 pm

I am unaware of any problem getting quartz lamps, I have a load which I should really dump, as unlikely to use them, but goes against the grain.

The MR16 means multi-faceted reflector 16/8 of an inch across, it has nothing to do with voltage or power connection, but the one you link to is GU10, there are three variants, GZ10 had a reflector which will allow heat to pass through it, and only reflects light, so behind it gets very hot, the GU10 has a tapered edge so GZ10 will not fit holder, but will work other way around, and the GU10L1 has a spike in holder and dimple in bulb so only LED bulbs will fit, they were used in new builds only to comply with building regulations don't think fitted any more, and they were all 230 volt in this country, and often there was a special sucker to swap the bulbs.

The G5.3 (it may be GU I thing the U means bayonet so think should be called simply G5.3 but not sure.) but in the main these are 12 volt, however there are specials for use with battery power which are rated higher. For quartz it did not matter if AC or DC supplied, but for LED some are clearly AC marked 50 Hz, and others are DC, those for motor vehicles like boats and caravans can be 10 - 30 volt DC, but in the main the DC versions are more expensive, however an electronic transformer output is in kHz range, so need a toroidal transformer which are heavier and more expensive.

I am sure most of the 12 volt MR16 equivalent LED bulbs would work with DC or kHz as long as the kHz electronic transformer will work with the 5 watt or so needed for a LED, old electronic transformers often needs at least a 35 watt load, new types will work from zero, however we don't know what is inside the bulb, so we don't know with 100% if the rectifier will be over loaded if using DC or if it will start transmitting if used with high frequency AC.

So it seems safer where you can to use 230 volt GU10, however two problems, one an earth must since 1966 be run to every low voltage (230 volt 12 volt is extra low voltage) lamp so if no earth they need rewiring even when the earth is not used, and with bathrooms they may be where regulations only allow up to 12 volt.

Distance buying is a problem, as G5.3 can be bought in a whole range of voltages, even found 230 volt versions for sale, and also you can by the GU10 holders, the whole idea with GU10 is the holder holds the bulb in position, and with G5.3 there is normally a cir-clip, but some it seems have a floating GU10 holder and a cir-clip.

Dimming is a problem with quartz, the whole idea is the quartz envelope is so hot the tungsten will not stick to it, so if dimmed the quartz goes black and the life is reduced, but LED can be dimmed but really only successfully where the dimmer switch uses a neutral, EU rules state it must state if not dimmable, but it does not have to say if dimmable with a switch not needing a neutral, so in UK we have a lot of problems with flashing when switched off, and flicker when on. And now not part of EU this is unlikely to improve.

Fluorescent and LED can switch on/off rapid, so with fluorescent we use high frequency ballast to reduce the effect, but with LED there is little we can do. There are many ways to drive a LED which is current dependent, it can be a simple resistor, or a pulse width modulated controller or capacitor, the word pulse gives a clue, and some people do have problems due to the flashing, most it does not effect, but using a DC driver with a 12 volt G5.3 will in the main stop the strobe effect even if the lamp should use an AC supply of 50 Hz.

As a result many people say you need a driver for 12 volt lamps, technically a driver controls current, however the lighting industry seem to use the word driver for any DC power supply be it current or voltage regulated, so a volt regulated driver is often used to stop the 100 Hz flashing which most can't see, however as already said technically if marked 50 Hz which many are, it should be an AC supply.

Have I missed anything?

The wiring is also a problem as we use our ceiling roses as a junction box, so you need special junction boxes to allow a single cable to feed light the Hager J501 is an example with cable clamps.
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