Conflicting advice on transformers for 5W MR16 LED bulbs

[Dave Plowman (News)]

Low voltage types usually have tails. Can you get similar tails for GU50? To avoid having to change the fitting?

[Andrew Gabriel]

A search for 'GU10 lampholder' returned loads.

This is only suitable if your existing MR16 fittings hold the lamps in place using the front ring and use a flying socket, rather than just gripping the lamp in a fixed socket.

Using fittings which grip the lamp by the front ring does allow the use of longer higher power lamps, which would otherwise stick out too far if used in GU10 fittings with a fixed lampholder.

[Dave Plowman (News)]

Yes. All of mine have a ring to hold the lamp in place. And some are mains, some low volts. But dunno what is around today.

[mick]

You can try just swapping them out, but you might find that they don't work. You need to meet the minimum load requirement for an electronic transformer to keep the output stable. However, if you can get the wiring in place, you could run several MR16 LEDs from a single existing transformer to meet the 20W minimum (35W if you want to feed the transformer from a dimmer). Alternatively you could put one halogen and several LEDs on a single transformer. That works well if you don't mind a colour difference although you don't gain all the power savings.

All MR16 LEDs contain a bridge rectifier so it doesn't matter if the supply to them from the transformer is AC or DC.

The advantage of a constant voltage transformer is that it's impossible to overdrive your LEDs. The maximum output is usually just below 12V (something like 11.8V) and it will stay like that even with mains fluctuations. The MR16 LEDs are designed for this sort of supply and contain their own current limiting.

Constant current supplies are used for direct drive LEDs which do not contain current limiting (usually power LEDs). The LEDs (not the MR16 type) are connected in series.

[ARW]

His wiring is easy to get to. He has posted photos of it before. Every spot light has a small 20A JB connected to the transformer. All very accessible by just pulling down all the spot lights.

Personally I would go for GU10 LED (remove all transformers and swap the lamp holders), however if the OP wants to stick with MR 16 then I would remove all the transformers apart from the first in line and buy a 12V constant voltage driver to go there (similar to Martins idea)

[ARW]

You know that we are back to Xmas tree light failure situations when one fails:-)

[Dave Plowman (News)]

But does that mean it would be easy to alter the wiring so one transformer feeds several lights?

[ARW]

It would be feeding all the lights

[MM]

Yep, there's no way I could connect more than one downlighter to the same SMPS. That would mean routing new cable through the ceiling space for a number of downlighters. My halogen downlighters each have their own electronic transformer (JC 4030 from JCC).

This is what I have now:

(Shows previous transformer, since replaced with a JC 4030.)

MM

[MM]

And route a rat's nest of new cables throughout the ceiling spaces?

MM

[MM]

In my case, it would be anything but easy. I'd rather buy LED drivers instead.

MM

[MM]

29 downlighters in total all over the house? Kitchen, annex, two bathrooms, hall, landing...

MM

[ARW]

Not at all if you are prepared to listen and learn.

[ARW]

I disagree.

[Dave Plowman (News)]

Unless you could get at the feed from the switch and use one unit for all? Then just remove all the others?

Assuming a suspended ceiling, if might be possible to run in some new wiring using the existing spot holes - depending on how the joists run.

But the easy way would be to just replace all the halogen 'transformers' with LED ones. You might be able to sell the old ones on Ebay, to defray the cost.

I had a very similar problem in my large bathroom. Was built with a new ceiling and totally replastered. The original lights were all RO80 downlighters which I wanted to change for LV types some way down the line. No chance of access from above as it's now a roof terrace. And didn't want to replace the perfect ceiling. Also wanted some additional lights.

Did manage to do what I wanted - but a right fiddle, compared to starting afresh.

I've no interest in changing the LV halogens to LED, though, given the bathroom lights aren't on for a vast time.

[The Natural Philosopher]

I've done it both ways.

Its detail dependent. No 'right' way for all cases.

[Chris J Dixon]

You could look around for lower rated halogens, which should save a bit of energy and reduce the brightness.

Chris

[MM]

Yes, I do that already when one of the 50W ones blows. I replace it with a 35W. But so far I've only ever had to replace about 7 bulbs in

12 years! And about 4 transformers.

Maybe I should use the microwave more for cooking, as I do tend to have the oven and/or grill on quite a lot. I expect if I only ate ready meals from the chiller cabinet and did hardly any cooking at all, my electricity bill would show a marked fall after a year.

MM