I thought I would order some 12v 3w LED MR11 bulbs to replace the halogen 20w bulbs in my bathroom but the website I want to buy from is warning me that the existing transformer may not cope with the drop in demand from the LEDs and might not operate at all with them.
Is this a real thing or are the sellers just covering their backsides?
Thanks,
Nick
It is possibly true of some 'electronic' transformers, but not true of any toroidal ones.
One 50W toroidal can run a lot of LED too.
Mind you they are hard to find these days.
You have to be careful. Some LEDs are rated for 12VDC, and burnout with
12VAC. Don't ask how I know!
Yes, expensive and inefficient.
It's a real thing.
Bill
I have had mains halogen replacement LEDs in my kitchen for many years (>12 years) and still working well.
Isn't the problem more that an unregulated power supply, intended to run
12V halogens, will probably be running at well above 12V with around 15% of the current for the leds that the halogens will take? That higher voltage might burn out the leds, or at least shorten their life. A properly-regulated power supply will give 12V over a wide range of current.This is not an issue with leds designed to operate at 230V when they are used to replace mains halogens.
No, the problem is that like some computer power supplies, they simply wont fire up without a load of some sort.
That's it. Our bathroom has 6 LED lights and a 35W Halogen. If the Halogen is replaced with an LED, the lights all flash on and off at about 2Hz. Originally, it worked with 7, but after about 18 months started flashing - and I have tried a number of replacements (supposedly suitable for LEDs and the loading) that do exactly the same thing.
I will eventually try a more expensive PSU or add a resistor that is just sufficient to stop the problem. It's not a priority at the moment though.
Apparently it depends on the transformer type.
The MR11 could be an "AC/DC" bulb, and if so, it would not use a capacitor dropper (dropper no good for DC operation), and would use something like a buck converter inside for a constant current source. The buck converter would have a rectifier and filter on the input.
It's a "hot mess of stupid ideas", all these variables.
If run off 12V DC, the thing is going to behave, but then the power source used is probably not rated for the re-insertion of a 35W halogen (which could draw 70W or more while starting up, the 35W value being when it is hot).
If run off a non-electronic transformer (a big chunk of iron with copper windings on it), it will also behave.
What's interesting about these MR11 bulbs, is you can never find a spec for "max voltage in". It's always rated at typical and "use your imagination" for any other set of input conditions.
Paul
You could always buy a new PSU intended for LED lamps, they are cheap enough. Assuming the current supply/ psu isn’t built into a unit swapping it should be easy enough. Don’t bury it under loft insulation etc, let air get to it for cooling although it will dissipate very little heat.
Plenty on eBay.
That's why I wrote *properly* regulated power supply.
I wonder why the OP's original power supply worked for 18 months and then failed. If it was stressed by the lowish (2A?) led load instead of the 20A load of the halogens it must have been pretty near to the level at which it would have continued working indefinitely. Perhaps it was an unrelated fault, but that wouldn't explain why the replacement supplies failed similarly.
Erme - I'm the OP and to the best of my knowledge my PSU has been working faultlessly for years. (Famous Last Words???)
But this does seem a good place to jump in and say thanks for all the insights into replacing halogen with LEDs. Just plugging in a few LEDs seemed like a quick and easy way to knock a few quid off my electricity bill but the transformer was installed ages ago, long before I moved here, and is now buried under the floor boards, underneath the floor panels underneath the carpet in a lived-in attic room and I don't think the savings are worth the cost of a new transformer - how ever cheap they are - and especially not worth the brain damage involved in turning the attic upside down.
But thanks for the information: I appreciate it.
Nick
If it's been in for many years, it may well be a simple toroidal transformer - in which case it will probably work fine.
If you replace all but 1 with LEDs you're normally fine, assuming they're on 1 transformer, not 1 per bulb. Halogens were a crazy choice before prices went up, now they're far worse.
Yes. When I installed my toroids in 2002, electronic PSUs were fairly new with unknown reliability.
I installed one - the rest were Newlec toroids. Ive lost two in 20 years out of god knows how many.
Many of the 50W halogens are original too. I have quite a few spares as well. But LEDS fit in the same sockets and work fine
>
My apologies - for some reason I had SteveW's post up on screen and thought it was your OP!
Yes switch mode ones are the design of the devil in any case, as most of them seem to be radio jammers in disguise. However I guess you need to find out if its the overall load or the different load conditions that might be the issue. Somebody told mye by keeping one Halogen over the shower it fixed the issue. well..... Brian
I'm about to replace all my 12v downlight bulbs with mains GU10's. They'll fit in the same lamp units as the original MR16's. I'll need GU10 bulb holders - but they're only pence each. I can then do away with the transformers altogether. The main problem is going to be that some of the transformers are a bit inaccessible to get at in order to by-pass them.
I have read that mains GU10s are less reliable than 12V MR16s, but having had GU10s in the kitchen and second bathroom and MR16s in the main bathroom for some years, none have failed in either. However, I have had problems with the PSUs for the MR16s.
certainly true for halogens, but no-one should be using those now.
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