Downlights dying

I've just had some downlights installed and they were working fine for a few weeks until recently. Basically what has happened in the living room there are 5 downlights 12Volt 50watt connected to a 500watt downlight leading edge dimmer switch, one day one downlight died and it was actually the electronic transformer, then not long after the dimmer switch itself died and could only switch on the remaing lights on and off, got it replaced.

Just now the same downlight died again (transformer dead) this is a new different brand transformer used by the sparky, another downlight also died, then the dimmer switch died again, then it flickered and the master switch went off cutting power.

I'm just abit lost to what is causing this (killing transformers and dimmer switch) it's just happeneing in the one room and the other rooms have been fine.......sparky is unsure aswell......

Ideas? :) thanks

Older downlight tranformers generate a lot of heat. Like a real lot of heat.
They need to have a reasonable amount of free air around them to dissipate this heat. The better tranformers automatically switch off when the output transistors reach a certain temperature only to switch on again when they reach a safe operating temperature. If they dont switch off the electronic components within the power supply will be damaged.

The newer more expenxsive transformers generate less heat.

Also most transformers are meant to power only one downlight. If they power more than one ,say two, twice as much current is drawn and again heaps of potentially damaging heat generated.

can you look at the transformer , check its output rating and If its connected to more than one downlight ask your electrician if this is appropriate.

Each downlight has its own electronic transformer....all recently installed...what i don't get is why the same downlight transformer died twice (even with different brand) and another has died but all in the same room.....also after one or two die it kills my dimmer switch! i dont want to replace everything without finding the cause of the issue...getting $$$

This is what I did about three years ago when trouble shooting my downlights.

There arent many components in the system so by elimination it should be solvable.

I jury rigged every downlight with the transformer intented to power it.

On a piece of 3mm plywood 30x30 cm I cut, with a holesaw , the hole for the downlight housing

Then fitted the housing for the downlight in that hole. Screwed the transformer to the same plywood plank and then fitted a a simple switch (not of dimmer type) . then connected the wires to make up the circuit . Then switched and left the whole thing on in a little cubby house the size of four shoe boxes made of some unused bricks lying around .

If the light survived for twenty four hours it got installed. Reason for going to this trouble ? My parents had trouble in their house with downlights. Turned out it was a heat issue. They had them installed in a ceiling which was very well insulated and in summer in particular the lights used to go on and off.
as the tranformers heated and cooled.

My approach to your problem would be to ask an electrician to take out the dimmer switch from the wall and the downlight and the transformer and jury rig them. See if they work . if they dont take out one component at a time and substitute. if they work before any substitution something is wrong with your wiring in the wall/ceiling.

Fluorescent lamps usually require a dimmer that clips the AC Sine wave (1 of 4 waves, 2 of 4 waves, 3 of 4 waves) to achieve dimming. (It doesn't really work that well but it does dim somewhat.) Fluorescent lamps require something that we call a ballast, a.k.a. Transformer.

Incadescent lamps are purely resistive and can be dimmed with a resistive device (VERY inefficient) or an electronic device called a triac. (Dual SCRs with a single gate electrode) These devices eliminate part of the AC Sine wave on every cycle. It keeps the voltage at zero until it is time to turn on for the remainder of the Sine wave. These devices do not work on Fluorescent lamps and can actually cause a fire if used with Fluorescent lamps.

The descriptions of what is happening to the down lights appear to be an incompatible combination of devices and heat. First I would remove any dimmers and second relocate the transformers to a position where any heat generated by the transformer can be easily carried away by the ambient air.

The only other suggestion that I could offer is to use a 60 or 70 watt transformer for each light. You can increase the wattage of the supply and still use the same wattage light bulbs.

I'd get rid of them, talk about efficiency, they havn't any, money going out the window, half your power usage on those lights is wasted, If you have cheap asian transformers then they can develop shorted turns due to too much heat and cause all sorts of havoc, get yourself some new led downlights they run on the smell of a oily tea_towel, are now much brighter with a pleasant white beam, you can find some cheapies on ebay If your carefull.:)

As far as I was aware, electronic transformers require trailing edge dimmers. I have the whole house done with trailing edge dimmers and cheap electronic transformers and have had no issues. My sparky mate said leading edge are fine for iron ballast and normal lights but trailing edge are required for electronic, they also do all other types of lights but seem to cost around 50% more than leading edge.

Cheers
Ben

Speaking with a downlight salesman, he reckons its the leading edge dimmer causing the problem aswell, since cheap electronic transformers state leading OR trailing. In real life you should get trailing edge (which is more expensive and better) Gonna give it a try and see how it goes....be interested to know if ppl out there are using leading edge dimmers with their electronic transformers? :)

Just about all LV electronic transformers for downlights require a trailing edge dimmer, they are easy to distinguish from the leading edge.

Leading edge have a red body on the dimmer mech
Trailing edge have a green boby on the dimmer mech

This applies to clipsal dimmers, cant remember about hpm

Ahhh....enlightenment!! Had a very similar problem a couple of years ago, only the fittings were cheap a## halogen spotlight racks, and they didn't just die, they actually exploded which was a bit scary. In the end after killing 2 dimmers (each costing more than the total light fittings) we just ditched the dimmer. Lesson in false economy there.

We have just moved into a new place and 1 room has downlights in it, they keep switching on and off, I think due to heat as it has a fairly small ceiling cavity.
Someone mentioned LED downlights, do you just change the bulb for an LED one or do they need different transformers etc ?
if changing the bulb = less power draw = less heat then I'll be a happy camper as it looks like its going to be a big job to get into the ceiling space to rewire or replace transformers.
Any suggestions greatly appreciated before I get the sparky in.

thanks
Kiwibrucee

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We have just moved into a new place and 1 room has downlights in it, they keep switching on and off, I think due to heat as it has a fairly small ceiling cavity

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there may be too much insulation surrounding the light fitting, which will contribute greatly to the problem. there is a minimum that needs to be removed, but i'm not sure of exactly how much.

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Someone mentioned LED downlights, do you just change the bulb for an LED one or do they need different transformers etc ?

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you may be lucky, but it will probably require a new fitting altogether. With the different characteristics of the globes - voltage, current drawn, physical size, and cap type- you'd be hard pushed to find a match.

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if changing the bulb = less power draw = less heat then I'll be a happy camper as it looks like its going to be a big job to get into the ceiling space to rewire or replace transformers.

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less power drawn does equal less heat, but when the voltage is stepped down, heat dissipated goes up.

but from the sounds of it, you'd want to have an electrican in soon enough anyway, so if you had enough fittings ready you should be able to get them installed cheaply enough.

Hi

You definitely have an incompatibility between transformer and dimmer. Removing the dimmer (temporarily) should prove this.

Electronic transformers have a switching frequency and it is possible that they can "lock" up or synchronise with another frequency and this would prevent to correct operation of the transformer a potential cause of failure.

Cheaper dimmers can be very "electronically" noisy eg interference.

It is also possible that the transfomer could cause the dimmer to fail, though I think this is unlikely.

Electronic transformers don't really get too hot unless they are overloaded or are not working properly. You can have as many lights eg watts as your tranformer can handle. eg a 50w transformer will allow 1 x 50w light or 2 X 20w lights. I use a 105w transformer to power *5* 20w halogen shelf lights. You could also use the 105w transformer to power 3 x 35w lights. A 200w transformer can power 4 x 50w globes. It is usually important though, to connect multiple downlights powered by one transformer, to have to lights *evenly* placed along the wire eg two either side of the transformer. If you put all the lights along the wire, the light at the end of the wire can be noticeably dimmer than the others.

0____0___[Xformr]____0____0

The thought the some people had, that 12v was cheaper to run than 240v, does not apply of course, 50w is STILL 50w. (of course is is a little cheaper to run than a 60w light globe - but usually, more than 1 downlight is needed).