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3
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Posted
24/5/2006
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
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4
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Posted
4/7/2006
Electronic transformers can present significant problems for dimmers. Different brands behave differently and even different models of the same brand can be a problem.
The following link to Clipsal's website provides information for using their dimmers with various transformers. Presumably the other dimmer manufacturers should be able to provide similar data.
http://www.clipsal.com/trade/__data/page/81/W619.pdf
The inputs to the electronic transformers are usually capacitive which causes a leading power factor to be seen by the dimmer. This causes significant problems for the dimmer. The dimmers usually fail as a short circuit hence the reason you could switch on/off but not dim.
The usual options are to oversize the dimmer or you can buy inductors from Clipsal to correct the power factor back to unity or split the lights across 2 dimmers. It is probably most economical to oversize the dimmer. Using 2 dimmers may prove to be incovenient. I have used the inductors in an installation where it was not feasible to increase the capacity of the dimmers and they worked perfectly.
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37
Posts |
Posted
5/7/2006
Why is it happening only in living room-is it because there are 5 lights there & not in other rooms-if so Craig is right, quite possibly- on the other hand is wiring absolutely correct in living room ? On another thread, why do people use 12v halogen lights? I am currently repairing electronic tx,s - I see no need for halogen lights- why not go for white leds?.
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4
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Posted
10/7/2006
The failing dimmer is almost certainly related to the number of lights connected to it. The failing transformer is a little harder to explain. The wiring is fairly hard to get wrong, however it would be useful to know how the multiple transformers are connected. Presumably they just in a string off the dimmer, if so then where is the failing transfomer located in the string?
The brand/model no. of the dimmer and the transformers would also be useful for checking their characteristics.
Why use 12V halogens? Essentially because people think they look nice. Interior designers and home owners love them! They are quite inefficient. The light output per watt is somewhat better than a normal incandescent but nowhere near as high as a fluoescent. This is made worse by using cheap copper/iron transformers instead of electronic transformers. There is also a popular misconception that low voltage equates to low power.
The efficiency of the good high power LEDs is similar to a halogen, probably a little better. The biggest problem with LEDs is dissipating heat. Halogens have the dis/advantage (depending of your perspective) that a lot of the heat they generate is emitted as infra-red energy. LEDs emit little or no infra-red, therefore the heat must be dissipated using a heatsink. To get similar light output to a halogen requires multiple LEDs and a large, bulky heatsink. Fan cooling could be used but this further impacts efficiency and fans are prone to failing or filling up with dust. Failing to properly control the LED junction temperature drastically reduces the operating life.
There are some good LED based fittings on the market but they are quite expensive and the light output isn't quite comparable with a halogen. They are generally only suitable for decorative lighting or small area task lighting.
Where LEDs are really winning is in coloured lighting. Traditionally white light is filtered to leave only the desired colour - very inefficient. Coloured LEDs produce their full output at a specific colour, therefore the efficiency at that colour is quite high.
Give white LEDs another couple of years and it could well be a very different story.
There are some small fluorescent fittings that are a direct halogen replacement. These are probably the best alternative at the moment. The downside with them is that they can't be dimmed. Have a look at www.neco.com.au and www.environmentshop.com.au
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3
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Posted
9/8/2006
Thanks for the replies, just thought I'd post to say I found the problem, which was my dimmer. My electronic transformers say they work with leading edge AND trailing edge. I had leading and changed to trailing edge, all ok now. Seems leading is more for old transformers and trailing for electronic :)
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Downlights dying?