I live in a new-build small estate of 10 houses. We are all having incidences of short lives of G10 LED downlighter bulbs. They are driven by dimmer circuits made by Deta. The Deta Connect system has been installed to control these dimmer light controls and some of the power outlets. The G10 bulbs are installed in metal pots in the ceiling and the insulation is clear of the pots. The failures appear to be of the small printed circuit inside the bulb. (I broke one bulb open and connected a 50 V DC power supply to prove that the LEDs still worked.) I measured the temperature inside one of the pots after a few hours "on" - the maximum was 42 degrees. I suppose the internal temperature of the bulb will be a few degrees higher. The DETA specification requires a minimum load of 20 Watts. This is marginal as we have some rooms with 4 x 5W bulbs - these sometimes flash. I have measured the mains voltage over one day seeing it between 237 and 243 Volts - so within mains spec. Various makes of dimmable bulbs have been fitted, all made in China, rated for 230 to 240V. I used an oscilloscope to view the voltage applied to the bulbs and did not see any spikes in the waveforms. I wonder if the small circuit produces more heat when operated dim? I suppose most of the heat comes from the LEDs themselves? I have a suspicion that some component in the internal bulb circuit cannot survive for long at the temperature that it is suffering. This suspicion is borne out by the observation that other LED bulbs mounted in unventilated ceiling fittings fail quickly while LED bulbs used outside seem to last well. Surely there must be general concern that short life is spoiling take up of "green" LED lighting? I would welcome comments and suggestions.
There is a general problem that folk expect an LED light to cost about the same as hot wire in low pressure gas, and there are a lot more steps to making the former, so in a bid to squeeze the price right down, the process corners tend to be cut.
Also matching up Dimmers and LED fittings is very much a dark art, in that there is no guarantee that the one maker's idea of a dimmable design is the same as another, and there is no standard set of tests for either dimmable lamps or LED lamp dimmers. There is near universal agreement with waveform slicing dimmers that it is better to cut the power off part way through the cycle and turn it on at the zero crossing, but traditional dimmers for filament lamps using triacs do the reverse, and a few LED fittings are set up to expect that, and some dimmers can be programmed to do either - if yours can, check the right mode is selected.
As you note cooling is a problem - actually I'd say probably the problem for electronics, and light fittings that look like traditional fittings re-purposed are not always the best at heat dispersal.
It should get better as the makers of fittings and lamps wise up, but right now the technology is immature, and everyone is also trying to recoup their outlay on re-tooling, new products etc. You could argue that we should be asking how reliable was the filament lamp in 1880 ? and comparing to that.
There is a general problem that folk expect an LED light to cost about the same as hot wire in low pressure gas, and there are a lot more steps to making the former, so in a bid to squeeze the price right down, the process corners tend to be cut.
Also matching up Dimmers and LED fittings is very much a dark art, in that there is no guarantee that the one maker's idea of a dimmable design is the same as another, and there is no standard set of tests for either dimmable lamps or LED lamp dimmers. There is near universal agreement with waveform slicing dimmers that it is better to cut the power off part way through the cycle and turn it on at the zero crossing, but traditional dimmers for filament lamps using triacs do the reverse, and a few LED fittings are set up to expect that, and some dimmers can be programmed to do either - if yours can, check the right mode is selected.
As you note cooling is a problem - actually I'd say probably the problem for electronics, and light fittings that look like traditional fittings re-purposed are not always the best at heat dispersal.
It should get better as the makers of fittings and lamps wise up, but right now the technology is immature, and everyone is also trying to recoup their outlay on re-tooling, new products etc. You could argue that we should be asking how reliable was the filament lamp in 1880 ? and comparing to that.
