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.
So it would seem to be a good idea when buying light fittings to choose ones which have the bulbs pointing up so that the heat does not flow past the electronics, and make sure there is plenty of ventilation. Choose function over style perhaps?
So it would seem to be a good idea when buying light fittings to choose ones which have the bulbs pointing up so that the heat does not flow past the electronics, and make sure there is plenty of ventilation. Choose function over style perhaps?
