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Thread: 12 volt LEDs??

  1. #1
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    12 volt LEDs??

    Hi
    Maybe someone knows something I don't here

    I have a client with 6 x 12 volt 5 watt LED's on a wire track (you know the where the wires are suspended across a 5 meter gap and there are MR16 lamp holders attached to the wire). Originally, a few years ago I went to look at this shop for the client and they had halogens and they were supplied by a 400Va transformer. Since then they converted to LED's and have installed 50VA transformers in some places (6 x 5 watt LED 30 watt) and there are some 250va and 400va which should be fine. The 50 VA transformers are Insanely hot and the LED's are failing one by one (different brands have been tried judging by all the different makes and type that are now on there). The 250VA and 400VA are also fairly hot but I put that down to ambiant temp in teh roof space (40 degrees)

    Incoming voltage to transformer is text book 230 Volt. Voltage out is good around 11.5volts

    Why are the 50 VA transformers so insanely hot (untouchable hot) and why are these LED's crapping out. Any thoughts.

    Thanks

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    Diamond Member Justloadit's Avatar
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    The only thing I can think off is that the transformers are marked with peak power, and not continuous power. Maybe get 100VA transformer and see the result.

    The LEDs failing is due to the LED junctions heating far beyond the allowable junction temperature of 70Degrees centigrade.
    When the LEDs are mounted in down light applications, the ceiling frame acts as part of the heatsink to reduce the over all temperature. Hanging LEDs in this case do not have this extra surface area to rely on to remove heat, and could be the cause of premature failure. Maybe as a test, place the LEDs in these frames and check it out.
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    Diamond Member AndyD's Avatar
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    If the transformers are too hot they're almost certainly overloaded. Are the transformers electronic or iron core type?
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