Premature Light Bulb Failure

Discussion in 'Electricians' Talk' started by ;-D_Man, Sep 28, 2004.

  1. ;-D_Man

    ;-D_Man New Member

    Just wandered if anyone can shed any light (no pun intended) on the subject of premature light bulb failure.

    I did do a bit of digging a while ago and found a document listing many causes i.e. surges, vibration, overheating, etc. but wondered if anyone knows of any other reason's why some bulbs appear to last forever and others don't even make close to the manufacturer m.t.b.f. and if there is anything in particular you can check :-D

    The two examples I have both relate to light fittings with several bulbs. In one case 240V 5x40W GLS in a star shape, wooden fitting, on ceiling, each has own mini shade above bulb.

    In another house there is mini 240V G9 halogen 40W bulbs, ceiling 6xbulbs and 3 sets wall lights 2xbulbs, all in one room, all affected.

    I also have a strange example of a single bulb bathroom light rose where tungsten bulbs work fine but low energy bulbs last a fraction of the expected life, (after three bulbs I gave up :( and switched back to normal bulbs to save money ;-)). Could it be the frequency of use ? An extractor fan is also wired in this circuit.
  2. motor head

    motor head New Member

    Your quit right about energy saving bulbs some are good and others are well you no,
    I have a glob energy saving bulb in the bathroom it is ok so far as it is seld.

    Your exstractor fan if it coming on as the light is it is putting surge on the starter in the light and it struggles to energize the light.
    A time delay on the fan mite help as it will come on if set 15 seconds after the bulb as the older the bulb the longer the starter takes limiting the strain on the light.
  3. Damocles

    Damocles New Member

    Fan motors use vey little power. I would imagine this is still true when starting up.

    Fluorescents in general do not like being switched on and off a lot. might be a problem in a bathroom.

    was it just the bathroom, did you try them anywhere else?
  4. Caveman

    Caveman New Member

    Fans are essentially an inductive load and as such will often put a spike down the mains during switch-off unless zero-voltage switching is used. Low energy fluorescents are driven by a semiconductor-based switching circuit that is particularly susceptible to surges, these damage the main switching element in these lamps. That would be my theory as to the short life of these lamps as described. I doubt it sits well with the regulations, but having measured spikes in excess of 4kV on domestic mains, I have a policy of fitting varistors (voltage dependent resistors) to most of the electronic equipment in my home to suppress these spikes. I used to have a problem with pops and clicks over my home cinema system - not any more!!

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