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Thread: Why do bulbs blow all the time?

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    Gold Member Houses4Rent's Avatar
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    Why do bulbs blow all the time?

    I am managing a flat where the light bulbs in the one bathroom blow all the time. The tenants did not tell us and basically did not use the bathroom for three months as there is no window (no light). Now they moved out and we found out about it. I doubt the old tenant had bought a bulk pack of dodgy bulbs which might explain the problem, so there must be another reason.

    What can be a possible reason why bulbs in one room/one fitting blow all the time?
    Houses4Rent
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    Diamond Member Justloadit's Avatar
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    Temperature

    What kind of bulbs, incandescent, CFL or LEDs
    Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
    Solar and LED lighting solutions - www.microsolve.co.za

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    Gold Member Houses4Rent's Avatar
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    Thanks, they are incandescent as far as I know (plain good all white standard bathroom ball type fitting), but could double check if need be.

    Bulbs should withstand its own operating temperatures I would hope.
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    Diamond Member adrianh's Avatar
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    Humidity. Our one bathroom light is the same. I think it happens in the paticular bathroom because the light fitting is very close to the shower. The moist hot air must be driven across the bulb given the airfow between the window and the door. A solution might be to ensure that the globe is housed in an airtight fitting.

    Anyhow, call this lot my own theory on the problem.
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    Gold Member Houses4Rent's Avatar
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    Hm, you might have a point. However, there is no window, just a small extractor fan, not much air movement I would think. The bathroom next door also has no window and an fan, but just a bathtub which they fitted with a handshower. Difficult to say whether humidity levels are really different.

    Either way you seem to agree with me that it its not an electrical problem?
    Houses4Rent
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    Diamond Member adrianh's Avatar
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    I doubt that there is an electrical problem. There is a tremendous amount of air movement in any bathroom even if it is totally enclosed. Remember that hot air rises due to its lower density. I think that one would find that the hot moist air first passes over the bulb before it cools and sinks down. I think that one could prove my theory by injecting a small amounts of smoke into different points in the expected path of the airflow and following the path that the smoke takes.
    How easily someone is offended is directly proportional to how stupid they are.
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    Diamond Member Justloadit's Avatar
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    I say that it is temperature, especially with incandescence. The fact that the globe is designed to run at about 180 degrees, it still relies on the ambient to keep the globe cool. Remember that the filament is being driven hard to be able to light up with the current flow, and it too has a maximum operating temperature before metal fatigue plays a roll in its destruction.

    There is also the number of switch on times to contend with. Being a mechanical device to create light, the cold resistance causing fatigue, and the mechanical 50Hz shock of every time being switched on probably all contributes to the demise.

    How many times have you heard the globe element pop at switch on when it fails.
    Victor - Knowledge is a blessing or a curse, your current circumstances make you decide!
    Solar and LED lighting solutions - www.microsolve.co.za

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    Gold Member Houses4Rent's Avatar
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    All makes sense, thanks. I also have seen many bulbs pop when the switching on spike hits it.
    However, I just cannot get my head around the fact that it only happens in that particular bathroom so often. They said a few days and its gone again. No fatigue should set in so quickly and so regularly.
    Houses4Rent
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    Bronze Member ACEsterhuizen's Avatar
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    Talking about temperatures can someone please advise on how an installation would be protected against "excessive temperatures" by means of disconnecting or limiting as described below? I have never come across a "temperature switch" which protects the whole installation? or monitors it?

    Page 3(a):

    "The aim of this part of SANS 10142 is to ensure that people, animals and
    property are protected from hazards that can arise from the operation of an
    electrical installation under both normal and fault conditions. An electrical
    installation has to provide protection against
    – shock current,
    – overcurrent,
    – fault current,
    – overvoltage,
    – undervoltage,
    – excessive temperatures, and
    – electric arcs.
    If any of the above arises, the protection should automatically disconnect the
    supply or limit currents and voltages to safe values....."

    5.1.2 Temperature

    5.1.2.1 Unless otherwise permitted by an applicable standard (see 4.3
    and table 4.2), electrical equipment shall be so designed, positioned and
    protected that accessible parts under normal operating conditions do not
    reach a temperature (safe touch temperature) that exceeds
    a) 70 oC in the case of metallic parts, and
    b) 90 oC in the case of non-metallic parts.

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    Diamond Member adrianh's Avatar
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    Quote Originally Posted by Justloadit View Post
    I say that it is temperature, especially with incandescence. The fact that the globe is designed to run at about 180 degrees, it still relies on the ambient to keep the globe cool. Remember that the filament is being driven hard to be able to light up with the current flow, and it too has a maximum operating temperature before metal fatigue plays a roll in its destruction.

    There is also the number of switch on times to contend with. Being a mechanical device to create light, the cold resistance causing fatigue, and the mechanical 50Hz shock of every time being switched on probably all contributes to the demise.

    How many times have you heard the globe element pop at switch on when it fails.
    If it is temperature then why don't outside globes blow all the time. Surely they are exposed to far greater temperature extremes during their lives. Outside lights are sometimes turned on and off during the searing heat of day or the freezing cold of night yet they don't seem to blow that often.
    How easily someone is offended is directly proportional to how stupid they are.
    ~GS Elevator

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