Anonymous asked in Home & GardenMaintenance & Repairs · 9 years ago

Why shouldn't you install a light bulb upside down?

I was about to replace some incandescent globe-shaped bulbs into a ceiling fixture and I noticed a graphic on the back of the package of the bulb right side up (base pointed down) and sideways, and a separate graphic of the bulb with the base pointing up with a line through it. Are they saying not to install it this way? What possible difference could it make? The fixture has the bulbs going straight in to its base, meaning they would be oriented globe down, base up.

8 Answers

  • 9 years ago
    Best Answer

    Heat rises, and as such accumulates on the base of a bulb if installed base side up. This can cause too much heat to travel up the base and into the fixture where it can become too hot and create a fire hazard.

    If the fixture was designed to be used a certain way, it is not a good idea to modify it as there may be insufficient insulation or other factors that may create a hazard.

    It will also cause the bulb to burn out sooner than a base down installation, as the seal in the base fails quicker as a result of the intense heat.

  • 9 years ago

    If it is a true incandescent bulb, then it shouldn't matter it's orientation. But if it is one of those new CFL bulbs that is designed to look like an incandescent bulb, then that's another matter. The electronics is mounted in the base of the bulb, so if you install it with the base up, then it will get too hot and possibly cause the electronics to overheat and burn out. In that case, if you are using CFL's then you would have to get one that is rated for like a "can" (enclosed) fixture that will take the heat.

  • 4 years ago

    The electronics for an LED is in the base. They are designed to have the heat,which rises, travel upward, away from the base. Upside down, the heat cannot disipate properly and the electronics will fail prematurely. There is an engineering discussion about this on line. The manufacturer's don't push this information as much as they should because they want to sell bulbs

  • Joe
    Lv 7
    9 years ago

    I'll agree with Mermiliz, and add that you could probably install the bulb base up - just expect a shorter bulb life.

    The bulb life estimates on the package were made by testing the bulbs in "base down" and "sideways" orientation.

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  • 9 years ago

    I believe its just because it would be too hard to change the bulb with the globe facing up.

  • 9 years ago

    That is the way some are made. Most will work in any application, but some are specific like yours. I would follow their guidelines or return them for a name brand that will work base up or down.

  • 3 years ago

    SYLVANIA just told me that it can cause the bulb to "separate" i.e. the glass to separate from the base, and perhaps hit you with broken glass. But no, it is not a fire hazard, unless the heated glass were to land on a carpet or something that it could start a fire with.

  • 9 years ago

    just guessing but it might have to do with heat dissipation...a downward facing bulb wont dissipate heat as well as an upward facing bulb...perhaps a slightly more expensive bulb is rated for any orientation?..........dan

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