• F32T8 bulbs in F40T12 fluorescent fixtures

    From augroups@gmail.com@21:1/5 to All on Sun Dec 24 12:58:37 2017
    How long does a normal F40T12 will last?

    I am facing the same situation here:
    I have some F40T12 with Robertson electronic Ballaster "RSW234T12120".
    The RSW234T12120 claims to work on Both F40T12 and F36T8 lamps. Today I visited Lowes, and got some F40T8 lamp. I put it in where the F40T12 was installed, it works. But I don't know how long it will work on the lamp and ballast.

    The RSW234T12120 is a normal power factor electronic preheat (Rapid) start Ballast.

    I measured the temperature near the end of the tube:
    T12: 35~40C
    T8: 50~57C
    Room Temperature: 19~20C.
    MIke D.

    On Sunday, April 22, 2007 at 2:36:48 PM UTC-4, mc wrote:
    Thanks for the very informative reply! The bulbs have lasted a couple of years already.

    "TKM" <nomail@no.net> wrote in message news:OyLWh.67761$VU4.25601@bgtnsc05-news.ops.worldnet.att.net...

    "mc" <look@www.ai.uga.edu.for.address> wrote in message news:sgCUh.5078$Zm3.2476@bignews1.bellsouth.net...
    We have a kitchen illuminated by 48-inch fluorescent lights above a
    translucent suspended ceiling. We are slowly upgrading them to
    electronic ballasts and F32T8 bulbs.

    In the meantime, here's tonight's discovery:

    F32T8 bulbs work fine in F40T12 fixtures. In fact, they even work in
    fixtures that are finicky with F40T12 bulbs (presumably because the
    ballasts are getting old).

    Have others had the same experience? Am I shortening the bulb life, or
    anything, by running an F32T8 bulb on a ballast designed for an F40T12?
    I know that *theoretically* I may be putting more current through it...
    in practice, does it make a difference?


    If your existing fixture does indeed have an electgromagnetic ballast designed for the F40T12 lamp, then the following applies:

    The major difference between an F40T12 fluorescent tube and an F32T8 tube is the current rating. The F40 is rated for 0.430 amps; the F32 is rated for 0.265 amps. Once a fluorescent lamp has started, the ballast acts
    like a current source and drives the lamp according to the load current rating of the ballast.

    In this case, it's a little surprising that the F32T8 lamp starts, but that can happen -- especially when the lamp is new. However, the lamp is being overdriven by about 60%. Fluorescent lamps can be overdriven by 10% or so without major problems, but you are likely overheating the cathodes and driving the lamp quickly toward end-of-life due to cathode deterioration.

    Putting an F40T12 lamp on an F32T8 ballast is less destructive since the F40 will be under driven. It will be low in light output, but it will start and likely last for its rated life.

    TKM


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