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Thread: T8 lamp on T12 ballast?

  1. #1
    Flashaholic* yuandrew's Avatar
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    Default T8 lamp on T12 ballast?

    So while walking home from my friend's, I came across a pair of flourescent tubes in someone's trash. I noticed they were T8 tubes so I took them out and examined them. They did not appear to be burned out; in fact both looked brand new and still had the pricetag on them. Both are Sylvania Octron Eco and say FO32/841/ECO under that.

    A few months ago, my Church changed out all their lights to electronic ballast and T8 lamps (I forgot what brand of lamps they used but they were some off brand) I tried the T8 tubes they had in an old shoplite in a storage room and they lit very dimly and didn't come to full brightness.

    I decided to try both Sylvania T8 tubes in my kitchen thinking they also won't work on a magnetic ballast but to my surprise, they worked. However, they lit the brightest in the one fixture in the middle; the other two fixtures off to the side didn't seem to light them to full brightness but they worked. As of now, I put the T12 tubes into the two fixtures on the right and left and have the T8 tube in the middle fixture where it seems to work the best. I guess a kitchen should have more than enough light. Now that I've done it, that brighter T8 tube makes my older T12 tube look dimmer and pinkish.

    Still, what will running T8 tubes on a T12 ballast do in the long run?

    Picture


    Here's the ballast that's in the fixture

  2. #2
    Flashaholic* yuandrew's Avatar
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    Default Re: T8 lamp on T12 ballast?

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    Last edited by yuandrew; 12-24-2006 at 02:00 AM.

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    Flashaholic* Morelite's Avatar
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    Default Re: T8 lamp on T12 ballast?

    T12 tubes on a T8 ballast will shorten the lifespan of the ballast.

    T8 tubes on a T12 ballast will shorten the lifespan of the tubes.

  4. #4
    Flashaholic* snakebite's Avatar
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    Default Re: T8 lamp on T12 ballast?

    i find that good(read old,heavy)ballasts for t12 tubes run t8 just fine.
    it seems the cheap 2 tube magnetic ballasts have an open circut voltage just sufficiant to start the tubes with the heaters warmed up.t8 tubes need a bit more voltage to start reliably.if it works and the ballast does not overheat its just fine to use t8's.i have a 2 tube 2' fixture in the kitchen that uses a magnetic ballat.put 2 t8/950 tubes in it and its brighter and starts faster.the 950's are also about the closest to daylight you will find in any tube.

    i am always looking for old radios and tv sets.tube stuff.ham gear.i repair all the above.
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  5. #5
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    Default Re: T8 lamp on T12 ballast?

    Quote Originally Posted by Morelite View Post
    T12 tubes on a T8 ballast will shorten the lifespan of the ballast.

    T8 tubes on a T12 ballast will shorten the lifespan of the tubes.
    With T8 tubes on a T12 ballast, how much shortened of a lifespan are we talking? Are we talking 25% shorter or 75% shorter? And if they are the 34w "energy miser" T12 tubes, will that make a difference.


    Sorry for necro'ing the thread, but it's still the most relevant page that comes up on a google search.

  6. #6

    Default Re: T8 lamp on T12 ballast?

    Quote Originally Posted by snakebite View Post
    i find that good(read old,heavy)ballasts for t12 tubes run t8 just fine.
    it seems the cheap 2 tube magnetic ballasts have an open circut voltage just sufficiant to start the tubes with the heaters warmed up.t8 tubes need a bit more voltage to start reliably.if it works and the ballast does not overheat its just fine to use t8's.i have a 2 tube 2' fixture in the kitchen that uses a magnetic ballat.put 2 t8/950 tubes in it and its brighter and starts faster.the 950's are also about the closest to daylight you will find in any tube.
    OLD post above, but sice it was brought back...I'd like to state that I HIGHLY disagree with the above. I've seen lamps fire than 'shouldnt' and vice versa. I would NEVER suggest to do that. The fact is, that the ballast and/or lamps WILL prematurely fail.
    Quote Originally Posted by Lack Thereof View Post
    With T8 tubes on a T12 ballast, how much shortened of a lifespan are we talking? Are we talking 25% shorter or 75% shorter? And if they are the 34w "energy miser" T12 tubes, will that make a difference.


    Sorry for necro'ing the thread, but it's still the most relevant page that comes up on a google search.
    Your guess is as good as anyone elses. I've seen anywhere from not firing to lasting a couple of years. 34Watt 'savers' make no difference. Also don't forget, there is no benefit/advantage to mixing the setups. There is only DISadvantages.

  7. #7

    Default Re: T8 lamp on T12 ballast?

    And I know that the general recommendation is to upgrade ballasts to something supporting T8.


    However: my question is does anyone make an electronic ballast that either autodetects T12 vs. T8 bulbs, or at least has a switch. So rather than throwing away all the T12 bulbs (and their attendant mercury), we can switch to T8's as the T12's burn out.

  8. #8

    Default Re: T8 lamp on T12 ballast?

    Quote Originally Posted by brycenesbitt View Post
    However: my question is does anyone make an electronic ballast that either autodetects T12 vs. T8 bulbs... So rather than throwing away all the T12 bulbs... , we can switch to T8's as the T12's burn out.
    Make someones day. Just switch over to T-8 and give away the T-12's. Or leave one fixture on T-12 until you run out of bulbs. Keep it simple.

  9. #9

    Default Re: T8 lamp on T12 ballast?

    Quote Originally Posted by Ken_McE View Post
    Make someones day. Just switch over to T-8 and give away the T-12's. Or leave one fixture on T-12 until you run out of bulbs. Keep it simple.
    Used T12's? Wow, almost as good as getting pre-owned underwear for Christmas.

  10. #10
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    Buttrock Re: T8 lamp on T12 ballast?

    we used to over-clock our tubes in the green house
    i forget the magic formula but it was something like firing a 36" on a 48" balast

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