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  1. #1
    Join Date
    May 2010
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    47

    Default flickering fluorescents

    i have (4) 4 foot fluorescent fixtures, with 2 40 watt bulbs each (t12 bulbs ? - they're old style, about 1" dia.)
    i replaced the bulbs in 2 fixtures with the new t8 32 watt bulbs, and they work great.
    but when i changed the bulbs on the other 2 fixtures, they didn't light completely, and flickered constantly. i ended uo with one old t12 light & 1 new t8 light in each fixture. it looks strange, but they are working.
    i mentioned this to the maintenance man at our office, and he said the old ballasts don't work with the new t8 bulbs. he said the old ballasts have two wires connected to each bulb holder, and the new ballasts only have one wire connected to each end, and all i need to do is cut one wire on each end? i don't really believe that would work.
    short of replacing the fixtures, what are my options ?
    is there any problem with (1) t8 bulb and (1) t12 bulb in each fixture ? should it even work that way, or is it a fluke ?

    thanks in advance

  2. #2
    Join Date
    Jan 2011
    Location
    Columbiana, Alabama
    Posts
    623

    Default Re: flickering fluorescents

    Ice, did you change out the ballast, receptacles and lamps in the fixtures? All need to be changed including how they are wired.

    Might be cheaper to just replace the fixture.

    Also, if the lamps are over 1/2" from the grounded shields, they may flicker, or not come on at all. Flourescent lights use a lot of advanced technologhy.

    Good Luck from Columbiana, Alabama
    Maurice Turgeon, http://thesemi-retiredelectrician.com

  3. #3
    Join Date
    May 2010
    Posts
    47

    Question Re: flickering fluorescents

    semi-retired,
    no, i didn't change anything except the bulbs. there really isn't anything wrong with the fixtures, just that the new bulbs seem to put out a lot more light, and i didn't know there would be a compatability issue.
    is there any problem with leaving as is (two different bulbs in one fixture), or sould i put the t12's back in?
    what about the 2 fixtures that the new bulbs are working in, any problems there?
    if i can't use the new bulbs in any of these fixtures, is there any other way to get more light without changing or adding fixtures? the old bulbs were 40 watt.

    thanks

  4. #4
    Join Date
    Jul 2010
    Location
    SoCal
    Posts
    5,081

    Default Re: flickering fluorescents

    Last year I remodeled a kitchen that had 3 of those fixtures. 2 out of the 3 were flickering. I replaced 2 old ballasts with the same kind - magnetic ballsats - and installed new t12 40W bulbs, and they work fine now. (magnetic ballasts run about $20 each, still easy to find in stores and other places, but they will disappear soon).

    The key is to replace with the same kind. If you mix a new t8-32W bulb and old ballast, or new electronic ballast with t12-40W - they may not work, I'm not sure.

  5. #5
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: flickering fluorescents

    Quote Originally Posted by iceman11 View Post
    i have (4) 4 foot fluorescent fixtures, with 2 40 watt bulbs each (t12 bulbs ? - they're old style, about 1" dia.)
    i replaced the bulbs in 2 fixtures with the new t8 32 watt bulbs, and they work great.
    but when i changed the bulbs on the other 2 fixtures, they didn't light completely, and flickered constantly. i ended uo with one old t12 light & 1 new t8 light in each fixture. it looks strange, but they are working.
    i mentioned this to the maintenance man at our office, and he said the old ballasts don't work with the new t8 bulbs. he said the old ballasts have two wires connected to each bulb holder, and the new ballasts only have one wire connected to each end, and all i need to do is cut one wire on each end? i don't really believe that would work.
    short of replacing the fixtures, what are my options ?
    is there any problem with (1) t8 bulb and (1) t12 bulb in each fixture ? should it even work that way, or is it a fluke ?

    thanks in advance
    T12 fixtures generally use a magnetic ballast whereas T8 fixtures use an electronic ballast.

    The design and constuction of the T8 provides 3 to 10 % more luminens per watt and combined with the electronic ballast makes them more efficient than T12 with magnetic ballast.

    Using T8 in a T12 fixture using magnetic ballast may work but it's hit and miss depending on the condition of the ballast and type --- pre-heat , rapid start , instant start. However the life of the T8 lamp and the old magnetic ballast will be shortened.

    The information you provided regarding what the maintenace guy told you is partially correct but incomplete.

    The T8 electronic ballast only supply one wire connected to each tube base socket unlike the T12 ballast which supplies two wires per base socket.

    What the maintenace guy was describing is a method of converting your T12 fixture over to T8 -- which is easier than replacing the entire fixture.

    Remove the old magnetic T12 ballast --- install a T8 electronic ballast --- at each existing base socket join the two wires together and conect to the single wire from the new ballast.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  6. #6
    Join Date
    May 2010
    Posts
    47

    Default Re: flickering fluorescents

    thanks canuk

  7. #7
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: flickering fluorescents

    I forgot to add the T8 electronic ballast requires a *grounded * circuit to function properly and to drain harmonic distortion frequencies.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  8. #8
    Join Date
    May 2010
    Posts
    47

    Question Re: flickering fluorescents

    semi-retired,

    "Also, if the lamps are over 1/2" from the grounded shields, they may flicker, or not come on at all."

    this might be the case, i'll need to look closer.
    if i change to a T8 32watt ballst, and the lights still flicker or don't light, would the T8 ballast power the old T12 30 watt bulbs, or would i need to revert back to the original setup?

  9. #9
    Join Date
    Aug 2007
    Location
    The Great White North
    Posts
    4,045

    Default Re: flickering fluorescents

    iceman --- You are trying to use T8 lamps in a fixture rated for T12 which are not really compatiable.

    T8 lamps require T8 rated electronic ballasts.

    Your ballasts are likely magnetic and rated for T12 & T10 lamps .

    T12 are 1-1/2 inch diameter tubes

    T8 are 1 inch diameter tubes -- which sit further away from the grounded shield

    Two options:

    1. Get T12 or T10 lamps.

    2. Get T8 ballasts to match the lamps you bought.
    "" an ounce of perception -- a pound of obscure "
    - Rush

  10. #10
    Join Date
    May 2010
    Posts
    47

    Default Re: flickering fluorescents

    yes, i realize now that there are compatibilty issues, and i was not aware that the distance from the shields could be a problem. i just don't want to switch ballasts, and then need to switch back to the original setup if they don't work properly due to that distance. cost is not an issue, as i can get the T8 32 watt ballasts for less than $10.00 each.

    i really like the better light output, and can really use it in my windowless 7'-0" x 17'-0" workshop. i also would rather not replace the entire fixture, because the previous owners drywalled around them alomost flush with the bottom of the fixture.

    if you look at my original post again, you'll see that i replaced the bulbs in two other fixtures (in a different room), and they seem to be working fine. the distance factor doesn't seem to be a problem there. could they be working better because they have electronic T12 ballasts? (still incompatible?), or could they be T8 ballasts and still worked with the T12 bulbs? i don't know what ballsts are in there, but i will check it out and probably replace them.

    FYI: i don't know how recently the T8 system came into play, but we have only been in this house for about 4 years.

    thanks for all the info. i learned something new (that's always good)

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