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T8 par

Discussion in 'Lighting' started by scottward, Nov 2, 2016.

  1. scottward

    scottward Guru Class Expert

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    Hi Guys,


    I don't have a PAR meter, but looking at the various typical PAR readings in the various tables on here, it seems reasonable to say that, a single T8 tube, measured at a light to substrate distance of 18", is approximately 30 uMol?


    This is, of course, assuming the water is clear, no dirty tubes, dirty covers over the tank etc etc.


    The reason I ask this is, the T8 tubes I am using are these: https://www.nelt.co.jp/english/produ...tfd/index.html (FL30SSBR - HG-36).


    These tubes supposedly put out "twice the brightness" of the non HG (High Growth) tubes.


    I'm sure there is some marketing BS here and there, rounding up etc etc.


    The values in the table are in LUX, which I know is useless from a plants perspective, they need PAR.


    Could I correctly assume though, that a higher LUX value will in turn mean a higher PAR value?


    So...my T8 tubes are possibly 60 uMol rather than 30uMol at 18" from light to substrate?


    I'm just going back over my system from top to tail and I may still be running more light than I need (2 rows of these T8's in total); I may be better running a single row of T8 right down the centre elevated a little higher to help spread the light.


    Thoughts on the above?


    (My goal is reduced CO2 consumption, less trimming etc)


    Scott.
     
  2. burr740

    burr740 Micros Spiller
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    Looks like a great bulb spectrum wise.


    Typically more lumens will equal more PAR, simply from it being more light, although Im not sure how it would scale.


    I do know from testing different CFL bulbs that PAR goes up roughly proportionate to lumens, or slightly less the higher you go. eg a 13 watt rated at 900 lumens vs an 18 watt rated at 1300 lumens (in the same fixture obviously)


    Just guessing Id say they probably dont have twice the PAR, 50-60% more perhaps, if the lumen ratings are accurate. But again that is a total guess.
     
  3. scottward

    scottward Guru Class Expert

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    If the 30uMol above is accurate enough, I guess I could potentially be beaming, at 50% more, 45uMol at the substrate....with a single tube. Supposedly this amount can grow most plants ok.


    I do recall Tom saying 2 rows of T8 per foot/30cm front to back, but maybe with the tubes I have, I could raise a single tube up a bit and do ok.


    I really want to get my CO2 consumption down, and just get everything nice and stable and clean with minimal work.


    I feel like I'm cranking through CO2 too fast, maybe I have more light than I think.
     
  4. burr740

    burr740 Micros Spiller
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    You may very well have. On a 20gal long Ive got two T8s in a homemade box with pretty good individual reflectors, bulbs about 4" apart. At 13" from the sub PAR is around 60
     
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