when do I replace halide lamps?

Discussion in 'Lighting' started by jarthel, 27 Jan 2010.

  1. jarthel

    jarthel Member

    Messages:
    212
    I saw a similar thread for T5 but I'm not sure if this is applicable as well to halides.

    thank you very much :)
     
  2. dw1305

    dw1305 Expert

    Messages:
    8,261
    Location:
    nr Bath
    Hi all,
    Depends whether you "need" all the photosynthetically active radiation (PAR) the lamp is producing. I would run the lamp until it fails, or plant growth begins to look "drawn" with long internodes etc.

    Magnetically ballasted "high intensity discharge lights" (HIDs) differ from electronically ballasted T5s in that the discharge lamps display fairly rapid "Lamp Lumen Depreciation". What this means is that there is a rapid fall of from peak light production to about 50%, followed by a much slower decline until the lamp fails. The lamp lumen depreciation values for fluorescents are much smaller, with a linear decline until the tube fails when it is still producing greater than 90% of its initial light production.

    What you have to factor in is that discharge lights are typically still more efficient at converting electricity into light than fluorescents, so a discharge light even during its long slow decline to failure may still be an efficient producer of PAR.

    If you have a very high value light demanding crop (step forward Britons hidden army of "grow your own recreational drugs in a wardrobe" growers) it might be worth changing your lamp every 6 months, however for Aquarists (unless you are growing corals for example) discharge lamps should last for at least a year, and potentially (as long as they don't re-strike to often) can potentially last for several years.

    If you can get an electronically ballasted fitting things improve a bit (although the pulse started electronic ballasts are much more prone to failure) but "
    ."

    All the technical bits are here:
    http://www.lrc.rpi.edu/programs/nlpip/lightingAnswers/mwmhl/abstract.asp

    cheers Darrel
     
  3. jarthel

    jarthel Member

    Messages:
    212
    very detailed. thank you very much :)
     
  4. dw1305

    dw1305 Expert

    Messages:
    8,261
    Location:
    nr Bath
    Hi all,
    It is really tricky with all lamps, because unless you can measure the PAR, the perception of colour, brightness etc are all subjective and not really relevant to the plant. A PAR meter is the best option, if you haven't got one (I haven't) then quantifying plant growth is the best you can do.
    cheers Darrel
     

Share This Page

Facebook Page
Twitter Page
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice