400w hps at 24" or 250w at 12" or less

Discussion in 'Growing Marijuana Indoors' started by Jamesdouglas, Sep 23, 2010.

  1. i have a dimmable ballast i am running for the last 2 weeks of my current grow, transitioned from cfls

    i have heat problems and adjusting/purchasing extraction equipment is not currently an option

    what are your opinions?

    i can run the 250 pretty close at about 12" or so
    or run the 400 but it has to be at least 24" away

    considering the higher lumen output i would think the 400 a little further away would be good
  2. #2 fonzi03, Sep 23, 2010
    Last edited by a moderator: Sep 23, 2010
    I keep my 400watt at 4" and it made a huge difference from where i kept it at 10" which caused tons of stretch....i wouldnt go passed 10 with the 400 or 8" with the 250....even 12"with the 250 is too far....you have to remember that each inch you go further the lumens divide by 2....so the difference between 10 and 12 inches is really 4times the lumens

    guess its not exactly 2 but heres a good chart for you

    Attached Files:

  3. 12's as far as I go myself / lil less sometimes.:cool:

  4. get an AC unit and drop you 400 to about 14".
  5. its all about fans man...get enough air moving on the canopy and you wont have heat building up
  6. Try to put your 400w as close as possible making sure of the temperature between the head of your plant and the bulb doesnt go over 28 Celcius or 82 F. I usually place a 600w at 10 to 12 inchs and 1000w at 14 inch!
  7. to keep it 82 it needs to be close to 24" away, at least until it gets cooler outside once winter hits i will be ok, 8-9 degrees above ambient will be ok in a month or so

    ac is not an option, neither is more extraction....i know i need to pull more air
    i am using a standard batwing reflector and a 6" inline booster fan

    i just bought the light setup so i need a while before i can buy the fan i want

    thanx for all the help
  8. wow according to this chart i am way better off with the 250 as close as i can get it
    will save me on heat and electric, i need to establish my grow cycles and do a straight up stare and compare with the 2 options and see for myself, hard part is it will be 6 months before we know, great part is i will enjoy every minute of it!!!

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