light distance

Discussion in 'Grow Room Design/Setup' started by qz420, Apr 20, 2006.

  1. my grow room is about 2x3 so its kinda small for the 400w hps that im using. It generates a good amount of heat so I thought it would be a good idea to keep it a far distance from the plants, BUT now my plants seem to be streached out so im thinking that my light needs to be closer. Im not sure if I should hang the light closer because it might burn my plants, what are your suggestions?? right now its about 30 inches away
     
  2. put your hand at the top of your plants. move your lights until your hand becomes uncomfortable after 60 seconds. Back it up one or two inches and that's your height. You can get a vented hood, or even better, a cool tube

    http://cgi.ebay.com/Sun-Tube-cool-t...itemZ7760692941QQcategoryZ42225QQcmdZViewItem

    they're only a hundred bucks. You hook up some ducting and a vortex to it and it takes all the bulb heat away.
     
  3. yeah, you got to vent that heat out of that room,,,when your plants get taller,,,, and you cant move the light no higher you will have a real problem,,,you may wont to try lst to keep your plants low,,,,or a horizontal tressling,,, i wouldnt suggest u letting them plants grow too tall or the heat will fry them,,,how tall is your room,,, thats the main unanswered question,,,:p
     
  4. If the plants are stretching they want more light. Keeping the light away from them because of heat issues will only make the problem worse, so you have to find a way to exhaust that heat.
     
  5. if tapping into your a/c duct,,is possible,that would help the heat,,,, although you cant leave that area unvented,,,,,,, you must vent that heat out;)
     
  6. light chart attached
     

    Attached Files:

  7. That is a great chart, it really shows just how close you can get, if you can deal with the heat. Remember, the distance is measured from the bulb to the nearest vegetation.
    2 by 3 is not a small area for a 400, it is large--I consider 2 by 2 to be better.
    The best reflectors are very close to the bulb. Since at least 50% of the output of the bulb reaches the plants after bouncing off the reflector, you want that light to travel a minimal distance to the reflector, so that it remains as intense as possible.
    The inverse square law: the E=MC2 of growing pot indoors!
     

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