How far away should my lights be?

Discussion in 'First Time Marijuana Growers' started by shottah, Jun 1, 2009.

  1. I have a thousand watt HPS light bulb how far away from the plants should they be?
  2. here you are kind sir :)

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  3. Well from that is says anywhere from 10 inches to 36 inches is optimal distance from plant? How do i narrow that down a little bit more. I have 4 about 7 inches babies.
  4. well then about 17 inches above the tops of the plants.
  5. Sorry, but that chart only shows the relative "lumens" from a certain type of bulb at a certain distance. It does not tell you how far away to keep the bulb from your plants, which is mostly an issue of heat management. Even to say that a bulb gives off a certain number of lumens at a particular distance really makes no sense, unless that distance is one foot, because lumens is a standardized measure of the light output of a bult at a distance of one foot. It's a rating of the bulb, not an actual measure of light output (but, since actual light output is expensive to measure, we use lumens to compare one bulb to another as a quick-and-dirty way to get a handle on "light output").

    To your original question, you want the bulb as close as possible without burning the plants. To test, hold the back of your hand under the light at plant-top level and if you can comfortably hold it there 30 seconds then it's OK for your plants. Get as close as possible and still pass that test. That distance will vary depending on your ambient temps, ventilation, if you've air-cooled the bulb, etc.
  6. If your lights are not air cooled keep them 20-24 inches away or you will have burning issues. Also have fan moving air between lights and plants. If its a sealed air cooled unit I dont know the answer.

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