MH/HPS distance question

Discussion in 'First Time Marijuana Growers' started by richirich_99, Jun 5, 2008.

  1. how far from the plants should i keep the light? I will be growing in soil using a 400 watt MH for veg and 400watt hps for flowering. Im just unsure of how far from the top of the plants i should be keeping the light? any help is greatly appreciated! Thanks!
  2. thats one of my concerns also maybe its too close, i use a 1000w HPS and i keep it about a foot
  3. put ur hand over the top of ur plants if its to hot for ur hand its to hot for ur plants
  4. alot of it depends if you have a vented hood with my hps bulb they can grow right up too the glass, my Mh is about 8 inches.... but if your unsure use your hand right over top your canopy and if it burns and gets real hot raise the light till it doesnt hurt and its tolerable also leave 2 inches or so for grow room.
  5. This is what I thought too the whole hand trick. However I was using no temp gauge. And my hand felt fine. After I threw in the brand new HPS 400w. But just to be sure I went to Target and bought an extra fan and an electric temp gauge. Hooked up the fan I had before to blow on the HPS bulb to keep it cool and the other fan blowing right over my LST'd plant. Threw the temp gauge in and it said 85F! I thought the gauge was broke so I grabbed like 2 others my roommates had and they where all saying around the same >.> After closing the closet door it said the max temp got up to 96F! This is right next to my plants.
  6. if ur just blowing air around in the closet ur temps will raise and raise u need to exhaust hot air and bring in cool air i feel ventilation is as important as lights (I pull fresh air out the crawl space under the house & exhaust into attic i can raise or lower temps by changeing the fan speed)
  7. You should have 50 watts per square foot. Per 50 watts measure 6 inches from the bulb.
  8. i have just about a 6sqft room, so the 400 watt should be good. By your way toker it would have the light at 48" from the plants, thats seems quite far....but then again im just a new at this growing stuff. thanks!
  9. i would say 6in per 50 watt is to far.
    i just got a 400 HPS today and its about 6 in from the plants
    my hand is nice and warm under it but not burning hot i can hold my hand there for 5 min. so i figure its a good distance
  10. For the hand test, you need to hold it there 30 seconds or so to see if it's too hot.

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