Would a 1000w HPS/MH be to much for a 78x48x48 grow tent? And how much heat do they emit without an inline fan hooked up to the hood?
Personally I think it would be great (with an air-cooled hood), I was originally planning on running a 4x4 grow tent with a 1000W HPS (actually 54"x54" Sun Hut Silver) but if I was going to stick with my plans of a space that size I would probably still go with the 1000W HPS. I think I have decided to run (2) 600W lights for each 1000W I was originally planning to run now though. If you're too paranoid about heat and everything else, I think you'd also be happy with a 600W HPS though, if you use an air cooled sealed hood I think you'll be fine, just have intake flow through one side and exhaust out the other.
Well the one I was looking at came with an air cooled hood and tempered glass. I would just have to get a fan and some ducting. Also with HPS/MH how far do you keep them from the plants? I know with CFLs you keep real close like 2 inches
[quote name='"Ismokemyown"'] Well the one I was looking at came with an air cooled hood and tempered glass. I would just have to get a fan and some ducting. Also with HPS/MH how far do you keep them from the plants? I know with CFLs you keep real close like 2 inches[/quote] The glass that comes with the light is very nice. Reduces the heat it puts out towards the plants, therefore you can have the light much closer. As far as how far you should have it from you plants... Do the heat test with your palm, keep raising the light if the heat on your palm would make you sweat so to speak.. Just basically keep the light far enough away where it's not psychically hot on your hand. Also get some fans in the tent, air flow is very important for plant growth. (simulates the wind like with outdoor growing). And the distance you have your light from your plants also depends on how big they are, when they're smaller you have the light closer because you don't have as much plant to disperse the light too, and as they grow you'll need to gradually raise the light so it's concentrated on a larger area. Hope this helps and good luck
I have a friend who runs a 1000W HPS with air cooled hood and he claims he has his light sometimes within about 4" from the top of his plants without any issues. Personally I think that's pretty crazy but if the temperature is controlled and is at a comfortable level within that range more power to him I say. I'm pretty sure everyone's mileage will vary depending on how they're compensating for the heat but I'd get them as close as I can while maintaining a comfortable heat level just above the plants. Lots of different opinions on this when it comes to light distance but I figure if the temps are safe and the plants are showing no signs of stress then you're good.
With an air-cooled 600w MH/HPS this past summer I had no problem keeping my light within 3''-6'' if necessary.
I direct vent my 1000 directly with 55 deg or lower air. Allows me to put it basically as close as I want. I usually keep it about 8-12 in. away though to cover a larger area. If you vent it properly you can def. do a 1000 in that space.