Controlling Temps in 60"x60"x80" tent

4 weeks into my second grow and I moved up to a bigger tent and 1000w lights. Been running a 1000W MH for vegetation and I am ready to switch to a 1000W HPS for flower. But, my temps are higher than I would like for the MH bulb and I know the HPS will run hotter. The only way I can keep the temps down is to either not run a carbon filter or run a 20" box fan to circulate air better. Without the filter, it obviously smells outside. When I run the box fan, I lose my negative pressure and my basement smells. I am running about 79-80* at the tops of the plants WITH the box fan running. With the filter and smaller fan to keep negative pressure it will creep close to 90*.

I am currently running a 390cfm 6" fan and 6" carbon filter. I have it routed filter, fan, hood, then venting outside. I have read that the fans may be more efficient pulling the air across the hood vs pushing like I have it. Any opinions on this?

I have also read that some use two fan systems, one that pulls air outside the tent, across the light and then back outside the tent. Then they use the second fan and carbon filter to remove the air in the tent. Before I spend the money, time and effort to try this, can anyone comment that it does drop temps?

For a 1000w light maybe you should consider a larger inline fan...I use an 8 inch, 900-1000cfm fan to keep my 1kw'er cool. No way a 6 inch fan would keep my light cool, and it sounds like its not doing the job for you either. Not to mention being on a carbon filter.

Logan Burke said:

For a 1000w light maybe you should consider a larger inline fan...I use an 8 inch, 900-1000cfm fan to keep my 1kw'er cool. No way a 6 inch fan would keep my light cool, and it sounds like its not doing the job for you either. Not to mention being on a carbon filter.

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Yeah it seems that the carbon filter cuts the CMF in half! I may have to step up to an 8".

Yeah, if you do size up your inline fan you will also more than likely need to size up your carbon filter to match it...if the CFM rating of your inline fan is higher than the CFM rating for your carbon filter, the air won't have enough contact time with the charcoal to neutralize odors.

So...I switched over to the HPS this morning and so far the temps are LOWER than with the MH.

C99newbie said:

So...I switched over to the HPS this morning and so far the temps are LOWER than with the MH.

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This is real interesting. Ive heard others claiming MH is hotter than hps, something to do with the actual filament running hotter. But im pretty sure HPS emitts more IR.

Rocket Soul said:

This is real interesting. Ive heard others claiming MH is hotter than hps, something to do with the actual filament running hotter. But im pretty sure HPS emitts more IR.

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I googled the hell out of it this morning as well. It does seem that some people claim MH runs hotter but most say the opposite. I'm a newbie so I was going off the general consensus that the HPS would emit more heat.

I did raise the light 4" to not shock the plants as much. But I'm running 5-6* cooler at the plant tops and overall in the tent.

1000w is suppose to be 1000w no matter what light. But i try to not go into thermodynamics cause its one of the trolliest subjects ever.
It might be that MH will run your tent hotter but your leaf surface temprature not as hot as HPS.
Leds, with no IR, allows you to grow at hotter temps. Or more like forces you to run hotter temps, + 80 minimum.

Maybe HPS runs hotter...maybe not, I have no clue, in any event I don't think it would be a large difference. it's certainly something for someone with some extra time and some extra energy to experiment with. But just do what works for you...screw what anyone else says. If the HPS runs cooler for you, run it! You and your babies are the ones who will reap the benefits of lower canopy temps, and that's all that matters!