# how many CFM's to cool a 1000W hps hood?



## newanimal

Hey folks, how big of a fan is needed in CFM's to cool one 1000W hps glass sealed hood. Will have a separate fan for tent interior. 
thanks


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## The Hemp Goddess

Well, what it takes to cool a light has a lot to do with how cool the incoming air is, however, I use a 6" Vortex 450cfm with my 1000W light.  I do not use 2 fans.  The one fan does all the work.


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## 4u2sm0ke

I use the same as THG  but I also have a speed control because the Winters are colder and need less air to cool than in Summer


Happy Growing

:48:


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## Hushpuppy

It will definitely depend on the air temp that is being pulled into the light and the space that the air is being pulled from. Any fan that will replace the air in the grow space at least once every couple minutes will be enough to cool the light sufficiently. The key is to balance the airflow with the temperature that you are wanting to maintain within the grow space. 

If you are pulling air in that is 35f and you want to maintain 76f in a space that is 16sqft, then you don't want to replace that air too fast or you will not be able to maintain the 76f.
However with the same fan and air temps in a space that is 30sqft, you will need to move that air a lot more to keep the space from getting too warm.

I used a single 6" 450cfm fan in a 5x5 space with 1200w of HPS and still had to slow it down some when the outside air was cold.


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## The Hemp Goddess

I have a speed controller, too.  I think they are essential.


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## WeedHopper

Always,,speed control.


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## newanimal

thanks for the replies. Having done some searching since I posted  I concluded one fan around 450cfm's w/speed control will probably do both jobs of cooling the light and circulating fresh air in the tent. I'll keep one end of the hood open and the other ducted to the fan outside tent. I decided the less noise the better so I splurged on a 8" Panasonic whisperline 440 cfm. A little painful for the wallet but I'll get over it.


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## newanimal

THG,  I'm setting up a 2'x4' cloning closet and plan to use T5's too. I'm going to install a 120mm PC fan (3 speeds) about 75 cfm's for air circulation. Installed at a top corner with intake at opposite corner.  That do the trick?


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## The Hemp Goddess

You will have to try it.  I have not had much luck trying to use axial fans like PC fans.


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## Hushpuppy

The problem with typical fans is that they don't create a vacuum to pull the air out of the space because the fan isn't enclosed to prevent the air from bypassing the blades. Air, like electricity, will take the path of the least resistance. I would get a 4" centrifugal fan and mount it at the top of the 2x4 tent.


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