new grow setup 400w mh/hps cooling question

Pinworm said:

For exhaust, you are going to want something a little more powerful. Like something 6" 240cfm (at least). Amazon has some ok deals on some cheap boosters. Make sure to setup a passive intake too (pull fresh air in from the bottom of the tent). You should be able to get away with using a 4 inch for that.

You are going to want to have a circulation fan in there, also. Tent's are notoriously tough to keep cool.

Good luck.

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Dubbz415 said:

thanks for the speedy reply i have circulating fan already waiting on its new home and the tent has passive vents at the bottom should this be ok with the 190cfm inline fan?

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Pinworm said:

I would cut a hole at the base of the tent, and pump fresh air in at half the strength of the exhaust's, that way you get negative pressure. That helps keeps the smell in check. I think using your 190cfm inline as intake will work great, just as long as your exhaust is twice as powerful.

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Dubbz415 said:

i was thinking of using it as a exhaust as it has a carbon filter too and a passive intake would this be ok?

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Pinworm said:

If that's all you have to work with, I suppose it's better than nothing. But, it's not going to be powerful enough to function as both exhaust, and a way to cool your hood, especially since it has to push air through a scrubber. Here's the math I used to find what size fans would work for my setup:

So, my cab is 39" x 23" x 92" (in reality, its a bit less due to some airspace being consumed by equipment. Some of that equipment gives off heat, so I'll ignore its space use and overcompensate)

Size in cubic feet - W x D x H: 3.25' x 1.92' x 7.67' = 47.86 cubic feet

Size x 3 to compensate for filter air flow restriction: 143.58 minimum cfm requirement
Adjust for 80% real world efficiency of inline fan - min. CFM @ 80% total: (143.58 / 8 ) x 10 = 179.48 total minimum CFM

So my minimum fan CFM should be at least total minimum CFM x 2, so that I can adjust up if need be. That means that my minimum fan capability should be 358.96. Choosing 2 Vortex inline 6" 449cfm fans, or 3 AbcoTech 240cfm Boosters give me enough overhead to provide enough negative pressure to ensure fresh air uptake at a rate of at minimum 1 full air exchange per minute at 50% speed..

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