How big to make passive intake holes

I'm almost all set and one of the last pieces I need is to know how big to make my passive intake holes. My set up will be 7th tall x 3ft wide x 22 inches long. I'm going to have a fan and carbon filter from htg, http://htgsupply.com/viewproduct.asp?productID=52531 and a 400w hps. So how wide should I make my passive intakes with this set up? Is there a formula or a rule of thumb?

Anyone?? This is the last piece of info I need!!

It is normally said for your intakes to be twice your exhaust. So if you have a 6 inch x 6 inch exhaust port make your 2 intake @ 6 inch x 6inch. You can start with the same size and just make it bigger as you need too in order to dial in temps.

gumball said:

It is normally said for your intakes to be twice your exhaust. So if you have a 6 inch x 6 inch exhaust port make your 2 intake @ 6 inch x 6inch. You can start with the same size and just make it bigger as you need too in order to dial in temps.

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agreed.

the general rule of thumb is

1sq ft intake for every 580CFM

but generally you want 2-3 holes the same surface area of your fan.

So as GUMBALL said 6inch fan = 2-3 x 6inch holes .



J