Pc fan or not?

Hay RIU!
I built this 2x2x4 tent a while ago but couldnt keep the temp down due to blazin summer heat. My bedroom temps drop to a decent 60 at night now, so I should be able to start it up. Passive 2in intake with a 4in exhaust fitting. I only plan on using a dozen cfl's and I dont want a big loud fan. Thinking a good 120mm case fan with a 70cfm rating will do fine. But this is my first indoor grow so I seek advice.

Thanks guys

im using a pc fan at the min and they work fine and they arnt to loud id go with a pc fan mate

Ill try one out

your passive intake should be as big s your exhaust.

a 4" exhaust and only a 2" intake will restrict airflow and make your fan work harder.
And if you've got the extra 12$, you can use 2 exhaust fans.
(use 2 for exhaust, not one intake/one exhaust.)

Make a bigger intake!

I agree with Rodman, a good rule of thumb: passive intake should be about 1.5x the exhaust.

Great advice! Im on it... I just ordered an antec 3spd 120mm off ebay for 7 bucks.. Ill update with further build soon.

Well you have 16 cubic feet, venting that 3 times a minute, you need 48 CFM, so with 70 you should be golden.
Now with 12 CFLs, in that small place, its gonna be getting hot. I'm assuming you're going to use small CFLs, like 23W or something. If that i the case then you need to upgrade your venting, I only had 6 of these and 70 CFM didn't cut it close for me, the space was only slightly larger than 2x2x4.

Your other option would be to get a small 70W or 150 HPW, it will give you almost the same or better light but will generate less heat than 12 CFLs in that space.

i'd advise 2 120mm fans for output(outtake, the fans blowing out ffs ) and 1 80 mm for the intake.... it will thoroughly swap the air inside you room and also keep it quite cool... i have a 2x1.6x2 room and i have 2 80mm outake and 1 80mm intake... but the holes through which they are blowing are made with a drilling machine( beehive holes... so it's not too efficient )

You don't really need intake fans, as long as the exhaust (the ones taking the air out from the grow area) fans are working, they will be pulling air passively from the outside through the intake holes (which should be 1.5 times the size of the exhaust holes) and other open fissures. In other words, the same amount of air (just the right amount needed to replace the exhausted air) will be rushing in to replace the air the has been exhausted out, without intake fans.

i'd advise 2 120mm fans for output(outtake, the fans blowing out ffs ) and 1 80 mm for the intake.... i

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I'd advise you don't, simply because 2 120mm fans blow a lot more air out than what 1 80mm fan could take in and replace. This in turn creates negative pressure inside the grow room, putting more wear and tear on all 3 fans.

Just dump the intake fan and put a hole there thats 1.5 bigger than the exhausts, two in your case.

Best of Luck.

Yeah mate, upsize your intake. Im using 2 80mm for exhaust of my cab but only have like 5x 1inch holes drilled for passive intake and i can genuinely hear the fans speed up and get loader when i close the door and they rely on sucking through those itty bitty holes. Gotta do something about it tomorrow. I got a question too though.. why have double the exhaust power to intake? Wouldnt that almost make the intake fan redundant?

I got a question too though.. why have double the exhaust power to intake? Wouldnt that almost make the intake fan redundant?

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The intake fan is in the first place redundant mate

You don't need double the exhaust power, you just need to have passive intake holes that are 1.5 times larger than the size of holes the exhaust fan is. For example if you have a 6 inch exhaust you will need to cut out a 9 inch passive intake hole for air to come through.

Im using 2 80mm for exhaust of my cab but only have like 5x 1inch holes drilled for passive intake and i can genuinely hear the fans speed up and get loader when i close the door and they rely on sucking through those itty bitty holes.

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Your fans are becoming louder because they have to struggle a bit more to exhaust the air when they only have that small intake available to them.

imagine a garden hose with water going through it. Pinch the end of that hose and the velocity of water will increase at the point where the water exits the hose. While pressure is building up inside the hose. This is what's happening to your cabinet when the intake holes are less than adequate compared to your exhaust.

Hope this clears it up a little