Computer Case Negative/Positive Pressure Question

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#1 Edited by jcbullen (865 posts) -

I never really cared about the overall pressure of my case (NZXT Phantom) so long as it wasn't overheating and there wasn't a ton of dust building up, but now I'm beginning to get tired of the dust and my components are always cool. I calculated my CFM and found that I've got negative pressure in my case, good for cooling, bad for dust. My fans are:

140mm front intake - 62.5 CFM

120mM side intakes x 2 - 59.1 CFM x 2 = 118.2 CFM

200mM top exhaust x 2 - 103 CFM x 2 = 206 CFM

120mM rear (near top) exhaust - 59.1 CFM

Overall I've got -84.4 which seems to be quite a bit. I've got 2 options. I can disable one of the top 200mM fans to get my CFM to +18.6, or I can reverse the rear exhaust and have that become an intake bringing my CFM to 33.8.

I like having my large fans exhausting so I'd prefer to reverse the rear exhaust, but is this a common practice or is there something about it that would cause me to not want to do this? I'm going to turn it around and test out my temps when I get home, but I don't think there would be any overheating issues.

#2 Edited by KHAndAnime (15593 posts) -

I did minor research on this many years ago, I think slightly negative pressure is preferred for air cooling, It's dustier - but it confirms that air is flowing through your case that much more. I remember reading articles where people tested various fan setups, and that negative air pressure provided the lowest temps.

Switching around the back exhaust should bring the pressure to a more desired level. It will be less dusty, but temps won't be as nice. As long as the air is moving in a general direction through your case and you don't have intakes facing each other - your cooling should be fine.

#3 Posted by IvanElk (3798 posts) -

if your cpu cooler blows horizontal at the exhaust if you switch that to an intake it could potentially hurt your cpu temperatures a decent bit. (I also have the same case and have the same fan set up as you but I don't have a major problem with dust)

#4 Posted by jcbullen (865 posts) -

So I reversed the fan and saw the temps go from 67C to 68C when doing some Furmark testing, which is completely negligible. You do bring up a good point though about the CPU temps, I do have mine oriented so that the CPU fan blows across the heat sink towards the exhaust, now intake. I could just swap the side of the heat sink that it's on, or face the air blowing up towards the top of the case, but then that would probably grab hot air from the GPU.

#5 Posted by PredatorRules (9553 posts) -

Full Tower (mostly built with 6 fans))

Pros: Excellent cooling

Cons: Collects huge amounts of dust because of all those fans