Is air pressure a non-issue?

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Glenifir

Glenifir

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Aug 24, 2014
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I read somewhere that a pc case has so many holes in it that it can hardly hold any pressure negative or positive.

I'm going to have a 200mm fan front on intake and my psu fan on intake, that's it. On exhaust I'll have a 200mm fan top, 120mm fan back, and 2 120mm fans on my noctua d14s. now that's a lot of air going out but will it mean dust will be sucked in?

I have filter on pretty much all my fan slots. my whole house has wooden flooring and is cleaned regularly, the pc will be on the floor beside my kitchen island. It will also be beside my freezer, any issues with that?

Question is will I have bad negative pressure because of my set up?
if I do then could I just open a bunch of PCi slots on my case to try and get static pressure?

if I do have negative pressure does it matter because I'm not on a carpet anyway?

thanks
 
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nukemaster

nukemaster

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Nov 23, 2004
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Dust can get into a system either way(filters are not perfect and even a positive system may have some air enter from other locations under some circumstances).

The goal of many of these systems are to minimize it.

So lets say you have a 200mm intake(lets say it is 100cfm) and a 30cfm out 120mm and 30cfm out psu. You have 40 cfm in that is not being pulled out. You now have Positive pressure. Any openings in the care may be used to exhaust this air. If the 200mm is filtered, you will have less dust in the case because it will get caught in the filter.

Now lets pull some Negative pressure for you.

You have a 200mm exhaust(not filtered because you do not filter exhaust fans) again lets say 100cfm and 30 out from the power supplies(most power supplies are exhaust). You also have 2 x 120mm intake fans totaling 60cfm. You now have more air out than in creating a vacuum effect. Any openings in the case(filtered or not) will pull in air because the fans need to get air and will pull from any opening them can. These non filtered openings will pull in more dust.

The overall dust depends greatly on your environment. Some places have more dust than others.

Positive or Negative pressure will work better or worse in some systems. No way is right or wrong.

You can test to see what works best for you.
 
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geofelt

geofelt

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Oct 9, 2006
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The theory on positive pressure is that the intake fan is behind a filter.
All cooling air is drawn in through the intake fans and get filtered which keeps your case more free of dust.
The cooling air can then exit through any openings in the case regardless of the presence of exhaust fans.
If the exhaust fans are stronger or more numerous, you will defeat the cleaning aspect of positive pressure as some air will be drawn in through unfiltered case openings.

A 200nn fan can deliver plenty of cooling air. No more is needed at all.
It is the equivalent of 2 140mm fans, depending on the rpm.
Consider that your cpu may have a 140mm intake, and a good graphics card may have a pair of 92mm intake fans.
I lesser fan to direct the exhaust airflow to the rear or top is ok.
Just arrange the fans and speeds so that your intake volume is greater than your exhaust.
I might start with the 200mm as intake and a 120mm as exhaust. That is the arrangement I have with my TJ08E and a noctua nh-D14 cooler. I have no cooling issues, and my intake is running on slow speed.
You can experiment with other arrangements, but I think that you will find little change in cooling.

The job of a psu fan is to keep the psu cool, not for case cooling. A gold rated psu fan may not operate at all.
 
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Glenifir

Glenifir

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Aug 24, 2014
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