Equalizing pressure to minimize dust in the case

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PHiZ

Limp Gawd
Joined
Apr 7, 2006
Messages
416
Now we all know that having neutral pressure in the case is the best scenario for keeping dust from accumulating. You want to basically balance the CFM coming in with that coming out.

Too much coming in, the dust will not be pushed out.
Too much going out and dust will be sucked in.

I think maybe a slight positive pressure in the case (more coming in) is what is considered ideal?

Now is there any kind of pressure sensor that is readily available and capable of measuring the pressure inside the case? I have two fans behind the front face that I know aren't getting the full CFMs that they can because their flow is restricted, and I am trying to compensate by placement and RPMs of the other fans.

-PHiZ
 
I'm not sure if I understand where you are coming from with respect to pressures. Firstly, I don't see how you could get significantly above or below atmospheric pressure with standard axial case fans, regardless of how powerful they are. As long as you have open holes in the case(which you almost always do, even if it's just through the cdrom or something) then the pressure will be equalized.

Even if the amount of air moved by your intake fans exactly equals the amount of air moved by the exhaust fans, you are still sucking dust into the case. The dust is still going to settle on components. The only thing I can think of is when your exhaust fans move a great deal more air than the intakes, in which case air could get sucked in anywhere it can and you could end up with a lot of dust in your cdroms and such.

But I guarantee the pressure inside your case will be the same as outside, so a pressure sensor won't do much good. If any fluid dynamics experts can correct me, please do. This is all pretty much just out of my ass. :)

If you really want to cut down on dust inside your case, why not just put filters on your intake fans?
 
Have a couple fans blowing in to create a large positive pressure, and put filters on the fans, and you will have a dust free case.
 
If you had a few fans blowing into your case, the interior of your case would be at a slightly higher air pressure, causing the air to blow outwards through any vents or cracks in an attempt to neutralize it. The pressure difference wouldn't be much but it would be plenty to effect the dust buildup in one way or another.

jpmkm said:
I'm not sure if I understand where you are coming from with respect to pressures. Firstly, I don't see how you could get significantly above or below atmospheric pressure with standard axial case fans, regardless of how powerful they are. As long as you have open holes in the case(which you almost always do, even if it's just through the cdrom or something) then the pressure will be equalized.

Even if the amount of air moved by your intake fans exactly equals the amount of air moved by the exhaust fans, you are still sucking dust into the case. The dust is still going to settle on components. The only thing I can think of is when your exhaust fans move a great deal more air than the intakes, in which case air could get sucked in anywhere it can and you could end up with a lot of dust in your cdroms and such.

But I guarantee the pressure inside your case will be the same as outside, so a pressure sensor won't do much good. If any fluid dynamics experts can correct me, please do. This is all pretty much just out of my ass. :)

If you really want to cut down on dust inside your case, why not just put filters on your intake fans?
Click to expand...
 
oh it does for sure, want to know the reason why?
if you have more fans pushing out, air will get in from all the cracks you could imagine, most of them unfiltered, whereas if you push in air, youre only going to have input from that specific hole which if filtered, will give you a dustless case, unlike mine where I have a 92 mm input 120mm +80 out with a high amount of dust
 
I just filtered the vents on my X-Qpack in order to prevent dust. It works and is much easier than trying to equalize pressure.
dirty filter and clean Qpack....
tn_DSC00751.jpg




Plus, it's like running an air filter when it's on.

 
I honestly don't see too much dust coming in from the vents that pressure would effect. The main source of dust is going to be your case fan, which will push it in no matter what. Unless I am missing something?
 
I have to agree w/ most of the guys here, have more fans intaking ("positive pressure"). the key is to force the air INTO the case through specific openings and filter them. It can exhaust through any openings it can find. Dust has nothing to do with "pressure", just the amount of air movement though your case and how often you clean your house! :D
 
There's more more to consider than dust.

Negative case pressure also tends to stall air flow through your power supply, possibly resulting in:
- PS overheating.
- PS thermal-controlled fans ramp up in speed, compensating for higher PS temps.

Hope this helps!
 
If you want to know if your case has a slight positive or negative air pressure....

Just remove a 5.25" drive and put a tissue next to that hole. If there is negative air pressure, the tissue will move towards the hole and inside your case. If there is positive air pressure in your case then it should swing away.

Put filters on your intake fans if you don't want to pop open the computer and dust the insides often. You still have to clean the filters because a blocked filter is just as bad or even worse for cooling. You still have to clean it though, because all that filter does

Considering everything, a slight negative pressurized case drops overall case temperatures a degree or two, until a layer of dust settles on the surfaces that need to be cooled. A slight positive air pressure will increase overall case temperatures, but better for your optical and floppy drives since dust won't be sucked in through the crevices in those devices.
 
...you could always throw away everything you are trying to do with pressure equalization and put your case in a dust free room.
 
WBILLC said:
...you could always throw away everything you are trying to do with pressure equalization and put your case in a dust free room.
Click to expand...

Which is rather cost prohibative and nearly impossible unless you are in a sealed body suit. You have any idea how much 'dust' is made by dead skin cells? :p
 
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