Case pressure

[rof3]

Maybe this is a stupid question, but how can I tell if my case has negative or positive pressure inside? Right now it has two intake fans at the front and two exhaust at the back (all 80mm) as well as my 400W X-Connect, although the X-Connect's fans barely move. Oh, and a slot fan under the video card, which seems to push a surprising amount of air, maybe 18-20 CFM. I have an Antec SX 1040 BII (or something like that). Thanks.

 

[d2arcturus]

I highly doubt these fans push enough air within the case to change the pressure. You could just buy a pressure guage if you really wanted to know.

 

[Suspicious-Teach8788]

No no, pressure still matters.

If you have more inflow than outflow you have positive pressure and vice versa. It matters because it has something to do with dust.

Can someone help me out here? Which way do you prevent dust, which way is better for OCing, etc

 

[vegetation]

You could try good old smoke.

 

[CrispyFried]

If your case looks like a crushed soda can, its negative pressure. If it explodes, its positive.

One way is to simply wait. If dust starts to collect around the I/O ports or the edges of your drive bays you have negative pressure.

Or take out a blank drive bay cover and see which way the air or smoke goes, in would be negative of course.

Positive pressure is better for dust as the dust wont be drawn into your floppy, I/O ports and such. It will all collect at one point, the filter in the front grill (hopefully you have one). As for overclocking it shouldnt make much difference, its the amount of air that flows, not the pressure. At least to a point. Ideally you want them to match but thats a bit hard with thermally controlled fan etc.

 

[Blain]

Under a higher air pressure situation, the air would be slightly more dense wouldn't it?
Denser air facilitates better heat conduction doesn't it?

I realize that the case fans may not be able to produce much higher pressure.

 

[Tiamat]

more exhaust then intake is better for cooling. More intake than exhaust is better for less dust.

 

[suszterpatt]

I just realized earlier today that my front grill has been completely devoured by a thick, consistent layer of dust. I may need another intake fan somewhere.

 

[fixxxer0]

Originally posted by: Blain
Under a higher air pressure situation, the air would be slightly more dense wouldn't it?
Denser air facilitates better heat conduction doesn't it?

I realize that the case fans may not be able to produce much higher pressure.

The pressure (which is really non-existant, its just barely enough to create a flow of air) does not end up compressing the air. It is really so minute that it is ignored, the only benefit would be dust control assuming you have filters, becasue otherwise it will just do the same thing in a different spot.

 

[CrispyFried]

Originally posted by: Tiamat
more exhaust then intake is better for cooling.

Why?

Assuming 1 psi diff (<- random number, that) of neg or pos pressure, the only diff I can see is that with neg pressure, air is sucked into the case from random spots, with pos pressure, its expelled from random spots. Total air flow is the same.

 

[suszterpatt]

Originally posted by: CrispyFried
Why?

Assuming 1 psi diff (<- random number, that) of neg or pos pressure, the only diff I can see is that with neg pressure, air is sucked into the case from random spots, with pos pressure, its expelled from random spots. Total air flow is the same.

I think because those random spots don't transfer air as quickly as the exhaust fans. More exhaust prevents hot air from stacking up inside the case.

 

[Suspicious-Teach8788]

I quote from XS Forums which I have read a few threads about case pressure.


"Incorrect, you always want to maintain positive pressure in a case as it keep more cool air in and helps keep dust out. Hence, you want more intake than exhaust if you can help it, or equal."

 

[rof3]

Originally posted by: CrispyFried
If your case looks like a crushed soda can, its negative pressure. If it explodes, its positive.

LOL...

So now I'm more confused than when I first asked the question. Well, I haven't vacuumed my case for a while, and looking inside there is a thin layer of dust on the bottom. So can I presume that means there's positive pressure?

My presumption was that negative pressure is better for cooling and positive better for dust...but now I'm not sure.

My intake fans are filtered by the way, the case comes with a filter.

 

[Suspicious-Teach8788]

My case is VERY dirty. It clearly has more outtake than intake (negative pressure).

 

[Valkerie]

how many of you had to take a look at your case for the first time in ages..? in result of these posts?

 

[Suspicious-Teach8788]

not me... its always dirty and i only half clean it up (clean cpu fan out) and wipe some crap off my case fans. I cleaned my SB Live last year but didnt bother to do so. I'm sure its sitting in a pile of dust along with my Radeon..