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Difference Between Negative and possitive air pressure?

post #1 of 43
Thread Starter 
Hello, Do they make the same or what?Which way keeps temps lower?
post #2 of 43
Quote:
Originally Posted by PontiacGTX View Post

Hello, Do they make the same or what?Which way keeps temps lower?

Positive case pressure results in less dust in the system and better cooling for your GPU.

Silverstone has a nice page detailing this information.

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post #3 of 43
Thread Starter 
and negative
post #4 of 43
Quote:
Originally Posted by PontiacGTX View Post

and negative

I think negative is just when you have more fans on exhaust than you have on intake. This means that air is being sucked in from every crack in your case.

With positive pressure every opening and crack will be having air pushed out instead of sucking in.

On my fractal define R3 I have 4 fans intake (two front, one botton, one side) and three fans exhaust (two top and one back). I also have a loose fan on the inside directing air towards my H80 rad just taped in next to the hard drive bays.

Essentially with positive pressure you always have fresh air being cycled. Your case isn't air tight, so there is always cracks for air to escape besides the exhaust fans.
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post #5 of 43
Quote:
Originally Posted by james_ant View Post

I think negative is just when you have more fans on exhaust than you have on intake. This means that air is being sucked in from every crack in your case.
With positive pressure every opening and crack will be having air pushed out instead of sucking in.
On my fractal define R3 I have 4 fans intake (two front, one botton, one side) and three fans exhaust (two top and one back). I also have a loose fan on the inside directing air towards my H80 rad just taped in next to the hard drive bays.
Essentially with positive pressure you always have fresh air being cycled. Your case isn't air tight, so there is always cracks for air to escape besides the exhaust fans.

^this

Basically, positive case pressure is the better way. I didn't want to sound all know-it-all or anything but pretty much, positive case pressure is the way to go because it provides advantages. Negative case pressure only introduces disadvantages.
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post #6 of 43
positive pressure advantage = put dust filter to the intake fan
really useful for dust prevention

negative could prevent heat trap inside the case
guarante the hot air from computer part get outside the case

the problem from the negative pressure was it will affected the PSU airflow
so if you really concerned about the PSU airflow, better choose positive pressure
Edited by salvanos - 3/10/12 at 10:43am
    
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post #7 of 43
Thread Starter 
and here it´s and clear example of negative airflow??

Here Do you think which is better for negative/best temps buttom fan for intake or exhaust

450
post #8 of 43
As noted above, positive air pressure means that there's a net outflow of air from the case, while the inverse is true from negative pressure.

That being said, every case is different as to which will end up cooling your system best. For example, while there's a poster above stating that positive pressure results in better cooling, I found the opposite to be true for my setup....in fact, my temps dropped 6c by flip flopping all the fans.

(currently have 2 120mm fans on exhaust from the top of the case, and a 120mm intake fan in the back. Temps were (as stated prior) about 6c with all the fans doing the opposite job.)

So I'd encourage you to test and see which works best for you! (keep in mind, with negative pressure you will have to clean the case more often, as it is much easier for dirt/dust to accumulate. Keep an eye on your temps over time, and if they start climbing, it's definitely time to clean!)

*using the diagram above, my setup is exhaust fans x 2 on the top (upper two red arrows) and intake as upper left corner red arrow...though mine is more center of the case. I don't use any fans from the front, as I've got a mid-size case that really doesn't allow for good cable management. So my cables all are jammed in the front section, so as not to impede airflow. I also get natural draft from an open air side panel opposite from the CPU/Mobo side. I love zip ties.
Edited by MrHyde - 3/10/12 at 10:57am
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post #9 of 43
Also be aware that if you have a partially sealed GPU, you definitely want positive case pressure. See the link in the first post I made in this thread which shows great animated graphics about why this will really make a difference.

That said, MrHyde is right - every case / setup is different, and who knows, you might do a lot better with negative case pressure. If so, do it that way! thumb.gif
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post #10 of 43
Thread Starter 
my gpu is going to be changed

what about bottom fan? intake or exhaust for lower temps
Edited by PontiacGTX - 3/10/12 at 11:11am
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