Krunk_Kracker

What are the differences between these "set-ups" in air cooling?

Positive Pressure - In a positive pressure set-up, you only have intake fans, generally in the front of the case. The air is pulled through the intake and forced out through openings or vents. (i.e blow hole, slots ect) As far as I can tell, this set-up is rarely used by the likes of us (on Overclock.net). This is found on stock cases from major venders.

Negative Pressure - This is sometimes known as evacuation. And this setup acts, yep, you guessed it, opposite the Positive Pressure set-up. This is achieved by having exhaust fans towards the rear of the case, (be it the rear wall or top of the case) where they pull air into the case from the front through slots, vents, blow holes, ect. As far as I can tell, this to is a set-up that usually mass producers use (Dell, HP, ect.) and not for the performance minded overclockers :D

Neutral Pressure - Ahh, now this is what, as far as I can tell, most air coolers use. In a Neutral Pressure case, you have equal CFM entering and exhausting from the case. In this set-up, the air is always moving and being evacuated along a certain route that can be manipulated by fan placement.

This is the set-up that I use, I have two rear exhaust (not including my psu fans) fans and three intake (but side intake is ducted to the CPU fan), so realistically, I have two exhaust and two intake which seems to work great for me.

Please correct me wherever wrong and I'll edit it. Thanks!

EDITS AND NOTES:

Adding ducting from the side intake doesn't help with the overall air flow through out the case, but it does add positive pressure into the case, therfore giving the case a slight postive pressure (even in a neutral pressure set-up) that is great for helping to keep dust build up from starting inthe case.
Another note worth mentioning, adding a duct from the CPU as an exhaust in co-op with the intake duct is another excellent way to keep hte case neutral if thats your choice. (As long as the exhaust duct has an equal CFM fan on it :D) - Thanks to Busa for bringing both of those to my attention.

Krunk_Kracker

Bump for questions/comments/opinions.

Let me know if anything needs to be added.

Inspire

Great FAQ! Really good information. :)

Krunk_Kracker

Thanks! It was my first FAQ and I'm pretty familiar with these set-ups, so I figured I'd try it. Thanks!

busa

well...even tho the cpu fan is ducted to the cooler.....it still adds pressure to the interior of the case. also, a slightly positive pressure is better to have as it will minimize the dust collected inside the case.

Krunk_Kracker

Doh! I meant to say that having intake fans slightly higher than exhaust is better. I'll add that.

Also, yes, now that I thnk about it, your right. I was thinking in continuos airflow. I'll edit it and make a note. Thanks!

DataX

strange, I thought negative pressure actually helped to improve temps. Are you 100% sure about that info? Because of so I need change my fan setup.

Krunk_Kracker

Hmm......I'm almost positive. I could be wrong though. That's why I put that "correct me if I'm wrong thing" thing at the end :D

Krunk_Kracker

OK, yes, a Neutral Pressure set-up seems to be the most effective after double checking my research. If you find information dating different, plese let me know :D

The Duke

A slightly Positive pressure is the best set up!
When it is as such the exhausting fans will ballance the flow! So in reality you have a netural or ballanced pressure system!
Unless of course you have a vastly excessive positive flow and a bunch or vent holes in your case causing your air flow volume to prematurely exit the case!