Case pressure and fans?

[cav58d]

Positive, negative, neutral?  Does it matter?

Exhaust in the back and top, intake in the front.  Does it need to be any more scientific then that?  Thanks!

[Chalenge]

I like to run with positive pressure (more air in than out), but either way you go you should start at even, or neutral pressure. I run two 120mm 1600rpm fans with a speed controller, plus two 200mm fans also on the speed controller. The rpm is set a little higher on intake, which keeps the case cool enough for me.

Fans do age, so it is a good idea to replace them on a regular basis, like every two to three years.

[Skuzzy]

Good and bad in all the scenarios.

Positive pressure is great to help keep dust out, but it also can suffer from dead air spots where stale air does not move due to the pressure, especially if the pressure gets too high.  Tends to create less static electricity as the air movement over the surfaces is slower, which is a good thing.

Negative pressure will suck more dirt into the case and tends to create more static electricity as air moves faster over the internal surfaces.  Less risk of dead air.

Balanced airflow is probably the best, but also the most difficult to achieve.

[Bizman]

I prefer a slightly negative pressure. For what I've experienced, the hoover effect can very easily be reduced by lifting the case off the floor or a large tabletop. A few inches is enough to prevent dust bunnies to be sucked in. CPU stands on wheels or a bracket under the table do a perfect job here. A tray made of mesh with wheels for large flower pots would be perfect for a modern case with the PSU air intake in the bottom.

[MADe]

my new build, I forced the case pressure high.
Air in from bottom- 1 fan, top- 2 fan thru radiator cooler, back- 2 fan, and side-4 fan . Air out thru front only, no fan.

case avg temp, 33C ambient.
backplate on vid card reaches 50C in gaming.

Whats most important is air flow directionality. You want to create a consistant flow pattern that passes fresh air thru the case and immediately exhausts it out with its added heat load. You do not what it swirling around inside the case, this will obstruct overall flow, keeping heat around.

luck
 

[cav58d]

I7-6700
MSI 1060 2 GB
EVO HYPER 212
Two Front Intakes / Two Rear Exhaust Fans

Idle temps CPU/GPU 27-30, Gaming temps low 40's.   

[Bizman]

Good temps. If you can also say that it's quiet as a whisper, it's as good as it can get. 

[eagl]

I prefer slight positive pressure, front to back.  Filters over intake fans.

My current setup has a single 120mm fan in the front pushing air over hard drives, a huge super-slow 200mm (or bigger) side fan just slowly shoving air over the whole mobo, the PSU fan exhausting at the bottom where the PSU is, and a top exhaust fan.

Overall its slight positive pressure so dust builds up only around the intake fans, but with exhaust fans at top and bottom I'm pretty sure I'm getting airflow through the whole case.  Plus, the front intake fan ensures cool air goes over the hard drives while the side fan makes sure there is no hot stagnant air around video card or cpu HSF.

CPU HSF is a tower design that blows the hot air towards the top exhaust fan.

To keep it quiet, all the fans are running at the slowest speed I can select using the case's fan speed switch and bios settings.  Plenty of flow directly onto components that need cool air, and the hottest air is directed in the general direction of an exhaust fan.

[Masherbrum]

Corsair 750D here.   Two Prolimatech Blue 140mm's in front and two more up top.   Hooked up to a fan controller.   Corsair H80i on the rear.

Case is on this:  https://www.amazon.com/gp/product/B001AJS3BS/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

We have a dog and I clean the filters about once a month or month and a half.   Inside of the PC needs only to be dusted out about twice a year.   But the stand makes a difference.