Case cooling: Positive, negative or equal airflow pressure?

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XdbodzX

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Nov 7, 2013
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Hi guys, I plan to get the antec 300 two case for my pc build, and would like to know what kind of airflow would be best, and how I would achieve it.

So for airflow...
Positive?
Negative?
Or Equal?


Also, how does this work? What do I need to do to achieve the different types of airflow?


Thanks!
Dan.
 
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Onus

Onus

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Jan 27, 2006
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Generally, you want to create a flow through your case. If you have rear and/or top exhausts, and front and/or side intakes, you'll get that flow.
I would not use negative pressure, ever, unless the PSU gets its own air from beneath the case. Otherwise, the PSU will struggle against all the other exhausts as it tries to cool itself.
Positive pressure will reduce the dust in your case, although you'll need to keep the intake filters clean. You still want to create flow, as stagnant air doesn't cool very well. If you choose this route, reverse the rear exhaust so it becomes another intake. Since hot air rises anyway, leave the top as your single exhaust.

 
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Rammy

Rammy

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It's worth remembering that in most PC cases, influencing pressure in any significant way is near to impossible.
While build quality has increased a lot in the last decade, they are hardly airtight at the joints and most high end cases have entirely vented front/top sections. Like Onus said, you are mainly just creating air flow.

The 300 two has room for six fans, but you probably don't want to use all of them as they will suffer to one degree or another from diminishing returns, and you'll probably need a fan controller to run them all.
As the two fans it comes with are both exhausts (on the top and rear) an intake fan on the front panel would make some sense though with the drive bay cage not being removable, a lot of that flow will be restricted. There are two fan locations here and you can fill both, but one is probably sufficient for most setups. The final two fan spots are on the sides of the case, one above the graphics card area, and one underneath the motherboard. You are unlikely to notice much of a performance increase from either, unless you are having issues with graphics card temperatures or running an SLI/Xfire setup.
 
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Rammy

Rammy

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Absolutely. Higher airflow fans are important to a point, but perhaps more important than their output is the fact that you can run them at lower speeds to achieve the same results, reducing the noise of your system (at 100% fan speed my system sounds like a cheap hairdryer, at 50% it's near to silent).
Locations are limited by case design, but refer to my comments above about where to put fans in a 300.
 
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Onus

Onus

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I used this case for my wife's last build. The two included fans are Antec "TwoCool" models and there is a switch for each one on the rear. On low, they make little noise, and easily keep her non-gamer i5-3470/HD6570 cool. On high, they become loud enough to be annoying, without making a notable difference in cooling.
 
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Paperdoc

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There have been several threads debating whether positive or negative pressure is better in the case. The result? Pretty much a tie, based more on opinion than fact, in my opinion.(?!)

Personally, I prefer slight positive pressure. However, as Rammy said, you can't really make much pressure, nor do you want to. My reason is only to ensure that at leak points (there are many!) the net airflow is out, to reduce dust intake. BUT you MUST put filters on all your intake fans and keep them clean.

I fully agree with the others here - the aim is FLOW, not pressure. For that reason, CFM ratings are useful - you can choose max CFM and have choices of high air flow or reduced flow at reduce fan noise. CFM is also a LITTLE useful in establishing a near balance between intakes and exhausts. The problem is that CFM ratings are for unimpeded fans, whereas all intake fans should have filters that reduce CFM performance. Thus you cannot really calculate and predict net pressure. Best you can do is set it up then test. How? You need a source of smoke, and some suggest an incense stick. With the comp running, move the smoke source near any leak openings. Does the smoke go into the case (negative pressure), or does it blow away from the opening (positive pressure).

By the way, I urge you to ignore two arguments I find specious: High-pressure air is more efficient at heat movement (the pressure is 'WAY too low to see any such effect!); and, hot air rises - if you have enough fans to generate good flow, the natural tendency for hot air to rise in still conditions will have NO effect with all the movement going on!
 
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XdbodzX

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