Case fan - sucking it in or blowing it out?

[SiRu]

Assuming I will fit just one fan into my case (Aopen HX45A), would it be better to have it sucking in the cooler air or blowing out the warmer air?

 

[buffhr]

i have always experienced better temps with sucking out the hot air but also that depends on the placemewnt of your fan and this will change from case to case , so i would suggest trying both out sincre it only takes a few secs to do anyways

 

[shathal]

Blow OUT (that's assuming your fan is at the "back" of the case - below/next to the PSU.

ATX spec works on under-preassure. AT (the previous one which we had with (for instace) Pentium Pro & all that) worked on blowing air INTO the chassis.

At the moment, you want the air to be BLOWING OUT of the chassis.

 

[Dan]

If you are only going to have one case fan I'd recommend that you place it as an exhaust fan in the upper rear of the case.

 

[SiRu]

Thanks guys for your input. I have a sneaking feeling that the only ready-made hole in the case is at the bottom and at the front. Can this be true? I will check it out when I get home as an exhaust fan seems to be the consensus.

 

[buffhr]

yeah usually atx case have on place for a fan lower front end and at the top back of the top or besides the cpu

 

[Cheetah8799]

Usually the PSU already has one blowing out, so I would have the new one blow in.

 

[RedWolf]

You probably already have a fan on the PS blowing out. If you only have one ready-made one in the front that should help cool things down. There are fans you can get for rear exhaust that install in a pci/isa slot that work pretty well, too.

 

[mgpaulus]

Make sure your PSU fan is blowing out. There was a short period where the ATX specs called for the PSU to blow air into the case. However, the consensus there was that that was a mistake, and the PSU should exhaust. If your PSU is "sucking" instead of blowing, it's a pretty easy change to make.

What kind of case do you have? I was able to get a squirrel cage cooler (nidec) from Radio Shack, and made a little adapter/holder for it, and then drilled a few extra holes in my Enlight 7237 (followed the pattern, just extended it up a few more rows). This gave me some additional exhaust in the case, and was very quiet.

I'm not sure which is a better philosophy in cooling, tho. Should your case have negative pressure, thus forcing a bigger inrush of "cooler" air through all those little leaky holes, or should your case have positive pressure, thus trying to force the hot air out of all those little leaky holes. Seems to me that negative pressure would be a bit more efficient in removing the heat, but you don't get much cooling in a vacuum, so I'm not sure. Probably the best would be to have a balanced system where the air is moving freely.

On a side note, how efficient would natural convection be in addition to either positive or negative pressure?

 

[NightTrain]

Too much negative pressure will cause alot of dust to build up inside the case.

 

[AThomas238]

I think the most important aspect of case cooling isn't negative or positive pressure, its airflow. Ex: i have a rear exhaust fan on my little ol super-micro ATX case (almost midtower, but not quite) and a gaping hole in the front of it -- my ambient temps are a little on the hot side.

My roommate, however, is running a 120 mm YS Tech intake on the side of his case, which is close to a window that is always open and cold, and a 120 mm Sunon exhaust on the top. When his case hits 40 degrees celcius, he switches those suckers on and his case temp drops about 8 or 9 degrees in less than 5 minutes.

So to answer the question directly, you want airflow -- a steady, balanced inflow/outflow in your case, if you can manage it; if you only have one fan slot, like me, then you might have to rig a blowhole in your case with a circular cutter, or hook up something in one of your open slots/drive bays.