Question Blow in/out fan ratio?

holmesc

Reputable
Jul 21, 2016
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Hey guys, I wanted to ask if my build has been wrong.

My desktop case has 3 pre-built fans, I set it so the 1 in the back blows cool air in while the two in the front near the gpu blows hot air out.

The two fans that came with my liquid cooling fans are set so they're blowing through the radiator, pushing the hot air out of the case. So total I have four blowing out and only one blowing in.

The temps for the cpu is fine, and the gpu seems fine too for now but I wanted to ask if this "airflow" is normal. I'd would have thought you'd need a balanced amount of "in" and "out".

Thanks!
 

alceryes

Distinguished
Optimal case airflow can depend on a lot of factors.
Normally, you'd want a slightly positive air pressure in your case. This allows you to direct airflow better and helps prevent dust monsters from being sucked in through all the cracks.
I would set it up with the rad and rad fans in the front of the case sucking in cold air and then exhausting out the back but lets get more info on your potential fan placement. Do you have space at the top of your case for exhaust? where is your power supply?
 
Jan 9, 2020
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One thing to keep in mind is also that if you have a fan at the back of your case bringing in "cool" air, and your power supply is pushing out warm air just underneath it, the incoming air might not be as cool as it could be. The more common setup would be to bring in air from the front and exhaust it at the back.
 
One thing to keep in mind is also that if you have a fan at the back of your case bringing in "cool" air, and your power supply is pushing out warm air just underneath it, the incoming air might not be as cool as it could be. The more common setup would be to bring in air from the front and exhaust it at the back.
There are no PSUs that push air in but if it's on top it will pull some of that fresh air away from that fan and CPU cooler.
Best way is to have air pulled from front and pushed out from back, That way it creates airflow over most components because that's main goal for having all those fans.
 
Jan 9, 2020
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There are no PSUs that push air in but if it's on top it will pull some of that fresh air away from that fan and CPU cooler.
To clarify, I said that if his PSU is at the bottom of the case, it will more than likely expel the hot air out at the back of the case, thus this hot air rises upwards and gets sucked into the case by his intake fan.
 
Jan 9, 2020
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Yes indeed, here is a random photo that I came across on the web, if you reverse the airflow of the top left fan, like OP currently has, it has the potential to bring in some of the hot air that the PSU has exhausted from underneath. How much gets brought back in depends on where the case is, if it's under a desk right next to a wall, this could be significant.
 

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