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Suggestions needed on Fans Directions

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December 16, 2009 6:15:03 AM

Ok, so I got 4 fans in my system that i built in 2003. The 92mm fan is coming in mail as we speak-it goes on the top of the case.

the 2 fans are at the back of the case

and 1 other fan is on the side of the case, which is blowing directly into the CPU. is this good?


what directions should the 2 fans in the back be facing, and the 92mm fan that will go on top? and why?


so far the 2 fans in the back are like this... 1 faces out, the other faces in. i was thinking to face them both in or out but I dont know which one cuz it would depend on what direction the 92mm will be facing too. cuz it seems like if one fan is blowing in and the other fan is RIGHT ON TOP, it sucks at least 30% of the air the one beneath it blows in. it's almost like air goes in>out cuz fans are so close to each other and it doesnt get a chance to circulate the computer case before it exists. so in a way it's kinda useless facing them against each other imo. im kinda confused and dont know cuz it's my first system I built and im trying to make it last another year or so before I upgrade and get myself a new PC...
a c 122 B Homebuilt system
December 16, 2009 1:57:53 PM

Quote:

Fans on the top typically blow out but that's up to you.

Hot air wants to rise. Why fight physics?
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December 16, 2009 2:41:12 PM

Quote:
The fans in the back should blow out, like the psu.


but my psu fan blows onto itself instead of out. should i change its direction?
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December 16, 2009 2:42:26 PM

jsc said:
Hot air wants to rise. Why fight physics?


maybe to push the hot air out the back where the 2 fans are blowing?
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a c 122 B Homebuilt system
December 16, 2009 2:46:19 PM

No, it doesn't - or at least it shouldn't. Hold a small piece of paper against the PSU exhaust at the back of the case and see if it is sucked against the back of the PSU.

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a b B Homebuilt system
December 16, 2009 4:48:21 PM

Quote:
If your psu is NOT blowing out, then obviously its because of the fact that you have some other fans blowing the wrong direction causing turbulance or passive intake.



You really should get that PSU to be exhausting. A few weeks back my 140mm PSU fan stopped working, and I saw my overall temps rise about 10C. That's how I knew something was wrong. Not only do they move a lot of air, they need to be blowing air across that PSU!
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a b B Homebuilt system
December 16, 2009 5:34:54 PM

Prepare for a long thread. There are more opinions than facts on the question of the "right" way to arrange case cooling fans.
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a b B Homebuilt system
December 16, 2009 7:00:57 PM

Paperdoc said:
Prepare for a long thread. There are more opinions than facts on the question of the "right" way to arrange case cooling fans.



And that's one of the facts. Another fact is that you need to keep fresh air coming in, and heated air going out.
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December 17, 2009 2:11:02 AM

Quote:
If your psu is NOT blowing out, then obviously its because of the fact that you have some other fans blowing the wrong direction causing turbulance or passive intake.


my PSU's fan is faced inwards...
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December 17, 2009 5:19:04 AM

Quote:
The fans in the back should blow out, like the psu.

Fans in the front should blow in.

Fans on the side should blow in.

Fans on the top typically blow out but that's up to you.


+1 to that.
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December 17, 2009 3:31:39 PM

Quote:
What do you mean it's facing inward?? It's facing inward or its blowing inward?


its blowing inward (inside itself) to keep itself cool i guess
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a b B Homebuilt system
December 17, 2009 3:32:48 PM

If that PSU is exhausting into the case, it's the first I've seen.
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December 17, 2009 4:47:35 PM

purple buzz said:
but my psu fan blows onto itself instead of out. should i change its direction?


Ok, what model is your power supply?

A lot of newer higher end PSU's have a fan on the inside side of the case so they can have a 120mm or larger fan instead of the restrictive space that the back offers. There is still an exhaust on the back but with how those fans are oriented it takes the air from inside the case and push's it though the PSU and out the back instead of the older, smaller fans that were on the back of the PSU pulling air from the case though the PSU and discharging it out the back.
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December 17, 2009 6:46:52 PM

DJRWolf said:
Ok, what model is your power supply?

A lot of newer higher end PSU's have a fan on the inside side of the case so they can have a 120mm or larger fan instead of the restrictive space that the back offers. There is still an exhaust on the back but with how those fans are oriented it takes the air from inside the case and push's it though the PSU and out the back instead of the older, smaller fans that were on the back of the PSU pulling air from the case though the PSU and discharging it out the back.


Coolmax AP-550X

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a b B Homebuilt system
December 17, 2009 7:19:31 PM

That's a standard ATX PSU. Unless you or someone else opened the unit and reversed the fan, it is exhausting correctly. The large fan sucks are out of the case, over the PSU's components, and then out the back of the case. Not to worry.
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December 17, 2009 8:13:58 PM

That PSU does vent out the back. So as Zipzoomflyhigh said in the first reply:

Quote:
The fans in the back should blow out, like the psu.

Fans in the front should blow in.

Fans on the side should blow in.

Fans on the top typically blow out but that's up to you.

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December 17, 2009 8:33:48 PM

well.. since i dont have a front fan... how about

Side fan blows in

Top fan blows in

2 back fans blow out

?
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a b B Homebuilt system
December 17, 2009 8:37:24 PM

I'd personally put the top fan as an exhaust too, because hot air rises. However, that will cause you to have negative case pressure, which will cause dust to be your enemy. I'd try both configs for the top fan and see how it affects your temperatures.
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December 18, 2009 2:28:11 PM

Side fans blows in
Front fans blows in
Bottom fans blows in(Mostly for PSU with bottom fan design)
Rear or Back Fans blows out
TOP fans blows out (Hot air goes up...Less energy require to get rid of hot air inside the chassi). This is common sense even in controlled room environment (clean room, raise floor)return ducks are on top of the ceiling. High School Physics.

PSU: FANS
Power Supply fans regardless of its mounting (bottom, front, back) has one end result. Hot air is blown out at the back/outside of the chassi. There is no point of keeping HOT AIR from the PSU inside the chassi.

DUST:

Is another matter. New Chassi have filters to deal with it.

Clean up your room and PC sorroundings and this will be less of an issue. Use Air/DUST cans to blow out accumulated dust. DUST will find its way inside the computer specially if there's a lot of it in the room.
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a c 122 B Homebuilt system
December 18, 2009 3:33:11 PM

Every commercial case with a top mounted fan that I have seen was oriented to exhaust the air upward, out of the case.

If you think you know more than the engineers who design cases for a living, feel free to install it any way you please.
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December 18, 2009 6:56:57 PM

ok so how about this...

Back fans blow IN

Side fan blows OUT

Top fan blows OUT


this way its 2 fans blowing in, 2 fans blowing out
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Best solution

a b B Homebuilt system
December 18, 2009 7:11:34 PM

How about this

Side fan in

Top fan out

back fan out.

That's going to give you the best airflow. Seriously. It's not a big deal to switch them around, so you can just tinker with them, but that's the way they're all designed, it's for a reason.
Share
December 18, 2009 7:17:27 PM

jack, wouldnt that be a problem with most of the air blowing out and only 25% of the air blowing in?
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a b B Homebuilt system
December 18, 2009 7:22:22 PM

No. Since you have two blowing out and one blowing in, you'll have what's called negative case pressure. If we're still on earth, it will find the air somewhere, and in your case, by sucking it from gaps in the case. I do know dust is more of an issue with negative pressure, but like Leon said, most newer cases have filters for that. Some of what you'll hear about positive/negative pressure is opinion, but in my experience, negative seems to work better. With positive pressure, you have warmed air sitting in your case to be exhausted, where as with negative, it's constantly circulating fresh air.
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December 18, 2009 7:25:28 PM

ok jack, you convinced my ass BUT just so you know i got TWO of the fans in the back so that's 3 fans blowing out and 1 fan blowing in...
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a b B Homebuilt system
December 18, 2009 7:27:09 PM

I know. Just make some air move already! :p 
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December 18, 2009 7:29:28 PM

i will... right after i fix my friggin PC! I really hope it will be fixed by Christmas or the New Years the latest. that's all I ask Santa.
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a b B Homebuilt system
December 19, 2009 5:19:18 PM

I have:
Intake
Three front 120mm fans blowing in
One side 120mm fan blowing in
Exhaust
Two rear 120mm fans blowing out
Bottom mounted PSU blowing out
One top 140mm fan blowing out
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December 23, 2009 7:21:00 AM

btw, wouldnt it be a problem for the side fan to blow in since it's blowing directly into my CPU's heatsinker which is blowing in the opposite direction?

it's like the 2 fans are blowing into each other...
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a b B Homebuilt system
December 23, 2009 8:28:24 AM

purple buzz said:
btw, wouldnt it be a problem for the side fan to blow in since it's blowing directly into my CPU's heatsinker which is blowing in the opposite direction?

it's like the 2 fans are blowing into each other...

Most cases the side fan is designed to blow over the GPU not the CPU, so you won't have that issue.
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