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Intake vs. Exhaust fans...


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#1
UV_Power

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Hey everyone,

I have read many debates over which makes for more effective cooling. I always thought it was something like:

- intake fans in the bottom front
- exhaust(outtake) fans in the top back
- make sure you have more exhaust than intake to create a vacuum effect to pull the hot air out

If you follow these three steps, then you should have proper cooling, so I thought. I have been reading up on some forums and there seems to be a high amount of people saying intake fans are counter-productive/ineffective. How true is this? I was thinking of getting a new computer case (related to this thread I posted earlier...) and would like to know if I should nix the intake fans for them or switch them to exhaust fans.

Oh, and in case your curious on what case I want...

So, bottom line, are intake fans good? or bad? :whistling:
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#2
warriorscot

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Some people say you should have a slightly lower pressure inside but really you want it slightly higher or at normal pressure because the pressure difference being lower isnt enough to impove cooling but it is enogh to suck every dust particulate in your home into your computer and without an intake you would have a lower pressure and in large fans it would struggle to get enough air in and there would be allot of recirculation as well without an intake. You need an intake for good cooling and in that system you have the 120-120 combo which is just about perfect for cooling a normal system, although you might want to get some quieter fans than the ones with the case.
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#3
UV_Power

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That's what I figured.

although you might want to get some quieter fans than the ones with the case.

Already ahead of you on that one... I am getting a couple of these...

Does everyone agree with warriorscot?
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#4
warriorscot

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Not a bad fan, its not as quite as some but assuming the noise levels are accurate for the flow its CFM is much higher than other 120mm fans that make more noise, you can get quieter though akasa and arctic less noise(about 17Db) but less flow but they are high enough, and noctua make really quiet fans the 800rpm one only makes 8db of noise for 48CFM which is average for 120mm fans.
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#5
UV_Power

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I saw those fans and have been considering the thermaltakes, noctua, and these 130mm fans. The problem with the 130mm is that I don't think I could mount it as an intake fan and I would like to stay consistent (if possible). My first priority is on airflow (with noise in a close second) and the thermaltakes seemed like the best way to go.

On the other hand, you do bring up a good point. 48CFM should be plenty to get the hot air out of my case and I do have this computer on alot, so I am going to have to reconsider. Thanks for the input.
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#6
AnthonyJ

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keep it cool or have a pc like in your avatar :whistling:, i need a new case for cooling. so do we want more intake or exhaust fans?
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#7
SRX660

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I thought i would add that you need to be aware the thermaltake130mm fans have shroudsthat will interfere with most installations in computer cases. I bought a bunch of these and found they won't fit at the front or back of any cases that even have 120mm mounts. The shroud stops the sidecover to be mounted. So far the only place i have mounted these fans is in the side panel.

SRX660
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#8
warriorscot

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Fans with the high CFMs are a little less practical than they could be, and the higher speed will reduce its lifetime, the thermaltakes have 30,000 hours which is quite low, akasa fans are 80,000 and arctic ones go as long as 400,000 hours. The high speed fans just dont last as long the 100-150CFM fans are lucky to get 30,000 hours most less.
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#9
-=blaster=-

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Here's the deal, you need to BALANCE the airflow through any particular case. Some cases can handle more exhaust fans than others due to larger intake openings. Merely adding exhaust fans may not increase airflow and may even decrease airflow as all of the exhaust fans fight over airflow. It's different for every case. Most cases start with an exhaust on the PSU and the back of the case. As more components are added, hard drives, more powerful video card, or addition PCI cards, add an intake fan. As the additional components will tend to inhibit airflow. So, starting with 2 exhaust, add an intake, add an exhaust, intake, exhaust, etc...

Clear as mud?

:whistling:
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#10
AnthonyJ

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Here's the deal, you need to BALANCE the airflow through any particular case. Some cases can handle more exhaust fans than others due to larger intake openings. Merely adding exhaust fans may not increase airflow and may even decrease airflow as all of the exhaust fans fight over airflow. It's different for every case. Most cases start with an exhaust on the PSU and the back of the case. As more components are added, hard drives, more powerful video card, or addition PCI cards, add an intake fan. As the additional components will tend to inhibit airflow. So, starting with 2 exhaust, add an intake, add an exhaust, intake, exhaust, etc...

Clear as mud?

:whistling:

technically i suppose, but my psu has 3 fans, 1 on front 1 on bottom 1 on back, all blowing into the psu out the back :blink:. and a 80mm fan on front spinning the [bleep] outta itself trying to get air through these poorly designed pinholes
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#11
warriorscot

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Your PSU would still really count as one fan and should really be considered seperately not as a fan for cooling its cooling contribution is relativley low its mostly dedicated to the PSUs cooling and they almost always are slow low CFM fans designed for low noise and long life.

If your case has a poor intake and its struggling A. lower the speed if you can after a certain point its useless, B. Expand the holes, drill more or dremel them join them up a bit but only if its not to much that it compromises the cases structure.
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#12
AnthonyJ

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Your PSU would still really count as one fan and should really be considered seperately not as a fan for cooling its cooling contribution is relativley low its mostly dedicated to the PSUs cooling and they almost always are slow low CFM fans designed for low noise and long life.

If your case has a poor intake and its struggling A. lower the speed if you can after a certain point its useless, B. Expand the holes, drill more or dremel them join them up a bit but only if its not to much that it compromises the cases structure.

the fan isnt controllable. and its the plastic with the tiny holes, the metal is fine
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#13
warriorscot

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If its just a plastic fronting its an easy enough job to drill some more holes or make the ones you have larger, even removing the whole fronting and replacing it with a new fan grill is an easy enough job.
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#14
-=blaster=-

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I refer to fans that actually intake or exhaust at the case boundary. So, CPU fans don't count, GPU fans don't count, usually only one PSU fan counts, etc...

:whistling:
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#15
UV_Power

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So, what I am generally understanding is that you guys are agreeing to the fact that intake fans are necessary for proper cooling... Good to know.

In the mean time, I have fallen in love with a new case. Even though they are all big fans, and even if I replaced them all with quieter ones, I am still worried about the noise. Check it out....The Antec Nine Hundred :whistling:

Edited by UV_Power, 17 March 2007 - 10:26 PM.

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