CASE FANS, overrated?

K

konsole

Member
I think its safe to say that the video card and processor are the 2 biggest creators of heat in a common computer case. Since these 2 usually have their own cooling with heatsinks/fans, I wondered how much the case fans were really contributing to the system cooling. I did some tests on what the temperatures were both idle and under load with different fan setups. First of all I have a pretty basic case fan setup with one 80mm intake on the bottom of the case front and one 80mm on the top of the case rear. I also want to point out that I have a duct running from the side panel to the processor assembly and there are some ventilation holes on the side panel near the video card. The numbers I came up with surprised me quite a bit.

Here are the test variables:
-video card: radeon hd 4870 1gb (good stock heatsink and fan)
-cpu: e8400 with stock heatsink/fan
-fans are 80mm and push 24cfm (not much I know but they do push air)
-front fan is intake and rear fan is exhaust
-load was playing Farcry 2 on mostly high settings
-temps were given about 2 minutes to settle
-room temperature was about 21 celcius
-change of 1 degree was considered no change

so here are the results with temperatures in celcius...

video card - idle...
1. both fans (60)
2. rear fan only (63)
3. front fan only or no fans (65)

video card - load...
1. both fans or only rear fan (76)
2. front fan only or no fans (80)

cpu - idle...
1. both fans or only rear fan or no fans (40)
2. front fan only (43)

cpu - load...
1. both fans or only rear fan (50)
2. front fan only or no fans (54)

So what I have noticed is this. If your processor has decent access to ventilation and can pull cool air in from the side panel and your video card has a pretty good heatsink/fan with a little bit of ventilation access, then the case fans don't make that much of a difference. The front case fan hardly affects anything and usually turning it off doesnt change the temperature and its often just as good to have just the rear exhaust fan running as it is to have both fans running.

If you have the video card fan exhausting its own heat and the rear exhaust case fan exhausting heat thats rising from the video card and the heat that was blown away from the processor by its fan, then a majority of the heat generated is taken care of. Still the best results were achieved with having atleast an exhaust fan but I don't think having either exhaust or intake case fans will mean the difference between a cool system and system that's too warm. If your video card and processor have access to their own source of ventilation then you might want to experiment with no intake fan and see what happens. I bet you'll be surprised how little the intake fan matters and how little having no fans increases the systems temperature. If you have more then 1 case fan for intake and more then 1 case fan for exhaust (plus psu), then ask yourself if the air being pulled in is absorbing enough heat before its being pushed back out. You might notice that more fans will just blow so much air through the system and so fast that its not efficiently absorbing the heat.
 
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Well its going to change with different case's. I know if i turn off my fans on my antec 900 case then im going to heating up quick.
 
IBEPCWIZ said:
Well its going to change with different case's. I know if i turn off my fans on my antec 900 case then im going to heating up quick.
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if your video card and cpu have their own ventilation then you should try reducing or eliminating the intake case fans and see what happens. The temperature wont go down but you might be surprised how little it goes up.
 
Your puny little fans don't have enough push to make a difference obviously.

You're comparing "no fans",
to "might as well not have any fans".
 
Well i think it depends on the quality of the fans,you can get some el-cheapo fans that cost something like £2 and they hardly move a thing.

Then you can get some real good quality fans such as Scythe,Noctua,Zalman or Coolermaster....and they move alot of warm air from the case while been quiet.

I wouldnt run my system without the case fans on as hot air would just sit in there.
 
When it comes to fans more does not mean better, rather it's the location of the fans. I have one 120mm fans in the front and one in the back and they keep my case reasonably cool. I also flipped my power supply around so it draws cool air directly from outside.
 
25cfm, on the front panel of a case you arent going to get more than 5cfm actual airflow because of how restrictive they are. Of course cheap fans arent going to make any difference...
 
And i have a question. I see a lot of people useing that vent for the cpu on the side of a case... WHY DO THAT? I have 2 good quality 120 fans on the side of my computer pointing at the cpu? Is that not better?
 
IBEPCWIZ said:
And i have a question. I see a lot of people useing that vent for the cpu on the side of a case... WHY DO THAT? I have 2 good quality 120 fans on the side of my computer pointing at the cpu? Is that not better?
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Possibly, but that might also screw up the front to back airflow. However, more fans also means more noise, which could get annoying.
 
Too many fans will cause Turbulence and impede air "Flow".

Turbulence will mean the hot air will just mill around inside the case
instead of flowing out of the case, being replaced by cool air.
 
Well understandable but not if you A. Have good fans that are not noisy and B. Which way you have all the fans blowing. Some of my fans are blowing in and some blowing out. It took me a while to get it right but its there.
 
just a noob said:
cases are overrated in the first place, thats why i just use an old mobo tray on my desk :P
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Then one day your lovely cat named "pooky" will decide that your tray is its new bed and when you get home from a hard days of work, your heat sink fan doesn't spin because there's too many cat hairs from keeping it spinning. Now you have a roasted motherboard and if your cat's still on it (don't know why you'd turn it on when you cat is on it though) you'd have a roasted cat too. Dinner :D
 
aviation_man said:
Then one day your lovely cat named "pooky" will decide that your tray is its new bed and when you get home from a hard days of work, your heat sink fan doesn't spin because there's too many cat hairs from keeping it spinning. Now you have a roasted motherboard and if your cat's still on it (don't know why you'd turn it on when you cat is on it though) you'd have a roasted cat too. Dinner :D
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lol i dont think he is chinees
 
aviation_man said:
Then one day your lovely cat named "pooky" will decide that your tray is its new bed and when you get home from a hard days of work, your heat sink fan doesn't spin because there's too many cat hairs from keeping it spinning. Now you have a roasted motherboard and if your cat's still on it (don't know why you'd turn it on when you cat is on it though) you'd have a roasted cat too. Dinner :D
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That was hilarious, but in all seriousness small children, pets, being a klutz, a book or any item being dropped on it, or spilling a water glass, could result in broken hardware

@ the OP, did you measure the temperature of your hard-drive?

You also dont take into account cases like an Antec 900 or CM-690 that have several 120MM fans with direct intake no obstructions, and several exhaust fans, that each do ~50-100CFM depending on the fan installed, 80MM fans do 20-30CFM usually, and way less if the front of your case has no ventilation to the fan

Run the test with a case that has better cooling and see if your results are the same.
 
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Springy182 said:
That was hilarious, but in all seriousness small children, pets, being a klutz, a book or any item being dropped on it, or spilling a water glass, could result in broken hardware

@ the OP, did you measure the temperature of your hard-drive?

You also dont take into account cases like an Antec 900 or CM-690 that have several 120MM fans with direct intake no obstructions, and several exhaust fans, that each do ~50-100CFM depending on the fan installed, 80MM fans do 20-30CFM usually, and way less if the front of your case has no ventilation to the fan

Run the test with a case that has better cooling and see if your results are the same.
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I just ran this hard drive monitor program and my hard drive temps were reading at about 35deg idle and under load and with different fan setups, but is excessive heat ever an issue with drives so much so that regular convection isnt enough? Maybe in rare cases but can't be that common. Since even my basic fan setup produces fairly average temperatures I would assume that my case was getting enough cooling from just the 2 case fans and the other various device fans. When the temperatures didnt dramatically change when turning off the 2 case fans then it leads me to believe that the case fans arent that critical. If your already have a psu fan, cpu fan and a video card fan and the cpu and video card have access to ventilation then any more then 2 case fans really seems like overkill to me. I think its smart to have 1 good exhaust fan (with the psu fan) and maybe 1 intake fan in combination with the video card and cpu cooling, but beyond that will probably just create excessive noise, turbulence and an inability for the large volume of fast moving air to absorb the heat from the system before being exhausted.
 
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My dad's a pilot and he tells me where to put fans and where to get rid of them. I want to go in his computer and just throw 80mm fans all over to piss him off. Imagine fans pushing air into the case from all sides, but no exhaust.
 
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