# More fans means better case cooling? NO



## P4-630 (Jun 12, 2008)

A few days ago I took out 1 120mm case fan which was placed at the back-bottom of my case with now 1 120mm exhaust fan left at the back-top in the case, my case temps dropped 7 degrees.


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## niko084 (Jun 12, 2008)

Its very possible because you can limit air flow in one section to drop temps in another. The more airflow to an area with escape the better cooling.


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## P4-630 (Jun 12, 2008)

niko084 said:


> Its very possible because you can limit air flow in one section to drop temps in another. The more airflow to an area with escape the better cooling.





I have 1 80mm intake(low db at 5V) fan lower-front blowing over 2hhd's and 1 120mm at the upper-back (low db at 5V) + my psu which is situated in the top at the back of case has 1 120mm fan.


(btw I'm thinking of replacing the 120mm fan from my enermax psu for a silent one, or perhaps connect it to my zalman fan controller)


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## Mussels (Jun 12, 2008)

fan layout is very important.

as an extreme example, if you have all case fans blowing out but none blowing in, you end up with negative air pressure - its attempting to create a vacuum.

What a good case needs is air FLOW, you need very similar amounts of air in, as to amounts going out.


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## jbunch07 (Jun 12, 2008)

airflow makes a big difference. 
here is a good guide to follow.
http://www.xoxide.com/computer-cooling.html


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## Mussels (Jun 12, 2008)

jbunch07 said:


> airflow makes a big difference.
> here is a good guide to follow.
> http://www.xoxide.com/computer-cooling.html



useful link.

also makes the point that i usually do, positive airflow (more in than out) really, really cuts back on dust problems.


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## lemonadesoda (Jun 12, 2008)

ONLY if the air is filtered on the way in.

You can also have FILTERED negative pressure. I have such a case. Basically the whole bottom of the case is open with a wire mesh filter that holds back most of the dust. Air comes in the front and bottom, and out the back and top.

P.S. The case is on rubber feet about 1cm high, on wooden floor NOT carpet.


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## rampage (Jun 12, 2008)

in gereral as the others have said it is best to have a positive/ equal air flow with cool air comming through the front of the case and exiting via the rear of the case, altho some cases are designed for a negitive pressure for example my cosmos 100 case 3 120mm exhausting and 1 120mm intake, the reason for this is so the air can be "sucked" in past the HDD's but it is rare for a case to be designed like this

as a side note you may also place fans inside of the case and direct them to "dead/hot" spots that get minimal ar flow


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## P4-630 (Jun 13, 2008)

I use a piece of cloth from a loudspeaker box as filter(the cloth simply attached with some scott tape to the case fan intake holes), this prevents from any dust getting sucked in and yet the fan has no problem to suck the air in the case.

You may have to clean the cloth from time to time, but I think it's worth it, it works perfect for me and I have a dust free pc


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## Mussels (Jun 13, 2008)

i have a very good reason for not liking negative pressure in most cases - fan wear and tear.

If you say, had 3 120mm fans out and 1x120mm in (assuming there was no other air ingress in the case) it would force the fan intake to spin harder, over-rev it and wear it out faster.

the exemption being  what lemonade soda said, cases with their own mesh/fanless intakes.


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## Kreij (Jun 13, 2008)

Positive airflow is better for reduction of dust in the environment than negative.
No case (or room or whatever) is completely air tight.

If the air pressure in the area exceeds that which is outside of it, no dust will be sucked in through the various openings. This is how clean rooms operate to keep them dust free.
This, of course, relies upon good filtering of the incoming air.

Negative pressure can be an advantage in certain cases, but is generally a poor design.
When the internal pressure of the area drops below a certain point, it will suck air in through any opening availalbe to try to offset the imbalance. You don't want to create a partial vacuum if you can use inflow fans to move air.

It is always better to force air across components to cool them than to try to suck air across them.


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## P4-630 (Jun 13, 2008)

The average ambient temps here are 29-33°C, I did some tests with different fan set ups and I concluded that a negative pressure (more air out then in) works best for my system.

My test results:

(room temps 33°C and fans spinning at low rpm 5V, steel case medium tower model)

Setup 1:
1x 80mm intake fan bottom front 
1x 120mm intake fan side panel
1x 120mm exhaust fan top back
Result: 47°C

Setup 2:
1x 80mm intake fan bottom front 
1x 120mm exhaust fan top back
a piece of soft noise reduction foam that covers the sidepanel holes
Result: 41°C

Setup 3:
1x 80mm intake fan bottom front 
1x 120mm exhaust fan top back
Sealed sidepanel holes
Result: 39°C

My conclusion:
The negative case pressure setup is at not-too-shabby 8°C lower then the positive pressure setup.
A closed/sealed system case results in lowest temperatures
(steel case medium tower model)


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## From_Nowhere (Jun 13, 2008)

Agreed, more case fans don't mean better cooling, it's about airflow. I only have only one 120mm Scythe Case fan and my case temps stay around 25 degrees Celsius, never going above 30. And my components aren't hot either, for example my Phenom idles at 21 Degrees Celsius (Cool and Quiet enabled) in a room with a zone valve broken on the heater (constant 75 Fahrenheit)

Me living in Alaska may play a role too, but hey.


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## Mussels (Jun 13, 2008)

From_Nowhere said:


> Agreed, more case fans don't mean better cooling, it's about airflow. I only have only one 120mm Scythe Case fan and my case temps stay around 25 degrees Celsius, never going above 30. And my components aren't hot either, for example my Phenom idles at 21 Degrees Celsius (Cool and Quiet enabled) in a room with a zone valve broken on the heater (constant 75 Fahrenheit)
> 
> Me living in Alaska may play a role too, but hey.



the alaska part explains the user name


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## P4-630 (Jun 13, 2008)

From_Nowhere said:


> Me living in Alaska may play a role too, but hey.



I think you don't even have to use a fan, you have nice low temps there..


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## From_Nowhere (Jun 13, 2008)

Yeah, it is isolated up here. Hence my username. And another trick to low case temps is to remove the aluminum plates on the back (where the back parts [DVI] are when you install a new graphics card etc.) and replace them with a screen to keep the dust out, but still enable airflow.


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## Skitzo (Jun 13, 2008)

remove some variables and it seems fairly simple, two rear exhaust venting the air from one lower front intake.  They share the air so less cool air makes it to the top of your case to cool upper components.  Remove the lower rear exhaust and the air that it had been moving is now free to party with the upper part of the case hence lower temps.  It would seem that an increase in temps of lower components might be expected.

other things to consider would be airflow path, airflow rate, ambient temps, case temps and the location of components with high thermal output.  

You may find that adding another intake midway up the front has a similar effect allowing you to keep the lower rear fan for a greater effect.

I like excessive cooling, but noise is definatly a factor
just my thoughts...


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