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Airflow direction on fan

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January 4, 2013 10:48:12 AM

I have just placed order for a 200 mm fan (Cooler Master MegaFlow 200mm), and I was not sure whether to have a positive air flow for the fan or a negative one. As shown in the picture below I have the Thermaltake Overseer RX-I, which offers a fan on the removable side panel. If installed the fan will be centered right above the dual GPUs.
At the moment I have a net positive air pressure inside the case: the top 200 mm fan, the lower right 200 mm fan, and the dual 120 mm fans for the corsair Hydro H80 are all providing positive air pressure. The 120 mm fan in the bottom on the right of the PSU provides negative air pressure.
Any suggestions on the direction of air flow for the new fan I will be installing.

System Specifications:
i7-3930K
dual GTX 690
Corsair Vengeance 64 GB RAM
Seagate Barracuda 7200 2 TB

More about : airflow direction fan

a b K Overclocking
January 4, 2013 11:00:59 AM

Wait... The fans on the H80 are providing positive pressure? So it's taking in air at the back, along with the 200mm fan on the top?

If so, that's pretty weird airflow. You want to have air intakes at the front and bottom, and exhausts at the top and rear. I would make the side fan an intake fan, along with the bottom and front fans, and then making the top fan and the fans on the H80 at the rear exhaust air out of the case.
January 4, 2013 1:32:03 PM

Sakkura said:
Wait... The fans on the H80 are providing positive pressure? So it's taking in air at the back, along with the 200mm fan on the top?

If so, that's pretty weird airflow. You want to have air intakes at the front and bottom, and exhausts at the top and rear. I would make the side fan an intake fan, along with the bottom and front fans, and then making the top fan and the fans on the H80 at the rear exhaust air out of the case.


Actually, my bad the top fan is an exhaust fan, but the H80 fans are intake fans that what was recommended in the H80 manual
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a b K Overclocking
January 4, 2013 7:10:46 PM

ChemWizard said:
Actually, my bad the top fan is an exhaust fan, but the H80 fans are intake fans that what was recommended in the H80 manual

Okay, that makes more sense. Having the H80 sucking in air from outside is generally better for CPU cooling. If it pulls air from inside the case, that air may be warmer so it's harder to cool the CPU.

It's just that this configuration poses some potential difficulties for case airflow. It's hard to do the usual setup of intakes at front and bottom (and side panel), if there's yet another intake at the back and just a single exhaust at the top. Having the H80 fans exhausting air out of the case would boost case airflow a lot. With a traditional case airflow at least.

You could perhaps experiment with compartmentalizing the airflow a little more, having intakes and exhausts in the bottom half of the case serving mainly the graphics cards, and then another set of intakes (H80) and exhausts at the top for the CPU, memory etc.
In that case I'd probably swap the bottom fan to an intake and use the side fan as an exhaust. I'm not sure it would work all that well though. You could end up sucking out the air before it's really gotten to the graphics cards. You might end up with the top graphics card stuck between the two independent airflow systems at the top and bottom, with little air going past it. I suppose it may still be worth a try just to see how it goes, but I expect a traditional airflow through the case from front/bottom (+side) to top/rear will work better. Even if the H80 will have to use the "bad" air inside the case.
January 4, 2013 9:29:32 PM

Sakkura said:
Okay, that makes more sense. Having the H80 sucking in air from outside is generally better for CPU cooling. If it pulls air from inside the case, that air may be warmer so it's harder to cool the CPU.

It's just that this configuration poses some potential difficulties for case airflow. It's hard to do the usual setup of intakes at front and bottom (and side panel), if there's yet another intake at the back and just a single exhaust at the top. Having the H80 fans exhausting air out of the case would boost case airflow a lot. With a traditional case airflow at least.

You could perhaps experiment with compartmentalizing the airflow a little more, having intakes and exhausts in the bottom half of the case serving mainly the graphics cards, and then another set of intakes (H80) and exhausts at the top for the CPU, memory etc.
In that case I'd probably swap the bottom fan to an intake and use the side fan as an exhaust. I'm not sure it would work all that well though. You could end up sucking out the air before it's really gotten to the graphics cards. You might end up with the top graphics card stuck between the two independent airflow systems at the top and bottom, with little air going past it. I suppose it may still be worth a try just to see how it goes, but I expect a traditional airflow through the case from front/bottom (+side) to top/rear will work better. Even if the H80 will have to use the "bad" air inside the case.


Thanks for your detailed response. The 200 mm fan did not fit on the side panel (couldnt close the panel) because of the H80. So I put it on the top as an exhaust. I also flipped the direction of the bottom fan. So right now to sum up:

Front: In 200 mm
Bottom: in 120 mm
Back: in 2x 120 mm
Top: Out 2x 200 mm fan

I think that is reasonable now?
a b K Overclocking
January 6, 2013 8:55:30 PM

Yea it's great, experiment with the side panel if you want, sometimes it increases temperatures dramatically because it disturbs the airflow, sometimes it greatly decreases temperatures. You might also want to try the H80 on the back as an exhaust rather than an intake, this way it will provide better airflow as it comes in from the front/bottom and goes out the top/back.
!