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PSU question

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January 25, 2010 2:59:34 AM

So I'm on an adventure of building my first PC. One of the first things I'm unclear about is the PSU fan orientation.

I'm going to be using a HAF 932 case which has a bottom mounted PSU. I know that bottom mounted PSU are said to run cooler because the draw in cold air from outside the case. However most PSU's I see have fans mounted at the top, is that blowing air out the top?

What about PSUs that have fans in the back of them? do they typically blow air out the back, or suck it in?

I know every power supply is different, I could just use some input on your preferred PSU fan orientation and why. What are the pros and cons?

~~~~~


Also if you have any suggestions as to a power supply I would be grateful I'm looking for something 750w+. I'm pretty set on putting a 5870 with plans of adding a second later on. I've heard you want at least a good 750w with 60 or so amps on the 12v rail if your running 2 cards.

Thanks guys, any help you can give me would be much appreciated

More about : psu question

January 25, 2010 3:31:07 AM

Psu with a fan at the back typically blow hot air outside the case... And intake the air from the inside through the vents... This would prove to be a better solution in eliminating heat... Try lookin at the cm silent or extreme power psu's with fan diameter of atleast 120mm
January 25, 2010 3:37:50 AM

Tophar said:

However most PSU's I see have fans mounted at the top, is that blowing air out the top?


Product pics all show the fan on top but when they are mounted correctly they should be facing down intaking fresh air from the bottom (unless you have one of those retarded Antec cases that forces you to mount the PSU upside down).

Tophar said:

What about PSUs that have fans in the back of them? do they typically blow air out the back, or suck it in?


Those are exhaust fans.


My personal favorites are Seasonic's. Most other PSU are rebranded. Seasonic makes their own. They were making >80% efficiency PSU BEFORE there was a 80plus initiative. Can't beat them in terms of quietness and reliability.
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January 25, 2010 3:38:46 AM

weather the intake is on the top or bottom is simply a matter of how you install it in the case. you can install it either way, so it will either be down facing and drawing air from outside the case, or up facing and drawing internally.

they all exhaust back outside the case.
January 25, 2010 3:48:58 AM

welshmousepk said:
weather the intake is on the top or bottom is simply a matter of how you install it in the case. you can install it either way, so it will either be down facing and drawing air from outside the case, or up facing and drawing internally.

they all exhaust back outside the case.


Ah ok. So if somebody were to mount a PSU on the bottom with the fan on top it would be sucking air down from inside the case? that seems like it would work against the case cooling which typically blows air back and up
January 25, 2010 4:13:04 AM

Tophar said:
Ah ok. So if somebody were to mount a PSU on the bottom with the fan on top it would be sucking air down from inside the case? that seems like it would work against the case cooling which typically blows air back and up


yes, thats right. and yes, its not the sensible way to mount a psu, but you can if you feel like it. the best configuration is always to have a bottom mounted psu sucking in cold air from below the case and exhausting out the rear.
a c 248 ) Power supply
January 25, 2010 4:44:12 AM

All modern power supplies exhaust air out the rear of the psu case.

I have a Lancool Dragon Lord case for my new system. I have a Coolermaster HAF 932 for my emergency backup system. I've also had other cases with bottom mounted cases. You have two choices with the a bottom mounted power supply.

First, if your case has sufficient ventilation, airflow, and cooling, then you could mount the psu fan side down so it draws in cool air from the opening in the bottom of the case and exhausts warm air out the rear of the case. The idea is that by drawing in its own supply of cool air rather than drawing in warm case air the power supply will be easier to cool and will last longer. However, do not place the case on a carpeted floor, especially deep pile carpeting. The carpet fibers will block air flow. A few years ago I made my own pc stand with casters.

Second, you could install the power supply with the psu fan on top. The concept is that the psu would help cool the interior of the case by drawing in warm interior air and exhausting it out the rear of the case. This concept goes back many many years when Intel started making cpu's that ran hot. The cpu's did not have cpu heatsinks or fans. In addition pc cases did not have case fans. In the original atx standards Intel specified that psu's should be placed near the cpu so the psu fan could help cool the cpu. Obviously this standard no longer applies. In modern tower cases we now have mutiple exhaust fans near the cpu.

The choice is yours to make based on your own specific ventilation, airflow, and cooling situation.

The ventilation, airflow, and cooling in my new Dragon Lord case and my older HAF 932 are excellent so I mounted my power supplies with the psu fans on the bottom.
January 25, 2010 5:29:05 AM

JohnnyLucky said:
All modern power supplies exhaust air out the rear of the psu case.


Ah awesome, I didn't know that, now this makes a lot more sense. I was thinking if you mounted your CPU in the bottom of your case fan side down that it would pull air through the PSU then exhaust its hot air out the top, into the case which seemed bad. But now I know thats not. . . the case . . . har har.

thanks man
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