View Full Version : Quick power supply question

1st Oct 2002, 23:12
We got a new power supply because the old one died(I think it was the fuse, I'll be tinkering with it later). Anyway, there are two fans on this one, the intake fan and another that outputs either out the top or out the bottom depending on how I put the supply in.

I was asking around an nobody knows how it should go in, I didn't think to ask where it was bought, the two possibilities are:

Fan pointing up pushing air out to the top of the case with less than an inch of space between.
Fan pointing down pushing the air along all the components of the computer.

If the fan is pointing down, sure it pushes air down along all the components, but it's warm air, and it may be interfereing with the heat dissipation on the processor. If it points up then the air at the top of the case will be that much warmer, or will it help to dissipate some of the warmer air at the top?

Looking at the construction doesn't help any, there is an extra piece of metal on this one with screw holes that seems would be best suited to fasten to the top of the case which would make the fan point down, but on the back the switch is on the bottom of the supply if the fan is pointing down and the power cord goes in the top.

Currently I have the fan pointing down.

Which way should it be pointing?

2nd Oct 2002, 02:15
are you positive that the fan that goes to the outside is an intake? (and the one on the "bottom" blowing out?) On all of my power supplies, its outgoing, and the bottom fan is in going. ATX power supplies, iirc, are supposed to draw air across the processor and out the back of the power supply then (while cooling the power supply too).

if it is the way you state, and if its that big of a deal, open it up and reverse the fans...

2nd Oct 2002, 02:19
Interesting question, especially without visual reference. The two power supply fans should be working together to pull air from the lower-front to the upper-rear of the case.

From the description you have given, the power supply can be mounted in one of two ways, but the description also confuses the issue by stating that the air will go up if the fan is up, or down if the fan is down (I think you are mistaken about the airflow of that fan). The airflow should be up when the fan is on the bottom, which is (in most cases) the correct way to install the power supply.

Hope this helps!

2nd Oct 2002, 02:52
I was wrong about the airflow, which exits at the rear. You know, maybe I should check important things like that.

However, in this case it raises other concerns. If the fan is on top sucking in the air it would be removing the warmer air and giving better air circulation. If the fan is on the bottom I can't see how it can help cool the processor any better than it is as the fan on the processor's heatsink pushes the air toward the front of the case.

Dunno how a diagram will help, but here you go, side view.

Back Front
|Power | |CD-Rom|
|Supply | |CD-RW |
|_______| |
| ___ |
| |CPU| -> fan |
| ___ |Floppy|
| | HD |
|____________ |
| | |
|PCI/AGP | |
| | |
| | |
| | |
|------------ |

Mr. Perfect
2nd Oct 2002, 03:13
With two fans there is one intake fan on the bottum(point twards the CPU) and one exauhst out the back of the case. If you put the intake twards the top you'll probably stifle the thing. :)

Like So. The tri-color is a case fan, the blue one is a PS intake fan.

2nd Oct 2002, 05:59
The typical configuration is for the air intake to be at the bottom front and the exhaust at the top rear. There may be case fans, in addition to the power supply exhaust, in both intake and exhaust locations. If you have case fans near the power supply, they and the power supply should all blow out. The diagonal airflow ensures the best overall cooling. The exhaust is at the top because warm air tends to rise anyway. The exhaust is near the cpu and graphics card because you do not want the heat from those components to linger in the case.

Nice case lighting, Mr. Perfect. Is that your rig?

2nd Oct 2002, 07:11
A POWER supply with two fans is usually bottom in side out for air flow.

As the supply fan locations vary, the usual configuration is interior POWER CORDS (device supply plugs) at the BOTTOM as the unit is mounted.

This automatically puts the fans in the designed orientation.

2nd Oct 2002, 20:16
I guess I have it set up right then.

Thanks for the help.

Mr. Perfect
2nd Oct 2002, 20:20
Nope, not my machine. It'd set you back $140 for the lighted PS and fan, otherwise I migh have them. :)