Rear PC case fan - which direction?

JustAnotherSaver

So this morning i've basically taken my PC apart to clean out all the dust that's accumulated over the past few years.

Everything has been put back, i was careful as to what went where ... except the rear case fan. I can't remember which way it went in.

I've had a google & find "blow the air out" & similar. I know that it needs to blow the air out.

Looking at the fan (Akasa. Model: DFS122512L)....

On one side there is just a foil label in the middle with the fan blades around it.

The other side of this is a label with all the model details but there's also a 'spider' like frame. Along one of these spider legs is the wiring to the lighting.

Now as i stand this fan upright, on the bottom edge of the fan is 2 arrows.

* one arrow is pointing in the direction of the spider leg side
* the other arrow is pointing out to the side to the 'corner' where the lighting cabling has been run.


What side should be on the inside - the side with the spider legs or the other side?

chrisw

Turn on the power briefly and see which way it blows.

cookie365

The arrow shows the direction of airflow, so it should point out of the case if you want the air going out.

Though also consider putting the fan at the front and pulling air in.

Strider590

Airflow in most axial fans, is toward the frame where the wires are routed across. They don't normal blow the other way because this pushes the fan blade away from it's bearings and it could potentially fall apart after many MANY hours of use.

Robisere

A brief idea of how air should circulate and be cooled by case fans:



A long link, but will give a good image of how a case should be cooled. Blue arrows are inducted cool air, red is the exhausted warm air that has passed over components and is drawing out heat.

When I fit a new fan or fans, I take note of the arrows on the fan, which are usually hard to see as they are embossed on the plastic body of the fan. I mark them with a "CD" pen, in a colour that will show up on the fan; usually red. Your rear fan should be blowing out, or exhaust.

JustAnotherSaver

Here is what i call the inside of the blade since it looks to me like the open side of the blade:



Here's what i would call the back side of the blade or the outer side:



And here is the arrows. As you can see, there is an arrow pointing to the 'inside' side of the blade, or the side that has the spider legs, or the side with the red akasa writing in the middle, whichever way you want to call it.



So should I have the red akasa label facing the OUTside to blow the air out?

esuhl

On most PCs the front or side fans pull air in, and the fan on the back acts as an exhaust. I think the idea is that the area behind a PC gets quite dusty, so it's better to blow the air out onto the dust rather than suck it in to the PC.

But really, the optimal fan direction depends on the case design, orientation of other fans, the air pressure inside the case vs. outside of it, etc.

There's no point having all your fans sucking in or blowing out; you want them balanced to draw cool air into the hot components, whilst maintaining optimum airflow speed.

It's all down to science... or... personal preference!

cookie365

JustAnotherSaver wrote: »

So should I have the red akasa label facing the OUTside to blow the air out?

What part of

The arrow shows the direction of airflow, so it should point out of the case if you want the air going out

are you finding confusing?

JustAnotherSaver

Yeah i have a front fan but that's it, no side fans.

I've installed the fan with the label at the rear.

Either i've now installed it incorrectly or i've had it installed incorrectly all these years because the wire to install to the motherboard now doesn;t reach the pins (without undoing the tie).

prowla

The front should be air in and the back air out.

If you've seen data centres, they are organised around cold aisles (the fronts of the cabinets where the coool air goes in) and the backs of the cabinets (wher the warm air is blown out); you couldn't have equipment breaking this model or things would go wrong.

(Actually I did work at one place, a bank, where they had placed one large system the wrong way around, so it blew warm air into the front of another large system; the second one (a very expensive computer!) could be unstable.)

Strider590

You also want to try to get slight positive pressure inside, so more air being pushed in, than being pushed out, the extra will force it's way out through gaps in the case (including the drive bays) and help stop dust getting in.