Computer case fan direction

Eli_1 · July 16, 2004, 08:18 PM

The case I ordered has a fan on the side of it that blows air OUT of the case. I'm sure this is probably right, but I don't understand why you wouldn't blow air onto the components.

I know I feel cooler when standing infront of a fan, as opposed to standing behind one.

quasi-modo · July 16, 2004, 08:44 PM

It is good to have your fans, most of them, blowing out, to get hte hot air out of the case, to let more cool air in. Otherwise there is high pressure in the case and you are just blowing the hot air right back onto the cards. Its similar to ware hoses, where the big fans in the back blow air out. Many heat sinks on processors and video cards also blow air away, but some blow it into the heat sink... like mine. I have the fan on my window blowing out, the fans on my back blowing out, and my blow hole on the top blowing out, the two fans in the front blow in, so I some pretty smooth air flow going.

Grok · July 16, 2004, 11:47 PM

Air flow is the most important factor. Make sure you provide a path for the air to flow across the components and out of the case. In-the-front and out-the-back is recommended, since the power supply is already blowing out the back, and you want a consistent direction of flow.

Some bad things you can do:
* point all fans in the same direction (all in, or all out) ... this prevents air from flowing through the case, so temperature inside just goes up.
* leaving the cover off the case ... this prevents air from flowing almost at all, so air just sits around the components, and they roast themselves.

quasi-modo · July 17, 2004, 12:08 AM

Quote from: Grok on July 16, 2004, 11:47 PM
Air flow is the most important factor. Make sure you provide a path for the air to flow across the components and out of the case. In-the-front and out-the-back is recommended, since the power supply is already blowing out the back, and you want a consistent direction of flow.

Some bad things you can do:
* point all fans in the same direction (all in, or all out) ... this prevents air from flowing through the case, so temperature inside just goes up.
* leaving the cover off the case ... this prevents air from flowing almost at all, so air just sits around the components, and they roast themselves.

all fans can be blowing out if all fans refers to 1 or 2 fans maybe on the top or back, because air could still be able to flow into case because of low pressure, assumeing there is a vent on the sides or front. But if there are fans blowing out on every side, you are right, there will not be a bit of air flow. But I tend to keep most of my fans blowing out.

I have a fun idea, I am going to make air flow diagrams in paint!

quasi-modo · July 17, 2004, 12:32 AM

ok this is how my case is, except I have the ide, molex, and so on all tucked nicely to the side of the back behind the little shelf thing. Be sure to practice wire management, use some cable ties and get those wires neatly bundled. Ok well here is my crappy diagram

see how I have it from front to back top to bottom? I have more output then input so the hot air is getting pulled off of the hardware and there is a vaccume there for the cooler air to move into. My case ambient air temp is just above room temp, and my mobo temp is about 80f. My processor temp is 86f. I am running intel.

iago · July 17, 2004, 01:29 PM

Arrows showing direction would help a lot.

muert0 · July 17, 2004, 01:49 PM

I think the in the front are in and the rest out.

hismajesty · July 17, 2004, 02:38 PM

Quote* leaving the cover off the case ... this prevents air from flowing almost at all, so air just sits around the components, and they roast themselves.

I've heard that before, but in the past my temperature alarm would go off and if I took the side cover off the temp. would go down and stay down.

j0k3r · July 17, 2004, 02:43 PM

Quote from: iago on July 17, 2004, 01:29 PM
Arrows showing direction would help a lot.

Blue is cold, red is hot, you decide which way the air is flowing.

jabird · July 17, 2004, 07:33 PM

I once saw a diagram very similiar to peofeoknight's except it was alot better (sorry lol).

A couple facts about comp air flow:
1. There is always one outtake fan (the power supply)
2. It is nice to have 1 or more intake fans in the front bottom, and 1 or more outtake fans on the back top... This way air flows over everything.. (From the bottom (likely hitting your hard drives) up over you video card likely, and your processor, then all the hot air out the back...)
3. CABLE MANAGEMENT!!! I cannot stress this enough! if you have some old IDE cables just lurking around in there, they block air flow completely!!! that is about the worst thing that you can do air flow wise!
4. If you do have IDE cables round them, or if your lazy buy some rounded ones...
I rounded mine myself, this is how I did it:
I took an exacto knife, cut a little notch in the wires every 3 wires, then pulled the cables apart, starting at the notch and working my way up, I then twisted the cable tightly, and put 3 zip ties on it (1 at top, 1 at bottom, 1 at middle) then I rapped electrical tape around it and plugged it in...

(There is some speculation that if you cut it in a wrong order, it may cause data loss... I have had mine like this for several months now, and I havent lost anything... I didnt do what people say to do wire cutting wise either, so I would say you are pretty safe...)

~Jabird

Hows that for a first post?

Hitmen · July 17, 2004, 08:23 PM

Quote from: jabird on July 17, 2004, 07:33 PM
There is some speculation that if you cut it in a wrong order, it may cause data loss... I have had mine like this for several months now, and I havent lost anything... I didnt do what people say to do wire cutting wise either, so I would say you are pretty safe..

Uhm, that's what happens if you cut a wire, not cut "in the wrong order".

quasi-modo · July 17, 2004, 08:34 PM

A power supply fan is a good output fan??? Really? Except not much air from my pc is flowing into my power supply, it is a box, there is a vent, but none the less it has sides that prevent a massive amount of air from going through it, it certainly will not have more air flow out then one of my 80mm fans.

Of course you have seen better diagrams then mine, I MADE IT IN MS PAINT LOL.

j0k3r · July 18, 2004, 09:31 AM

When I noticed my computer was generating alot of heat, I just took the side off, it's been like that ever since.

hismajesty · July 18, 2004, 10:02 AM

Quote from: jabird on July 17, 2004, 07:33 PM
3. CABLE MANAGEMENT!!! I cannot stress this enough! if you have some old IDE cables just lurking around in there, they block air flow completely!!! that is about the worst thing that you can do air flow wise!

http://www.ramsinks.com/IDEmod.aspx

Grok · July 18, 2004, 10:06 AM

Quote from: peofeoknight on July 17, 2004, 08:34 PMA power supply fan is a good output fan??? Really? Except not much air from my pc is flowing into my power supply, it is a box, there is a vent, but none the less it has sides that prevent a massive amount of air from going through it, it certainly will not have more air flow out then one of my 80mm fans.

Peofeoknight, let me offer a different explanation. For air to have good flow across the components, it needs to have blocked sides and open ends. This creates a wind tunnel, where the air flows across the components.

Another way to view it is as a wind-system. If you place a power-supply cooling fan in the middle of the desert, and turn it on full blast, what does it cool? Nothing, because the fan is not the interface to an external destination for hot exhaust, and there is no vacuum side containing cooler air. So that is a closed system. An open system has interfaces of cool air on the vacuum side, we hope, and low resistance on the exhaust side.

j0ker, taking the sides off your case is probably reducing the heat across your motherboard and CPU, while frying your hard drives. Cases are engineered with an air-flow in mind. The designer usually wanted cooler air to enter the front/bottom of the case, flow across the hard drives, then motherboard/CPU, and exit the back, and in some cases, the top fan. If you have cooling problems with the cover on, you need an additional back fan, pointing out, to increase the vacuum from the front. Or, place the additional fan at the front, pointing inwards.

In my system, I have 2 fans cooling the hard drives, a single fan in the back. The Antec 460W power supply fan is heat controlled. When it is not needed, the fan slows down. My cooling works so well that sometimes my power supply fan cuts itself off, having no additional heat to remove! That's a little annoying since the Asus Probe utility sets the low threshold warning at 600rpm, and it pops up an alert. So, I turned off the BIOS power supply fan RPM monitoring.

Computer case fan direction

Eli_1

hismajesty

jabird

hismajesty