good or bad fan position?

gophynna · 08-11-2005, 07:48 PM

Okay, I'm going to ask my first question.. It'll probably be pretty newbish...

How do I tell which way is the intake direction and which way is the outtake?

Also, is this setup okay...and which fans should be blowing in which direction...

I have one fan on the top of my case inbetween the space where the psu and cdrom are.

I have another fan on the side panel of my case.

And I have a fan at the very back of my case just below the psu.

The psu is dual fan.

Which way should each of these fans blow for proper airflow?

Tumbleweed36 · 08-11-2005, 07:56 PM

Hi,

You will get some disagreement on the fans on the top of the case and the side panel of the case. There should be no disagreement on the fan in the back of your case.

The normal case should have the rear fan blowing air out and a front fan drawing cool air in. I would assume that the top fan would serve the same purpose and should be drawing cool air in.

the side fan is done differently by many people. In my opinion, I would have it drawing cool air in, but you have to be very careful that you don't create case turbulance. Therefore, how it impacts the normal airflow might depend upon how it fits in the total airflow.

That is my personal opinion.

**kodi** · 08-11-2005, 08:00 PM

The front fan should draw air inwards and all other fans should blow air out.
If the fans are working just try to place a piece of light grade cardboard over the fans,if the fans are notworking there usually is a small arrow on the side of the fan indicating the direction of the airflow

EDIT looks like we posted at the same time

**toxict3arz** · 08-23-2005, 07:57 PM

i always thought .. back fan blows out and everything else blows in... am i wrong?

Tumbleweed36 · 08-23-2005, 08:10 PM

Hi Toxict3arz,

No, you aren't exactly wrong in many cases (get the pun). Anyhow, if you have just tow or three fans, that is the rule. However, there are times when that is not always the case with certain top and side case fans. I think mainly though, that you are right on track with your assumption.

The thing that must be preserved, is that you don't create a turbulance within the case. If some alteration needs to be made to fan direction to prevent turbulance, then take that action. An area that is widely misunderstood is the direction of the CPU/heatsink fan. It must blow DOWN over the heatsink and CPU and NOT blow up drawing air from that area. That alone can acocunt for considerable temperature change with some units.

Kodi,

Got you on that one. For once in my life I either typed faster than you did or just hit the button earlier. Anyhow, glad that I beat you for this time. Have a great evening.

Volt-Schwibe · 08-24-2005, 02:29 AM

i remember almost arguing about that here at this forum.

i was saying it needs to blow onto the heatsink, and there was some seriously strong resistance to the idea.

since then, i have decided that the majority opinion is that it should blow towards the heat sink, and if someone wants to disagree, i just hope it doesn't cost them a processor.

this here is a diagram i had made to explain...

in figure1, we see a fan, and the airflow around it. the blue is where is is sucking in and creating a pocket of low pressure air, causing it to draw air in from all directions, and the red shows the high pressure stream of air blowing out of it. you will notice the output is a more tightly controlled funnel of air.

figure 2 shows the high pressure blast flying cleanly into and around the heatsink, reaching fully to the base.

figure 3 shows the low pressure suction drawing air past the heatsink fins, but only the tips... this makes for a higher heatsink base temp. (the colors are backwards in fig 3)

ebackhus · 08-24-2005, 10:30 AM

In regards to an inverted (top exhaust) CPU fan solution, I've seen people put tape around the top of the heat sink to force airflow at the base of the heatsink, eliminating the problem. Now, I don't know if this is the greatest idea so I won't risk it on my PC. I also prefer the downward flow because it also sends air across the MOSFETs and RAM sitting nearby.

**w00t** · 08-24-2005, 11:57 AM

I used temp tape (the stuff they wrap exaust in) for the heat sink once and it sucks do not do it, the pressure builds up in the enclossed space slows the fan and heat seems to just build up after the first minute. The air must pass over the heat sink then "carry the hot air away" not stay there. Also cool air for the mobo and related is critical.

ebackhus · 08-24-2005, 12:38 PM

Which is also why liquid coolings can be a problem. Sure, you can OC like you're mad but there are other parts of your system that heat up as well. That's why more and more chipsets are coling with sinks and fans.

08-11-2005, 07:48 PM	#1 (permalink)
gophynna Registered User Join Date: Aug 2005 Posts: 1 OS: windows xp pro	good or bad fan position? Okay, I'm going to ask my first question.. It'll probably be pretty newbish... How do I tell which way is the intake direction and which way is the outtake? Also, is this setup okay...and which fans should be blowing in which direction... I have one fan on the top of my case inbetween the space where the psu and cdrom are. I have another fan on the side panel of my case. And I have a fan at the very back of my case just below the psu. The psu is dual fan. Which way should each of these fans blow for proper airflow?

08-11-2005, 07:56 PM	#2 (permalink)
Tumbleweed36 Asst Manager Hardware Join Date: May 2005 Location: USA Posts: 19,672 OS: XP Professional	Hi, You will get some disagreement on the fans on the top of the case and the side panel of the case. There should be no disagreement on the fan in the back of your case. The normal case should have the rear fan blowing air out and a front fan drawing cool air in. I would assume that the top fan would serve the same purpose and should be drawing cool air in. the side fan is done differently by many people. In my opinion, I would have it drawing cool air in, but you have to be very careful that you don't create case turbulance. Therefore, how it impacts the normal airflow might depend upon how it fits in the total airflow. That is my personal opinion. __________________ ---------- I don't receive email notifications of replies to subscribed threads. (Internet provider policy) Therefore, if I don't respond to your post within 24 hours, please send me a reminder PM and include the link to your thread.

08-11-2005, 08:00 PM	#3 (permalink)
kodi Moderator Hardware Team Join Date: Jun 2004 Location: Sydney Australia Posts: 7,407 OS: Windows 7-Ultimate 64 Bit My System	The front fan should draw air inwards and all other fans should blow air out. If the fans are working just try to place a piece of light grade cardboard over the fans,if the fans are notworking there usually is a small arrow on the side of the fan indicating the direction of the airflow EDIT looks like we posted at the same time __________________ Brian Last edited by kodi; 08-11-2005 at 08:01 PM.

08-23-2005, 08:10 PM	#5 (permalink)
Tumbleweed36 Asst Manager Hardware Join Date: May 2005 Location: USA Posts: 19,672 OS: XP Professional	Hi Toxict3arz, No, you aren't exactly wrong in many cases (get the pun). Anyhow, if you have just tow or three fans, that is the rule. However, there are times when that is not always the case with certain top and side case fans. I think mainly though, that you are right on track with your assumption. The thing that must be preserved, is that you don't create a turbulance within the case. If some alteration needs to be made to fan direction to prevent turbulance, then take that action. An area that is widely misunderstood is the direction of the CPU/heatsink fan. It must blow DOWN over the heatsink and CPU and NOT blow up drawing air from that area. That alone can acocunt for considerable temperature change with some units. *Kodi,* Got you on that one. For once in my life I either typed faster than you did or just hit the button earlier. Anyhow, glad that I beat you for this time. Have a great evening. __________________ ---------- I don't receive email notifications of replies to subscribed threads. (Internet provider policy) Therefore, if I don't respond to your post within 24 hours, please send me a reminder PM and include the link to your thread. Last edited by Tumbleweed36; 08-23-2005 at 08:16 PM.

08-24-2005, 10:30 AM	#7 (permalink)
ebackhus Manager, Design Join Date: Apr 2005 Location: SATX Posts: 14,303 OS: WinXP Pro SP3/Windows 7 RTM My System Blog Entries: 28	In regards to an inverted (top exhaust) CPU fan solution, I've seen people put tape around the top of the heat sink to force airflow at the base of the heatsink, eliminating the problem. Now, I don't know if this is the greatest idea so I won't risk it on my PC. I also prefer the downward flow because it also sends air across the MOSFETs and RAM sitting nearby. __________________ ----------------------------- There are no dumb questions, unless a customer is asking them. Help in the fight against cancer and other serious illnesses.

08-23-2005, 07:57 PM	#4 (permalink)
toxict3arz TSF Enthusiast Join Date: Oct 2004 Posts: 1,283 OS: windows XP Pro	i always thought .. back fan blows out and everything else blows in... am i wrong?

08-24-2005, 11:57 AM	#8 (permalink)
w00t Chex mix and Cream soda! Join Date: Jun 2004 Location: Oahu Posts: 596 OS: Slackware 11.1, Fedora Core 3, K12LTSP, Suse ES 9, Windows 2000sp4, Mac OSX, Knoppix, Mephis	I used temp tape (the stuff they wrap exaust in) for the heat sink once and it sucks do not do it, the pressure builds up in the enclossed space slows the fan and heat seems to just build up after the first minute. The air must pass over the heat sink then "carry the hot air away" not stay there. Also cool air for the mobo and related is critical. __________________ Elvis didn't die he just went open source w00tb0t, because you can't make tea with potatoes

08-24-2005, 12:38 PM	#9 (permalink)
ebackhus Manager, Design Join Date: Apr 2005 Location: SATX Posts: 14,303 OS: WinXP Pro SP3/Windows 7 RTM My System Blog Entries: 28	Which is also why liquid coolings can be a problem. Sure, you can OC like you're mad but there are other parts of your system that heat up as well. That's why more and more chipsets are coling with sinks and fans. __________________ ----------------------------- There are no dumb questions, unless a customer is asking them. Help in the fight against cancer and other serious illnesses.