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Best fan placement?

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  • Power Supplies
  • Graphics Cards
  • Fan
  • Components
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July 20, 2007 2:56:52 PM

Hi, i'm wondering what the best fan placement would be in 3 different scenarios.

1. 2 8cm fans in the back, one above the other. the top one is currently on exaust and the one below it is on intake.

2. same rear fans, but with a 12cm blower in the top of my case.

3. the 2 8cm rear fans, the blower on the top and 1 12cm fan on the side panel ( its all the molex connectors and 3 pin mobo's that i have left.) Where should it go, near the cpu or video card?.

I was thinking have intake in the bottom and outake near the top. Unless i can mod the front of my pc somehow to fit a front intake fan. But I would then have to disconnect one of the other fans. In total all the fans i can have is 4.


More about : fan placement

July 20, 2007 4:40:01 PM

What case do you have?

More exhaust then intake is standard rule of thumb... but you can't overdo it or you'll reverse airflow through your PSU.

Side vents and fans can work for you and against you depending on you're video card setup.
July 20, 2007 5:08:56 PM

The best option would be to have a front fan sucking in. I don't think it is a very good idea to have one back in and one out your best option would be to find some way of mounting one in the front going in and the one on the side in and have one in the back and the top one blowing out. That configuration combined with the PSU blowing out will provide negative pressure and give you good air flow.
Related resources
July 20, 2007 5:15:46 PM

if possible
Fans in from the lower front
Fans out upper back
July 20, 2007 5:53:41 PM

These are good examples of Good airflow







The idea is to keep the air moving in one direction

July 20, 2007 7:06:51 PM

"The idea is to keep the air moving in one direction "

Very true. And also to get the hot air OUT of the case as quickly as possible.

Your example in #1 sounds like you have an intake fan and an exhaust fan right next to each other. This is a bad configuration.

Rule of thumb: Intake in the front, exhaust in the back, exhaust in the top. You don't really need intake fans *and* exhaust fans. One or the other is enough. But if you have restrictive vents you'll need fans to force enough air through them and the turbulence from intake fans can sometimes be helpful (sometimes harmful).
July 20, 2007 7:31:03 PM

yup, nice pics too!

unless you do some kind of modification your psu is going to be shooting hot air out the top end of the back of your case so you want to stay with that. cool air from the front and bottom, hot air out the top and back. and dont forget to...

have fun!
July 21, 2007 1:48:52 AM

ok, I have a generic case, and i would need to cut off what holds the front pannel together to add a front fan. I wish i could but that will probably be fairly difficult. I have an 478 socket p4 too. I know about the equal cfm stuff, and about more exaust then intake and the front to back airflow. All those seem to fight each other lol, because with the blower I will have alot more air going out then comming in, then if i manage to add the front as intake i will have the psu fan, 2 80mm fans and a 12cm blower all blowing out and only one 80cm as intake. I could skip the intake and and put in a 12cm fan near the video card but it will still be 4 exhaust and 1 intake. Thanks to everyone that posted, put im still kinda lost lol. Rember, I can only have a total of 4 fans+ psu, so should I take out 1 rear fan and then mod my case to have a front intake, top exuast blower and then a side intake?

PICS:

Whole case:


Front where intake could be with some modding, hopfully the front usb/audio pannel will stay intac


and rear fans, one on exaust and one on intake currently


Tomorow That cpu hsf is being switched, and hopefully I will have the blower in soon.

*say* That I could not add that front intake, blower or side panel fan, how should I arrange the two that are currently in there?

Sorry for the huge post, but i saw this and could not believe it, In their test they got the lowest temps with just rear fans and a blower. http://icrontic.com/articles/pc_airflow_heat_cooling_gu...
July 21, 2007 3:48:37 AM

You need a new case!!! To answer your question I think it might be best to just make them all out and the air will find it's way in. Having a in and out in the back like that will only make the air circle around the back of the case and won't do anything for the HDD's, RAM, Video or anything else.

You can see where they planned for a front fan on the bottom but then they put the USB/Firewire I/O right on top of it, Very poor design.

Even if you make the 2 back fans out the air will flow in the path of least resistance and just come through the holes down by the PCI slots there by cooling your video card but nothing else.

You could always buy a USB hub that fits in a floppy bay and remove the case USB and add a fan. You didn't show your side panel, you could put a hole in the side panel (if there isn't already one there) near the front and add a fan that way.

How many fan headers does your board have? You aren't limited to 4 fans, most molex fan connectors have male on one side and female on the other to allow you to daisy chain them.
July 21, 2007 2:21:48 PM

the mobo has a total of 3- its a intel d856perl and I only have one molex connect left lol. I don't want to buy a new case though lol. For a good one it will run me well over 150 in Canada. Then I will have to take apart my whole computer and put it back together, then do it all over again if I wish to use that case in a future build. for this one the top and side panels screw off so I can mod it fairly easily. Im not looking for the best cooling, I'm just hoping that with the new hsf and a few mids, that I can get my cpu idling below 40c and my 7600gs ideling below 55c.
July 21, 2007 3:35:51 PM

smokedyou911 said:
the mobo has a total of 3- its a intel d856perl and I only have one molex connect left lol. I don't want to buy a new case though lol. For a good one it will run me well over 150 in Canada. Then I will have to take apart my whole computer and put it back together, then do it all over again if I wish to use that case in a future build. for this one the top and side panels screw off so I can mod it fairly easily. Im not looking for the best cooling, I'm just hoping that with the new hsf and a few mids, that I can get my cpu idling below 40c and my 7600gs ideling below 55c.






I think your best bet would be to put a hole or two in the side near the front, buy a fan guard and install a fan or two to get some air flowing from front to back.

As I said before you are not limited by the one molex, you can daisy chain fans. If you run the two back on the molex then use the headers for a top and a couple of side fans your system will be significantly cooler.

What ever you do you should switch the back fans to both be blowing out. A setup like you have does nothing for cooling, in fact it hurts it, and even if you do nothing more than face them both out your temps should drop a little.

What HSF are you planning on buying? Keep in mind that if you buy a tower heat sink with the way your fans are setup the air will enter, bounce off the sink and exit out the back. Also the air entering through the back flowing against the flow of the heat sink fan will hinder it's performance.

Buy a Dremel and just start playing around, switch the rear fans to blow out and add some vent holes in the front. You could even buy a thermometer with a probe and tape it in a couple different spots in your case to find where the hot spots are then you will know where to concentrate your efforts.

July 21, 2007 4:44:29 PM

Thanks, I switched them to both exaust and it droped my temps a bit, 46c on processor, 35 on system zone 1 and 38 on system zone 2. I'm going to try cutting the top of that front hub to fit a fan in. The one thing I dont under stand is what did you meen by daisy chaining the fans? How could I run two of one molex? Then i would try to add the blower, side fan and front intake. the fron already has holes, It is just that I need to cut that hub to mout the intake fan. Thanks again Im going to the computer shop in a few hours to get that new hsf, i was origonally going to get a tuniq tower but I would need to take apart my computer, and it would barley fit. The store owner is a family friend and he said that he would pick out a good hsf fan for me. Thanks again to everyone who helped.
July 21, 2007 4:50:57 PM

smokedyou911 said:
The one thing I dont under stand is what did you meen by daisy chaining the fans? How could I run two of one molex?










Most fan molex connectors have a female on one side and a male connector on the other to allow you to plug them in series with each other. As long as your not using fans that draw a lot of current (most don't) you should be fine running a couple fans off the same molex.


Fan molex connector

Female connector

Male connector
July 21, 2007 11:19:49 PM

weird, None of mine have that :( . I got a cooler master one, Its a bit bigger then the stock intel one, silent and has an 80mm fan on it. IT droped the temps down to 40 idle and below 60 when at full load. For $18 I couldn't ask for more. thanks for all the help again. Ill see about the case mods, I orobbaly can't this weekend and I leave for bc tuesday for two weeks :) .
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