chassis fan blow in or out

This is probably a real dumb question but usually depend on the processor fan to keep things cool enough.

Have a chassis fan installed on a AMD Athlon 1800 with a biostar m7viq board. Currently, I have the fan blowing air out of the chassis. What direction should the fan be blowing air ???

Again probably a dumb question so forgive. Just never did much with chassis fan before this athlon.

 

No such thing as a dumb question.

Always try to bring air in from the front of the case, and try to exhaust it out the rear.
So, front in, rear out.

Dale

 

I guess thats the way I have it installed cuz the air is definitely blowing out from the inside of the case and actually its quite a cool air coming out.

Have done a bit of looking at articles on this subject and some mention blowing air directly on the board and processor to keep things even cooler than what the heatsink and fan already do. So what am I missing in this ???

Thank you.

 

Nothing. Air comming in at the front blows over the mobo and out the back. Cooler the better!

 

Thanks to all you. It is appreciated. This site is great can always get good information here.

 

...or side in, top out as for my case.

 

Yes, there are alot of possibilities when it comes to moving air in a case. As a matter of fact, I like Paul's scenario the best but never had a case with the right holes for it.

But yes, in general, air comes in in front and exits out in back. If you had a rear fan blowing in, you'd be working against your power supply fan - which blows out.

I have:

- one front intake fan
- a 5.25" triple bay fan blowing air in and over the top and bottom of my hard drive
- two rear fans on exhaust
- two (?) power supply fans on exhaust
- a PCI slot fan (not what you think) that simply blows air up directly onto my video card (prevents video card overheating)
- an adjustable 80mm fan attached to a Zalman arm hovering directly over my Thermalright SK-7 copper heatsink

But I'm also running a mobile XP 2600+ cpu at 2.4Ghz with some serious overvolting.

So remember the basic rule but don't let your imagination be stifled when it comes to fans!

The new ATX standard called BTX(???) will turn this air movement model on its head.

Gary

 

a slightly different approach to this...

...a couple of months ago I finally "bit the bullet" and completely reversed the airflow in a Compaq. That's right, in the back, through the PSU, and out through all the other orifices and apertures - particularly the slots where you put in floppy disks and CDs.

I was getting no end of trouble with dust. CD drive particularly, but floppy drive too. And with floppies the heads actually touch the disk, all you need is a speck of dust in the wrong place and the floppy is a-goner (combination of bad luck and the head positioning algorithm => track 0 tends to get hit worst)

CD drive would only stay working for ~ 1 week (carpetted environment, Compaq has powerful fan)

==

I thought back to the HP 'scopes I was using back in the 1980's - these had purpose made (quite large) filter boxes on their rear panels, through which air was drawn by a fairly powerful fan. Result: a slight excess pressure of clean air inside the case => they stay very clean inside.

I've fashioned an air filter box which is attached to the back of the case - still working on the best materials to use, currently using a perforated plastic substrate, and trying all sorts of things from thin sheet of cotton wool through stuff meant for central heating to even crepe bandages. All with pretty good results. Actually the perforated plastic sheet works quite well by itself as soon as it has built up a slight layer of dust... Important to use as large a surface area as poss, don't restrict the flow unneccessarily.

I've measured a temperature differential of only 4 Celsius between the air in and the air out of the PSU. So, my "base temperature" is 4C hotter.

But the processor heatsink no longer cakes with dust. Although I haven't measured the change in heatsink temperature directly, experience with heatsinks in general (over more years than I wish to discuss here!) leads to a guesstimate of 15C, perhaps even 20C (there's no processor fan just a finned heatsink in this creature)

So I'm "worse" 4C (ie hotter) but something like 15C "better" colder.

Of course, this requires opening the PSU unit - so don't do it unless you know how to do it safely. The High Voltage sticker on the PSU means what it says.

Having "caveatted" though, remounting the fan the other way round is straightforward (don't overtighten the screws) the worst I encountered was that in the original construction the wires going to the fan had been threaded through one of the holes which was now required for mounting - so had to be cut and re-routed with insulating sleeving etc.

2 months "down the line" and I have reason to open the box to put an ethernet card - bliss. Squeaky clean.

Not to say that this technique would be suitable in every case - but it certainly works for this Compaq.

When speaking of computers and temperatures people first consider the processor temperature - of course. But it's not the only sensitive zone. Often overlooked is what's happening inside the PSU itself. I've opened a well-used PSU (failed) to discover 7mm (no exaggeration) of caked dust buildup on the side of the parts facing the oncoming air.

Some parts in the PSU (notably the smoothing capacitors) are really stressed - right to the limit. Failure rate of these parts is a function of temperature - and when they go it can make serious problems for the motherboard - there's other ways to cook a CPU apart from letting it get too hot. Using this reversed airflow scheme, the whole of the chassis stays clean, PSU included...

==

now time to put head down and wait for the flak "incoming... "

best wishes, HJ.

 

FYI Gary,
This is my case, except mine is blue. The side fan (fancy LED one ) is the intake and throws it right at the processor fan to help further cool the CPU and M/B in general, with the top "blower" fan sucking warm air out. The box runs cool, but is a bit noisy. I have 7 fans all up in that case. These include the chipset, Graphics and 80mm fan in front of the hard drives.

http://www.cws.net.au/case/black.html