120 mm fan on bottom of case? i need help figuring out airflow paths

[kgraeme]

Not to seem rude, but are you absolutely sure that your PSU is an intake? The ATX standard requires the PSU fan to exhaust. If it's the 400W Antec you mention in your system description, then I'm fairly certain that it blows out.

Just checking.

You might also want to read the AMD System Cooling/Airflow Guidelines for Cases and Power Supplies.

 

[Fizz]

<< Lithium381, I made my duct fron some PVC pipe fittings I got from the plumbing hardware store.
I found a fitting with a 75mm ID. with a collar that I modified to screw onto the fan through the normal mounting holes, and then another fitting to extend that to the HSF.
It cost about four Aussie dollars.
I assume you have the same sort of stuff where you live. >>





Something like this?...= my case and ducting

 

[Mikendi]

Nice work Fizz &quot;See what you started Glow!?!?!?&quot;

 

[sanaka]

With some excess intake CFM's, you know that your total exhaust CFM will in fact move through the case.

If all your intake is tightly installed and filtered, then the positive case pressure eliminates the possibility of dust accumulating inside (I credit Scott Mueller for this concept).

With all the turbulence and dynamics involved, perfect CFM balance is very improbable. So intuitively I'd rather be forcing some extra cool air in than trying to drag extra hot air out.

 

[Mikendi]

Sanaka has a point in that the amount of structure in the case will impede an &quot;ideal&quot; air flow pattern. &quot;OK break out the slide rules&quot;

 

[Glow]

Yeah you are right actually, I figured out 2 days ago that the PSU fan was actually an exhaust, sorry i didnt post it cuz i didnt think it mattered too much. i was just confused the first time i checked it out because it felt like it kinda sucked, i think its just a fan with weird airflow, like the center feels like it sucks and the edges feel like they blow....and this is what i hoped to start. This is what the case cooling forum is for. I bought my dremel kit today, and now I just need to order some fanage and a window kit and im ready to accidentally cut myself in half. The sound sensitive lights at pcmods.com are scratching at me...too bad they would probably look better sitting on the desk than inside a computer. Its so hard to decide what you want when your modding your case Thanks everyone for responding.

 

[borumas]

I would go with the &quot;L setup&quot; and have 2 fans on the side, one blowing air onto the cpu and one blowing air over the video card. I have it setup that way and the other day my cpu fan stopped working and the side fan cooled the cpu so well that it only got up to 127F and stayed there. Normally my system runs at 88-95F motherboard temp and 105-115F cpu temp, my room is at the back of the house so it is usually hot like 87F.

 

[Lithium381]

&quot;Not to seem rude, but are you absolutely sure that your PSU is an intake? The ATX standard requires the PSU fan to exhaust. If it's the 400W Antec you mention in your system description, then I'm fairly certain that it blows out.&quot;


kgraeme - if i'm not mistaken, the ATX standard calls for the psu fan to intake, although most manufacturers ignore this to benifit the system, i haven't actually looked at the standards, but i've heard it a few times around....please put me in my place if i'm wrong!

 

[rogue1979]

Ever since summer has gotten here I have struggled with my temps. My cpu temp hits 50c under full load and my case hits 39c, ambient temps are usually 30-31c. I am still stable, but I don't like to run this hot. After taking the scientific approach and trying to figure out case air flow and positive pressure and all that stuff, I came up with a simple solution. Blast as much cold air as possible directly on the cpu and the hell with anything else. I have an 80mm fan in a side blowhole directly over the cpu, and another in the upper back of the case close to the cpu also, both blowing in on the heatsink. One 80mm blowhole on top sporting a 60mm YS-tech 26cfm exhausting air, the bottom front of the case has a second power supply exhausting also. Not very scientific, but damn it works! Cpu 43c under full load and case holding steady at 35c, good enough for me.

 

[mstudd]

Nice work Fizz, mine is similar, although the fan is in the side cover and the duct is solid.

 

[kgraeme]

<<
kgraeme - if i'm not mistaken, the ATX standard calls for the psu fan to intake, although most manufacturers ignore this to benifit the system, i haven't actually looked at the standards, but i've heard it a few times around....please put me in my place if i'm wrong! >>



Well crap. My memory is totally shot and it would seem that I'm living in a make-believe world. Here's what the ATX 2.03 spec says:



<< The preferred airflow solution is to pull air through the power supply from outside the chassis and direct it onto the processor. However other airflow solutions may be implemented to meet the specific cooling requirements. >>



However, according to the supplemental ATX / ATX12V Power Supply Design Guide v1.1:



<< Fan location/direction In general, exhausting air from the system chassis enclosure via a power supply fan at the rear panel is the preferred, most common, and most widely applicable system-level airflow solution. >>




So I was only slightly off my rocker. The ATX spec doesn't require one or the other. Intel obviously thought blowing on the CPU was better, but due to industry input, the supplemental PSU docs reflect what the preferred approach is in the marketplace.

I know this is all just slightly off topic, but if anyone is interested, here are the official specs.

 

[Glow]

So, I bought my dremel and now I am ordering my case fans. I want to have more intake than exhaust like you guys said, but how much do you think is ok? 3 fans I have right now that im going to keep im not exactly sure of the cfm, so its hard to figure out. When you talk about having a little more intake, is that like 5 cfm more or 15 cfm more intake?

 

[Lithium381]

geez rouge, that's some pretty high case temps...almost 10 above ambient?!?! i'd get some serious airflow in there, yeah, i'm going to duct to my CPU soon...blow &quot;colder&quot; non-preheated case air directly on my cpu from the outside of my case...i'd go with an excess of 10-15 if anything, 5 cfm isn't really much, although most cases are barely 2 ft^3 anyways...send pictures when you're done glow


FIZZ - Nice work, although i've seen that posted about 50 different times...heh, you take every chance you can to gloat and show of your craftsmanship.....i would do if mine turned out like that,

 

[sanaka]

Intel obviously thought blowing on the CPU was better...

They were probably thinking in terms of the PSU being a (or the) primary air source.

 

[kgraeme]

[qThey were probably thinking in terms of the PSU being a (or the) primary air source.[/i] >>



Yeah, processors have heated up a bit since the ATX design came out. Here's something else that's interesting, according to AMD's system cooling guidelines:

&quot;A front cooling fan does not seem to be essential. In fact, in some extreme situations, testing showed these
fans to be recirculating hot air rather than introducing cool air.&quot;

 

[Lithium381]

&quot;A front cooling fan does not seem to be essential. In fact, in some extreme situations, testing showed these
fans to be recirculating hot air rather than introducing cool air.&quot;


what are they talking about!??! i've read that before, when i was browsing their cooling site...
i geuss this would apply in some cases that didn't have a clear air path to the outside, that just sucked from underneith the front cover(bezel?) of the system......i think mine helps ALOT, just a 43cfm 80mm on the front, but that's quite a bit of new air to heat up if you ask me, besides, i've got a 120 on the side blowing 125cfm....muahahaha that's more than enough cool air for my system to chew on!

 

[mstudd]

I disconnected my front fan one day to see what would happen.
My Mobo temp crept up slowly from 21deC to 30deg, at which stage I reconnected it and the temp came back down to 21deg.
It must do something.

 

[rogue1979]

Lithium381, yeah that was real hot, but now it is about 4-5c warmer in the case. I have two power supplies in there and an overclocked V5 with two .25 micron VSA-100's dumping alot of heat in there. I have had up to 4 fans in there, about the only thing that cools it down to ambient temp is case off with a small house fan. But no case cover with a delta is unbearable. I can get about the same results with the YS-tech 26cfm on the cpu and no case cover with little noise, but then my kids are playing on and around the computer and that makes me nervous. So case cover back on just to be safe, heat under control now.

 

[iLoveDivX]

It'd be really helpful if you guys can take picture of your comp like Fizz. Also tell us what your comp specs are and its temperature; that way we all know how efficient your cooling systems are.