Case airflow setup help. Which is best?

pepsi_max2k · Post by **pepsi_max2k** » Wed Jan 28, 2009 10:50 am

Hey all, I'm about to set up a system in an Antec 900 and was wondering if you could all help me with some air-flow based choices.

There's a pic below but I'll try to explain first:

I have a sapphire 3850 blue pcb (pic) with the fan on the left, taking air from the rear bottom of the case and blowing it out towards thefront and left hand side (red arrows in the middle).

PSU so far has two 80mms, both blowing air from front to rear (could be changed I spose). It's also heavily heatsinked up so will leak some heat from the top.

CPU fan is a 90mm, only mountable *either* on the top or bottom of the heatsink, blowing air either towards the top of the case or the bottom (across the northbridge / back of gpu, where it'll no doubt head towards the left and front with the gpu air).

Then I have case fans, two 120mm tri-cools at front, can be placed anywhere along the front but I think it's best to have one down feeding the psu, and one up feeding the cpu.

200mm on top, and 120mm in rear, and a possible 120mm in the left side, all mountable either way.

My main idea is I can either do things a standard way, front in, psu/rear (& maybe the top) out, not bother with the side, have the cpu blow up and make do with the gpu's air likely feeding the cpu.

But I was thinking...

Have the top blow in, have the cpu blow down from the top (with top air feeding), rear out, and the side blowing out.

That way the cool air from the top feeds the cpu and exits via the rear. The cpu cools the NB and gpu too. and the gpu air gets sucked out the left side as it exits the card's heatsink. I could probably get rid of the top front fan too, and let the bottom just cool the HD's and psu. Looks a bit like:

Could always reverse the rear fan too and suck it out the front. Or have the side blow in. Preferably I'd rather use as few fans as possible anyway. Anyone have suggestions?

Shaman · Post by **Shaman** » Wed Jan 28, 2009 1:21 pm

You want to use as few fans as possible, so how about just using the top and rear fans blowing out in a negative pressure setup?

I can assure you an intake fan blowing fresh air at the PSU is not needed. And what PSU is it that with two 80mm fans?

pepsi_max2k · Post by **pepsi_max2k** » Wed Jan 28, 2009 1:41 pm

A tagan 480-u01; I believe it shuts off one of them at low loads, not sure what'll happen in my new pc but anyway... The bottom intake fan is mainly intended to cool the HDs and bottom of the case (gpu, southbridge, tv card, etc) not just the psu.

Just top and rear? Sounds like it'd get a bit hot... Easy to try though I guess.

jhhoffma · Post by **jhhoffma** » Wed Jan 28, 2009 10:01 pm

Take a look at my post on the Antec 300. The airflow pattern is the same basic design.

Running intake fans should not be necessary at all, but blocking off the side panel is a good idea. Removing PCI slot cover(s) underneath your GPU can also help airflow around it.

pepsi_max2k · Post by **pepsi_max2k** » Thu Jan 29, 2009 2:24 am

Just got my mobo today, so as long as everything works I'll be setting up over the next few days. As suggested I'll start with top and back out, but also keep the two fronts in (and test temps with/without later). I've also stuck some dust filter foam on the side; doesn't block it off completely but keeps my options open

One thing I'm still wondering about is the HSF placement. Assuming I stay with the above (top and back out), would it be better to have the fan underneathe blowing up (feeding the hot air from the NB and GPU in to the HS) or blowing down (cooling the NB and GPU but going against the airflow from the top fan)?

TBH I didn't even want to use the top fan much, just intake top front and out top rear, passing straight over the HSF. I kinda only considered the top as an intake. But I guess we'll see what happens

test42 · Post by **test42** » Mon Mar 16, 2009 5:28 pm

I am new to SPCR and just ran across your thread. I wondered if you set up your system like your sketch and what the results have been.

One of my systems is in an Antec 900 and I have been thinking about using the top fan opening as an intake port (similar to your sketch except taking out the top fan completely), but am not ready to make all of the changes unless I have some degree of confidence that there will be an improvement. The system does fairly well, at 9C idle/25C load (over ambient) with an over clocked Opteron 185 processor and over clocked 8800GTS video. This is currently using a front-to-back air flow and all fans set on low except for the rear exhaust fan on medium. I would like to get rid of some of the fans and was thinking about taking out the top fan, rotating the processor heat sink for a top to bottom air flow and building a duct so that the 120mm heat sink fan pulls outside air directly in from top opening. I would keep the rear exhaust fan, but eliminate one of the front intake fans.

The idea came from observations of two other systems I have had over the last 4 years where there was a ducted path from the outside directly to the processor heat sink. Both of these systems ran very cool and were surprisingly quite. One system was built using an Antec 640B that included an adjustable side intake duct. I positioned this right on top of a Scythe Samurai top down design cooler which had a 92mm fan that mated up perfectly with the side intake duct. Using only a single rear 120mm exhaust fan (in addition to the heat sink fan), it was running an over clocked Pentium 4 at 3.7 GHz with a 6800 Ultra video card and had idle temperatures that were 7C over ambient (idle at 27C and load temperature of 43C).
I also have a Dell Optiplex 745 that is a BTX form factor with a 120mm intake fan pushing air through the duct to the passive heat sink. This system idled at 38c until I took a slow 92mm fan from a scrap Dell and fastened it to the back as an exhaust fan. This dropped the temperatures to 30C idle/47C load while system is virtually inaudible.

Any suggestions based on your experience would be welcome.

pepsi_max2k · Post by **pepsi_max2k** » Tue Mar 17, 2009 12:58 am

Hey, unfortunately I've not tried anything strange yet. The current setup is as the top sketch - two fronts in on low (one on bottom 3 slots, one is one slot down from the top), top fan and rear fan out on low. there's also a foam filter over the side mount allowing some air in, and a 92mm hsf fan blowing from bottom to top.

temps are currently ~27 idle, ~40 load (probably similar to yours in terms of ambient) on a 5200+ with a xigmatek hdt-s963.

one of the reasons I haven't inverted the top fan is dust - I can't really filter a hole that size, but I have just stuck it under a desk so it could be ok now. I've no idea what the temps would be like if I did though, can't really be bothered to try unless someone can confirm it's cooler that way.

Plekto · Post by **Plekto** » Wed Mar 18, 2009 3:54 pm

I'd be tempted to reverse the exhaust fans and have it all blowing inward at lower RPMs. The 200mm on top would of course be the only one venting outward.