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Airflow check

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October 4, 2011 4:23:04 PM

Hey guys,

Following up on another thread from the graphics page, I found my old case didn't allow for enough airflow for my crossfire setup. As such, I'm upgrading my case to a COOLER MASTER HAF 912.

I'm new to the "airflow actually matters for this rig" game, so I wanted to run my plan by you all.

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1st: The case allows for either 3x + 3x 120mm fans or 3x + 2x 200mm fans. I was hoping I could get away with 6x 120mm.

2nd: I have 3x 133 CFM Fans coming, I'd planned to use all 3 as intake fans. Is the ok? Or is there a better arrangement.

3rd: The picture below shows my airflow plan. Look ok?
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The exhaust fan in the back can be replaced with a 200mm, and the two top exhaust fans can be replaced with 1x 200mm as well. [Edit - I was misinformed, the top exhaust 2x 120mm and/or front intake 2x 120mm can be swapped for 1x 200mm]




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a b B Homebuilt system
October 4, 2011 5:27:06 PM

3 - 120's in and 3 - 120's out? Looks like it will do the trick. You say you have 3 - 133cfm fans coming? Do you already have 3 133cfm fans making it 6 total all @ 133cfm's? Reason I'm asking is because the cfm's is what makes the difference. If you have 3 133 cfm's and 3 95 cfm's you will have a ~400 cfm in (133+133+133), and only 285 cfm's out (95+95+95). See the difference? That will make it harder to displace the heat because you're building positive pressure inside the case. Or I guess we could just turn them around and mix them up a bit. Point is, need to know what your current fans cfm ratings are. A lot of 120mm case fans are only 30 to 40 cfm.s so it's important. And you usually want a little more going out of the case then going in. Due to the fact that hot air expands and believe it or not it's actually harder to get hot air out of a case than it is to get cool air into a case. You can probably do it with the fans you have and the ones you have coming in. Just a matter of cfm placement and whether or not it's going to be enough.

There is a reason that the HAF- known for it's cooling abilities, has the 200mm fan setup. Then we will need to take into account which processor are you using in the case? And what cpu cooler are you running? If you're running an i7 9xxx series chip it's still gonna get hot in there. Whereas the 1155 only draws 95 watts compared to the 130. And you will want to make sure that all air passing through the cpu cooler gets tossed out. Position the cpu cooler so that the exhaust blows directly towards the back exhaust fan and not up and down. Also, what type of cooling is on the video cards? They're gonna draw a extra air in and blow more hot air into the case.

My second choice would be to put the 200mm exhaust on back and top. 120's for both fronts and the other 120 on the side sucking air in. Make sure you put the cpu cooler exhaust blowing toward the rear 200mm exhaust. The video cards will probably suck air into the case, designed to get the cooler air from outside, so that will add a little to the suction. I would do the calc's but I need to know what the cfm's are for the 200mm fans. I'd like to say 200 +200 = 400 out + 120 +120 +120+~ 40 for the 2 video cards = 400 in gives us a 0 balance but it don't work that way. Need the cfm's.

Think on that and get back with the specs and lets go from there.
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October 4, 2011 5:38:48 PM

Whew, thanks for the post!

#1. I'll have 3x120mm high CFMs + 2x120mm (that come with the case - unknown CFM) + 1x older 120mm (came with another coolermaster case, unknown CFM). I presently have no 200mm fans. Also of note, I was misinformed, the top exhaust 2x 120mm and/or front intake 2x 120mm can each be swapped for 1x 200mm. (according to Coolermaster).

Also of note, a coworker gifted me a Corsair Cooling H50 that I've not installed, I take it this would be worth doing now?

#2. Specs - I've got hot gear it would seem.

Case:
COOLER MASTER HAF 912 RC-912-KKN1 Black SECC/ ABS Plastic ATX Mid Tower Computer Case

Case Fans:
2x Cooler Master 120mm (coming with new case)
1x old Cooler Master 120mm fan
3x Scythe DFS123812-3000 "ULTRA KAZE" 120 x 38 mm Case Fan

Power Supply:
CORSAIR Enthusiast Series CMPSU-850TX 850W ATX12V v2.2 / EPS12V v2.91 SLI Certified CrossFire Ready 80 PLUS Certified Active PFC Power Supply

Motherboard:
ASUS Sabertooth x58 Motherboard

CPU:
Intel Core i7-950 Bloomfield @ 3.06GHz

CPU Cooler:
Stock

RAM:
12GB (6 x 2GB ) Kingston HyperX T1 Series 240-Pin DDR3 SDRAM DDR3 1600 (PC3 12800)

GPU:
XFX HD-587X-ZNFC Radeon HD 5870 1GB 256-bit DDR5 PCI Express 2.1 x16 HDCP Ready CrossFireX Support Video Card with Eyefinity

SAPPHIRE 100281-3SR Radeon HD 5870 (Cypress XT) 1GB 256-bit DDR5 PCI Express 2.0 x16 HDCP Ready CrossFireX Support Video Card w/ Eyefinity

HDD:
Intel X25-M 120GB 2.5" SATA II Internal Solid State Drive (SSD)

HITACHI Deskstar 7K3000 HDS723015BLA642 (0F12114) 1.5TB 7200 RPM 64MB Cache SATA 6.0Gb/s 3.5" Internal Hard Drive

Western Digital Caviar Blue WD5000AAJS 500GB 7200 RPM 8MB Cache SATA 3.0Gb/s 3.5" Hard Drive

CD/DVD:
HP DVD Writer 1270t ATA Device

Monitors:
Soyo Topaz S 24-inch Widescreen LCD Monitor

AG Neovo F-419 Black 19" 3ms (GTG) LCD Monitor 300 cd/m2 800:1
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October 4, 2011 5:52:31 PM

[Edited for accidental double-post]
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a c 84 B Homebuilt system
October 4, 2011 6:22:04 PM

I would think that two good 120mm intake fans would be sufficient. You will have a positive airflow case which supplies good cool air to the graphics cards.

Experiment, but I suspect that a side intake fan could disrupt the natural front to back airflow.
Or, with cf graphics, it mitht help. Try it both ways.

Let the psu get it's own air from under the case.

If you can, remove the upper drive cage to give you better airflow to the graphics cards.
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a b B Homebuilt system
October 4, 2011 7:37:17 PM

Since we don't really know all the cfm's we'll go the easy route. We know the "ULTRA KAZE" will do the 133 so I would take 2 of them and put them in the top to remove the heat rising. The top hdd cage is removable, which you might need to do just to get your video cards in there, and it looks like your new case is designed for the side fan to be used on the video cards so I would put the last KAZE there blowing on the cards. That leaves the 3 other fans. I would probably put two of them on the front of the case sucking in and the last one on the back blowing out. So we're back to your original 3 in and 3 out. Hey, just like you suggested in the first place!! I guess I just wasted a bunch of your time. I never could get enough cooling from just fans without ALOT of noise so I went the water cooling route. Cooler is better and all. When you get it all set up and running you can run OCCT and it will give you the temps of all your cpu cores and the temps of the video cards. Run it to check them and then try different combinations and see which gives you the best cooling.

Just curious but is your stock cpu cooler the copper with the 2 speed switch on it or is it the older model?
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October 4, 2011 7:41:24 PM

To my knowledge, it has 1 speed.

But that said, I did some more reading after seeing your post (learned a LOT, stuff I never even thought to look for). Assuming the old fans are uniform, or at least close, wouldn't that set up a negative pressure issue? Would it not be better to have positive pressure - something like below?

I also learned that the side vent should only have enough CFM to stir the air, too much makes it work against the GPU coolers. GOOD TO KNOW!

stars = high CFM fans


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October 4, 2011 8:06:35 PM

You will want to turn the kazes down a bit using mobo controls ( from BIOS), those can get pretty loud, to about 2000 rpm, that way you'd balance the pressure inside the case too.

IMO positive pressure is better cause it'll get less dust due to passively pushing dust particles out of the case through vent holes, also it's not like it matters that much, it'd be very hard to make any significant difference in pressure in such an open, vented space, the difference will be subtle at best.

While the H50 is not the best cooler around for it's price it will do a decent job at cooling your i7 and give you some OC headroom, ANYTHING is better than stock, also swap the stock corsair fan for a kaze one, the stock fan is kinda crappy and performance can be much improved, the kazes are designed for heatsink use because they have a high water pressure level so air moves through hetsink fins more easily, it'll drop a good 4-5c over the stock one
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a b B Homebuilt system
October 4, 2011 8:45:33 PM

I prefer the negative pressure theory. The faster the outside air moves into and out of the case the cooler the interior will be. It might suck more dust in (or you could clean the filters more often) but it keeps the hot air from just sitting around getting everything hotter as it slowly moves around the case. When I did my checks with different fans in different spots, some with greater inflow and some with greater outflow, I found that greater outflow produced cooler temps. Balanced is always best of course but good luck measuring for that. Like I mentioned earlier, when you get yours set up use the OCCT (FREE DOWNLOAD HERE) to test the different configs and see which works better in your environment.
As for the H50 - not a bad idea. The H70 is also workable and yes, either one I would change out the fan to one of the KAZE since it will also be the backpanel outflow fan. You can use the coolit or antec also. I have a coolit domino - yeah yeah I know junk junk junk, but mine works great for some reason - that works great even for small overclocks. I use it to test systems when I build em. But I like those as good options.
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a c 136 B Homebuilt system
October 4, 2011 8:55:13 PM

suteck said:
3 - 120's in and 3 - 120's out? Looks like it will do the trick. You say you have 3 - 133cfm fans coming? Do you already have 3 133cfm fans making it 6 total all @ 133cfm's? Reason I'm asking is because the cfm's is what makes the difference. If you have 3 133 cfm's and 3 95 cfm's you will have a ~400 cfm in (133+133+133), and only 285 cfm's out (95+95+95). See the difference? That will make it harder to displace the heat because you're building positive pressure inside the case. Or I guess we could just turn them around and mix them up a bit. Point is, need to know what your current fans cfm ratings are. A lot of 120mm case fans are only 30 to 40 cfm.s so it's important. And you usually want a little more going out of the case then going in. Due to the fact that hot air expands and believe it or not it's actually harder to get hot air out of a case than it is to get cool air into a case. You can probably do it with the fans you have and the ones you have coming in. Just a matter of cfm placement and whether or not it's going to be enough.

There is a reason that the HAF- known for it's cooling abilities, has the 200mm fan setup. Then we will need to take into account which processor are you using in the case? And what cpu cooler are you running? If you're running an i7 9xxx series chip it's still gonna get hot in there. Whereas the 1155 only draws 95 watts compared to the 130. And you will want to make sure that all air passing through the cpu cooler gets tossed out. Position the cpu cooler so that the exhaust blows directly towards the back exhaust fan and not up and down. Also, what type of cooling is on the video cards? They're gonna draw a extra air in and blow more hot air into the case.

My second choice would be to put the 200mm exhaust on back and top. 120's for both fronts and the other 120 on the side sucking air in. Make sure you put the cpu cooler exhaust blowing toward the rear 200mm exhaust. The video cards will probably suck air into the case, designed to get the cooler air from outside, so that will add a little to the suction. I would do the calc's but I need to know what the cfm's are for the 200mm fans. I'd like to say 200 +200 = 400 out + 120 +120 +120+~ 40 for the 2 video cards = 400 in gives us a 0 balance but it don't work that way. Need the cfm's.

Think on that and get back with the specs and lets go from there.



This is an awesome post even if you only consider its length . When you factor in the false assumptions and bad science it should qualify for an award .

Positive pressure would be a huge advantage to heat dissipation . Heat transfer is affected by density of the cooling medium ie air . Make the air more dense then heat transfers to it faster .
Many case makers are promoting products as " positive pressure" for this reason , though in practice the fan arrangement will make only tiny differences because the fans in and out will just simply adjust thier current draw to load they experience [ like all ungoverned ] electric motors
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October 4, 2011 11:33:17 PM

Let's try to keep things civil, this discussion has been really educational for me - even if some assumptions (especially my own) turn out to be false.

These discussions are why I love this forum.

suteck - I'm not planning on overclocking, but are you suggesting the use of OCCT to monitor MB/CPU temps? I have a few other programs that can do that too - what's the advantage to OCCT?

Outlander - so what you're saying is that as long as I have positive air pressure I should be ok regardless of fan arrangement? Even with a CF setup? This whole thing started b/c my cards were overheating and throttling.
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a b B Homebuilt system
October 5, 2011 12:07:50 AM

The OCCT will monitor both your video cards temps as you run your computer. There are probably other programs that do that also, That's just the one I use. And it will monitor a the cpu core temps too. Gets the readings off the mobo sensors. It will run tests on the cpu, gpu and psu. While you run the gpu in fullscreen mode it shows the current temps and FPS up in the top left corner. That usually tells you how it will look during intense use. Many different monitoring programs have different advantages and disadvantages, but the OCCT you can test and monitor to make adjustments on the fly to find the best one that works for you.

And don't worry too much about Outlander_04 post(s). A good ribbing never hurt. And I like awards - I've got a few awards here at tom's, and some hecklers. Part of the game, And besides. If you pull the side off your case while running you can usually watch all your temps drop a couple of degrees. That tells me that no pressure and free air flow does better than "positive pressure" that SOME, sorry, many, manufacturers are promoting about their cases. Besides, what good is having heat transfer faster if it's just going to sit inside the case?

Anyway, that's why I suggested running the OCCT to see temps and then changing the fan arrangement around to see if it makes a difference. You'll see for yourself what works and I can talk all the bull I want - didn't hurt anybody. I'm sure one will be better than the other so give it a try and see which one works in your environment.
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October 5, 2011 1:46:09 AM

temps will drop with the side of the case off only if the airflow inside is poor, the cards will benefit from active ventilation from the side fan
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a c 136 B Homebuilt system
October 5, 2011 4:13:06 AM

wiinippongamer said:
temps will drop with the side of the case off only if the airflow inside is poor, the cards will benefit from active ventilation from the side fan


Absolutely correct . If the temperature drops when the side panel is off there is something WRONG with the fan set up , or there are too few fans .

Suteck Im obviously just a grumpy old guy today , and for that I apologize , but the fan advice you have given is still completely wrong .

It will not matter whether you pump air in to the case or out of the case in a balanced or unbalanced fashion .
The total amount of air in the case remains unchanged . Its pressure may change very slightly . It its pressure is slightly higher then it will cool better [ assuming the speed remains the same ]. If the pressure in the case were slightly negative the reverse would be true .

In practice the airflow from a fan is not going to exactly match the quoted flow rate [ even if the manufacturer was exactly right ] . Fluids , especially the compressible variety , just dont behave that way , and double especially in a computer case that offers no impediment to air flow in or out regardless of the fans

The only rule anyone needs to know is " blow in from the front and bottom , and out at the top and back "
and even that has exceptions
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October 5, 2011 3:34:12 PM

Outlander_04 said:

The only rule anyone needs to know is " blow in from the front and bottom , and out at the top and back "
and even that has exceptions


What kind of exceptions?

I ask because if I mount my Corsair H50 CPU cooling rig, I'll have to draw air in through the rear exhaust (weird requirement, but a requirement nonetheless). That would leave the only exhaust as through the top. Is that still ok?
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October 5, 2011 5:38:51 PM

Corsair says so in the manual, but many people have reported good results using it as exhaust fan, using those kaze monsters it shouldn't be a problem, also the air inside your case wouldn't be so hot because the GPU exhaust the heat outside the case, so the only significant source of heat would be the cpu.

You could get away with top exhaust using 2 kaze's but I woulnd't recommend it as it disrupts the airflow cycly from the front.
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October 5, 2011 6:44:10 PM

Since I'm not overclocking the CPU, I think I'll stick with the stock air-cooling heatsink/fan. My first priority is keeping the crossfire GPUs cool enough whilst in the two x16 slots. Once I get the airflow sufficient for that I might take a look at installing the H50, but for now I think the rear intake required for the H50 would just confound the airflow issue or make it worse. I haven't seen a lot of convincing evidence that the H50 works better than stock when set up to exhaust without effect on GPU/overall case cooling.

Failing that, I'll fall back on your (wiinippongamer) suggestion to just switch the secondary card to the 4x slot further down.

Still, I hate having the H50 look so lonely in it's box there.......staring me down....... :kaola: 

Case should arrive tomorrow! I'll set everything up and let you know how it goes! If everything works I'll mark this thread down as SOLVED!

My current plan based on this thread and what appears to be, insofar as there is one, consensus on and around the interwebs, is to set up a (mildly) positive pressure situation. With all the ventilation on the HAF912, I'm hoping that will keep some of the dust out.

Two Kaze 133cfm fans on the front, with last Kaze as the rear top exhaust fan. Weaker fan on the side panel to avoid excessive disruption of the airflow, and avoid interference with the existing GPU fans. Same as the second pic I posted, reposted here. Remaining fan slots filled in with the weaker fans.

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a c 136 B Homebuilt system
October 5, 2011 7:18:11 PM

I would probably not use a fan on the side of the case .

Or at least try it without , establish where your temperatures are , and then fit it to see if it drops the temperature or just disrupts the airflow through the case
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October 5, 2011 10:54:21 PM

in this case I think it would help because of the little space there is between the cards, that's the reason the top one overheats so much, it has no fresh air to breathe, the side fan would force some fresh air between the two.
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October 7, 2011 1:16:46 PM

Good news everyone!

I've got the new case set up, and though I haven't fully stress tested it, preliminary results keep my top Crossfire GPU sitting at 80C. Airflow did it. Install taught me a few things though! Lessons which I'll relate here for posterity.


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1. Scythe Ultra Kaze fans are THICK! Too thick, in fact to install on the front of my case in the normal fashion. Fortunately, since I didn't need the extra HDD cage anyways, I could install at least one of them on the inside front. I didn't have an extra thin fan at home, so atm I only have the one Kaze in the front. I've got a spare smaller fan here at work that I'll take home and install later this weekend to restore my system to ~neutral/positive air balance. It means I have an extra Kaze, but extra materials never hurt, right? Except that one screw..... :kaola: 


2. You also can't install more than 1 38mm thick fan on the top exhaust on in the HAF 912. It conflicts with the rear exhaust fan, as you can see below. Fortunately I just installed it in the more front location, and it seems to be doing fine.


3. I bought a fan controller for the Ultra Kaze's and it was really worth it. Sunbeam Roebus. Those fans get LOUD at full speed, and I really don't need them when idle. I've nearly got enough airflow to leave them off at idle temps, and once I install the smaller front fan I should be fine. Crank 'em up under load, though, and they perform beautifully for cooling my GPU.

4. The side fan seems to really help my GPU temps, wiinippongamer appears to be right (but again, full stress test is yet to be completed). I did NOT put a Kaze there, but over the weekend I think I'll put the extra one in, wire it to my fan controller and test out the validity of my too much airflow = bad for GPU cooling assumption. That way I can also run a full suite of tests from full off to full on. Since I can already control the front and rear Kaze's, that should allow for a full suite of Positive/Negative fan flow testing too!

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So that's the end of the beginning for my airflow learning experience! My final case setup is below, though I'll be switching that middle fan around shortly so I can do some formal testing of airflow theories. Thanks so much to all of you!

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October 7, 2011 1:24:52 PM

I wish I could give the medal to everybody, since the full discussion really helped, but I'm going to have to give the medal to suteck's first post as it was what sent me down my own rabbit hole of research to find answers and learn a TON!

Sincere thanks to all!
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October 7, 2011 1:25:09 PM

Best answer selected by SheerLunacy.
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!