water cooling: intake fan or exhaust fan?

Imacflier

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If the radiator is fed with a fan drawing air into the case, you will have the maximum cooling of the processor (maximum delta temp)....BUT you will dump the heat into the case raising the internal case temperature. Conventional wisdom is to take the hot air from the case to cool the cpu....this cannot cool the cpu as much.

SO: just what temperature for the ambient inside the case is TOO warm?
 
Solution


From what I see on most benchmarks for temperature, I'd assume that a normal ambient temperature outside the case is around 23 - 24C. Inside, if any of your components (mainly the motherboard, cpu, and gpu) spike above 70, something is wrong. Just use a tool like Speccy to track the temperatures all in one...

Andrew Buck

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I would use it as exhaust, and if you have terrible airflow, still use it as exhaust and try to get better airflow. Using it as intake will radiate the hot air into the case, making other components around it hot.
 

Shadowblade2652

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Now I am curious as I have an AIO installed with an intake radiator and I'm wondering if making it an exhaust will change my temps. Can you confirm this?
 

Andrew Buck

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Yes, it will. As long as temps in your case with it being exhaust are good, you will be fine. Intake will bring the heat into your case to the other components.
 

Shadowblade2652

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What kind of temperature differences are we talking? 5C? or 10C? If it's between 1 - 5C I'm not going to worry too much yet, but if it's 10C then there's an issue.
 


Why then are there cases from like corsair and cooler master where they advertise you can put a radiator in the front? Even though you can it will just pump hot air into the system.
 

Shadowblade2652

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Because you can have a large loop running through your system that requires you to put radiators all around in order to make it cool more effectively. If you have two SLI GPUs with water cooling and a CPU water cooling system, you're going to need lots of rads. that's why they have so many extra spaces.
 

Andrew Buck

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They are saying that you CAN, not that you should. It is a marketing tactic making you think you have more upgradability. My HAF 912 can have a dual-120mm rad in front, but it would hinder performance.
 

Imacflier

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Amazing! Thank you all for your answers.

Basically everyone agrees with my proposition: better CPU cooling with intake, but higher internal ambient. Still and all, no one has suggest just how hot an ambient is TOO HOT!

I am building a HAF XB case and want the ONLY exhaust to be a temp controlled 200mm fan at the top (I really, really, really want a positive pressure inside the case!)....so what internal temp is too much?
 

Andrew Buck

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35 C or more is bad. My old Rosewill case at full load with my H60 and my 8320 hit 40 C ambient in the case. WAY too hot.
 

Shadowblade2652

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From what I see on most benchmarks for temperature, I'd assume that a normal ambient temperature outside the case is around 23 - 24C. Inside, if any of your components (mainly the motherboard, cpu, and gpu) spike above 70, something is wrong. Just use a tool like Speccy to track the temperatures all in one place. It's good to know the relative temperatures of all the components.
 
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Imacflier

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Thank you, Shadowblade. It is always nice to be able to pick as the best answer what one had intended to do from the beginning. Once up and stable, I will take readings, then reverse the radiator fan, repeat the readings and report back.

Larry
 

Shadowblade2652

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I'm not the only one with the answer :) Everyone here who posted contributed something useful, however small or large. Honestly picking the best answer is really too discriminate and is really only applicable if someone summarizes everything that's been said in the thread.

TL;DR
Being humble.
All the rest of the answers are important too; you should make sure to look at them because all of them contain useful information that'll help you

Also,
What cooler do you have? Is it an AIO cooler (like a cooler master or corsair) or a custom loop that you created?
 

Andrew Buck

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Thank you for clearing that up for him. Regardless of it being custom loop or AiO, it is the same. It is usually best to use it as exhaust unless you have good cooling for the rest of your parts and you have bad airflow. You don't want the only intake to be intaking warm air. I recommend having a secondary intake that will take in cool air.
 

Andrew Buck

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Well, it depends. AiO cooler radiators are usually the same size if they are 120mm. My H105's rad is about the best 240mm rad you can get. The thickness can be any size for a rad on an AiO or custom loop. The bigger the radiator and the more thickness it has, the better cooling it has. It has more surface area to pass heat to the air.
 

Shadowblade2652

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Custom loops typically have longer rads though, don't they? That could limit where he could mount it. The back usually only has a 120/140mm fan mount, so mounting it on the back wouldn't work for him.
 

Andrew Buck

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Well, custom loops have the option of 480mm rads, which AiO coolers don't. It doesn't make much of a difference, though.
 

Shadowblade2652

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but for mounting it, it would make a difference as to how you could move air through the case, right? If you put it on the back, it would be different than putting it on the top in terms of airflow. That had to do with OP's question of positive air pressure through the case.
 

Andrew Buck

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Technically, but the pressure would be determined mostly by the amount of fans, their CFM, and their orientation.
 

Dblkk

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I have a 360mm rad intake in front, 240mm rad intake on top, and dual 140mm exhaust fans in back. My mobo temps 'might' be 1c higher than before the rads being used. My loop consists of 8350 at 5.2ghz, and dual 770's sli.

It doesn't make sense to cool the most important components (reason you bought a loop to begin with) with warm case air?

The most important part to remember, is to follow ideal case airflow, front intake, rear exhaust. Make the air move how it wants and help it along, vs forcing it to go where you want.
 

Imacflier

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As mentioned earlier, this is a HAF XB case. I am configuring it with a pair of 120mm intake fans in front, and a pair of 80mm intake fans in the rear lower section....then the 120 Seibel XL as intake....and a 200mm exhaust fan on top....all intake fans except the Seibel are under variable speed fan control and have each pair controlled by separate temperature sensors so there a lot of things to adjust. I believe the balance between ambient internal case temperature and the GPU temperature (currently a GTX 660 DirectCU II OC) is what will make the final decision on using the Seibel as intake or exhaust.

This thread and all its contributors has made it more likely for me to succeed than I had hoped when I initially posted!

Thanks again to all,
Larry
 

rhapdog

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I've got the HAF XB case now, and absolutely love it. I've also got the exact same setup as you have except I'm using my 120 Seidon XL as exhaust on the back, and I have the 200mm on top also as exhause. The 2 120mm fans on front intake, of course, and the dual 80mm exhaust on bottom rear for HDD cooling.

When I stand behind the case, I can feel the airflow up to 6 feet away, and it is cool air coming at me. When I plug in my portable USB 1TB HDD, I set it on top of my case so it can be cooled by the 200mm on top. When doing a large backup, it really helps in keeping my USB HDD temps down.

Temperatures inside my case stay within 1-8 degrees C of ambient room temperature at all times. It raises 8 degrees C above ambient when I'm gaming and the graphics card is pumping out heat, which you can feel from the top of the case. The heat from the graphics card in this particular case gets vented through the top before it can get around to the back of the card where the CPU or AIO cooler sits, so there is minimal heating up of the radiator from other components, and you still get virtually optimal cooling for the CPU.

Bottom line is this:
Using this case, I get the same temps for my CPU whether the AIO cooling is set to intake or exhaust, probably because of the 200mm top fan. However, when set to intake, my GPU temps go up 3-4 degrees C. Your mileage may vary depending on actual CPU and Graphics card setup. I'm just reporting what I get with the same case, fans, and cooler.