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Fan Placement Theory


Greg7579

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I'm about to build my first system using a Corsair 780T case and 115 CPU Cooler. It is obvious that the radiator goes on the top of the case, but fan placement options are immense. I read on some studies from a few years ago that it is counterintuitive. Blow hot air into the case from outside with pull fans mounted under the radiator inside the case pulling air from outside through the hot radiator. That cools the radiator better and thus the CPU. Others say to set it up as an exhaust to keep the case cooler.

 

The theory also states that setting this up as an intake also pressurizes the case better for anti-dust. The air in the case compresses because of all the intakes and pushes air out all the little nooks and cracks, allowing no incoming air and dust unless through the intake fans which are filtered.

 

Furthermore, some say to use four fans for push pull, mounting two fans on top of the 780T case in the allotted slots to push air in through the radiator and use the two stock fans underneath the radiator inside the case to pull. However, one article said that 4 fans is not necessary. The two stock fans will suffice for pulling air into the case through the radiator. No fans needed on top to push air in. Four is overkill, they say.

 

Many on this forum say that the fans on the 115 should be immediately replaced because they are noisy. But Corsair claims the 115 improves the 110 with better fans. Amazing that one would immediately have to replace both stock Corsair fans on the 115. Is that true? Should I order the 115 plus two fans to replace the stock fans and an additional two fans for the top for pushing air into the case?

 

Imagine how confusing this is to a newbie like me that is about to spend 3500 bucks on a build.

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  1. What is a 115 and 110? Use the correct designations so we don't have to guess.
  2. The CoolIT H110i is a far better cooler than the Asetek H115i, see http://forum.corsair.com/forums/showthread.php?p=795986.
  3. I general specify URLs when quoting others and "some studies". Quoting urban myths does not help.
  4. What will work best for a system often depends on the GPUs so you should specify these.
  5. Better still add the intended PC specs to your profile.
  6. Imagine how hard it is to sensibly comment without this information.

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Thanks Red-Ray for your prompt response. Glad you are willing to help a newbie. I will update my profile as I just opened this account. However, I haven't pulled the trigger on ordering the parts list yet. I'm trying to prepare myself for the build and am confused on fan placement for the cooler. The parts:

-- Corsair H115i

-- Intel i7 6700K

-- Corsair 780T case

-- Samsung 950 PRO 512GB M.2-2280 SSD

-- WD Black 5TB HDD

-- MSI GeForce GTX 1080 8GB Founders Edition GPU (maybe another 1080 as they emerge)

-- Corsair 1000W 80+ Platinum Certified Fully-Modular ATX PSU

-- Gigabyte GA-Z170X-Gaming 7 ATX LGA1151 Motherboard

 

As far as all those links to the urban myths, I can't help you there. I was just summarizing what I read. I have no clue if it is correct. I was not espousing a theory. I was establishing a base-line to convey a start point. I was seeking opinion if on this build as to whether or not I should put the radiator at the top of the case with intake fans (either 4 or just the stock two) as I described.

The "115" I thought was a Corsair since they claim on their website it is their replacement for the "110." It is branded as Corsair and promoted as such. So you think I should instead order the Corsair H110i is better than the Corsair H115i? OK. I will change my order. Thanks. Any recommendation on setting this up as an intake vs exhaust? Thanks, Greg J in San Antonio Texas.

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Most people are going to be happiest using the traditional front intake and top/rear exhaust configurations in a 780T. It provides a clear air flow pattern and most manufacturers design their components with this in mind.

 

Radiator placement - Unless something forces you to do otherwise, you want to dump the radiator exhaust outside of the case. You haven't specified what CPU/Chipset you have in mind, but given your projected cost you might be looking at Haswell-E or Broadwell-E. Those CPUs are going to have a steady stream of heat to get rid of, even in low power states. In general, the exhaust coming out is going to be 5-10-15C over the case ambient temperature, depending upon load. If you turn that inward, you will raise the temperature of every internal component by the same amount. Will your motherboard wear itself out? Certainly not, but why run in a configuration that makes everything run 10C warmer than necessary? The theoretical gains associated with using "cold intake air" are usually lost once the system heats up. The rise in internal case temperature will also increase the temperature of the water in the cooling system, negating any potential gains. If you need to run the cooler as an intake, the front placement would be preferable to top, but not to to top exhaust for most users. One exception to this may be when you have multiple GPUs that create an intense amount of heat on their own and have a thermal effect on the radiator itself, in the top position. In those cases, moving the it to the front, further from the GPU waste heat stream, might have some benefit.

 

Fan Orientation - This is not as critical as placement, but does make a small difference. It is fan dependent, but most fans will offer a small 2-4C cooling advantage in the "push" position. For most people this is negligible unless you are right at your limit. What can be more important for day to day use is the resulting sound characteristics. Most fans will have a "buzzier" sound profile in the pull postion. The fan blades are closer to the radiator fins and this creates the effect. It can be countered by moving the fan further from the radiator with thin 2-7mm spacers or gaskets. Again, all of this is fan dependent and falls into the category of fine tuning. If you prefer the look of a smooth black radiator instead of the fans, by all means mount them above "pulling" air out. If it doesn't work out, it is easily changeable, as are the fans themselves. There is no reason to start considering alternative fans until you give the originals a whirl and have some basis for comparison. They are designed to provide maximum performance at high RPMs. It's not a zero noise system.

 

Push/Pull multiple fan combinations - I do not feel this is needed on a standard 27mm thick AIO radiator. These radiators do not offer enough resistance to cripple most fans and 4 fans are louder than 2. Where push/pull can be useful is if you are forced to use fans not optimized for a radiator with weak pressure capabilities (<1.0 mm H20) or if you had some sort of system requirement that mandated the absolute lowest fan speeds at all time. 4 fans at 500 rpm will move more air through a radiator than a single identical pair at the same speed. As fan speed increases, this advantage diminishes substantially. More importantly, no matter what CPU you choose, airflow across the radiator will not be the limiting factor in your cooling capabilities. CPU design, heat transmission through the materials, and voltage are going to be the prime obstacles.

 

Fan airflow volumes do not stack between pairs. Two 60 cfm fans in a sandwich do not move 120 cfm of air, only 60cfm. What is cumulative is the pressure between fans, usually referred to as static pressure. This specification gets twisted around to mean something is does not. Is the measure of how much negative pressure it takes to make a fan blade completely stop at a given RPM (usually at maximum speed). This makes the resulting number extremely RPM dependent. A tiny 20mm fan with a 5000 rpm limit will have a remarkable static pressure rating, but will only be able to move a paltry 7-10cfm. Airflow is what matters. There is no fan you can buy that won't be able to turn when faced with the resistance from the radiator.

 

Most people end up with the traditional set-ups because they are the most effective in most situations. At this point in your planning, I don't see any reason why this isn't the case for you and the choices we are discussing are not binding upon completion. The radiator can be moved, fans can be re-orientated and replaced if necessary, without massive cost or hassle.

 

EDIT: Oh, and please ignore and claims about dust management from positive vs negative pressure. There is an urban myth where we know the source and unfortunately is gets endlessly repeated. If a speck of dust comes near your intake fans, it will come in and probably stick the the first charged surface it finds. Pressure doesn't matter and air still enters your system. What people really mean to infer with this is if you put dust filters on all of your entry ways, but have a strong negative pressure environment, dust can bypass the filters by entering through the any of the mesh holes found in some cases. The thing is, if you are a dust freak 1) don't buy an open half mesh case; 2) if you do, putting duct tape across all that mesh or dust filtering every single opening is the only way to really clamp down on dust accumulation. Of course, most people are OK with taking 5 minutes to dust their system every 1-2 months, rather than spend $150 on extra filters and suffocate their case. Either way, pressure balance is not a dusting tool. The case fans primary function is to take the existing case air and exhaust it while simultaneously replacing it with cooler outside air. This works best when your intake and exhaust flow ratio is balanced or reasonably close. Going to extremes either way usually results in an extreme reaction somewhere else. This is not situation where we are trying eek every single ounce of performance out of your fans. You most certainly don't intend to run them at their maximum speed all the time, and until you reach that state, trying to compute the increased flow from a pressurized environment is silly. You can simply bump up your fan speed by 100 rpm rather than compromise your case air flow in some other way. Besides, without doing the actual PV=nRT calculations, an increase in Pressure has a predicable result on the Temperature or Volume of the air.

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Yes, the H110i :biggrin: and H115i :(: are much the same cooling wise and the H110i :biggrin: offers far more facilities in the firmware.

 

There are 4 different 110s, H110 :(: + H110iGTX :(: + H110iGT :biggrin: + H110i :biggrin:. Could Corsair have come up with more a confusing set of designations?

 

I suspected you would have GTX 1080s and given this you would be better off blowing hot air out of the top of the case as this would mean the air in the case used to cool the GTX 1080s will be far cooler. OK the CPU may 2/3°C warmer, but the GPUs will be rather more than 2/3°C cooler. Were it my system I would start off with this setup. I also prefer to mount the fans below the radiator.

 

I suspect others will also comment, if c-attack comments what he says is worth taking note of. Oh, I see he has just done so.

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Red Ray. Thanks! Beautifully said and I have been searching everywhere for a clear explanation like this. Corsair should use this as a basic explanation for builders. There does seem to be some argument about this. I have read other posts by other people on PC Part Picker who strenuously argue the opposite -- that it is better to blow hot air into the case by setting the radiator and fans up as intake. This baffled me and seemed completely counter-intuitive. I will do as you say. However, there are several high-end builders using this case that have set the radiator and fans up as top intake. Mostly they say this provides better case pressure for anti-dust, and that the CPU cools better with cold air hitting the radiator. But what you say makes by far the most sense to me. That is what I am going to do, and I am going to just use the stock fans (not an additional two on top). I will face the fans down into the case and they will blow up and out of the case through the radiator.

By the way -- look at my answer to you again and I listed the CPU. i7 6700K. I'm a photographer and not so much a gamer, but I plan to start gaming some. I know my rig is overkill, but I don't care. Thanks, Greg J

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I actually thought c-attack was your answer. It was extremely well stated. Very nice of you guys to help an amateur like me. Actually, that answer could help a lot of people. I appreciate both answers and will do as you both suggest. No push/pull, set it up as top exhaust using the 2 stock fans. Blow the hot air out of the case. I'm a little confused on the Corsair H115i vs one of the 110s. Corsair markets the new 115 as the latest and as an update to the 110 family. But if the H110i or H110iGT is better, I will of course get one of those. That is indeed confusing. Look at the Corsair promotional material and they advertise the H115i as the latest update with better fans and some improvements to the pump over the "older" 110 series. The prices are all almost the same for all of those, maybe 10 dollars apart, so it is confusing.
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I know my rig is overkill, but I don't care.

 

So are mine, but boys do like their toys :laughing:.

 

I have written software that controls both the H110i :biggrin: and H115i :(:. The facilities provided by the CoolIT H110i firmware are far more sophisticated than those offered by the Asetek H115i :(:. If you look at http://forum.corsair.com/forums/showthread.php?t=120092 you will see the CoolIT protocol offers a rich selection of facilities that AFAIK are not available in the Asetek protocol. The H115i :(: is not as poor as the H110iGTX :(:, but the H110i :biggrin: would be my choice ;):.

 

One hardware difference is that the CoolIT coolers report the pump speed to the CPU_FAN header so you can see the pump speed in the BIOS. Asetek coolers report a fan speed, so this is not possible and the only way to know the pump speed is to read it via USB using software once Windows is running.

 

As to why Corsair push the Asetek cooler I am at a loss. I suspect one of the reasons may be down to http://vr-zone.com/articles/the-battle-for-liquid-cooling-asetek-sues-coolit-is-corsair-in-danger/17078.html, http://www.gamersnexus.net/industry/1809-asetek-vs-coolit-liquid-cooling-market-shrinks or http://www.asetek.com/press-room/news/2015/asetek-announces-settlement-of-lawsuit-with-coolit-systems-inc/.

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The naming system is confusing enough in day to day conversation and the underlying details mysterious as well. You should consider the H110i and H115i to be contemporary products. The back story is a bit complicated, but there was a H110i GT (now just H110i) as the flagship cooler. Business reasons forced the creation of the H110i GTX (now H115i). They are manufactured by two different companies, but from a cooling standpoint they will be essentially the same and the physical specifications are near identical. Their differences are in the obvious cosmetic changes, but also the far less obvious firmware and software capabilities. This is something Ray has documented on several occasions and he may be able to provide additional insight. Whichever you choose, it will not affect the physical nature of the build, but more likely the flexibility of your control options.
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This is amazing and I have learned more from this thread than in a week of searching for answers about fan placement, radiator placement, push/pull vs. just the two stock fans, exhaust vs. intake set-ups, and dust management from positive and negative case pressure (case pressure NOT being a dust management tool). Amazing, and it goes against much that I have read on other threads on other portals.

 

Also amazing is that you pro's are saying that the new Corsair H115i is NOT as good as the H110i. This is because of the firmware differences (Asetek vs CoolIt). I of course do not understand this and had no idea what CoolIT was when you stated it as a difference. They are both Corsair coolers so this is baffling to me. But I am going with you guys. I just changed my order from the new Corsair H115i to the older Corsair H110i. I of course am wondering why Corsiar says what they say on their promotional material, which clearly indicates that the newer 115 is an update and thus the better and quieter cooler. Am not even going to ask why Corsair has all these different like models with various other companies behind the firmware. They are actually manufactured by different companies? Wow. Anyway -- doesn't matter. I'm getting the H110i (not the H115i) right?

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I'm getting the H110i (not the H115i) right?

 

That is what I would get.

 

I am none too surprised you found it hard to figure thing out. Looking at https://linustechtips.com/main/topic/537195-corsair-h110i-vs-h115i-vs-h110i-gt-vs-h110i-gtx-whats-the-difference/ I noticed:

 

That's exactly what they are, we've just updated the SKUs. They are technically the same in terms of performance. The only thing that's worth mentioning is that the V2 models all have had their blocks slightly tweaked to ensure compatibility with Skylake Mini-ITX boards that may have components right next to the socket.

 

This statement totally fails to mention that the H115i/H100iV2/H80iV2 can use any temperature source when the H110iGTX/H100iGTX/H80iGT can only use the coolant temperature to control the fan speeds. It took me a few months to figure this out as . Several of the guesses from other posters are also incorrect.

 

I asked about firmware changes and the reply I got is http://forum.corsair.com/forums/showthread.php?p=832507. This is also incorrect.

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Wow. I just went on PC Part Picker to change my order from the H115i to the H 110i (for all the reasons stated on the above posts in this thread), and it should have been cheaper. But it is not. The Corsair All-In-One Closed Loop Water CPU Coolers are as follows:

 

H110i - $109.99

H115i - $99.99

 

Note: This is a recent reversal. The 115 had been the most expensive for many weeks at and is supposed to be the new flagship with improvements over the 110i.

 

Here are some others:

 

H110iGTX - $99.99

H110 - $111.99

H100iGTX - $107.99

H100iV2 - $94.99

H100i - $119.89 (why is this the most expensive?)

H100 - no price listed

H105 - $93.99

 

Do I have a right to be confused?

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I'm not surprised. Maybe many have realised the H110i is the better cooler and they are concerned that they have lot's of H115i sitting on the shelf ;):.

 

The H100i is the only 240mm CoolIT cooler and are getting rather rare. It's also $99.99 via http://www.corsair.com/en-us/hydro-series-h100i-extreme-performance-liquid-cpu-cooler :confused:.

 

Still no PC specs and you did not list the DIMMs. Have you checked the QVL for the motherboard? See http://forum.corsair.com/forums/showthread.php?t=159930.

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I agonized over cases even more than about this fan placement theory. I decided on the big 780T after much advice, but yes, I will look into the 750D. I think I looked at all the Corsair cases as I will go with Corsair. I know this is not a case thread, but tell me why I should switch. If it sounds good I will. I bet the 780T is not even half full with this build.
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Snapper, I just answered to please tell me about the 750D Airflow, but it didn't post. So I just looked and it is the same interior as the 780T but a year newer and more traditional look. I'm getting it. Changing the part list now.....
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I have no idea what I'm doing so I doubt if it will. But I'm trying to prepare. My wife predicts total failure and a blown-up rig. Maybe I should just hire some kid to put it together for me. Or maybe just order a completed HP or Dell. But what is the fun in that? Besides, this rig would cost 5 grand if you bought it already assembled from one of the big makers, right? In fact, you could probably not buy one like this....
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There's a lot of satisfaction in building your own system (and proving your wife wrong). It's not really that hard, but prepare for the fact that something (probably the GPU) won't work first time, just take your time and be methodical. There are quite a few articles about building a PC. Oh yes, make sure that you plug in the 24 pin power lead AND the 4/6/8 pin cpu lead on the top left of the motherboard, before you install the water cooler.
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