Case Fan Guide for Better Temperatures

Discussion in 'Die-hard Overclocking & Case Modifications' started by Psychlone, Sep 3, 2009.

  1. Psychlone

    Psychlone Ancient Guru

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    Case Fan Guide

    Here’s a little guide that I wrote up for everyone’s benefit.
    I’ve been in the position of answering questions about this for long enough that I thought a well-written guide would be more beneficial – this way, everyone can read the same information and get what they need rather than me regurgitating the same stuff over and over.

    Case cooling is just as imperative to cooling a system as is a good CPU heatsink/fan assembly (CPU HS/f assembly). Unfortunately, *most* people completely miss this aspect and blame their poor temperatures on their CPU’s heatsink, fan(s) or both, when in fact, a simple rearranging of their existing case fans, or replacing them with more efficient fans, can have a dramatic affect on overall system temps…sometimes 3*C, sometimes up to 10*C or more. And, it’s not just the CPU that will benefit from this; it’s the Northbridge, the MOSFET/choke area and the RAM that will reap the benefits as well.

    First of all, know that case manufacturers have a set place and direction for their included fans, and then they pay someone minimum wage to slap those fans where their bosses say they should go.
    Well, if you think about it, there are so many variables in system types, and differences in individual needs, that there’s just no way that the default placement and direction of airflow can be the most efficient for *every* rig out there.

    It's already a pretty well-known fact that a computer will have better temperatures inside a case...IF that case has sufficient airflow.
    We'll explore a couple simple options on how to maximize your case airflow and get greater efficiency out of *all* your case fans below:

    Fan Selection

    Selecting the right fan for your system is going to depend on many variables. We’ll touch on a few here, but your needs may go beyond what we’re going to cover.

    1) Cooling Efficiency
    > It’s obviously imperative to have good quality case fans that push a lot of air – within the noise parameters that you’re comfortable with.

    2) Noise
    >Noise usually is a limiting factor in the purchase of case fans. You most certainly want to purchase fans that have a noise rating somewhere near the limits of what makes you comfortable, but also push the most amount of air in that range.

    3) RPM & CFM
    > RPM (Revolutions Per Minute) is the amount of times the blades make a full rotation in a minute’s time. i.e. Fans that have an 800RPM rate will make 800 full revolutions in a minute. As a general rule with RPMs, the faster the blades rotate, the louder the fan (and the faster the blades rotate also equates to a higher CFM rating – but there are many, many efficient fans on the market that have very low RPM ratings that actually push a lot of air!!)
    CFM (Cubic Feet per Minute) is the amount of air the blades actually push – for this rating, the higher the better, but as a general rule, the higher the CFM rating, the louder the fan. (Again, not always – there are many fans that have high CFM ratings that function at low RPMs)

    4) Fan Size
    > Obviously, size matters. Some cases will only accept an 80mm diameter fan, where others may accept sizes up to 240mm and beyond.
    Your case and its fan mounting areas are what is going to determine what size fans you can purchase.
    As a general rule, larger fans don’t necessarily mean more air.

    Ok, so with that said and done, the main point of purchasing any case fans is first and foremost to cool your system efficiently and effectively.
    Make any fan purchases by doing your due diligence and researching several fans of the correct size for your case to determine which is going to have the best combination and balance of CFM and noise.

    Even though there are lots of reviews of this sort on the 'net, these are 2 of the ones that are easy to read and are pretty comprehensive.
    25 Case Fan shootout from IXBT
    Decent fan guide over at XS

    Any way you do it, research the fan you buy before just jumping into it blind – even Newegg has a ‘Specifications’ tab that will show you many variables that you’ll need to know. Also, going direct to the fan manufacturer’s website will have specific information that you can use to do a comparison for YOUR needs.

    Fan Placement

    Like I said above, there’s just no way that where and/or direction the manufacturer places their case fans is the most beneficial to *every* system.
    I’ve found through trial and error, that effective airflow is generated by creating a ‘vortex’ inside the case.

    Obviously, having your wires tied and out of the way is paramount to even having efficient airflow in the first place, so we’re not going to discuss proper wire-hiding techniques here, but know that it is *very* important to let the air have easy access to travel. Remember, air will always take the path of least resistance, so if you’ve got something solid (anything that has mass) in the way, it will impede airflow and decrease the efficiency of the fan that’s near it. (This includes fan covers, fan mounting baffles (before or after the fan) as well as any internal case obstructions)

    Nowthen, from my experience, every case is different, as is every scenario (meaning the desk and even the room that the case sits in) – so, there’s no single way that’s going to work for everyone, but we’ll cover a couple different ways here and it’s up to you to test what’s going to work for you.
    Testing fan placement and direction can be a very daunting and arduous task, especially when considering several fans at the same time.
    What helps to make this easier, is to remember the ‘vortex’ theory. If you can create a ‘vortex’ of cool air right where you need it the most, you’ll experience the largest decrease in temperatures in that general area, and as a rule of physics, that vortex can only turn in 2 directions inside a computer case – clockwise and counter-clockwise.
    Let’s look at a simple system setup the way that most manufacturers have their fans set up:
    [​IMG]


    Now, let’s look at the same system with the existing fans reversed:
    [​IMG]

    You can certainly visualize exactly what I'm talking about here - there's more cool air entering the rear of the case, right where all the components that need it most can get it!

    So, if you can imagine what the air looks like as it enters and exits your case, along with the CFM ratings of each of the fans, you can visualize just where the vortex is going to be.
    Sometimes it helps to imagine the air looking like smoke – you’re obviously not going to be able to see the air, so this little exercise should help you to visualize what’s going on.

    I’ve actually found (as in pic2 above), that reversing the airflow can be more beneficial to some systems than having the back of the case as exhaust (as most case manufacturers have their fans by default) – if you think about it, the CPU, MOSFET/chokes, and the NB are all toward the back of the case, so reversing that fan (or fans) to blow cool air IN across those components can really help in some situations (not all, and it’s going to be different for every system and place – i.e. if your case sits inside a computer desk ‘cubby’, then there may not be sufficient airflow BEHIND the case to allow for enough cool air to enter)

    When reversing the airflow (as in pic2), it’s important to deflect the hot air coming from the PSU and video card away from the new rear intake – otherwise, you’re sucking in the exhausted hot air from them. Simple cardboard cut and bent in the proper direction is sufficient, but you can easily make your own from plexiglass or even find cool looking vents/deflectors at an auto parts store or a craft store that will match your case better. (Obviously only important if the looks of the rear of the case bothers you or you take it to LAN parties, etc.)
    [​IMG][​IMG][​IMG]
    These 'vents' come in every shape and size you can imagine - I'm positive that everyone can find one they really like that's within their price range!



    You’ll find that by changing up the direction or placement of the existing fans, that you’ll receive better temperatures all around – and purchasing better fans that have a higher CFM rating along with this technique will surely decrease your temps.


    **Special thanks to Barwell1992 for creating the pictures for this guide

    Good luck!!
    Psychlone
     
    Last edited: Sep 3, 2009
  2. Tat3

    Tat3 Ancient Guru

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    Interesting, but isn't there one problem with reversed airflow ? GPU's dump out hot air and then case fan sucks that hot air back to case which is pushed down by those 3 fans on top of case back to GPU's.
     
  3. hallryu

    hallryu Don Altobello

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  4. Psychlone

    Psychlone Ancient Guru

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    You're right, Tat3, heat does indeed rise, but in an open room, if the hot air is deflected down and away from the rear intakes, then there's no hot air (or at least *very* little) that's actually re-entering the system.
    The same can be said about the front fans in some scenarios - they could certainly draw in warm air coming around the side from the back when the case is in a desk 'cubby'.

    To add to this, a side panel fan can both create worse temps or better temps depending on the direction of the vortex inside the case. If the vortex is near the CPU and is rotating clockwise, it makes more sense to have the side fan EXHAUSTING the hot air, since the fan is going to be spinning the same direction as the vortex inside.

    All in all, this is a general guide and by no means is the second layout going to work for every possible scenario - as stated before, there are too many variables to account for, but, there are many, many people that will benefit from rearranging the airflow in their case to some tweaked form from the default placement. I've personally seen HUGE decreases in temperatures by simply changing the direction of airflow - it just takes a little imagination and ingenuity.

    Thanks Hallryu ;)
    That link was quite informative - but I'm *really* surprised that they didn't do any testing at all with the airflow reversed. They say it's a 'Golden Rule' that the fans *have* to be pulling in from the front and exhausting out the rear - I say: WHO SAYS?
    They did show some incredible results with different fan placements in that limited arrangement though, and certainly more fans doesn't equate to better temperatures.


    Psychlone
     
    Last edited: Sep 3, 2009

  5. ascl

    ascl Active Member

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    Nice guide. I definitely agree that there are no hard and fast rules... and sometimes counter-intuitive setups work very well.

    One thing I'd add however. DO NOT BELIEVE MANUFACTURERS SPEC'S FOR FANS! Just because coolermaster (or whoever, not singling them out) claim 90 CFM at 19 db does not make it true!

    Yate Loon's specs are somewhat accurate, but they are about the only ones. You are much better off going off a decent review -- xs and spcr are the two I'd trust most.
     
  6. DementeD

    DementeD Master Guru

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    ..honestly man..id take this guide with a grain of salt..

    this may hold true on SOME cases..but fact of the matter is..not all cases are created equal..and id have to see some hard numbers over a variety of cases to believe it..
    not saying it wont help some but surely not all?..

    the diagram ur using has 5 intakes and 3 exhaust(case fan wise)..
    most cases dont have cooling of this degree..and what about inverted atx cases??..

    just saying its something to try i suppose but..doubtful that it will work in all or even most cases..


    EDIT:: i didnt read through everything so you might of already agreed or said what i did in a certain manner..

    anyway..the placement of fans in a case is usually done by the design of the case..atx btx inverted atx and what seems like the more logical air flow

    cases nowadays are so different that this cant be a yes or no arguement..

    psu's being on the floor of the case a lot more now then on the top..being able to flip the psu upside down even in the top of case or bottom..
    more n more you see fans on the roof of the cases/side panels etc..

    so i definitely agree that fiddling around with it may decrease temps and try to have things flowing in a general direction instead of fighting eachother.. in that sense its a good guide just gotta make sure people realize this wont work in every situation..
     
    Last edited: Sep 4, 2009
  7. barwell1992

    barwell1992 Ancient Guru

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    ^^ yeh the case was made as thoght it had been modded and i just added the arows on to show the air flow for psyclone if you look at the image the cpu block is actul a water block as i was going to make it in to a water cooled pc but lost intrest so just used this as a basis for what was needed :) and saved me the hours and hours of graft making another case up :p
     
  8. Psychlone

    Psychlone Ancient Guru

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    (Thanks again Barwell!)

    @ DementeD: You're absolutely right - there's no way that either configuration is going to be the best for every possible case or scenario, and like I stated, even the way the case is situated (being under a desk, crammed in a corner, stuffed in a desk cubby, etc.) can have a dramatic effect on the case's internal airflow.

    All in all, it's just logical to realize that there's absolutely NO way that the default placement of fans is going to be the best and most efficient for every possible computer out there - the variables are literally staggering!

    But, to sum it up, don't shy away from doing your own testing on your own rig - it's different than ANY other rig out there - it's components, it's fans, it's placement in the room it sits...there isn't another one just like it anywhere, and it's highly doubtful that the default placement of fans is already perfect for it.

    Psychlone
     
  9. DementeD

    DementeD Master Guru

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    ^ definitely agreed
     
  10. Darkiee

    Darkiee Master Guru

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    I think most can get the point from the 2 pics, as to me, i know how to get the air moving in the case, but those 2 pics are so simple to understand, even if the case aint like in the pic, all you need to, is to improvise abit to fit the arrows to your case.

    Very nice guide to start to work with case cooling.
     

  11. Psychlone

    Psychlone Ancient Guru

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    Thanks!
    I really needed help with the rendering - I *SUCK* at Sketchup and any other modeling program - it's not my forte...but what I really wanted to do is show 2 simplistic ways of changing up the airflow to show just how easy it can be.

    Now, with a system that has several fans like the 2 pics above, it gets increasingly difficult to determine which one should be facing which way - as with each fan, there are 2 possibilities in each location. My case has 7 Scythe Slipstream fans - MOST pulling air into the case - but my case is special, my circumstances are special, and I wouldn't think that a single other person out there would have the same exact setup or scenario as I do - EVERYONE'S case, contents, and circumstances are completely unique.

    I just helped out a Brother in a thread about case fan setups here: http://forums.guru3d.com/showthread.php?t=304054 that explains in detail how my system functions best - and don't think for a minute that I arrived at my case fan arrangement by accident...it was tested in *every* possible combination until I found the one that proved to be best for me.

    That being said, I need to reiterate once again that even though I've only outlined 2 scenarios in the guide above, it's up to the user to determine which way to set up their fans after doing their due diligence and research, and testing each configuration on their own personal setup - after all, all our systems are different, even if only in the way we set our cases on the floor or desk.

    Psychlone
     
  12. ascl

    ascl Active Member

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    (bold mine).

    This cannot be emphasised enough. Doing what is logical sometimes results in worse temps.

    I had a case where if I increased the speed of the bottom intake fan, temps got *worse*... and the case had negative pressure. So test test test!
     
  13. Cybermancer

    Cybermancer Don Quixote

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    Really nice guide, Psychlone. :thumbup:

    Maybe you could add a picture of a PC with good cable management, so that inexperienced users get a better idea what you are talking about?

    Also: what where the temperatures in the "test-PC-case" with the "traditional" airflow and then with the reversed one?

    Maybe you could also include at least some of the information that you're linking to in the two guides about fans?

    Otherwise I think this guide is a very good starting point for people to get an idea about how to configure their fans to get decent airflow in their case.

    Stickied. :nerd:

    @ all: Please feel free to share your experiences and suggestions regarding a good fan setup.
     
  14. Psychlone

    Psychlone Ancient Guru

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    ^ Thanks Cybermancer!

    I'm on the pics - I actually have quite a few, but none of them are to my liking (most that show the cable management show some dust...pics from months ago) so I'll be taking some new ones in the next little while.

    As for temps, I do have before (default case fan placement) and after (completely tweaked as current) temp comparison that I'll pull off my notes and post up...look for an update to the guide soon.

    Psychlone
     
  15. spas87

    spas87 Member

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    Yep but on that diagram the cold air comes from the top as well its just not natural because the hot air goes up and if you got the top and back pushing air out and front pushing air in is better I would think.
    And as low you intakes are the cooler air you would get into the case I mean just get a thermometer and measure the temperature at the floor at your room and after that measure the temperature higher in your room and you would see.

    Maybe swap of just intake from back and pushing air from the front will be better if you PC is under desk because there will be nothing on top of the case(e.g desk) and the hot air will go up but that will be hard because most of the top fans of the case are at the back like my 1200 and it will get cold air from the back and take it out from the top instantly without circulating trough the case cooling the components and then going out.

    Also most of the cases have filters only on the front and bottom fan holes if they have any.
     

  16. wlw_wl

    wlw_wl Master Guru

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    I had a problem with PC that had rear outtake fan, the system and CPU temps were getting to the point where it was shutting down. I tried several configurations such as rear+front, rear+side, rear+front+side, and adding more than just rear fan caused the temps to be the same or higher.
    Mystery remains.

    I'm planning on doing some extensive tests when I get new case, right now I have open case so there's no point in any tests.
     
  17. studabakahawk

    studabakahawk Master Guru

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    Master Psych
    Your wisdom ranges far and wide, much thanks for all your help O\C'ing My AMD cpus.
    I have a neat trick for venting GPU's using stock cooling shrouds. I 2 GTX 260 in SLI in a 3xSLI M\B (Asrock) there is almost no space between these 2 slot cards, the #1 card will be running hotter as its sucking heat from the back of the #2 slot card.
    I have a Hi speed fan blowing air directly into the shroud forcing air through to the back of the case. and have a DIY duct set up with an old CPU cooler sucking air out of the exhaust ports at rear of the case directly from the cards.
    this set up has dropped about 5-7 degrees of the Hot running card and lowered the temp of both by as many as 6-7 degrees as well.
    Cheers. to you Psych
     
  18. Psychlone

    Psychlone Ancient Guru

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    ^ Thanks Bro.
    Nice to see that people are thinking outside the norm and experimenting!

    The greatest airflow isn't always what the manufacturer intended in their 'general' design.

    Congratz on your temp drops Studabakahawk!

    Psychlone
     
  19. Technot

    Technot Member Guru

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    Hot air will always want to rise, go up.

    Intake low from the front and side and back.

    Exhaust from the top and top back.
     
  20. hallryu

    hallryu Don Altobello

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    It's not always that simple.

    The right airflow setup can overcome this easily. Plenty of folks sometimes get better temps reversing the airflow across their rigs. For the myriad of different cases and individual component setups its always a case of trying different configurations until you get the best results for you
     

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