Direction of Case Fans


  1. Posts : 151
    Windows 7 SP1 x64
       #1

    Direction of Case Fans


    I have an 80 mm fan on my heatsink that is directly below the 80 mm fan on the side of the case. The side fan is sending airflow out of the case. If I install a 120 mm fan in the rear of the case, should it draw air out of the case or into the case? Or should I reconfigure a different way?
      My Computer


  2. Posts : 12,012
    Windows 7 Home Premium SP1, 64-bit
       #2

    Rear fans are usually to exhaust air---pull it out. But feel free to experiment with various combinations and go with the one that has lowest temps. You might want to try the side fan as an intake rather than exhaust?
      My Computer


  3. Posts : 97
    Windows 7 Ultimate x64
       #3

    Also remember that cold air descends, warm air rises in a case, so your intake fans should be towards the bottom of the case, and your exhaust fans should be towards the top (as an example, my PSU has a fan, so the way I have it oriented in my LanBox Lite is that the exhaust is blown out the top of the case from the PSU).

    Also, make sure all of your fans are dust free as possible (use a can of compressed air to clean 'em off) and get a few spares as well (so you have extra when one does croak).
      My Computer


  4. Posts : 2,726
    Windows 7 Ultimate 64bit
       #4

    This image depicts what is commonly known as "positive air flow" (although some people may beg to differ on this)

      My Computer


  5. Posts : 151
    Windows 7 SP1 x64
    Thread Starter
       #5

    Thanks for the input. I will experiment. The diagram is very helpful.
      My Computer


  6. Posts : 7,878
    Windows 7 Ultimate x64
       #6

    That diagram is the way that I would do it.

    But with that said, I rarely have a case with fans in the front of the sides. And my temps are fine with very minor overclocking.
      My Computer


  7. Posts : 2,752
    Windows 7 Pro x64 (1), Win7 Pro X64 (2)
       #7

    dogbert2 said:
    Also, make sure all of your fans are dust free as possible
    Certainly a good recommendation.

    Another reminder is to clean the fine mesh "filter screen" in front of the front intake fan on better cases periodically. This is where dust from room air gets largely "filtered out" so that it doesn't make its way into the interior of the machine. That's great, of course, but it now just accumulates on this "filter screen" instead of getting inside the case. Still needs to be cleaned out, periodically.

    My AcoustiCase has a washable/removable "filter screen" protecting the intake fan for exactly this reason.


    use a can of compressed air to clean 'em off
    My own personal feeling about this is to NOT use this "blown air" approach to cleaning things like fans, motherboard, case interiors, etc. All you're going to do is BLOW the accumulated dust up into the air around it in a big cloud, and then the dust has to settle again somewhere anyway... either right back inside the case, or on your floor or room, or somewhere.

    I've always preferred to use a vacuum instead... i.e. the "sucked air" approach.

    I normally use the round upholstery brush (?) attachment, which not only is part of the vacuum's "sucking" action but you can use it to brush the surfaces you're trying to vacuum clean of dust and not do any harm (just be careful, of course). This works on the motherboard and case interior and interior surfaces, and also on the fans.

    For "tight squeezes" I may also use the drapery (?) attachment which is kind of a plastic cone with a narrow slit at the end. This can get between expansion cards, and other deep corners of the case, and suck up loose accumulated dust and debris. It has no ability to "brush" dust loose of course, but it's effective.

    Anyway, I prefer to vacuum the dust out of my case interior and fans, rather than to blow it all over the place with compressed air (or the vacuum cleaner hose plugged into the "BLOW" hole).


    One word of warning about using vacuum cleaners: they should never be powered up while too close to electronic devices that have magnetically-sensitive components in them. The magnetic field generated by the startup of the vacuum cleaner's motor can do significant harm to things like old CRT monitor screens (including old CRT TV's) which then need to be de-gaussed to eliminate the "rainbow flares" stemming from these magnetic fields. Fortunately, newer CRT TV's all included built-in de-gausser circuitry to do exactly this every time the set is powered on.

    But the magnetic field from the startup of the vacuum cleaner can also affect computers in their magnetically-sensitive components, such as the contents of the hard drives, etc. That's also why desktop speakers intended for computer use are (or should be) "magnetically shielded" so that you can put them right next to your computer and/or CRT monitor and not cause any magnetic impact from the magnets in the speaker enclosure.

    Maybe I'm over paranoid about this, but I always power on my vacuum at the other corner of the room, far away from my HDTV and computer.
      My Computer


  8. Posts : 8,398
    ultimate 64 sp1
       #8

    cool picture, PooMan

    as far as my case goes, i've only got a rear and top fan, both blowing out, and they do a good job even with relatively high (33%) cpu overclock combined with marathon gaming sessions.

    having front fans blowing in will also cool your hard drives nicely, if that's what you think you need...

    anyway, to answer the OP, it should work better if the rear fan exhausts air out.
      My Computer


  9. Posts : 97
    Windows 7 Ultimate x64
       #9

    Only one problem...vacuums generally put out a large amount of static charge while in use, which can play hell with electronics...If you can, take the machine outside of the home and blow out all the dust bunnies there, then bring the machine back inside and you'll be in good shape (static is a problem in environments where you have a relative humidity of less than 20%, as a rule).
      My Computer


  10. Posts : 1,653
    Windows 10 Pro. EFI boot partition, full EFI boot
       #10

    oneextraid said:
    I have an 80 mm fan on my heatsink that is directly below the 80 mm fan on the side of the case. The side fan is sending airflow out of the case. If I install a 120 mm fan in the rear of the case, should it draw air out of the case or into the case? Or should I reconfigure a different way?
    What do you have in the front of the case? Are there any other openings where air could be drawn in? If those are all you have, then I would either

    1. Blow into the case from the rear since you have no air input to the case OR
    2. blow the air out of the rear and turn the side fan around so it blows in.

    I would definitely choose #2 if the side fan were below the CPU fan, but it isn't. If you did #2 it would have the effect of the rear fan pulling the air from the side fan up , away from the CPU.

    If you had some kind of front or bottom air inlet, I would also choose #2 over #1
      My Computer


 

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