Fan blowing direction?

Discussion in 'Computer Cases, Power Supplies and Cooling' started by Stildawn, May 13, 2009.

  1. Stildawn

    Stildawn New Member

    Messages:
    1,734
    This may sound like a silly questions haha, but....

    With case fans how/is it possible to change direction it blows??

    Is it just the way you mount it to the case or cant the blades spin both counter/clockwise?

    Cheers
     
  2. Euklid

    Euklid Member

    Messages:
    620
    Most fans can only be installed correctly facing one direction. And most will not allow you to change the direction.

    With that said, I'm sure there's nothing wrong with having all the fans blowing out :D Maybe the power supply blows in?
     
  3. bomberboysk

    bomberboysk Active Member

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    13,257
    Unscrew it and screw it back in facing the opposite direction;)
     
  4. Stildawn

    Stildawn New Member

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    1,734
    Yeah I thought you'd just spin it around.

    Now for another question regarding fan lay out.

    Ive got a CM690 case.... which as we all know comes with a front fan, a back fan and a side fan.

    Tell me what directions are the existing fans blowing (in/out etc)

    I also have a further 2 140mm fans to install in on the top and a 80mm fan for behind the mobo, which direction should I have these extra fans?

    Cheers
     
  5. epidemik

    epidemik Active Member

    Messages:
    4,100
    Front should be sucking in and drawing cool air across the motherboard.
    Fan in the rear should be blowing air out (because the air is heated as it goes across the mother board)

    I believe top fans should be blowing out of the case as well.

    Im not sure about behind the mobo.

    I'm not a cooling guru but i think your supposed to have abalance (to some degree) of in and out to achieve maximum cooling so you may want to consider putting more fans in the front (since you have 2 140s and a 120 going out and only 1 120 going in). But im not 100% sure on this...
     
  6. Stildawn

    Stildawn New Member

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    1,734
    I assume the stock side fan (120mm) is also blowing in. Theres no room for another front fan.
     
  7. epidemik

    epidemik Active Member

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    4,100
    My bad, I was thinking antec (currently trying to decide between a300 and CM590 ;) and everythings getting mixed up in my mind )

    So just disregard the last part of that post.
     
  8. viper110110

    viper110110 New Member

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    236
    to tell which way a fan is blowing, you can take a tissue and hold it near the fan.
     
  9. Vipernitrox

    Vipernitrox New Member

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    1,319
    the fan has somewhat of a grill on 1 side. That's the direction it's blowing.
     
  10. bomberboysk

    bomberboysk Active Member

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    13,257
    Not really a grille, but the side that holds the motor to the fan is the direction it blows. As far as fans, negative pressure is better than positive, more fans blowing out is better than having more fans blowing in, due to the fact that through all the nooks and crannies and vents in your case it will also suck in air. usually i would do Front intake, side intake, top exhaust, rear exhaust.
     
  11. Vipernitrox

    Vipernitrox New Member

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    1,319
    yea that's what i ment :p

    best way to test your airflow is to light a smoke in front of your intake fans and the faster it gets out the back the better it is :p
     
  12. Stildawn

    Stildawn New Member

    Messages:
    1,734
    Haha got to give that a try...

    Yeah ok so Ill put the top and back as exhust, what bout the little fan behind the mobo?
     
  13. Vipernitrox

    Vipernitrox New Member

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    1,319
    well you've got 2 x 120mm intake and 1 x 120mm + 2 x 140 mm + psu outtake
    simple math. i'd put the 80mm intake.
     
  14. Okedokey

    Okedokey Well-Known Member

    Messages:
    9,506
    lol, if only

    W=(1/2)mv^2 is the work produced by the fan. It makes sense that the mass of the air moved by the fan times the velocity of that air equals the work of the fan. It is simply the amount of air moved multiplied by how fast it is moved.

    P=((1/2)(mv^2))/t is the power consumed by the fan during operation. Basically the amount of work done by the fan on the air divided by the amount of time the fan has done the work will equal the amount of power the fan consumes. This also implies that you can find how much work the fan produces if you multiply the power it consumes by how long it consumes.

    A=D^2/1974 is simply the outlet area of the fan set equal to the diameter of the fan blade squared divided by 1974. This equation by itself is not important but it helps you find terminal velocity which is important.

    V=.932(cfm/D^2) is the terminal velocity equation. Terminal velocity being when the fan has reached its max push/pull at which the air is no longer accelerating. This equation multiplied by 1/2 of 1 cfm equals the power consumed by the fan. Think of this as the terminal velocity (max output of the fan) has a direct relation to how much power is consumed by the fan.

    Reworking the last equation gives you cfm. I don’t know if that helped you any but hopefully it makes a little more sense now.

    Simple mathematics...

    Anyway, to answer the original question, swap the wires, its dc so if you swap the polarity, it will spin the other way.
     
    Last edited: May 17, 2009
  15. Stildawn

    Stildawn New Member

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    1,734
    Lol thanks for that, are they ment to spin the other way?
     
  16. StrangleHold

    StrangleHold Moderator Staff Member

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    19,543
    It will work, but the fan blades are not curved to spin the other way, not as good air flow. If its not blowing the way you want, just flip the fan around.
     
  17. PohTayToez

    PohTayToez Active Member

    Messages:
    4,873
    Since when? The only fans I've seen that couldn't be installed either way were crazy LED fans. All of the standard, cheap 80mm and 120mm fans I've owned could be easily installed either way.

    Also, having all of the pointing outward wouldn't be very good for air flow. Ideally, you'd want to try and form an air current going through your case, coming in at one end and being blown out the other.
     
  18. Mitch?

    Mitch? banned

    Messages:
    2,983
    The best setup would be:
    Rear Top Fan Out, Front Top Fan In (in front of CPU)
    Rear Fan Out
    Side Fan Out (videocard will need to be exhausted, trust me :p)
    PSU Fan Out
    Front Fan In
    Behind-Mobo Fan Out
    It'll create a pseudovacuum, but the negative pressure will be okay because it'll bring more hot air out than bringing in more room temp air, and will also make the 80mm mobo fan more effective.
     
  19. Stildawn

    Stildawn New Member

    Messages:
    1,734
    [​IMG]

    I hope this works lol first time using Photobucket.

    Ok the picture above is all my fans that I have.

    As you can see the CPU will go over that vent thing that is Fan 4. I dont know which way my Cooler Master V8 fan blows but the fan in that is mounted vertical in between the heatsinks.

    Im doing the build tomorrow so could you all please write up which direction each of the labeled fans should be haha.

    Cheers
     
    Last edited: May 18, 2009
  20. Vipernitrox

    Vipernitrox New Member

    Messages:
    1,319
    1,4,6: intake
    2,3,5: outtake
    psu is probably outtake to
     

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