Will 3 fans help or mess up air flow?

Discussion in 'Asus' started by Wilson, Dec 9, 2005.

  1. Wilson

    Wilson Guest

    I just put in a new and powerful video card. I already had 4 ide devices
    inside the comp, so it got hot anyway, though not to the point where it was
    dangerous. I have a fan on top of cpu chip and a front panel fan. If I put a
    new one on the back of the comp right above the pci slots, will that mess up
    air flow? Or will it help?
    Wilson, Dec 9, 2005
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  2. It should help a lot, if you've installed it to exhaust hot air out of your
    Peter van der Goes, Dec 9, 2005
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  3. Wilson

    Wilson Guest

    How do I do that? Turn the fan around and aim it toward the back of the comp
    instead of into the middle? There really is no outlet in the back to run air
    out the back.

    Also, couldn't I just leave one of the side panels off the comp if I wanted
    air to get out? My case has only a small hole showing on one side of the
    comp when I remove the side panel. So the noise is not bad at all.
    Wilson, Dec 9, 2005
  4. Wilson

    Paul Guest

    The side should be on the case, to "define" the airflow. If
    removing the side on the case, you would want a large room fan
    blowing on the computer, to simulate how effective it is to have
    the side on the case. If placing the side on the computer case
    makes the internal air hotter, there are not enough fans or
    intake/exhaust vent area to match them. (The original Antec
    Sonata doesn't have enough intake vents, for example.)

    Airflow goes in on one end of the computer, and out the other.
    Arrange the fans so they don't fight that relationship.

    The sum of the CFM ratings of the intake fans should match the
    sum of the CFM ratings of the exhaust fans. That will help a
    bit with dust.

    A classic configuration is like this. Air comes in at the front of the
    case, down low, and is exhausted from the back, a bit higher than the
    intake fan. The disadvantage of this configuration, is the two drives
    in the upper drive trays are not getting any airflow. And hard drives
    are the most sensitive element, from a reliability perspective, so
    do the best for them first.

    |\/ PSU Drive1 |
    |/\ Drive2 |
    | |
    |\/ Exhaust |
    |/\ fan |
    | Intake \/ |
    | fan /\ |
    (rear) (front)

    Depending on the computer case, there may be a lower drive bay. There
    may also be a vent on the front of the computer. Moving the hard drives
    only (don't have to do the CD or DVD) into the lower bay, as long as
    there is a vent and some incoming net airflow, is one improvement.

    |\/ PSU |
    |/\ |
    | |
    |\/ Exhaust |
    |/\ fan |
    | Drive1 \/ | <--- Intake vent is most important
    | Drive2 /\ | <--- Intake fan is optional
    |-------------------------| (Fan to the left of the drives
    (rear) (front) would be less effective.)

    With an older case, I have also done this. Placed a fan on the
    exterior of the computer case, to blow air directly onto the
    drives. The older case only has an upper drive bay. The older
    case also did not have an exhaust fan on the back, only the PSU.
    By removing a couple of PCI slot plates, it is possible to make an
    exhaust vent for the air to escape. The processor in this machine
    is low power, so it doesn't get too hot in any case. The cooling
    on this case, is actually pretty good, even though there is only
    one useful fan (the front one) at work.

    |\/ PSU Drive1 | \/ <--- External intake on custom
    |/\ Drive2 | /\ <--- metal frame
    | CDROM |
    | |
    <--- (removed |
    | PCI slot |
    <--- plates) |
    (rear) (front)

    Using a duct plus blowhole on the side of the computer case,
    raises the question of how it affects the rest of the airflow.
    If the blowhole is an intake port, the blowhole fan is fighting
    against the fan or passive vent that is cooling the hard drives.
    If the blowhole is an exhaust port, it may end up working against
    the CPU fan, which blows onto the motherboard. (Reversing the
    CPU fan is not always possible, or desirable.) I don't see an
    easy answer there, as to what to do. If a CPU ducting scheme had
    its own intake and exhaust holes, then it would not affect the
    rest of the airflow.

    "Go with the flow" is the rule of thumb :)

    Paul, Dec 9, 2005
  5. Wilson

    milleron Guest

    On Fri, 09 Dec 2005 16:50:09 GMT, (Paul) wrote:

    Intuitively, one would think that having positive or neutral pressure
    inside the case (by having more or bigger intake fans than exhaust
    fans) would lessen dust accumulation, and I think ones intuition would
    be correct. Studies and user experience, however, have shown that
    negative pressure (more exhaust than intake fans) gives the best
    cooling. Cases very commonly come from the factory with one more
    exhaust than intake fan. This is not an important point, though,
    unless the case is very hot and leading to actual problems with the
    computer, as in heavy overclocking situations. It's entirely possible
    to get adequate air flow and good cooling with neutral pressure inside
    the case. I always have negative pressure and simply plan to do a
    little housecleaning from time to time. With FILTERS on the intake
    fan(s), I've found dust to be no problem. (Of course, I don't live
    next to a dirt road in a house with open windows ;-) YMMV.)




    milleron, Dec 9, 2005
  6. Wilson

    Ed Guest

    On Fri, 09 Dec 2005 18:12:09 GMT, milleron

    Yep, I tried it the other way, my CPU went up 5C at idle, I didn't like
    that. I have air filter on my case so dust is really no problem.
    Ed, Dec 9, 2005
  7. If your case has no mounting point for an exhaust fan, and you have mounted
    a fan where there *should* be a mount point for an exhaust fan, the fan
    could make things worse.
    I want to be sure I have the picture correct here:
    You mounted a fan on the upper back wall of your case where there are no
    holes (in the case wall) for airflow?
    If that is correct, all the fan will do is recirculate already hot air.
    You might want to consider a new case which has fan mounts needed for proper
    air circulation for modern processors, or consider some Dremel mototool
    Peter van der Goes, Dec 9, 2005
  8. Wilson

    Bill Guest

    If there is no outlet in the back to exhaust air through, how are you
    going to install a fan?
    Can you produce a picture of this case from somewhere on the Internet,
    or give us the manufacturer and model number?

    If I were you, I'd seriously be thinking of a new case. This one
    doesn't sound like it's going to meet your cooling requirements.

    Bill, Dec 9, 2005
  9. What you might want to try is a slot fan. They fit in the back in one
    of the slot covers. I had one installed in the slot under my video card
    on my previous case. It lowered the temperature enough for the video
    card to quit overheating and causing games to crash. I could feel the
    heat of the air being exhausted by the fan when running games.
    Michael W. Ryder, Dec 9, 2005
  10. Wilson

    grumpy Guest

    I've put one of those "fans on a card" next to my video card. It extracts hot air from around the
    heatsink/fan on the video card and dumps it out the back of the computer. It really does a good
    grumpy, Dec 9, 2005
  11. Wilson

    Wilson Guest

    Please see my other post titled "What fan should I use and where to put it
    in my comp?" I have included pics of my comp in that new thread.
    Wilson, Dec 10, 2005
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