Adding a fan to medium tower - extract or intake?

Discussion in 'DIY Computers' started by ferrymanr, Dec 13, 2006.

  1. ferrymanr

    ferrymanr Guest

    I have a medium tower system which has just been upgraded from a Duron to
    Athlon XP 3200. To assist cooling in general I want to add a second fan. I
    have options of a 4" fan at front or rear. I have placed some filter
    material in the front of the case to reduce dust intake - this works and
    gathers a lot of dust/dog hair. I was going to fit a fan as intake to the
    front panel mounting posiion with the idea that this would be less likely to
    draw dust into the DVD drive. I have had a problem in the past with another
    machine whre the powerful extract fandrew in dust wherever possible
    including the CD drive and this caused me grief.
    Questionis which is better - a rear mounted 4" extract fan or a fron mounted
    4" intake fan?
    Richard
     
    ferrymanr, Dec 13, 2006
    #1
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  2. ferrymanr

    BigH2K Guest

    Your 4" fan mount is probably for a 92mm standard size fan.

    You should have it as an intake fan so that you have positive air pressure
    inside the case, this will push warm air out and, as you've already
    discovered, will stop dust being sucked into the case from every available
    orifice.

    The filter material you've placed in the front of the case will cause
    resistance to air intake, hence higher temps. If you can you should try to
    raise the base unit off the floor as much as possible, even a few inches can
    make all the difference and then try to see how you get on without the
    filter.
     
    BigH2K, Dec 13, 2006
    #2
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  3. ferrymanr

    ferrymanr Guest

    The filter material I use is a very loosely woven type. I ran the machine
    for one hour with the filter in then one hour with it out. Temperature
    samples with a probe near the centre of the case (away from the CPU fan)
    showed less than degree difference and the CPU temperature was unchanged so
    don't think the airflow is restricted too much. In fact most air is
    probable entering the case through the unused rear panel fan aperture which
    is only just below the PSU fan.
    I will order a low noise fan from RS today.and run some tests. I also need
    to measure the sound levels which are presently below the minimum range of
    my SPL meter at 6" from the case (as long as I deaden the vibration of the
    very flimsy side panels of the case). Next job will also involve finding
    some damping material for the panels.
    Richard
     
    ferrymanr, Dec 13, 2006
    #3
  4. I'd go for the (filtered) front intake. You probably already have a rear
    extract (look in the PSU!), and as you've noticed having dust sucked in
    through every device with a slot in (CD, DVD, FDD, etc) is not a great
    plan.
     
    GSV Three Minds in a Can, Dec 13, 2006
    #4
  5. ferrymanr

    Douggie Guest

    Douggie, Dec 13, 2006
    #5
  6. I have a recent Antec case (small midi tower) which has a permanent 3-speed
    120 m/m fan fitted at the rear, and an optional 80 m/m one that fits in the
    front. I only need to use the fan at the lowest speed.

    Sylvain.
     
    Sylvain VAN DER WALDE, Dec 13, 2006
    #6
  7. ferrymanr

    ferrymanr Guest

    I fitted an intake fan to my case some weeks ago and am well pleased. The
    case perforations were rather small and air whistling through them made a
    lot of noise so I got out the hole cutter and made a full size hole for the
    fan and fitted a wireframe fan guard. Much quieter.If anything the fan is
    too efficient. It is connected to the three pin connector on my Gigabyte MB
    marked SYS-FAN. I'm not sure if the MB is supposed to control the fan but
    it seems to run at full speed all the time (what does the tghird wire do -
    just senset he fan speed?). I am considering dropping the 12V supply to
    about 10V to reduce speed and noise using my old method of three series
    connected diodes giving about 1.8 to 2V drop.
    Richard
     
    ferrymanr, Feb 9, 2007
    #7
  8. Or 7v by using the 12V and 5V lines instead - that leads to less heat
    generation inside the case and often gives you enough air flow.

    Cheers - Jaimie
     
    Jaimie Vandenbergh, Feb 9, 2007
    #8
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