fan direction help

By old tecno ยท 7 replies
Jun 10, 2005
  1. Sorry it is a such a basic question, but it's my age

    I hav 3 fans, 1 side 1 top 1rear plus power supply fan. all 80mm which is best direct combo

  2. Rik

    Rik Banned Posts: 3,814

    Hot air rises so you want all top fans blowing out and all bottom fans blowing in.

    Hope that helps. Rik.
  3. haden9

    haden9 TS Rookie

    Also you may want to make sure that the fans are properly aligned. So that a flow of cool air will be going in and hot air will be going out instead of just accumulating inside your pc.

    Good Luck! :wave:
  4. SNGX1275

    SNGX1275 TS Forces Special Posts: 10,742   +421

    Unless you have some really obscure setup. Have the side blow in, and the top and rear blow air out.
  5. old tecno

    old tecno TS Rookie Topic Starter

    thanks I feel better now
  6. CMH

    CMH TechSpot Chancellor Posts: 2,039   +9

    Found this usefull as well, as I have the top and side blowing in. I'll do some tests and see if there is a difference. Will post back in here when I'm done (probably take a couple of days, exams on the 16th).

    Or of course, someone can do those tests, shouldn't take more than a few hours (try to generate the most heat, to get the biggest heat difference).
  7. CMH

    CMH TechSpot Chancellor Posts: 2,039   +9

    The idea of switching the fans couldn't leave me!!! arrgh!

    So I just went and did the short experiment.

    The results? I found that changing the top fan from inhale to exhale made it worse for at least the CPU. Had the computer running at full load for all tests, for 30 mins (which IMO is long enough to generate all the heat needed).

    This is how I did it:
    I just ran the comp with CPU fan at min, ran 1xtoast.exe (nice little prog to use all CPU power) and ran 3DMark 2005 with that (to use up graphics). Takes a couple of runs to meet the 30 min requirement. Had Everest running in the background on sensor page to get the reading as soon as 30 mins is up.

    Without doing anything, I turned the CPU fan to max, did everything again for 30 mins, and recorded the temp.

    Switched the fan so its now on exhale. (Found that I had to rethread the fan to do that)


    Fan on inhale:
    CPU fan running on min: 31C
    CPU fan running on max: 26C
    Case temp from case sensor: 24.5C
    GPU: unreadable, kept jumping from 33-64C. Unreliable so I'll just dump this data.

    Fan on exhale:
    CPU fan running on min: 31-32C
    CPU fan running on max: 26C
    Case temp from case sensor: 24.7C

    Conclusion: Not much of a difference, but it is clear that for me at least, having the case fan at exhale doesn't seem to lower the temp, but increases it very little. Of course, this test has to be repeated a few times before we can make some solid conclusions.

    As I see it, my comp even at max load doesn't really produce much heat, especially in winter. I might just wait for summer to come up to re-do the test, but someone else is welcome to try it and share the results.
  8. Rik

    Rik Banned Posts: 3,814

    Thats interesting. When I first built my pc I upgraded from P1 166 (didnt even need a processor fan) to amd xp 2000+. I didnt know anything about how much heat a faster pc generates. I made a mistake and had all fans blowing in. I didnt have any temp sensors at the time, but in the summer i had to leave the case open. I then set my front and side fans to blow in and my top ones to blow out and was able to run with the case on. Also, i fitted a slot cooler by my graphics card and that seemed to make the biggest difference as it was mostly that causing my pc to freeze.

    This is a great idea for a new thread about cooling effectiveness.
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