Changing Fan Direction Lowers Temps By Almost Half?

By Obi-Wan Jerkobi ยท 28 replies
Jun 18, 2008
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  1. I've noticed Stock CPU fans tend to point the fan downward and push cool air down onto the heatsink. My side fan, for some reason, was facing outwards. This made the temps go up to 150*F at times. I reversed the fan so it points inwards and noticed even at peak my temps stay around 110*F! It's noticeably louder though because of all the moving air. :p

    If this is the case, then why do Case makers put the fans facing outwards? :confused:
  2. zipperman

    zipperman TS Rookie Posts: 1,179   +7

    Well i just have a 3 inch rear fan to draw the hot air "out"
    What temp measurement are you refering to ?
    Do you have a utility to check temps or use the bios ?
    I see you have asus,use Probe and post results i'll compare.
    They told me 65 C - 149 F was ok for my Motherboard temp in this model.
    My cpu is 75 F 24 C
  3. Obi-Wan Jerkobi

    Obi-Wan Jerkobi TS Maniac Topic Starter Posts: 502

    CPU Temps, the side fan is right next to the HSFan.
  4. larryiam

    larryiam TS Rookie Posts: 476

    On my new case i purchased i got 2 120mm fans 1 for intake and 1 for exhaust. my hdd stays at 23C and my cpu stays at 40C(idle) inside my case stays at 29C when under load my cpu only goes to 50C. Much better airflow than that HP case!! Oh and i use speedfan.
    What kind of case you got?
  5. zipperman

    zipperman TS Rookie Posts: 1,179   +7

    Installing a cpu

    Who installed yours.That does seem too hot.But it may be installed wrong,
    Leave a side off for now,should cool it down some.
    ? again.what is HSF ?
    Have you installed and used asus Probe ? It's on the mbd cd and other
    important installations.
  6. Obi-Wan Jerkobi

    Obi-Wan Jerkobi TS Maniac Topic Starter Posts: 502

    lol sorry, I spoke like I was to one of my friends I know. HS Fan is the Heatsink fan or CPU Heatsink and Fan in my dorky tech lingo. :p

    Yeah, I've used PC probe. I've been tweaking for hours now and it looks like they did install it backwards as on one of my cheaper cases the fan pointed towards the CPU Fan through a little funnel thing. I think since the AIR is moving faster it's dissipating more heat.
  7. zipperman

    zipperman TS Rookie Posts: 1,179   +7

    Thank you

    Installing a cpu has to be done right and needs a manual diagram to follow.
    Do you feel you have it right now ?
    Do you have the new Probe2 ?
  8. Obi-Wan Jerkobi

    Obi-Wan Jerkobi TS Maniac Topic Starter Posts: 502

    Sorry for the confusion, it was actually an airflow question, not CPU installation. >.<

    I was just thought because the CPU fan points downwards, wouldn't you want the window fan or whaterver (Maybe side fan) that's right next to it to point downwards too, so that it could get more air flowing through the heatsink.

    Wow, this is confusing. :D
  9. captaincranky

    captaincranky TechSpot Addict Posts: 12,961   +2,518

    Many of the rest of us recognize "HSF" as "heat sink fan" as well.

    OK: The rear case fan is always exhaust. (It blows out the back of the case)!

    A front case fan is intake. (It blows into the case)!

    The "processor" fan always blows toward the heatsink, period.

    If you're using a side case fan, it should be an intake fan as well.

    A CPU fan's purpose is to infuse the heatsink with cool, outside air. The air that escapes after it has done it's job, is instrumental in cooling the voltage regulator components on the motherboard.

    Now, with the rear case fan creating a vacuum behind it, (right where the processor is). And with another fan, (the processor fan), creating yet another vacuum, (inside the heatsink itself, WTF did you think would happen, the CPU was going to cool itself correctly inside a partial vacuum?
  10. Obi-Wan Jerkobi

    Obi-Wan Jerkobi TS Maniac Topic Starter Posts: 502

    Well, this is the first time I have ever started getting obsessive-compulsive about temps, as this is the best PC I have had and am learning a bit more from this site. :D
  11. captaincranky

    captaincranky TechSpot Addict Posts: 12,961   +2,518

    The use Computers There all the Time.....!

    Don't get me wrong here, a vacuum will cool something, if it's well under the temperature of the material that is to be cooled.

    For example, you could get outrageously low temps if you shot the computer into outer space. However, M$ wireless devices simply don't have the range to permit this.:rolleyes:

    It's OK to obsess, in fact here, it's almost required:)
  12. Obi-Wan Jerkobi

    Obi-Wan Jerkobi TS Maniac Topic Starter Posts: 502

    I don't doubt that. :haha:

    It is!? Okay! Cause I wanted to complain a bit about site organization... :p
  13. TimeParadoX

    TimeParadoX TS Rookie Posts: 2,273

    For some odd reason when I built my Gaming Computer ( one in profile ) I put the CPU fan backwards, since it's a horizontal fan the air blew towards the Hard Drive instead of the Back vent. Temps recorded 38c idle / 50c stress, when I reversed the fan to face the back vent the temps went to 35c idle / 48c stress. :)
  14. Obi-Wan Jerkobi

    Obi-Wan Jerkobi TS Maniac Topic Starter Posts: 502

    Heh, you never know till you try! :rolleyes:
  15. raybay

    raybay TS Evangelist Posts: 7,241   +10

    Interesting if true. Interesting if not true.
  16. zipperman

    zipperman TS Rookie Posts: 1,179   +7

    Final comment

    Since your not replying to my ?'s.
    Do you or do you not have a manual with cpu installation diagrams ?
    If not download a pdf version.It has to be done right.
    Do your Probe readings say OK or flash off and on ?
    Also is your case crowded ? Get the new round IDE cables for more space.
    Do you have a mid tower ? A small one like Dell's is bad for air circulation.
  17. mopar man

    mopar man TechSpot Ambassador Posts: 1,379

    I have a question. My GPU temp stays at 40C, and my processor stays anywhere from 16 to 25C, which I guess is pretty darn cool. My question is about my side case fan, which is an exhaust fan, and puts out a good bit of air. My system has a rear fan that is exhaust, and the HSF, which is intake, apparently. The side case fan can't be switched around, I don't think, and the Rear fan is about the same size of the side fan (they are all large fans, about 120mm. For optimum cooling, what would be the best setup?
  18. SNGX1275

    SNGX1275 TS Forces Special Posts: 10,742   +421

    Captaincranky is right with his fan direction discriptions.

    If you have a fan and funnel system on the side of your case, that needs to be blowing air into the case (intake). If your heatsink is like most stock ones the fan lays parallel to the processor/motherboard, and you want that blowing air onto the heatsink not sucking air from it.

    I will offer a slightly different way of saying what captaincranky did about the vacuum. When you have the fan blowing air "up" away from the processor and heatsink you are pulling warmer air that comes off the motherboard and it is taking the path of least resistance to get there, so it is likely going through just the outer and upper edges of the heatsink fins, not doing much cooling at all. Now if you blow air onto the processor you are forcefully pushing cooler air down, along the fins and to the solid plate that is touching the hot processor. This is much better, it should be obvious why. Now with that style HSF you still have a 'dead zone' of air in the very center where the fan's motor is, and therefore no blades pushing the air, so its not perfect, but the air there isn't still, its got quite a lot of turbulance in it, so you are still cooling that area, just not as effectively as you are directly under the fan blades. An aftermarket setup with heatpipes would take care of that.

    That side fan needs to be blowing air into the case, should help with your GPU temps too. Surely you can remove the fan and attach it the other way. If you are sure you can't, clip the wires and solder them up backwards, then tape them up so they don't short.
  19. mopar man

    mopar man TechSpot Ambassador Posts: 1,379

    Hehe, ok, will do SNGX. Thanks! I am learning so much about Cooling, and considering I just Overclocked both my 6200 and the Sempron, (just for fun, but gave a 10fps boost somehow....) it is probably for the better.
  20. captaincranky

    captaincranky TechSpot Addict Posts: 12,961   +2,518

    This is the result of the vacuum created by the rear case fan causing that effect. I'm sure it would be even more pronounced on an "orb" type or stock Intel HSF.
  21. insoman

    insoman TS Booster Posts: 102

    I also reversed my fan (same place) and get cooler temps. but I positioned my two 120mm HSF fans to suck the air in and out through the HS. What ever works works
  22. mopar man

    mopar man TechSpot Ambassador Posts: 1,379

    Yes, I reversed my side fan and it lowered my gpu by 3 degrees celcius, then I placed a PCI card right under it and it went a whopping 1 degree back up. It stays at 38 now.
  23. SNGX1275

    SNGX1275 TS Forces Special Posts: 10,742   +421

    Told you so :)
  24. jobeard

    jobeard TS Ambassador Posts: 11,122   +982

    Consider another environment; How to cool a room?
    Blow air in or face the fan to evacuate the room?

    The 'evacuating hot air' as a principle is more effective in lowering the room temperature when another source of air can be used to replace it.

    The need to cool the heat sink, is quite a different matter.
    That device is designed to be a radiator and thus needs air flow to pull the heat off
    so it may continue to absorb heat generated by that xxx ghz device.

    Given a choice, the HSF blows directly on the device, but the case fan should
    evacuate the 'room' (ie your case).
  25. raybay

    raybay TS Evangelist Posts: 7,241   +10

    Alas, there are many studies which show case fans are only marginally effective at best... It has to be special fans in very well designed locations.
    The CPU fan, on the other hand, is so critical that even a slight change in position or of thermal paste can make a difference of 7 to 9 degrees... and brands of cpu fans (models) can even make a difference of 13 degrees, depending on blade design and a clear channel to move air out of the area.

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