Fans sucking or blowing?

Discussion in 'OT Technology' started by Kieffer87, Nov 9, 2006.

  1. Kieffer87

    Kieffer87 Orly OT Supporter

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    Ok I have basically a Dell computer in Aftermarket case because of HDD cooling. Anyways I have 1 120mm fan with a duct going right to the CPU. Do I want this blowing or exhausting air? Second I have a fan in the side of the case this is blowing out, and I have one in the front of the case right in front of the HDDs also blowing out. The more I thought about it wouldn't it make more since to have the 2 smaller ones on the side and front suck air in and the 120 suck out?
     
  2. rsxm5

    rsxm5 OT Supporter

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    Basically, my theory has always been have the fans in the front blow in. That way they pass air over the cards and components, and out the back fans, which should be blowing out. The side fan I'm mixed on. I've seen cases where it went either way, so I'm not 100% sure on that.
     
  3. Kieffer87

    Kieffer87 Orly OT Supporter

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    I just checked them and I did have the front suckin in and side blowing out. Everything stays really cool when im doing normal stuff. However my main problem is when I play games. My graphics card fan is basically sittin on my sata card so there isnt much flow to it and the 120mm cpu fan is cranked on high the entire time. This led me to believe that maybe I didn't ahve somthing set up right.
     
  4. Wolf68k

    Wolf68k OT Supporter

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    This fan with the duct that is right at/on the CPU's heatsink&fan. It's tightly fit then you want it to do whatever the CPU's fan is doing.
    Normally (without ducts) CPU heatsink&fans are blowing air onto the heatsink. So if this is the case with you then you want that 120mm fan to intake air.

    If on the off chance the heatsink's fan is pulling air off the heatsink, then you want the 120mm fan to blow the air out of the duct; aka exhaust.


    Side fans, well as rsxm5 said, it is a bit mixed. I had one case with a side fan that was aimed more or less at the CPU and was used as an intake. I tried running with that fan off and even flipped it to work as exhaust and the CPU temps went up. Flipped it back to intake and the CPU temps went back down.

    But I've also seen case with side fans that were placed very low, because of that I would say to make them as intakes because of the whole "colder air is lower to the ground and hot air raises" thing. Plus if you also have a front fan which should be intake and they are always lower on the case, then having another fan lower on the case as exhaust would in theory exhaust the cold air which wouldn't be good.
     
  5. Kieffer87

    Kieffer87 Orly OT Supporter

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    Ok well like I said its a dell computer so the CPU just has a heat sink, no fan. The side fan does have a duct I can put on that goes directly to the CPU however my mobo controls the speed of the 120mm so I was a bit worried about not using it to cool the cpu.
     
  6. deusexaethera

    deusexaethera OT Supporter

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    If the CPU fan is also the main exhaust fan, you want it blowing hot air out. If it's not, then you want it sucking cool air in.
     
  7. Kieffer87

    Kieffer87 Orly OT Supporter

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    ok I think im gonna remove the duct to the cpu and change the CPU fan to exhuast and have the side and front sucking air in and see what happens. I think it should be more efficient.
     
  8. skinjob

    skinjob Active Member

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    I'd recommend against taking air away from the CPU, unless you can monitor the CPU temps and verify that it doesn't cause a significant rise.
     
  9. deusexaethera

    deusexaethera OT Supporter

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    I'm thinking I did a bad job explaining myself.

    On Dell cases, the CPU fan is also the primary exhaust fan. As such, if you were to make it into an intake fan instead, the rest of the case would have problems with heat buildup.

    Since you're not using a Dell case, it's pretty unlikely that your CPU fan was ever intended to be an exhaust fan. Therefore, you should leave it in the intake position.

    Also, if you make the CPU into an exhaust fan without shrouding the heatsink so that air has to get pulled through the heatsink to go into the fan, then the air will just curl around the edge of the fan and leave the heatsink to get screaming hot for lack of airflow. That's why Dell cases have those green shrouds that go about halfway down the heatsink.
     
  10. Coottie

    Coottie BOOMER......SOONER OT Supporter

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    I've always set the CPU fans to blow onto the heat sink. I was told, dunno if it's true, that if the CPU fans are set to suck then you can't guarantee that the air is passing over the heatsink at the lowest level (the part touching the CPU).....or to say it a different way, there may be pockets (like in the center of the heat sink) close to the CPU that would not get any air movement and overheat. Blowing air onto the heatsink is supposed to prevent this.

    As far as case fans go, I too have my front ones drawing air into the box and the ones on the back blowing air out. This creates a nice flow through my box that helps keep everything cooler.
     
  11. MrBrotato

    MrBrotato New Member

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    If your CPU has no fan on it, just an air duct that connects to a fan, do not remove that duct.
     
  12. Kieffer87

    Kieffer87 Orly OT Supporter

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    Any good programs to monitor CPU temp? I have speedfan but that will only tell me my HDD temp.
     
  13. deusexaethera

    deusexaethera OT Supporter

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    MotherBoard Monitor. It's made by LiveWire.

    Or, if you have a laptop, Notebook Hardware Control will monitor temps AND let you control a bunch of power-related stuff.
     
  14. Kieffer87

    Kieffer87 Orly OT Supporter

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    I tryed motherboard monitor but I didn't see my model under the dell section, or my model number under intel. Any other ideas?
     

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