Asus P5L VM 1394, should CPU fan blow or suck?

Discussion in 'Windows 7 Hardware' started by CJ12, Jan 9, 2013.

  1. CJ12

    CJ12 New Member

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    Please, I recently discarded my CPU fan (an Intel E18764) in favour of an Akasa one. My new fan seems to suck air in through the side panel, whereas I am sure the old one used to blow it out. I have an Antec Minuet low profile case. Thanks! :)
     
  2. Pauli

    Pauli Extraordinary Member
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    As such, both ways to do the air flow are in order. In most cases fans blow air towards the CPU, that's the standard. Not knowing your precise model of cooler, I can't tell if a change of connections could reverse the air flow = the rotation of the fan. Fans are DC, meaning that if you change the wiring, your fan will start running in opposite direction.

    It is possible that Akasa has fans that suck air, instead of blowing. Thus, you may have bought such a one? Main issue is, of course, what temperatures your CPU reaches.

    Regards,

    Titanic / Pauli
     
  3. Digerati

    Digerati Fantastic Member
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    That's actually one reason to keep the OEM coolers. They are designed to work with the CPUs they come with where 3rd party coolers are "universal" and like most "universal" products, they make compromises to fit the most applications, and rarely are a "perfect fit" for any.

    Studies have shown that heatsinks are more efficient when "turbulent" air is blasted "on to" the heatsink as opposed to an easy flow "across" the heat sink, which occurs with horizontally positioned fans.

    As Titanic correctly noted, you did not tell us what model you are using so we don't know how your fan is oriented or which direction it pushes air.

    Note too that many, if not most fans with DC motors only spin in one direction and reversing the power leads often results in no spin, or damage to the motor. But even if the motor's rotation can be reversed safely, it is important to note the fan blades are aeronautically designed like an airplane propeller and their shape (pitch, twist angle, blade angle, leading edge, trailing edge, etc.) are designed to provide the most air movement in ONE direction only. Meaning, if you reverse direction of the rotation, you reduce dramatically, the air flow (CFM - cubic feet per minute) and heat extraction. This is exactly why most cooler and case fans have two arrows pressed into their housings; one showing spin direction, the other showing flow direction, as seen here.

    Note a ceiling fan. The blades are mounted at an angle, but the blade surfaces are flat so you can reverse rotation direction. But CPU heatsink and case fan blades have a twist in them. The are not designed to spin in both directions. So the proper way to reverse air flow on a heatsink fan is to turn the fan over (or around), not switch wire polarity.

    Note the other main reason to use the coolers that come with our Intel and AMD CPUs is because using 3rd party coolers on CPUs that come with coolers, voids the 3-year CPU warranty! For that reason, contrary to false rumors by way too many, OEM coolers are excellent coolers. Perfectly capable of providing adequate cooling, even with mild to moderate overclocking.

    Exactly!

    And lastly, it is important to note it is your case's responsibility to provide an adequate supply of cool air flow through the case. The CPU fan need only "toss up" the CPU's heat into that flow. In most cases, you are looking for good front-to-back flow through the case. I generally recommend at least two large (120mm or larger) case fans, one in front drawing cool air in, and one in back pulling heated air out (not counting the PSU fan).

    If you are not doing "extreme" overclocking and your CPU is not staying cool enough, look at adding case fans. The coolest temperature possible is not necessary. You just need to keep the CPU in it's normal operating range for it to remain stable. I get nervous when CPUs temps hit and stay above 60°C. Below that is fine.
     
  4. CJ12

    CJ12 New Member

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    Ah thanks Guys that's really helpful. Just out of interest I attach diagram of direction of airflow in my low profile case.
    In my opinion, for what it's worth, I think it does work okay, since the air is sucked in the side panel down onto the heatsink and CPU, then is drawn over the other components, including the RAM, on it way out via the chassis fan. It might be better if the CPU fan was to blow instead but it probably wont, unless I put the original Intel fan back on.

    minuet case drawing.
     
    #4 CJ12, Jan 20, 2013
    Last edited: Jan 20, 2013
  5. Digerati

    Digerati Fantastic Member
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    Slim/low profile cases often have unconventional air flow patterns. I recommend you use a hardware monitoring program to keep an eye on your temps. Here's my canned text on that:

    Your motherboard utilities disk should have a monitoring program (or check for a more recent version on your motherboard or PC maker's website). If none, I use and recommend CoreTemp for newer Intel and AMD64 CPUs, or RealTemp for Intels. SpeedFan is a great and popular alternative, or you can try Motherboard Monitor. Open Hardware Monitor is also becoming very popular. Unfortunately, I have found that these programs often have problems properly identifying and labeling the sensor they are reading. The temperatures shown are as accurate as the inexpensive, low-tech sensors will allow, but it may say System Fan instead of CPU Fan. Fortunately, the programs do allow you to edit the labels, so I use Everest to verify the temperatures (as it is able to match sensor with label correctly), then edit the label in the monitoring program. In Everest, look under Computer > Sensor, then wait a couple seconds for the readings to appear. Unfortunately, Everest does not minimize to the system tray to show real-time temperatures, otherwise, you could use Everest instead of the others. Check but do not rely on the temps shown in the BIOS Setup Menu. While they are likely correct, running the BIOS Setup Menu is probably the least demanding task you can ask of your computer so it does not show the temps when the system is being taxed. But if the BIOS Setup Menu temps are high, you have a problem that needs to be corrected. HWMonitor, from the makers of CPUID is also very informative, but does not minimize to the system tray.

    I get nervous when CPU temperatures hit 60°C. While most CPUs are capable operating at higher temps, system stability issues arise and long term exposure to very warm temperatures increases component aging (including the CPU socket and surrounding devices). GPU (graphics processing unit) temperatures typically run considerably warmer with 80°C not uncommon.​
     
  6. CJ12

    CJ12 New Member

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    Thankyou Digerati.
     
  7. Pauli

    Pauli Extraordinary Member
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    About air flow in general, it's not electrical or electronic, it's physical, just as "the wind blows". I've drilled holes in cases, and added new fans, with only my imagination as limit. It's about getting the whole picture, how cool air comes in, and how hot air gets out. As cool as possible air in, as much as possible air out.

    I've thought about building a computer inside a minibar / refrigerator... in order to avoid the noise of fans. One expert stated that he would sink the whole apparatus in concrete, as it would both absorb the noise and the heat.

    Like they say in X Files: The answer is out there. Many bingos to be found, still and yet.

    Hooray!
     
  8. Digerati

    Digerati Fantastic Member
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    I would say he is not much of an expert then. While concrete is not known for its insulating properties, it is certainly a better insulator than it is a conductor. This means the heat generated by a computer sealed in concrete would be trapped in the computer, with no where for the heat to go and the computer would surely fry. The good news is after that, it would sure be noise free.

    The better way to avoid fan noise is to use large, quality fans in a quality case. The better fans use precision bearings. Precision bearings result in smoother operation and that results in less vibration - thus less noise.

    Larger fans move massive amounts of air at a lower RPM. And lower RPMs result is less fan noise.

    Finally, a quality case suppresses noise and isolates vibrations.
     

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