Direction of air flow

Power Supply


Video card

Mother Board

Hi everyone,

I am considering these components for a my first build and I have questions about the direction of air flow in to/out of the power supply, video card and assembling them to keep heat moving out of the case.

I believe air flows into the rear side (AC power plug) and out of the fan side.
Is this right and if so, could some recommend products/ideas to keep dirt from being sucked into the power suppy?

I believe air flows into the round hole of the card cover and out of the metal bracket (next to DVI connectors).
Is this right?

If my understanding is correct, these components can be assembled so that the power supply pushes air at the intake for the video card (provided no other cards are installed).
Is this a good plan?

Thanks in advance for you time.
5 answers Last reply
More about direction flow
  1. I think you have the airflow backwards on the PSU if I understood you correctly. I'm not a big fan of bottom mounted PSU cases, but as long as you have a good top vent it should work fine. Basically you want the air to flow only in one direction in your from the front and out the back (and top back)...this will prevent dead air areas and heat build up in the case.
  2. No, that would not be so good. Your plan would push air already warmed by the PSU into the video card, whereas cooler air would be preferred. However, I believe you have the air flow on the PSU backwards, anyway. I think this one, like most others, takes air in at the large fan opening from inside the computer case and blows it out the back grillwork beside the power cord and switch.

    Looking at your case, it comes with 2 fans both mounted at the upper rear of the case. I suggest they both should blow out. (If you mount them as one out and one in, there will just be a lot of air flow right through that top corner for little benefit.) The PSU fan at the bottom rear, likewise, will blow out, as will the video card fan at center rear. So far there are no intake fans.

    The case contains spaces for up to three 120 mm fans (buy separately) to be mounted - two inside the case front, with a dust filter already supplied there, plus a third on the side panel. With no fans in any of these positions, air flow will be provided by the exhaust fans outlined above. Most will come through the front panel with its filters, some through the side panel grill (you could at least add a dust filter there), but certainly some will just leak in anywhere it can, like through the front of your DVD drive. I would suggest you buy and install two 120 mm fans in the front panel to suck air into the case. It will flow through the dust filter (remember to clean sometimes), over the fans, over the hard drives, and into the mobo area. They will increase the air flow significantly (compared to no intake fans) and ensure that the majority of incoming air has been filtered first. If you want max cooling, consider adding a third 120 mm on the side panel (and try to mount a dust filter between the panel and the fan, or outside the panel). It is located just about where the graphics card intake will be. That would put you with 2 (or 3) 120 mm intake fans partially restricted by filters, against two unrestricted exhaust fans plus the PSU exhaust plus the video card exhaust. If you're going to add these fans, pay attention to their noise levels as well as their CFM ratings - adding 2 or 3 fans will certainly add more sound! You probably will need to power these extra fans from Molex connectors - your mobo won't have that many controlled fan ports. So maybe you will also need some simple fan speed controller system for the added ones. The top and upper rear fans that come with the case probably should be plugged into the mobo's SYS_FAN ports - if there is only one of these, you'll have to choose which - that will monitor and control those fans according to measured temperatures within the case. Most of the time they should NOT be running at full speed, so there is reserve cooling capacity when things do warm up.

    Personally, I prefer to set up the fans so that there is more intake capacity that output (in fact, intake always = output anyway) so that the interior of the case is at slightly higher pressure than outside and uncontrolled airflow is from inside to outside. If you ensure that almost all the intake is filtered, that will keep your case interior relatively dust free. Others, I will agree, disagree with me on this. Once it is operating, you can test for direction of air flow around small openings by putting a smoldering incense stick near the hole to see which way the smoke flows.
  3. WBTL said:

    I believe air flows into the rear side (AC power plug) and out of the fan side.
    Is this right and if so, could some recommend products/ideas to keep dirt from being sucked into the power suppy?

    Backwards. The PSU fan will exhaust air from inside the case.

    In an Antec 300, 900, 1200 case, airflow will be in from the front or side (if side fan fitted) and out the back and top.
  4. Thanks to all for correcting my understanding.

    Based on that new understanding and recommendations herein I'm going with a top mount power supply case something like this:
  5. With that case you have a Side Duct system that is a fresh outside air entrance point approximately lined up with the cooler mounted on your PSU. This has two advantages: the CPU air supply is cooler, and it effectively turns the CPU cooler fan into an intake fan adding air to the case instead of just circulating it around inside. That certainly is not its real function, but a side effect. You also have two outside air entry points in the square side vent and the rectangular rear vent both near the PCI card slots. These provide air in the area of your video card which blows warm air out the back. So you have two fans blowing air out - the PSU fan and the case's rear central 120 mm fan. You have one dedicated intake fan - an 80 mm in the front panel - plus two other fans (CPU and video card) that partially draw in fresh air for their own purposes. The video card fan discharges directly out of the case, but it does not use exterior air exclusively on its intake. The CPU cooler, by virtue of the round side vent duct, does draw in mostly outside air but its discharge is just to the general case interior. On balance, I would guess the case will have slightly more exhaust capability than supply, and the overall cooling is quite good.

    IF you wanted to increase the air flow more, you could mount another fan in the side square air vent, with an exterior-mounted dust filter, to increase air supply to the case, especially in the PCI card area. I'm not making a recommendation for or against this - just saying that is a choice available to you.
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