PSU Fans intake or exhaust???

Im installing a bottom mount PSU in my new build and assumed it would be pushing air up to the top of the case and then i realized theoretically it should be intaking air to cool itself off. So are PSU fans intake?

I've heard bottom mounts are better but it seems like it would be intaking warmer air and at least if it was at the top it would be intaking air and cooling itself off at the same time while venting out the back. I guess either way it's venting?
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More about fans intake exhaust
  1. Point the psu fan downward.
  2. theres hardly any space between the bottom of the case and my desk. wouldn't that be pointless? Its not like it has that much air to intake and i read that plenty of people install bottom mounted PSUs upside down
  3. Doesn't matter. Will give you much better airflow than pointing it upward.
  4. Bottom mounts are designed to intake air from outside the case and vent outside as well. If you reverse the flow (to take air from inside the case) you will be defeating part of their design advantage, and making for a conflict with airflow. This will adversely effect the cooling.
  5. Well incase anyone with a similar question is reading, from my research it seems to not matter at all. Top mounted PSUs have done the same thing for the longest time before bottom mounted came into play. They all drew 'warmer' air from the incase and exhausted it. The original idea of a PSU fan was to pull air out of the case as processors became more powerful since there were no case fans or even CPU fans.

    We all know heat rises so top mounted PSUs would actually be sucking out much hotter air than bottom mounted (fan facing up) PSUs.

    From tests done on this topic there's hardly a difference in CPU temperature. The theory that the life of the PSU will be shortened from pulling in warm air seems to not make much sense either since it's bottom mounted and heat rises.

    It seems to just come down to good airflow in the case.

    upside down bottom mount it is.
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