PSU fan facing UP or DOWN? I see points for either orientation, but I can't deci...
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PSU fan facing UP or DOWN? I see points for either orientation, but I can't decide on one!  


New Member
Joined: 2 years ago

Hello everyone,,
I'm building a new PC and I can't decide on whether to orient the PSU fan up or down.

  • hardwood flooring

  • PSU: Corsair RM850i (mounted at bottom of case)

  • GPU: RTX 2080 (plenty of space between PSU shroud and GPU)

  • Case: Fractal Design R6 tempered glass. There is a fan filter mesh along the entire bottom. The PSU shroud covers the entire PSU (so you can't see it)

  • Fan config: 3 intake (2 front, 1 bottom), 1 exhaust (back)

So as far as I understand, the main PSU fan is an intake, and it exhausts through the back mesh (where the power cable plugs into).

In eco-mode, the fan of the RM850i doesn't turn on until it goes >500 W output, which for me is basically never (I reach around 400 W max under stress test / gaming).

Benefits of having the fan point up (into the case):

  • heat generated from PSU can rise upwards through the fan shroud into the case so that it isn't trapped around the PSU components

  • cable routing is done (since this is how I currently have it)

Benefits of having the fan point down (towards the floor):

  • dust from within the case can't fall into the PSU

  • potentially less heat will be put into the case, since most of the heat stays trapped inside the PSU

  • if ever the PSU fan does turn on, it makes more sense to pull cold air into the PSU, rather than pull hot air from the case (if pointed up)

Will the heat generated by the PSU be bad for it, if allowed to remain in the PSU? I'm kind of more inclined to point the PSU fan up, let the heat rise into the case and then be exhausted by the case fans.

What are your opinions?

This topic was modified 2 years ago

To do: Create my signature with system and expected eGPU configuration information to give context to my posts. I have no builds.


Active Member
Joined: 2 years ago

I'd say go with down because the PSU shroud will be quite close to the fan and thus the PSU will have trouble getting fresh air, thus there may be heat trapped inside the PSU and PSU shroud in the case. When the fan is down, the PSU may be cooled by convection with cold air entering from the bottom and exiting from the side while when it'll be facing up you may start seeing the fan go on at lower power draw because it can't get convection going and the PSU shroud in the case makes it hard for the PSU to breathe even with the fan on.

Edit: the convection will probably pull air from the (unfiltered) side, and then the hot air will be trapped inside the PSU shroud when coming out of the top. If you'll have spinning drives inside the same PSU shroud, I'd doubly advise against it because the lifetime of the spinning drive is directly correlated to the operating temperature.

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