PSU placement...

[GaryG]

maybe a dumb question but... building first system in a while and looking at a psu with a large 120mm fan on top (only ever used ones with rear fans before), do I assume you shouldn't mount this in a classic psu-at-the -top style case with no vent above it? I thought the psu fan should always vent straight out, not contribute to the other components in the case etc. That mean either at the top with a top vent (haven't found a case like that) or at the bottom facing down..? Cheers.

[whyterabbyt]

quick read indicates this seems to be intended to be at the bottom of the case, facing up.

concept is that warmer air is lighter, so there's cooler air at the bottom of the case, which is pulled through the PSU and expelled upwards. presumably with in-case airflow and expulsion handled by the case fans.

[GaryG]

That makes sense, just seems extra heat being dumped in the case which I thought people avoided. I did find a high end gaming case with a psi mount at the bottom with a filter under so it vented out (into the floor…)

This is a low power system with no separate gpu or anything I’m building so probably immaterial in my case but, y’know, curiosity…

Thanks.

[whyterabbyt]

Yeah, it does seem slightly counterintuitive, but i guess if the heat is rising, that means its got an intrinsic 'natural' airflow... maybe less turbulence/recirculation.

just guessing tho.

[PAK]

maybe a dumb question but... building first system in a while and looking at a psu with a large 120mm fan on top (only ever used ones with rear fans before), do I assume you shouldn't mount this in a classic psu-at-the -top style case

They're made more for case designs which have a PSU chamber at the bottom. There they should (some might not) provide a vent at both the bottom and the top. So you can mount the PSU with the fan facing downwards, or just point it upwards.

EG Go to this page and look at the photo where it says "Dimensions" near the bottom of the page. You'll see vents both above and below where the PSU mounts at the bottom back of the case.. https://www.antec.com/product/case/ax90

How well the PSU works facing downwards (obviously) depends on the sort of clearance the case feet will provide, and surface it's on, in order to allow air to circulate. IE Low clearance + Thick carpet = probably better mounting the fan facing upwards.

If mounting at the top (of an old style case) you'd likely need to do it with the fan facing downwards, which would be directly above where the CPU normally is.. Not the best place in the case, and why many designs switched to using the bottom of the case to house the PSU.

[uOpt]

No way any case with top-mounted PSU will turn the fan toward the top.

[GaryG]

No way any case with top-mounted PSU will turn the fan toward the top.

Thanks, I noticed this while browsing a few cases this afternoon; realised the psu mounting holes would only allow it to go one way and all the ones i looked at had the top of the psu (with the fan) pointing down.

with the fan facing downwards, which would be directly above where the CPU normally is.. Not the best place in the case, and why many designs switched to using the bottom of the case to house the PSU.

Thanks, I don't recall any case having bottom mounted psus the last time i built a pc from scratch but makes sense, if only from a weight perspective too.

[jamcat]

Get a hybrid 80+ Platinum PSU where the fan only turns on if the PSU is overheating. Chances are it will never turn on. Modern efficient PSUs really aren't a source of much heat.