PSU at the top or bottom?

[_33]

I prefer the PSU located in the bottom of the case specifically because the PSU being there is on it's own air circuit, so basically it doesn't get hot air from the motherboard+CPU (if it were a top mounted PSU). Also I would have to say the center of gravity being lower means it's easier to handle the case when I bring it elsewhere, but barely still. For cable management I haven't got into any trouble being bottom mounted, it's not a flawed design imho and it does make a lot of sense. Now, if your PSU (with filter supplied in the case) accumulates a dirt layer like a carpet of dust, then I would ask myself some serious questions about the rest of the room where the computer resides. I am not a swiffer fanatic and I must tell that my computer isn't filled with dust and what not. But say, if you can't tell if you have light coming from that front mounted 120mm led fan, then you might have some concerns.

 

[cever89]

I would say a bottom-mounted PSU is much better for thermals. Also as someone already mentioned, the lower center of gravity makes your case much more stable. The only caveat would be for those that have super big cases to make sure their cables are long enough to reach their components. Of course, there are plenty of cable extensions out there - and some nice looking ones too!

 

[sic_doni]

I think PSU in the bottom should be the best one
it looks better and feels like more space inside the case

 

[lilhasselhoffer]

Do the Math

Hello,

Beyond the fanboy, and personnal experience stories; the placement should be relatively simple to calculate. Think of this in terms of lost energy, and that 99% or more of all lost energy is converted into thermally dissipated power.

PSU = 80%
650 watt draw = 812.5 watts from wall = 162.5 watts TDP
850 watt draw = 1062.5 watts from wall = 212.5 watts TDP
PSU = 85%
650 watt draw = 764.7 watts from wall = 114.7 watts TDP
850 watt draw = 1000 watts from wall = 150.0 watts TDP

If we assume that the processor has a TDP somewhere in the range of 100 watts (ballpark based on low as 65 and high as 130 watt TDP for Intel and AMD processors), we can find the maximum TDP of a GPU (or set of GPUs) that would warrant a top or bottom mounting for thermal reasons. They vary so much that you should look online for what you have, not ballpark a figure.

SO:
If GPU TDP + CPU TDP > PSU TDP then you should mount it at the bottom, so maximum heat generation is at the top.
If GPU TDP + CPU TDP < PSU TDP then you should mount it at the top, so the maximum heat generation does not influence the rest of the items in the case.
Finally, consider the dust a thermal insulator. As such, if GPU TDP + CPU TDP ~= PSU TDP (within 10% or so) you should mount it at the top to minimize the amount of dust that is sucked into the case by the PSU.


A little bit of foresight, assuming a couple of future upgrades increasing thermal generation (woo hoo next gen of GPUs!) and wiring lengths, and your answer should be relatively clear. This is why some people prefer the bottom, and some people prefer the top. There are cases where both work well, and additional aesthetic reasons, that have little influence on performance that people base their preference on.

 

[Melvis]

@lilhasselhoffer so you answer is top or bottom?

 

[X1REME]

A psu will produce more heat and get hotter when at the bottom, will also require an extra/or faster fan on the case...

All depends on the Case Airflow; my case is optimized to be on top

 

[thebluebumblebee]

The location of the PSU within a case does not determine how hot it gets, how much heat it produces, or how much dirt is drawn into the case. 4 things determine how hot a PSU gets and how much heat it produces: efficiency, load ,airflow and the temperature of that air. If you take a case that has a bottom mounted/bottom intake for the PSU and put it on deep carpet, you will have a problem with airflow for the PSU.

A PSU should not be considered an exhaust fan. Heat is a determining factor in the life of a PSU. Why would you want to have the system heat going through the PSU?

BTW, I think the standard ATX tower case is a poor design for heat dissipation. That is why I am a fan of the Silverstone Raven and Fortress cases. Their price seems high until you consider the fact that there are no more fans to purchase. I recently bought an inexpensive case and then proceeded to spend more on additional fans than the case cost.

If my choice is between top or bottom mounted PSU's, I'll take bottom. But make sure it's a well designed case with cable routing in mind.

 

[lilhasselhoffer]

@lilhasselhoffer so you answer is top or bottom?

My apologies for not making it clear. Neither answer is correct, but neither answer is wrong.

I prefer lower TDP CPUs and a single mid-range graphics card. I've thus chosen a case with a top mounted PSU.

 

[Brandenburg]

10 lights? How do you mean?
I still like to check whether the PC froze up or not at times by the way (not too often, yeah, but still).
Guess I am old-fashioned too.

thought i was the only one.. just like to "see" my machine working

 

[Peter1986C]

10 lights? How do you mean?
I still like to check whether the PC froze up or not at times by the way (not too often, yeah, but still).
Guess I am old-fashioned too.

thought i was the only one.. just like to "see" my machine working

At my student room, there is a vent system that makes so much noise that my Seagate HDD is barely hearable. So I am among you two.