Top VS. Bottom mounted power supply

[Jakeisbest]

I have noticed that many companies are offering more cases with bottom mounted power supplies. Examples include: P182, some of the new Lian Li, the Antec 900, the Cool Master 690, ect. However, I dont' understand what benefits are gotten from having the PSU mounted on the bottom of the case.

It would seem to me having the PSU at the top of the case is the most optimal position. The PSU at the top of the case acts as a great case fan pulling the hot air off the processor and pushing it out the back of the case. the PSU also remains relatively dust free at the top of the case as opposted to being at the bottom of the case (where it would be sucking dust bunnies into is circuitry).

I guess for some cases cable management might be easier with the bottom mounted PSU. But then extra heat from the PSU is floating up into the video cards!

Am I just missing some obvious benefit?

 

[Somniferum]

I never understood this phenomenon. Heat rises (as we all know), and PSUs give off a LOT of heat. Why disperse all that heat into the chassis of your case when you don't have to? If there's some mysterious engineering principle at work here that I'm ignorant of, I'd love to know what it is.

 

[RallyMaster]

My CM590 is arranged in this manner and it takes in air from the bottom of the case (there are vents at the bottom of the case that allow this) and the fan of the PSU is placed directly over that. In that regard, the PSU won't heat up the rest of your computer.

Not all PSUs give off that much heat (at least my Corsair HX520 doesn't...even when loaded).

 

[Zepper]

Modern PSUs rarely radiate much heat and generally don't have a strong enough fan(s) to contribute much to overall cooling (in the old days you had an 80mm fan running full speed 24/7 which may have been the only exhaust fan in the case, and perhaps the ONLY fan period), so now isolating the PSU's air circuit is a good idea whether on the top or the bottom, but being in the bottom location makes that easier to do and several cases specifically isolate the cooling by separating the case chambers. Besides putting the PSU in the bottom keeps the center of gravity low to help prevent tipping. So, IMO, bottom mounted PSUs are a good idea, but in the grand scheme of things it makes little diff. where it's mounted. Heck, I just bumped my thread on a compact ATX case that puts the PSU sidesaddle in the bottom front... It just don't matter any more.

.bh.

 

[RallyMaster]

Originally posted by: Zepper
Modern PSUs rarely radiate much heat and generally don't have a strong enough fan(s) to contribute much to overall cooling (in the old days you had an 80mm fan running full speed 24/7 which may have been the only exhaust fan in the case, and perhaps the ONLY fan period), so now isolating the PSU's air circuit is a good idea whether on the top or the bottom, but being in the bottom location makes that easier to do and several cases specifically isolate the cooling by separating the case chambers. Besides putting the PSU in the bottom keeps the center of gravity low to help prevent tipping. So, IMO, bottom mounted PSUs are a good idea, but in the grand scheme of things it makes little diff. where it's mounted. Heck, I just bumped my thread on a compact ATX case that puts the PSU sidesaddle in the bottom front... It just don't matter any more.

.bh.

lol...too bad my CPU cooler weighs so much and it's at the top portion of the case...

 

[error8]

Maybe this type of mounting at the bottom of the case is meant specifically to protect the PSU. Having it at the top of the case will force it to exhaust all the time the hot air the components are heating up and so will force the PSU to work at higher temperatures, thus reducing its life and maybe its efficiency too. At the bottom, the PSU will always suck cold air from outside the case, reducing its operating temperature substantially.

 

[Somniferum]

Hmm ... I guess you guys have convinced me that it's not such a terrible idea after all. I wish I could see some hard data though -- the same system put together in a traditional top-mounted PSU case, and then rebuilt in a bottom-mount model, and compare all the temps. That would be interesting to see. But the cases would need to be nearly identical in every other way.

 

[Jakeisbest]

Originally posted by: error8
Maybe this type of mounting at the bottom of the case is meant specifically to protect the PSU. Having it at the top of the case will force it to exhaust all the time the hot air the components are heating up and so will force the PSU to work at higher temperatures, thus reducing its life and maybe its efficiency too. At the bottom, the PSU will always suck cold air from outside the case, reducing its operating temperature substantially.

I would bet the amount of dust is sucks up from the bottom of the case (worse if it sucks air from out side the case) is much worse for it than hot air from the processor. Also many PSU have big fans like .This one! 120mm fan. Does the PSU have to work harder at higher temperature? That is a good point.

I would really like to see a test done on top vs bottom mounted PSU configurations.

I think the Cool Master Centurion 5 has both a top and bottom mounted design. So if some one has $200 to burn, pick them up and run the test lol!

 

[Team42]

At a guess, there's prob benefits and disbenefits for each mounting position. My Antec 900 uses the bottom mounting position, but it allows for a 120mm and a 200mm fan at the top of the case, unobstructed. The PSU fan only has to deal with the heat from the PSU, and not the heat from the GPU and CPU. That said, it means there is ah heck all space above the motherboard (no room for an IFX backplate cooler, for instance), and the main power cables (ATX and CPU) have to stretch a long way to get from PSU to the sockets.

I think it really only becomes an issue when you consider the location of the PSU fan intake. The PSU in my old AMD system has a bottom- (or top-, if you turned it upside down) mounted intake and is (I think) more suited to a top-mounted case, whereas the PSU my newer Intel system has a back-mounted intake and sits well at the bottom of the case.

Horses for courses, says I.

 

[Zepper]

Well, I'm sure most are smart enough to filter the intake air on the PSU if it's on the bottom AND the case is on the floor. Some self-stick Velcro hooks and a square of AC filter foam will do it. Isolating the PSU air circuit also reduces the heat of the air coming into the PSU so its fan(s) won't have to ramp up as much as if it was drawing in preheated air off heat producing components = less noise.

RM,

You'll have to get one of those inverted (I call 'em "perverted") ATX cases that also have a bottom PSU (my Aerocool Coolview is like that...). Those will put your monster CPU cooler lower.

.bh.

 

[Modelworks]

Its true that heat rises, when the air is calm.
Put a fan behind it though and the heat is going any direction the fan is blowing.
So put it at the top or bottom, really doesn't matter unless the air in the case is stagnant.

 

[aigomorla]

i like top supplys better.

here is my theory.

when your comp is loaded, the air coming out of a psu is HOT.

Hot air rises.

I have radiator intakes in my rear so i dont like hot air going up into them.


unless this type of scenario applies to you, it doesnt matter where its at. As long as that hot air isnt coming back into your case, all is good.

 

[Zepper]

Geez, aigo, isn't that painful? Those intakes in your rear and all. I thought all along that that was for exhaust only. <BSEG> Definitely want that hot air going down and out...

.bh.

 

[aigomorla]

Originally posted by: Zepper
Geez, aigo, isn't that painful? Those intakes in your rear and all. I thought all along that that was for exhaust only. <BSEG> Definitely want that hot air going down and out...

.bh.

ROFL...

wheres that ban button!

j/k

 

[JEDIYoda]

Originally posted by: aigomorla
i like top supplys better.

here is my theory.

when your comp is loaded, the air coming out of a psu is HOT.

Hot air rises.

I have radiator intakes in my rear so i dont like hot air going up into them.


unless this type of scenario applies to you, it doesnt matter where its at. As long as that hot air isnt coming back into your case, all is good.

All I have to say besides--OUCH!!! Is it takes all kinds....heheheee