Todays Hot Mod: Reverse PSU Cooling

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I looked at cases with the power supply at the bottom and ultimately decided to get one with it mounted on top.

People keep repeating over and over that heat rises. Yeah, we all get that. We're all over the age of two. Yes, heat does rise, but the power supply itself can get pretty hot under load, even though it has a fan.

So in a case with the power supply on the bottom, down with all the dust and hair, the heat from the power supply is rising, rising, rising up to the video card, the CPU, the mainboard, the RAM, etc. Personally, I'd rather have my $140 PSU run a bit warmer at the top of the case than put it on the bottom and have it heat up my $275 video card, my $275 CPU, etc. Not only that, but maybe all the dust and hair that accumulates at the bottom of a case would be more damaging to the power supply than it running a little warmer at the top.

Just my opinion of course.
 


Actually, the PSU doesn't radiate heat like you are describing. That's why the fan is there. It pulls the heat out of the power supply and out of your case. And all that dust? You need to keep your system cleaner than that!

And, Crashman, you can get ultra quiet 120mm fans that move more air than a little 80mm fan on a PSU does. Scythe has a fan that outputs 8dba, that's almost no noise. But, being an extreme overclocker, I really don't care about noise. I care about my hardware not shorting out.
 


The fan helps, but does not eliminate, internal heat in the PSU. When I touch the outside metal on my PSU, it's hot. It is therefore radiating some of its heat exactly the way I described.

The dust issue can be helped by cleaning, but even if you vacuum your case often, gravity is still guaranteeing that you will have a dustier, dirtier power supply if it's on the bottom of the case.
 
My place is pretty dusty, but I don't end up with more dust in my power supply with it at the bottom. Actually, it's the same amount as the rear radiator has that is mounted at the top back of the case. Your PSU case may get hot to the touch, but most of that heat is pulled out by the power supply. All you need is a thermal imaging device to see exactly how the heat is radiated in your case. Maybe you have a crappy PSU. Yeah, you spent $140 or so on it, but that doesn't mean quality. Oh, and for the record, my PSU is on the bottom, with $500 worth of video cards above it and a $1000 processor above them.
 


LMAO! You're using the exception to disprove the rule? That's just a modified version of someone else's case, a case that was designed to appease you rather than provide the perfect configuration.

I suppose all the "engineered" computers from other brands don't matter then.
 
Korbie,

Do you live on the international space station? If not, you will have more dust/dirt on the bottom of your case. I can't imagine how/why you would be trying to argue this.

Your PSU is radiating heat too. Obviously the fan is blowing most of the heat out of it, but not all. I can't imagine how/why you would be trying to argue this.

The fact that you spent $1000 on a CPU might have something to do with it...

 
Each case tends to have a different air flow path.

Example

Sonata 2 and 3
Air is drawn in at the front bottom and back bottom next to the expansion slots. this allows the cooler hard drives to get the air first then the video card(which gets some fresh air from the back as well). Now the semi warm air moves over the cpu taking the last heat source on its trip out the rear fan and PSU. Since the air at the top of the case is now hot the PSU has to suck hot air, thereby lowering its maximum wattage output(its even worse with cheap ones). This is why many people say the psu is warm or even hot to the touch. it's not making all that heat by itself(but its still makes some. about 20-25percent of its power goes away as heat).

Now you look at a case with a bottom PSU. I am going to use the 900 as a example.

Cool air comes in the bottom front passing the cool hard drives(this depends on how you have it set. mine comes in all over) and in the back near the pci cards again. So now some air goes out the bottom of the case through the psu. This air since is cool to begin with causing the psu to spit out cooler air. In this case my psu air has never been warm since its getting rid of its own heat and not the full systems heat. The rest of the air goes over the normal path of video card(s) over the cpu area and out the rear fan and large top blow hole. The top air is much cooler since has skipped the psu.

Neither item is excessively hot but when all the air goes to one place the heat builds up quicker. So if the psu raises the heat by 3-5 c and the cpu raises it my 2-5 c, together it can be 5-10c hotter then the case air that has already passed over the hard drives and video card(s)

Both ways have a flaw anyway. the massive variation in hardware on the market. The lower rear intakes while good backfire when a video card dumps its heat out the back(or even when the psu does this, but it has less impact since its cooler) of the case since that hot air is drawn back in. This ends up being like a short circuit of air that gets heated by the video card dumped out the back them drawn back in and heated more and it just keep looping. So in some cases sealing off those rear inlets(as long as you have enough other inlets like a side vent or more front vents) forces the computer to get fresh air elsewhere and can lower the internal temperature of your case.

Ohhh and just for a point i had a old HP that ran the psu fan backwards and pressurized the case forcing out hot air through a vent of the front after it passed over the hard drive on its way out. As long as one thinks of airflow any case can be made to work well.
 
You guys are childish. Honestly, how old are you? You must not build your own systems or your ridiculous arguments would have stopped a long time ago. Dust is negligible. The heat radiated is negligible when the fan pulls most of it out. Don't be jealous that I can affoard a $1000 cpu and you can't. Is it wrong for someone to want the best processor out? No. My next cpu will be the penryn extreme processor and I'll drop another grand on that. Heat is a big issue, and obviously a psu mounted on the bottom is the preferred way to go. That's according to Silverstone, Gigabyte, Antec, Voodoo, just to name a few companies that incorporate the bottom mounted PSU into their products. Get with the program. Your arguments are invalid. Mine are based on reviews that I've read from Anandtech, Tomshardware, xtremesystems and HardOCP to name a few. Do your research and come to your senses. Oh, and don't hate on a guy that has better stuff than you.
 
Yeh Korbin, get with the program: Everyone is copying everyone else and VooDoo is just using popular designs from other companies. Lian-Li came out with a power supply at the bottom and a bunch of people like you asked Silverstone if they could have one, so Silverstone made one. Gigabyte said "Let's design a case with all the features that people like Korbin want" so they looked at the Lian-Li and said "People want the power supply at the bottom, let's do that"

It's easy to see that this is all a huge case of Monkey See Monkey Do, which is why Cooler Master waited YEARS before giving up and caving in on it's latest designs.
 
As crashman said a while ago, for the people that this would even remotely concern, their internal case temperatures would most likely be in the low 30's, so the minute difference between having the power supply at the top or the bottom is really a moot point.
As for the power supply being "hot to the touch" in electronics terms that means nothing. Most people exhibit uncomfortable sensations around 43C, and pretty much all electronics can and will run forever at that temperature. Also, if you look at the specs for any power supply, (visit antec's site, for example), they state that the supply can deliver its full rated power 24 hours a day at 50C.
 
Heat radiation from a PSU is negligible. Remember that we don't care about trivial differences of a single-digit % or single digit watts. Not in an actively cooled system with thermally adjusted fans that produces at least 200W (below 200W, you can do darn near any config and it'll still stay cool enough so long as the case at least has a basic passive intake of suitable size and the AMD / Intel recommendation for a PSU exhaust plus one smaller fan.

When things get more interesting is when the video card alone produces over 100W, the CPu produces over 70W and you're trying to use the OEM heatsink, or there are so many hard drives in front that it's half blocking the intake airway (of course, ignoring all the really pathetic old case designs out there which were designed for the Pentium 3 era and put mostly stamped out metal around all the fan mounts because all they cared about at the time was EMI).
 
I have a Lian-Li PC-Q07, a teeny-weeny mini-ITX that leaves only about 9-10mm of space between the PSU and LOW-PROFILE CPU COOLER(!), as well as pretty much everything else inside the case, AND there are no room for other system fans at all inside this tiny aluminum case: solution would be as the top of this thread suggests; to REVERSE the PSU fan so that it draws air through the PSU and into the case, and being a regular ATX 400W+ PSU, there no worry about hot air from the PSU blown into the case; the Shuriken(sp?) LO-PRO 32.5CFM CPU cooler (blows down into the CPU/board) would totally get a nice BOOST from the PSU fan; these are the ONLY TWO FANS in this mini-ITX configuration... average IDLE temps were 58C Mobo/62C CPU (ASUS MoBo/PhenomII X3 65W ONLY)... now they're only 42C/45C respectively. You'd have to break the rules when the engineering+styling become tortured as in the case (pun intended) with Lian-Li PC-Q07.

B. Chan
 


Then why does my Antec 750W HCG PSU, which is an ATX PSU, pull air from outside the back of the case and exhaust it inside the case? I wondered how my PSU internals got so dusty when the rest of my components were relatively clean. Definately going to be flipping my fan around.
 
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