Much as a fanless PSU seems a natural part of the SPCR holy grail, my assessment of ALL the ATX fanless PSUs I have seen, examined or read about are not encouraging. Here's what I think about fanless PSUs:

1) The power ratings are almost meaningless because there's no way that cooling can be effective enough in real applications. Even on a standard test bench, I think fanless PSUs cannot meet their rated power for any meaningful length of time. A slow 80mm fan at even 6V moves far more air than convection alone can do -- unless the PSU is carefully engineered as a chimney style structure.

2) Conversely, the failure of a fanless PSU to deliver rated power is not that big a deal because few current systems actually draw anything more than 200~250W in DC, , but it is annoying that PSU makers keep playing the meaningless specs game. I would be much happier to see real specs -- rated at 50C. 250W at 50C would be enough for most systems especially if the 12V current can be decent -- say min 12A, 15A preferred.

3) A fanless PSU cannot be run in a fanless PC unless total system heat is very low, the ambient temp is modest (say under 25C) and the system is superbly designed to take advantage of convection cooling.

4) A medium or high power system can be run with a fanless PSU only if the case is custom-designed for fanless operation with that PSU. In a standard ATX case, there is simply no place for the heat from the PSU to go. Which means it stays in the case and cooks -- everything. The PSUs with external HS may fare a bit better, but it's all going against the thermal flow.

If you have a 90% efficiency PSU with really clever heatsinking in a case that is custom-designed to draw cool air across the HS and OUT of the case, then a fanless PSU (and system) is a practical reality.

The best example of this kind of integrated design is the HUSH ATX PC, which I believe is limited at this point to the P4-2.8. (Thermally speaking)

UPDATE March 27, 2015
As forum member Silencer56 pointed out recently, the above post and much of the discussion that follows have become largely obsolete in the current age of super-efficient PSU.

The only current fanless ATX PSUs we know about are at least 80+ Gold efficient, which means they are ~90% efficient, producing only 10W of heat to deliver 90W of DC. Because there's much less heat from the PSU, as long as overall power draw isn't very high (say under 250W), silencers should be able to employ fanless PSUs in a modern case with good airflow design without risking overheating of other components.

The maximum power ratings of such efficient PSU are also far more believable, as we saw in our 2010 Fanless PSU Torture Test Roundup.

Point #3 of the original post is still relevant -- a fanless PSU is best not used in a fanless PC unless total heat/power is modest.

As high efficiency CPUs, PSUs, GPUs and silent SSDs proliferate, one noise issue has become increasingly serious: Electronic whine. This mostly high frequency noise has always been present in PC and electronic gear -- TVs, monitors of all kinds, and power circuits in VGA cards & motherboards & PSUs almost always emit some degree of this noise. Even when audible, in the past, such noise has been masked by fan and vibration-induced noise. But now with more people option for PCs that have no moving parts, this electronic whine has emerged as a nasty gotcha for those who seek silence from their computers. There is no simple cure-all, and sample variance is broad.

Well after seeing this Coolmax fanless PSU, the wheels started spinning again for me. Since this PSU is designed for sort-of fanless operation (it has to rely on some airflow by the case fans), it seems to me it would work just fine as the outlet point for a positive pressure case.

I'll bet you could run a moderate power setup...say P4C 2.8..... with one 120mm fan blowing in from the bottom at medium speeds. Seal the case well and all the air would exit the case through this PSU.

I already have one low power setup running like this. I'm using a TruePower 330 with both fans removed. All the exhaust exits my case through the TruePower. So I'm using only one case fan (Evercool 120). Mine works well, even though the TruePower was never designed to work this way.

With the Coolmax, designed to run fanless, I'll bet this setup could work fine with a 2.8.....maybe somebody will try this. I'm running out of space for any new projects.

And I'll bet this setup would be no better than ~25 dBA/1m, judging from what I know and have observed about 120mm fans and the noise they make in PC cases. It would be a fair amount of effort to do, especially if you want to do away with the CPU fan as well. The end result would be considerably louder than the ~20 dBA P4-2.8 systems l I have achieved with multiple 80mm fans running at low speeds and 80mm fanned PSU with fresh air duct. So what's the point/advantage?

Frankly, I'd rather mod a leftover ATX PSU in the horrifyingly obvious way to make it fanless than pay good money for that Coolmax.

Personally, I think a fanless ATX power supply could work--IF the actual power supply electronics and heat sink were in an external "brick". The ATX "box" would merely be a grill face with fan mounting holes.

There are several advantages to the setup I suggested.....first, you would only have one intake fan to deal with, from a mounting and location stand-point.

And since there would only be one intake point, total case filtration could be achieved with one intake filter.

And since the exhaust point is directly above the CPU, you would have good airflow over the CPU and it's heatsink/fan. Running the CPU fanless is a possibility....but a separate issue to deal with.

One exhaust point equals only one point for noise to escape. One intake point means the same.

MikeC.....I wonder how many setups you've examined have been constructed like this? Frankly I've been surprised with the good results (noise-wise) with the several setups of mine similar to the one I suggested. I'm willing to try this super-positive pressure setup, but I hesitate at the cost of this PSU. Maybe when it gets cheaper.....

Whether a single 120mm fan running at medium speed is quieter than several min speed 80mm fans might be a point of debate. When I asked what's the point, I was referring not to your general technique, but to a fanless ATX PSU.

I accept you have achieved good results with 120mm fans & directed fresh air intake with lots of customization of the case. (This last is an issue; there are few people who can or are willing to do the kind of case customizations you have done. Even here.)

But the main issue I am addressing here is the value of a fanless ATX PSU. There are many appearing in the market, and there will naturally be takers. You & I don't need one to get quiet results and neither do lots of others. Having a fanless ATX PSU does not make for a system that's quieter than a PSU which is fanned. A fanless ATX PSU also is nowhere as reliable as one that is fanned. It simply causes more problems at higher cost without really solving anything.

That is the main point.

I mostly agree with you, with at least one exception. Since these new fanless PSUs are built heavy-duty, made to run without a fan.....the owner of this new PSU conceivably has one less possibility of failure: no PSU fan to worry about, and maybe a longer operating lifetime.

I firmly believe the fewer the number of fans, the better....noise issues aside.

Bluefront, silentmaxx's 550W fanless gave me an idea that I might try. I'm hesitant about trying, so you might want to go ahead first.

It involves putting a single low speed fan at the intake end of the PSU. The silentmaxx has that. It's a safeguard against overheating. They have a thermistor inside the PSU. Whenever internal temps exceed 60C, the fan comes on and runs until temps drop below 45C. This solves the problem MikeC pointed out while doing away with one fan most of the time.

I have a cheapo FSP-300W PSU and a nice VERY quiet Acoustifan 80mm with thermistor that I'm thinking of using. I have two hesitations though. (1) how to safely mod the PSU to remove the fan, (2) how to control the on/off behaivor of the fan.

Well removing a PSU fan is pretty easy.....you just have to be careful not to get shocked. Drain the PSU completely before taking it apart.

Controlling a fan as you suggest would be easy using a DigitalDoc5. It comes with remote sensors that could turn your fan off/on at adjustable temps. You'd just have to place the DD5 sensor in the PSU at a spot that gets hotter with higher usage. No big deal....but you might have to experiment with the sensor location.

Heh.....I've already got at least one home-made fanless PSU system running right now, so I know it works.

Pictures

More photos of cooler box w/fanless PSU

Bluefront, I agree with the fewer-fans theory--but in my case the argument is based on cost, compactness, and simplicity. I'm now on my third quiet computer, and it's yet another single fan design.

However, I just can't see spending $150+ on that Coolermax if you're going to make it the sole exhaust for a positive pressure case as you suggest. A leftover el cheapo PSU with the fan removed should do fine since you're using positive pressure to force air through it anyway.

IsaacKuo....you're right, but I think by using a PSU designed for fanless operation, you have a better chance of reliable operation. And you might be able to use a more powerful/hotter CPU. All theory of course till someone builds a hot system designed this way.

A fanless PSU may be good inside the new Lian-Li PC-V1000 case. The PSU section in that case appears to be separate from the rest of the PC. Whether the PSU will be able to operate fanless in these conditions remains to be seen.

I guess we will have to wait for a review of a fanless PSU to see how well it can perform....

Slightly OT....just saw a TechTV show. This caller had a computer in a wood workshop. He wanted something to lower the amount of dust getting into the case. Those two guys (Norton and the other guy, Kevin) recommended a new "fanless PSU", even though the callers computer only had the PSU fan blowing out.

They were serious....apparently not even considering the implications of no airflow through the case. Jeez.....

Don't do that.

) A fanless PSU cannot be run in a fanless PC

wanna bet? i'm making this post on a fanless PSU and fanless PC.
how?
SOYO TISU undervolting the TUALATIN.

Here is a new fanless candidate, a pretty sofisticated one, and cheaper than ALL the others:

Silver Stone SST-ST30NF

http://www.dirkvader.de/frame.php?site= ... stone.html

EDIT: what do you think about this PSU, boyz?

My argument:

I think fanless PSUs are so terribly expensive because they are made to last under heavy conditions, that is, high temperatures, without a fan. The Silver Stone and the Yesico, for instance, boast 2 year guarantee, like any other fanned PSU. Besides, as said by someone before, there is no longer a fan to take care about, and dust inside the PSU is reduced. So much for the "fanles is unreliable" argument, don't you think, MikeC?

Besides, when you use a fanned PSU with low airflow, and you go to fanless PSU, there is not much airflow to compensate, since the fanned PSU created low airflow. You get to reduce the noise a bit, and that's it.

What cannot be denied, is that a fanless PSU that transmits heat to its walls, will heat up the inside of the case, and you'll have to take care of that, which means either more fan speed/noise, or simply take the PSU out of the case (put it right ON the case), seal the PSU hole, and done (providing there is enough cable length to that).
Ain't that a solution, people?

Besides, are there cables in the market to extend the length of the molex/ATX connectors of a PSU, ocan they be done easily? With that you could use the PSU as a "fanless power brick", right?

I think you've missed MikeC's point. Even with low airflow, the cooling is MUCH better than with no airflow. Think about it. Why do we use undervolted L1As on CPU heatsinks, even though an undervolted L1A has very low airflow?

And if you're going to remove the PSU from your case ANYWAYS, then you can save yourself a considerable amount of money by purchasing a good fanned PSU and placing it outside the case, where it will be VERY quiet since it won't be heated by processors.

But you'll hear the PSU fan harder because it is not enclosed by the case!!

But the fan won't have to spin as fast. Check out MikeC's PC
http://forums.silentpcreview.com/viewtopic.php?t=10549

That link is interesting: the Fortron 350 is the quietest PS that has anywhere near comfortable temps: ~25dBA and "good" temps across the range.

BTW, I used Babel Fish to translate the page:

http://babelfish.altavista.com/

Unless a fanless PSU is completely sealed, it will still get dusty. They may do away with the fan and instead use positive/negative case pressure or convection currents, but that means there's still air flowing through the PSU. Air with dust in it!

Also, a fanned PSU moved outside the case won't be much more audible than the same PSU inside the case, even if one doesn't account for the reduced fan RPM's of an externalized PSU. The PSU fan is almost always located on the back panel of the case anyway, so it's not like there was much baffling to block the fan noise in the first place.

MikeC seems to use extensions to molex and the ATX connector, doesn't he?

Also, when you left holes open like MikeC does, what about electromagnetic emissions? PCs were designed to be run in closed, metal cases. That dampens electromagnetic emissions a lot.

Think about all the dual-fanned and 120mm PSU's on the market today. There's a big hole at the bottom where all that nasty EMI can get out of the PSU and zap the rest of the PC. Apparently, though, the EMI doesn't seem to be much of a factor after all!

If your computer is in a lab with sensitive equipment, then EMI might be something to consider when you've got the dremel in your hand and you're ready to make Swiss cheese of your case. But for PC's at home or at the office, I just haven't heard much fuss made about EMI emissions.

I must insist in those long PSU cables. Mine are not that large! Do expensive, good quality PSUs ship with such large cables, which allow to take the PSU out of the case?

Try an Antec Truepower.....my truepower 330 has an ATX cable about 21".

No, the cables are long enough to reach everything. No EMI issues with my cell phone in the same room -- except when the case ccover is open. Then my cell tends to have poor reception with bad interference. It's running with a Panaflo at 5~6V. My guess for noise level is something like 15~18 dBA/1m. Haven't measured it separately. It's not audible under the desk.

@MikeC: do you mean that almost all silent PSUs carry cables long enough for such operation?

I am having a look at MikeC's exterior PSU rig and I've post in that thread an idea I'd like to hear your opinion on. Here is the thread address again:

http://forums.silentpcreview.com/viewtopic.php?t=10549

Please have a look at my post and tell me what you think.

No... just that Zalman. You were commenting on my external PSU setup; I was responding to that comment.

I don't see any comments from you in that thread, btw.

One thing that interested me with the SilverStone SST-30NF is it has nice flat areas ie...
http://www.systemcooling.com/images/rev ... ge8big.jpg

I'm thinking spend $10 to add some copper tubiing and watercool them... I'm wondering if wtih that power supply will deal better with very little (no) airflow though it :/

I don't trust myself to mod a ps to watercool it... but I can add stuff to nice flat surfaces that arn't hot(live-hot). If spcr reviews th eSST-30NF and says it isnt crap I might get one for fun; $155 isn't the end of the world, just gotta go without food for a couple weeks TOO EZ ;P

I plan to buy Yesico 420 watt fanless PSU but have read that usually such PSU should work at temperature not above 25 with and at the greater heating they can lose power to give out her less

Also it is rather strange that on a site there is no engineering specifications on PSU not clear where also by whom it{he} is made in Germany or on Taiwan, that is simple if in Germany as a rule quality of the German goods very high!

http: // sg.hardwarezone.com/priceguide/newsview.php? id=595
Before I have found this link I thought that it is only German firm! Now I doubt what that OKAYA not clearly who for whom releases this PSU

And if fanless PSU to place not inside the case and to put from above on the case on a sticky tape (thermotape?), wires there long enough to get up to the bottom of the case!

There will be an excellent cooling and PSU will not be overheat!

And the case in general open to leave and put on CPU the big radiator with 12 Nexus fan. The fan by the way not necessarily rigidly fix to a radiator it is possible to suspend in general it in 3 sm from a radiator at me now so suspended on a wire for lattice PSU