Fanless PSU Torture Test Roundup

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That the Seasonic X-400 Fanless would excel in this roundup was a forgone conclusion. Our full review last week showed that the X-400 Fanless passed our torture hotbox test at 400W for 15 hours without any problems whatsoever. It seems able to run indefinitely at full rated power with minimal airflow (at ~24°C room temperature). Efficiency and electrical performance is top notch. The X-400 is an SPCR Editor's Choice product and our #1 recommendation among fanless PSUs. Add totally modular cables and a 5-year warranty, and the $140 MSRP looks like good value in this roundup.

The Silverstone ST40NF is a solid second choice, with 80 Plus Bronze Efficiency (>87% at 50% load), good electrical performance, proven market longevity, and an effective OTP system. The latter seemed a little too aggressive, kicking in at a fairly modest 41~42°C in the hotbox. While the unit protects itself well from thermal damage, you will be hard pressed to get anywhere near the 400W maximum output without resorting to a fair amount of forced airflow in your system, which negates the reason for a fanless PSU in the first place. But up to perhaps 250~300W, the ST40NF should be able to run well with minimal airflow. The typical $160~170 market price puts it at a distinct disadvantage against the Seasonic. (Postscript, 23 Aug 2010: Silverstone informed us that effective immediately, the market price of the ST40NF will be reduced to $130~140.)

Even though our sample of the misleadingly numbered Silentmaxx MX-560PEL01 was the only one to fail and become inoperative in the torture test, we still put it (and its variously badged brethren) in third place... but it is hard to recommend without caveats. The efficiency and electrical performance is similar to that of the Silverstone, as its overall design and build. Obviously, the OTP circuitry is remiss, allowing the unit to overheat and fail without intervention. Still, if the total load is kept under 250W, we think it would work fine with at least a bit of airflow. Any higher, and you'd be well-advised to add significant forced airflow. The price seems to be extremely variable; we've seen the FSP branded 400W version with 2-yr warranty for as little as $110 in the US, but the identical Silentmaxx "560W" version as high as € 175 in Germany (warranty unknown). (Postscript, 23 Aug 2010: Why this sample failed when the virtually identical FSP-sourced Silverstone ST40NF did not is a bit of a mystery. It is possible that the OTP circuit in the Silentmaxx is tweaked to allow higher temperature operation without shutdown while that in the ST40NF is set for best protection. Perhaps the aggressive OTP setting is required for this PSU to run safely.)

The Coolmax CF-480B fared far better than expected, given its low efficiency. Electrical performance was quite solid even through the torture test, but it ran so hot that caution is advised. Its OTP feature worked well to protect itself, but the low efficiency requires a lot of forced airflow at 400W or higher for the unit to work without thermal shutdown. The high power consumption, hot operation, and typical market price of $100~120 in the US makes it a tough sell; at least Coolmax offers a 3-year warranty. Still, most users would be better off with a more modern, higher efficiency, quiet, fan-cooled PSU.

The SilenX Luxurae 460 proved to be poorly documented, and a poor performer in almost every way. It had only one edge over any of the other contenders: Higher efficiency than the Coolmax. In every other way, the SilenX did not make the grade. The horrific electronic whining noise at 250W load was enough after just an hour for us to pull the plug on it and fail the unit. The MSRP of $240 is a joke; we obtained it from Directron at a sale price of $46 with a 1-year warranty. We're hoping they will take it back. Enuf said.

Only time can really tell, but it seems safe to say that with the X-400, Seasonic has single-handedly transformed the fanless PSU into a really viable product, not only for the users but for the resellers.

Fanless PSUs Balance Sheet
Likes Quibbles
Seasonic X-400 Fanless
* Highest >90% efficiency
* Silent
* Extremely hardy in hot conditions
* Top Electrical performance
* OTP works well
* Hardly any buzz
* Innovative engineering
* Top quality components & build
* All modular cables
* 5-year warranty
* Price? About the only thing we could quibble about... but then all fanless PSUs are pricey. At $140, this is one seems well worth the money.
Silverstone ST40NF
* High >87% efficiency
* Silent
* Excellent electrical performance
* Hardly any buzz
* OTP works
* Long market presence and decent distribution suggests good reliability
* 3-year warranty
* OTP kicks in too early for full output to be reached in a low-airflow setup
* Price. With Seasonic at $140, typical market price of $160~170 is too high. (PS: Apparently ro be reduced to $130~140 in light of Seasonic price. Still a FSP Zen 400 can be had for only a bit over $100.)
* Not quieter than quiet fan cooled PSU in real >250W system due to PSU cooling requirements
Silentmaxx MX-560 (FSP Zen 400)
* High >87% efficiency
* Silent
* Excellent electrical performance
* Low buzz
* 2-yr warranty (on FSP version) is better than 1-yr; not clear about the Silenmaxx warranty
* Misleading model number
* Thermal failure
* OTP did not work
* Not quieter than quiet fan cooled PSU in real >250W system due to PSU cooling requirements
* 2-yr warranty still short
Coolmax CF-480B
* Silent
* Good electrical performance
* Low buzz
* OTP works
* 3-yr warranty
* Efficiency way too low
* Runs too hot
* Not quieter than fan cooled PSU in real >250W system due to PSU cooling requirements
SilenX Luxurae 460
* Didn't blow up
* Cheesy add-on fan that isn't even quiet
* Poor electrical performance
* Poor efficiency
* Runs too hot
* Screw holes that can't be used
* High electrical noise / buzz noisier than quiet fan cooled PSU in >250W system
* Terrible documentation
* Ridiculous $240 MSRP

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SPCR Articles of Related Interest:
Power Supply Fundamentals
Recommended Power Supplies
SPCR PSU Test Rig V.4.1
Seasonic X-400 Fanless
Silverstone Nightjar ST45NF: 450W Fanless
Silentmaxx Fanless 400W MX460-PFL01 PSU (FSP Zen)
Coolmax Taurus CF-300
Tiny, Silent and Efficient: The picoPSU
Winmate DD-24AX DC-DC Module for Silent, Efficient Power

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