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SilverStone ST30NF Fanless ATX12V PSU

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The SilverStone ST30NF is probably the most sophisticated fanless PSU we’ve examined thus far. It weighs 6 lbs, uses a heatpipe cooling system, has twin LEDs for operational and temperature status, Active PFC, and even looks really slick. Rated at just 250W (for 120VAC input) but priced at US$159. Hmmm…

Sept 4, 2004 by Mike Chin

*POSTSCRIPT
added Oct. 22, 2005*

*POSTSCRIPT #2
added Jan. 11, 2007*

Product
SilverStone ST30NF
250W/300W ATX12V v1.3 Fanless Power Supply
Manufacturer
SilverStone
MSRP
~US$159; street price is probably lower

SilverStone’s forte is in stylish aluminum cases, but like most brands in the PC business, they’ve branched out into several related areas, including CPU coolers, case accessories, fans, and power supplies. This last category of products has seen a high number of new players in the last year or two. There used to be only a dozen or so PSU brands for years; now, brands associated with memory, cases, heatsinks, or motherboards — just about every kind of brand! — sport new lines of PSUs. Naturally, very few, if any, of these new PSU are actually made by the companies whose brand they sport. They are made by a handful of manufacturers, mostly in China, who happily churn out OEM PSUs on demand in accordance with whatever the client company specifies.

Such is probably the case with SilverStone’s several PSU lines, but it’s difficult to be sure with the SilverStone ST30NF. This fanless PSU features a great deal of aluminum extrusion in its design, and given the company’s expertise and resources in aluminum fabrication, it is just possible that the ST30NF is the result of a cooperative effort between SilverStone and a PSU maker.

Whatever its origins, the SilverStone ST30NF makes a strong first impression. Its high >6lb weight, sleek silver lines and the logo embossed into a side panel — all these create a sense of quality and rugged substance. The appearance, weight and feel certainly raised my expectations.

BASICS

The ST30NF comes well packed in a large box (for a PSU) with a power cord, an L-bracket and screws for securing the unit to the top panel (when mounting holes are available in the case) and a very impressive 24-page manual with detailed use and troubleshooting instructions along with full specifications of the product.

Despite its obvious desirability for silent computing, I have yet to find a fanless PSU that does not require special care in use to avoid overheating. I’ve come to the conclusion that this is not really a fault of the fanless PSUs, per se, but of the ATX case standard which (in a tower case) places the PSU at the top rear of the case where it is the recipient of all the rising heat in the PC. The fact remains that this is the environment for which a fanless PSU has to be designed to work within.

The ST30NF has a feature that addresses the heat issue: It features a warning LED that changes color from green to red when the PSU gets too hot. The LED is inconveniently loaded on the back panel where it is unlikely to be looked at by most users except when there is already something wrong. But perhaps that’s enough. It is reassuring to me that this feature is there. It is a sign of practical, realistic thinking. To me, it means the designers have thought about heat seriously: Even if the unit is well-designed to cool itself fanlessly, the designers are aware that they have no control over how it is used, so provide the user a means of gauging when the conditions for the PSU are not optimal.

FEATURE HIGHLIGHTS

This information is culled from the very comprehensive manual.

FEATURE & BRIEF COMMENT
ATX12V V1.3 Intel PSU Guide compliance
One standard behind, latest is 2.03; does not support PCI Express.
Extruded Aluminum Casing with Heatpipes for good heat dissipation
Most fanless PSUs have lots of heatsinks, but this one is more stylish and a bit heavier than most.
No-Noise Fanless Design (0 dB) Nice; the reason this PSU is under review, of course.
Dual LEDs for Power Status and Temperature Status Unique and potentially very positive.
MTBF >100,000 Hours at 25°C, full load; 3 years warranty
Both are very good, but how you’d keep the temp at 25°C while running the PSU at full load is a mystery.
Universal AC Power Input (100-240VAC)
Nice, but maybe more useful for inventory control than for users: PC users don’t travel between different AC zones w/their ATX PCs.
Active PFC for improved energy efficiency and reduced current load on AC delivery systems.
Definitely a plus. ALL PSUs should have APFC, especially higher power units.
Protections against Overvoltage, Short-Circuit, Over-current, Over-power, and Over-temperature Pretty complete!
Safety / EMI Approvals: UL, cUL, CB, TUV certification / CE, FCC class B and CISPR class B
Generally, the more the better.

SPECIFICATIONS

As mentioned previously, the ST30NF accepts 100-240VAC without any manual switching. But the rated power output is higher with 200~240VAC compared to 100~120VAC, and the manual actually provides two separate tables for output specifications. For Canadian and U.S. users, then, this PSU is a 250W unit.

Interestingly, the product web page claims that the ST30NF can deliver “abundant reserves of power… [with] a peak rating of up to 400W+.” This is not reflected anywhere in the technical specifications.

SilverStone ST30NF Output with 200-240VAC Input
DC Line
+3.3V
+5V
+12V
-12V
+5Vsb
Max Output
23A
25A
18A
0.7A
1.5A
Ripple & Noise
±50 mV
±50 mV
±120 mV
±120 mV
±50 mV
Min Load
0.8A
1A
0.5A
0
0
Max Power
180W (3.3V + 5V combined)
8.4W
7.5W
35A (5V + 12V combined)
300W

*

SilverStone ST30NF Output with 100-120 VAC Input
DC Line
+3.3V
+5V
+12V
-12V
+5Vsb
Max Output
20A
21A
17A
0.7A
1.5A
Ripple & Noise
±50 mV
±50 mV
±120 mV
±120 mV
±50 mV
Min Load
0.8A
1A
0.5A
0
0
Max Power
140W (3.3V + 5V combined)
8.4W
7.5W
30A (5V + 12V combined)
250W

*

Other SilverStone ST30NF Specifications
Ambient Operating Conditions* 0~25°C; 90% maximum relative humidity
Power Efficiency 70% (min) at full load
Temperature Status LED
Indicates surface Temp of PSU housing
Red: High > 55°C
Green: Low < 55°C
Power Status LED
Indicates PSU working status
Amber: Stand by
Green: Power ON
Red: Power Fault
* The operating temperature range is very low; however, test results indicate otherwise, as does the Temp Status LED, which does not light red till 55°C is reached at the PSU housing.

VISUAL ANALYSIS

The ST30NF external casing is composed of many well-fitted aluminum extrusion panels. Some are connected directly to internal heatsinks. The design is very much like a clam shell, one with too many parts for me to pull apart safely, as you will see below.


As you may have already noticed in the photo on the previous page, there
are vent holes on the back panel.


The inside front panel (opposite the back panel) is much more generously
vented.

The bottom panel is also vented.

There’s no doubt that the vents on inside panels are meant to act as air intakes. The vents on the back panel are supposed to allow the hot air to escape, but they seem a bit too small for effective airflow with just passive convection alone.

UNDER THE HOOD


Under the top cover is a clear plastic insulating sheet between the PCB and
the cover.


The inside intake vent panel came off without too much trouble.


The PSU is packed very tightly indeed! (PSU is sitting on top of the top
panel).


On the other side, there are soft rubbery thermal pads with TIM on both sides
for efficient conduction of heat between the heatsinks and the other casing.


A view of one side…


…and the other side. Note the copper heatpipe.


A closer view of that heatpipe.


An animated image from SilverStone shows what the heatpipe cooling system
does.


This side label indicates a different model number.

The label above indicates a different model number. A Google search on EFN-300 led me to the Etasis web site, which details a fanless PSU with this model number. It looks very similar to the SilverStone ST30NF, and the specs are virtually identical. I am quite certain that Etasis is the maker of the ST30NF.

The tape measure is extended to three feet.
OUTPUT CABLES:
20″ sheathed cable with ATX connector
29″ cable w/ 2 standard 4-pin power connectors
2 x 34″ cable w/ 2 standard 4-pin power connectors & 1 floppy drive connector
Sheathed 20″ cable split at end into AUX connector and 2x12V connector
2 x 20″ cable w/ SATA connector

(Update Jan. 11, 2007: Silverstone has made some changes to the cable sets
to keep the ST30NF up-to-date. It now sports a 24-pin ATX header, two extra
SATA connections, and a PCIe plug. Details in postscript
#2
.)

ON THE TEST BENCH

For a complete rundown of testing equipment and procedures, please refer to the article SPCR’s Revised PSU Testing System. It is a close simulation of a moderate airflow mid-tower PC optimized for low noise.

In the test rig, the ambient temperature of the PSU varies proportionately with its actual output load, which is exactly the way it is in a real PC environment. But there is the added benefit of a precise high power load tester which allows incremental load testing all the way to full power for any non-industrial PC power supply. Both fan noise and voltage are measured at various loads. It is a very demanding test, as the operating ambient temperature of the PSU often reaches 40°C or more at full power. This is impossible to achieve with an open test bench setup.

Ambient conditions during testing were 26°C and 17 dBA, with input of 119VAC / 60 Hz measured at the AC outlet. The intake temperature was read by a sensor in the testing box positioned about an inch below and behind the PSU; this can be considered the operating ambient temp. The casing temp was measured with a sensor placed in one of the exhaust vents on the back panel.

TEST CUSTOMIZATION FOR ST30NF

The test rig was modified slightly for the fanless operating of the ST30NF, as for the Coolmax Taurus Fanless PSU review. In SPCR’s PSU Testing System, there are four medium speed 80mm fans at 5V that blow the heat from the loaded resistors in the PSU load tester into the thermal simulation box. There is a slight positive airflow pressure in the box which actually helps with PSU cooling. An exhaust Panaflo 80M fan at 5V just below the PSU serves to reduce the positive pressure somewhat and to better model a typical low noise system.

  • The sides and top of the ST30NF is open to the outside in the test rig. This allows heat to be radiated directly to the outside air, something that never happen in a normal system setup. So the top and side were blocked off with a piece of cardboard. It’s true that close proximity allows some transfer of heat to the top panel of a typical case, but I wanted to err on the stringent or conservative side in testing.
  • Testing was done with the 80mm exhaust fan removed from the test box. Because the PSU has no fan, the amount of air that flows through it depends on convection and the positive pressure in the case. The exhaust fan was removing some of the heat, on the one hand, but also reducing the amount of positive pressure in the case. In an attempt to answer the question, the exhaust fan was removed and the hole for that fan was left open.

After an initial minute or two of temperatures dropping and rising, once things stabilized, there was no change in temperature with the fan blowing out at 5V versus the fan completely removed. This held true for test loads. I believe this means that the airflow produced by the fan is effectively no greater than that created by convection alone, although it does not feel like that — when I place my hand in front of the hole. Perhaps some cool outside air enters while some hot air exits.

On to the results…

SilverStone ST30NF TEST RESULTS
DC Output (W)
65
90
150
200
250
AC Input (W)
86
117
192
247
312
Efficiency
76%
77%
78%
81%
80%
Intake Temp (°C)
30
34
38
41
44
PSU Casing* (°C)
33
46
52
60
77*
NOTES:
The ambient room temperature during testing varies from review to review.
Please take this into account when comparing PSU test data.
* PSU Exhaust: The unit was accidentally left running at full power load (250W) for nearly two hours.

1. VOLTAGE REGULATION was excellent. Throughout the range of test output levels, the range was as follows:

  • +12V: 11.79 ~ 12.25V
  • +5V: 4.98 ~ 5.11V
  • +3.3V: 3.27 ~ 3.37V

2. EFFICIENCY (AC-to-DC Conversion) was excellent, starting at 76% at the low 65W load test where even high efficiency models tend to drop. The efficiency range was also very tight, varying only from 76% to 81%.

3. POWER FACTOR was excellent, always 0.97~0.99, regardless of power load.

4. NOISE: There was no noise to be heard at all. No whine, no buzz, nothing. It was dead silent. It must be pointed out that rare is the PSU that buzzes with the pure resistive load of the power tester. This is no guarantee that the unit will not hum or buzz when faced with the more complex (though lower power) loads of PC components. Coil buzz is often the result of interactions between components.

3. POWER OUTPUT & TEMPERATURE: Care was taken to ensure than neither the 140W (3.3V + 5V combined) max power nor 30A (5V + 12V combined) max current was exceeded during testing. The unit ran with good stability at all output levels. The full 250W output at 100~120VAC input was confirmed. As the lab is not equipped to provide 200~240VAC, the higher 300W output at this input voltage could not be confirmed.

The ST30NF test sample was accidentally left running at full power (250W) for nearly two hours.
As noted in the results table above, the casing temperature reached 77°C and was too hot to be touched for more than an instant. Much of the insulating foam strips on which the PSU rests in the test rig ended up melting due to the high temperature. Yet the sample PSU showed no signs of any distress. Amazingly, there was not even the electronic burning smell that usually results when a PSU is overheated. Finally, a second set of load tests yielded exactly the same results.

Interestingly, neither of the back panel LEDs changed color from green during the lab testing, except once: When the 250W full load test had been running for about 10 minutes, the PSU temp was at 64°C, and the temperature LED had not changed from green. With the casing temp at 77°C two hours later, the temp LED was glowing red. I did not witness exactly when the LED color changed, but obviously the 55°C trigger point mentioned in the manual is not correct, at least for this sample. With the power load reduced to absolute minimum and external fans turn out to help cool off the unit, the temp LED stayed red as the temperature dropped to below 50°C. It was only after the power was turned off for a couple of minutes and turned back on that the temp LED changed back to green.

IN-SYSTEM TESTING

This is not a standard procedure for all PSUs, but fanless ones do require extra attention. The test system is a mid-high end one similar to that used in the Coolmax Taurus Fanless PSU review but with a different case.

  • Chenbro Xpider case
  • Zalman 400B PSU (ATX12V v1.3) modified with Panaflo 80L fan
  • AOpen AK89 Max (nVidia3 Athlon 64 board)
  • AMD Athlon 64 3200+ (Cool ‘n’ Quiet enabled)
  • Zalman ZM7000A-AlCu heatsink w/fan at 6V (via SilentBIOS of motherboard)
  • ATI 9800 Pro VGA with Arctic Cooling VGA Silencer (fan set to low)
  • Crucial PC3200 memory, 256MB
  • Samsung MP0402H 40G 2.5″ 5400rpm notebook HDD (for Windows XP OS), placed on foam in 3.5″ drive bay
  • Seagate Barracuda V SATA 80G hard drive (for data), placed on foam just behind front intake fan
  • Asus QuietTrack DVD/CDRW Drive
  • Panaflo 92mm low speed exhaust fan set to 7V
  • Panaflo 80mm low speed intake fan set to 7V
  • Case placed on thick piece of closed cell foam to insulate vibrations from hardwood floor

This case is set up with a PSU intake vent and duct. The top optical drive bay is left open, and a piece of close cell foam divides the PSU and intake path (from the optical drive bay to the PSU). This ensures that the PSU stays well cooled to ensure its fan never ramps up. The duct/vent was left in place for the ST30NF.

Some temperature and power measurements were taken on the above machine. Then it was shut down and the modified Zalman PSU swapped for the SilverStone ST30NF PSU. No other changes were made.


SilverStone ST30NF simply swapped in place of the Zalman PSU.

A thermistor was placed on the back exhaust grill of the ST30NF (in the same spot as during the lab testing). The following temp measurements were taken after 30 minutes in each state. The ambient temperature for the in-system testing in this room (my office) was 23°C, 3°C lower than in the lab.

PSU
State
Temperature (°C)
AC Power
Noise dBA@1m
CPU
Board
PSU
SilverStoneST30NF
Idle
38
37
47
104W
23
Folding
56
42
52
142W
CPUBurn
64
44
55
155W
Zalman 400B modified
Idle
38
37
42
112W
24
Folding
56
42
45
151W
CPUBurn
64
44
47
166W

Ambient room temperature: 23°C.

THERMAL ANALYSIS

It’s
evident that the case and CPU temperatures were unaffected by the PSU swap because
the PSU intake channel / vent isolates the PSU from the rest of the system.
The open duct to the front helped keep the ST30NF stay a bit cooler;
in the absence of a fan, the difference was probably not more than a couple
of degrees.

More significant is the insulating effect of the duct in keeping the PSU heat from the rest of the system. Chances are, the CPU and case temps would have gone up by a couple of degrees without the PSU duct. As the table shows, the CPU and case temps remained identical with either PSU. The casing temp after 30 minutes of CPUBurn was 55°C. The 155W AC draw puts the DC output load at around 120W; with the 3°C differential applied, this is a couple of degrees hotter than it would have been in the PSU thermal simulation box (on the test bench). Both LEDs on the PSU always remained green throughout the in-system testing.

The top panel of the steel case became quite warm during stress testing, but remained relatively cool when the system was idling. Folding@home is probably fairly close to the max stress a home system would see with real applications. The temperature stayed relatively modest even after many hours of Folding.

The voltage lines were perfectly stable throughout the in-system testing, which took place over a 4-day period. See the screen capture below (showing the highs and lows) from one of the several runs of stress testing.


Screen capture of high/low report in Motherboard Monitor 5 (MBM5).
NOTE: This motherboard does not draw on the -5V line.

CONCLUSIONS

The SilverStone ST30NF is the most capable fanless PSU I have tested or used thus far. The features alone are impressive enough, but more importantly, real performance was exemplary throughout bench and in-system testing.

The isolation of the PSU with the closed-cell foam sheet helped to keep its heat from affecting other components in the in-system test. This is a technique fanless PSU users may want to experiment with. Given the high efficiency of this PSU, even without the isolation, the increase in the temps of other components would have been minor.

The aplomb with which the ST30NF shrugged off the extreme high temperature it was accidentally subjected to is impressive. Few systems can actually draw 250W DC; if you have one that can draw this much power on a long term basis, good airflow cooling around the PSU is recommended. It would be particularly beneficial to cut an opening in the case to expose the top PSU panel.

I believe a key to understanding the performance of this PSU lies in the unsubstantiated comment in the product web page, “a peak rating of up to 400W+.” It is likely that the core components could allow this PSU to be fairly rated at over 400W if it was fan-cooled. Despite the modest 250W output rating, this unit can easily handle much more than the power demand of the system used for the in-system test. With some additional airflow it can probably do more than 250W fairly easily.

The ST30NF may be the perfect PSU for use in aluminum HTPC cases like SilverStone’s own SST-LC01, where the high conduction of the aluminum would help dissipate the PSU heat more efficiently than a steel case. The SilverStone SST-LC01 deserves a firm SPCR recommendation.

PRO
  • No fan; silent operation
  • No buzzing or whining during in-system trial
  • Very high efficiency
  • Very high power factor
  • Very good passive cooling system
  • Easily meets output claims
  • Excellent voltage regulation
  • Stable in-system operation
  • Great manual
CON
  • What’s not to like?
  • Price?
  • No PCI Express compatibility

Much thanks to SilverStone for this ST30NF PSU sample.

POSTCRIPT: Efficiency Correction
October 22, 2005
Recently, we discovered that our power supply testing equipment and methodology were providing erroneously high efficiency results. In general, the biggest errors occurred at higher
output load points above 300W. At lower output levels, the efficiency error
was often no more than one or two percentage points. No other tested parameters were significantly affected.

Through a fairly arduous process of discovery, analysis and old fashioned problem solving, we modified our testing equipment and methodology to improve the accuracy of the efficiency results and described it all in the article SPCR’s PSU Test Platform V.3. As part of this revision, we re-tested most of the power supplies on our Recommended PSU List. In most cases, the same sample was used in the second test.

The corrected and original efficiency results for all the re-tested PSUs are shown in in the article, Corrected Efficiency Results for Recommended Power Supplies. The relative efficiency of the tested power supplies has not changed.
If the tested PSUs are ranked by efficiency, the rankings remain the same whether we use the original results or the new results.

This
data is also being added to relevant reviews as postscripts like this one.


CORRECTED EFFICIENCY: SilverStone ST30NF

Target Output


65W


90W


150W


200W


250W

Actual Output
65.0W
93.6W
149.6W
200.5W
251.5W

Efficiency

Corrected
75.6%
78.7%
80.8%
80.5%
79.6%

Original
76%
77%
78%
81%
80%

In this case, our original efficiency calculations were very close: Slightly low through to about 150W output, then a touch high at 200W and 250W.

POSTCRIPT #2: Updated Cable Sets
January 11, 2007
As power supplies go, the ST30NF has good longevity. It’s been on the
market for more than two years, and a lot has changed since it was first
released. As such, Silverstone has updated it to keep up with the times.
Most significantly, the new revision includes the connections that are
now standard in the industry. At the time of writing, the ST30NF now comes
with the following connections:
  • 20+4-pin main ATX connector — changes for the old 20-pin plug
  • 4-pin AUX connector — unchanged
  • 6 x 4-pin IDE connectors — unchanged
  • 2 x Floppy connectors — one more than before
  • 4 x SATA connectors — two more than before
  • 1 x 6-pin PCIe connector — this one is completely new

 

 

* * *

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