Seasonic SS-400HT power supply, 80 Plus version

Power
Viewing page 3 of 3 pages. Previous 1 2 3

TEST RESULTS

For a fuller understanding of ATX power supplies, please read our article Power Supply Fundamentals & Recommended Units. Those who seek source materials can find Intel's various PSU design guides, closely followed by PSU manufacturers, at Form Factors.

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 output load, which is exactly the way it is in a real PC environment. But there is the added benefit of a 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 standard loads. It is, in general, a very demanding test, as the operating ambient temperature of the PSU often reaches >40°C at full power. This is impossible to achieve with an open test bench setup.

Great effort has been made to devise as realistic an operating environment for the PSU as possible, but the thermal and noise results obtained here still cannot be considered absolute. There are far too many variables in PCs and far too many possible combinations of components for any single test environment to provide infallible results. And there is always the bugaboo of sample variance. These results are akin to a resume, a few detailed photographs, and some short sound bites of someone you've never met. You'll probably get a reasonable overall representation of that person, but it is not quite the same as an extended meeting in person.

REAL SYSTEM POWER NEEDS: While our testing loads the PSU to full output (even >600W!) in order to verify the manufacturer's claims, real desktop PCs simply do not require anywhere near this level of power. The most pertinent range of DC output power is between about 65W and 250W, because it is the power range where most systems will be working most of the time. To illustrate this point, we recently conducted system tests to measure the maximum power draw that an actual system can draw under worst-case conditions. Our most powerful P4-3.2 Gaming rig drew ~180W DC from the power supply under full load ° well within the capabilities of any modern power supply. Please follow the link provided above to see the details. It is true that very elaborate systems with SLI could draw as much as another 150W, but the total still remains well under 400W in extrapolations of our real world measurements.

No acoustic recordings were made of this PSU, as it is essentially identical to the S12-500/600. Please check the sound files in the S12-500/600 review if you're interested.

INTERPRETING TEMPERATURE DATA

It important to keep in mind that fan speed varies with temperature, not output load. A power supply generates more heat as output increases, but is not the only the only factor that affects fan speed. Ambient temperature and case airflow have almost as much effect. Our test rig represents a challenging thermal situation for a power supply: A large portion of the heat generated inside the case must be exhausted through the power supply, which causes a corresponding increase in fan speed.

When examining thermal data, the most important indicator of cooling efficiency is the difference between intake and exhaust. Because the heat generated in the PSU loader by the output of the PSU is always the same for a given power level, the intake temperature should be roughly the same between different tests. The only external variable is the ambient room temperature. The temperature of the exhaust air from the PSU is affected by several factors:

  • Intake temperature (determined by ambient temperature and power output level)
  • Efficiency of the PSU (how much heat it generates while producing the required output)
  • The effectiveness of the PSU's cooling system, which is comprised of:
    • Overall mechanical and airflow design
    • Size, shape and overall surface area of heatsinks
    • Fan(s) and fan speed control circuit

The thermal rise in the power supply is really the only indicator we have about all of the above. This is why the intake temperature is important: It represents the ambient temperature around the power supply itself. Subtracting the intake temperature from the exhaust temperature gives a reasonable gauge of the effectiveness of the power supply's cooling system. This is the only number that is comparable between different reviews, as it is unaffected by the ambient temperature.

On to the test results.

Ambient conditions during testing were 23°C and 20 dBA, with input of 120 VAC / 60 Hz measured at the AC outlet.

SS-400HT Active PFC F3 TEST RESULTS
DC Output (W)
40
65
90
150
200
250
300
400
AC Input (W)
54
83
110
180
229
283
337
443
Efficiency
74%
78%
81%
83%
87%
88%
89%
90%
Intake Temp (°C)
25
28
30
34
35
39
41
45
PSU Exhaust (°C)
26
30
32
36
38
43
46
50
Fan Voltage
3.8
3.8
3.8
3.9
5.1
7.4
9.3
11.0
SPL (dBA @ 1m)
22
22
22
22
23
30
36
38
Power Factor
0.96
0.99
0.99
0.98
0.99
0.99
0.99
0.99

NOTE: The ambient room temperature during testing varies a few degrees from review to review. Please take this into account when comparing PSU test data.

ANALYSIS

1. VOLTAGE REGULATION was truly excellent, within -/+2% on all lines from the lowest to the highest loads. The low and high voltage seen on each of the main lines is shown. Actually, it was only at 400W output that voltage regulation fell outside 1% tolerance.

  • +12V: 12.00 -12.09
  • +5V: 4.89 - 4.98
  • +3.3V: 3.25 - 3.32

2. EFFICIENCY was the best ever measured, reacing 90% at full power. The PSU was generating just 43W of heat within itself while producing 400W DC output. The 80 Plus certification assures that efficiency is 80% or higher at 20%, 50% and 100% loads, which works out to 80W, 200W and 400W, respectively. Our closest test points were 90W, 200W and 400W, where the calculated efficiency was 81%, 87% and 90%. respectively. The 80 Plus test configuration is somewhat different from ours, and their published report for the Seasonic SS-400HT Active PFC F3 shows considerably lower numbers, 81.5%, 85.3% and 83.2%.

The discrepancy between the 80 Plus test results and ours at maximum load is significant, and a bit disconcerting. We're actually in touch with the 80 Plus PSU testing team to try to determine the source of the measured efficiency difference.

3. POWER FACTOR was typical for a unit with active PF correction: Excellent, at or near the theoretical maximum. This, along with the high efficiency, ensures the lowest AC current (amperes) draw for any system of PC components. As previously mentioned, >0.9 PFC and high efficiency are the main requirements of the 80 Plus program. This sample certainly meets and exceeds the requirements.

4. TEMPERATURE AND COOLING

The design of Seasonic's heatsinks combined with the high efficiency worked to keep the temperature rise through the power supply stayed at just 5°C of better throughout the power range. At lower loads, it barely went to 3°C. This is outstanding performance.

5. FAN, FAN CONTROLLER and NOISE

The test environment is live, so readings are higher than would be obtained in an anechoic chamber readings, due to reflections and reinforcement of sound waves off the walls, ceiling and floor.

Overall, the noise performance is excellent, bettered only by the current fan-cooled PSU champ, the Seasonic S12-430. By most standards, this would be considered an extremely quiet PSU. It's mostly wind turbulence noise at most levels, along with a touch of the buzziness that's characteristic of a ball-bearing fan. The behavior of this fan and its fan controller is essentially identical to that of the S12-500 / 600. The fan controller circuit is the same, as is the the fan. The heatsinks, too, are the same. The small reduction in heat output does not seem to have been enough to make any significant change in noise. The same slow rise to speed is seen in the fan controller, which keeps fan voltage at the default start level till >34°C intake temp level, which equates in our test setup for the SS-400HT, to a high ~200W output.

As mentioned earlier, no acoustic recordings were made of this PSU, as it is essentially identical to the S12-500/600. Please check the sound files in the S12-500/600 review if you're interested.

6. COMPARED TO S12-500 & S12-430

We couldn't help wondering how this PSU fares against the S12-500, which is the non-80 Plus approved version of the 500W retail model, and the S12-430 (Rev.A2 with ball-bearing fan), which is Seasonic's retail model closest to the SS-400HT in terms of power rating. The S12-430 is based around a slightly lower efficiency circuit and a slightly quieter fan. It is also the quiet champ among fan-cooled PSUs.

So we set up a comparison table of summary data.

Comparison: Seasonic SS-400HT, S12-500 & S12-430
Model
Output (W)
65
90
150
200
250
300
400
S12-430
Efficiency
77%
78%
79%
82%
82%
80%
80%
400HT-80+
78%
81%
83%
87%
88%
89%
90%
S12-500
77%
83%
85%
87%
87%
87%
87%
S12-430
Temp Rise (°C)
3
4
5
5
7
8
8
400HT-80+
1
2
2
3
4
5
5
S12-500
2
1
3
3
3
5
5
S12-430
Noise (dBA@1m)
20
20
22
25
29
32
37
400HT-80+
22
22
22
23
30
36
38
S12-500
21
21
22
25
28
34
39

The measured data between the 400HT and the S12-500 is very close, and a bit inconsistent, ° the 80 Plus model does not edge out the S12-500 in all categories, although it does reach higher efficiency. Most of the other differences can be easily explained away by sample variance. The comparison probably tells us more about the margin of error in our testing setup and procedure than about the differences between these PSU samples.

The measured differences between the SS-400HT and the S12-430 are more interesting, actually. The efficiency difference is very clear. At 300W output and higher, the difference amounts to double the heat generated in the S12-430 -- 20% of incoming energy lost as heat versus 11% in the SS-400HT. This is also reflected in the temperature rise through the PSU, which is only 5°C for the SS-400HT and 8°C for the S12-430. However, this temperature rise difference is not attributable just to the efficiency difference. The SS-400HT also has a slightly more powerful fan. From an acoustic perspective, the lower efficiency S12-430 wins out because of the slower, quieter fan. But remember, the S12-430 is the low noise PSU champ .

It must be noted that all three PSUs in the comparison table are very quiet at <200W load, which is where most systems run most of the time.

CONCLUSIONS

The 80 Plus version of Seasonic's OEM SS-400HT Active PFC F3 power supply is exactly what we expected: Aside from the lower maximum power rating, very similar to the S12-500 / 600 models in terms of noise, with slightly better efficiency at the extremes. From a retail consumer point of view, the S12-430 offers better value because it is quieter, with a more user-friendly package and longer cables for greater flexibility in case and setup options.

Still, it's good that Seasonic is planning to offer the 80 Plus version to the retail consumer. Some users will be interested in obtaining this PSU for its highest efficiency. Swapping out the stock fan for a quieter one -- the one used in the S12-430 would do fine -- would give it true championship performance in every category: Efficiency, cool operation and acoustics. The MSRP is reasonable, given the performance level of this product.

The case for system integrators to use the 80 Plus approved SS-400HT seems quite strong. Not only is the price reduced by the $5 or $10 rebate, the product has great stability and performance, along with the potential for long, reliable service, given its cool operation. The acoustic performance is probably unmatched by any PSU meant for the OEM market, which has traditionally been inattentive to noise. With the 80 Plus approved SS-400HT and reasonable care in other component selection, almost any system integrator could list low operational noise. One imagines that in the large order quantities sought by commercial system integrators, the additional cost of an 80 Plus version would be easily offset by the rebate.

* * *

Much thanks to Seasonic USA for the opportunity to examine this power supply.

POSTCRIPT: Efficiency Correction
October 20, 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 level 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 both tests.

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: Seasonic 400HT Active PFC F3 "80 Plus"
Target Output
40W
65W
90W
150W
200W
250W
300W
400W
Actual Output
42.1W
63.6W
90.2W
153.5W
197.2W
251.2W
297.9W
401.3W
Efficiency
Corrected
76.6%
81.5%
82.8%
85.3%
85.3%
84.3%
83.9%
82.6%
Original
74%
78%
81%
83%
87%
88%
89%
90%

In this case, our original efficiency calculations were 2~3% too low through to about 150W output. Above that, the original results were too high, and the error kept increasing with rising output power till it reached over 7 percentage points off at maximum load. The new figures closely match the published results of testing done by the 80 Plus program. The new efficiency figures show that this model would comfortably pass the 80 Plus requirements of 80% minimum efficiency at 20%, 50% and 100% of rated power.

Discuss this article in the SPCR Forums.



Previous 1 2 3

Power - Article Index
Help support this site, buy from one of our affiliate retailers!
Search: