Fanless PSU Torture Test Roundup

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B. COOLMAX CF-480B

Coolmax offers several fanless models, 350W, 400W and 480W; the last is the one we're examining here. We reviewed a 300W fanless Coolmax previously. It's surprising that the current model looks so similar, considering the first sample was received was over six years ago. There have been tremendous improvements in computer PSUs in those years.

There were inconsistencies in labeling and specifications between the web site and the PSU label. Still the presence of the RoHS sticker, a three-year warranty, and more current/power on the 12V lines than on the lower voltage lines (according to the web site info) are encouraging.

Coolmax CF-480B Specifications
AC Input
115/230V @ 50/60 Hz
DC Output
3.3V
5V
12V1
12V2
-12V
5Vsb
28A
20A
10A
16A
1A
2.8A
180W
280W
12W
14W
452W


Modest size/appearance retail box for the Coolmax. The photos on the box are slightly misrepresentative; the actual PSU has no vents on the sides.


There's no printed manual, but a sheet with links to download a PDF copy. The PSU itself uses extruded aluminum for its outer casing, with large vent grills on the front and back. It weights about 4 lbs. There are no vent holes on the sides, top or bottom.


The bottom is a serious heatsink-style extrusion... which takes the place of a 120mm fan. The inside panel is quite an open grill. The front/back open grills enable cooling airflow through the PSU, especially if there is an exhaust fan on the back panel of the computer case; it will tend to suck air from the outside through the PSU.


The output cables are mostly quite long, and only the main 20/24-pin ATX cable is sleeved. There is one PCIe 6-pin connector.


Even though the label suggests a switch for 115V/230V, there is no such switch. The PDF manual also states the Voltage Selector should be set to 115V or 230V. One assumes the PSU was upgraded for auto-range AC input but the manual and tags not changed. 230VAC operation was not checked. NOTE: The output specs on the label differ from those given on the product website; we used the web site info for our loading formula.

TORTURE TEST SUMMARY
Coolmax CF-480B
480W Rated Output
Duration
Output (W)
Efficiency
Hotbox °C
Power Factor
10~20 min
22.0
48.9%
24
0.69
43.2
60.8%
25
0.82
66.1
68.1%
27
0.85
92.1
72.0%
32
0.86
151.0
72.8%
35
0.88
198.7
73.4%
38
0.89
251.0
73.1%
43
0.89
478.0
68.9%
62
0.93
15 hr
251.0
72.2%
43~46
0.89
15 hrs
(w/ Fan)
400.5
71.5%
43~45
0.93
478.0
68.9~67.0%
44~47
0.93
+12V Ripple (peak-to-peak): <90mV @ <250W ~ 130mV @ 400W
Output Voltages during 15 hr test:
250W -
12.2V, 5.10V, 3.37V
460W - 12.2V, 5.04V, 3.33V
AC Power in Standby: 0.3W / 0.2 PF
AC Power with No Load, PSU power On: 14.7W / 0.97 PF
OTP Shutdown: Almost immediate shutdown at 400W. No-fuss recovery. Repeated several times without incident.

ANALYSIS

The CF-480B turned out to have efficiency in the low 70s, similar to the first fanless PSU from Coolmax we reviewed all those years ago. The change to auto-range AC voltage input was not accompanied by an improvement in efficiency, but Active PFC was probably part of the change, as the PF was quite high.

Overall electrical performance, apart from the low efficiency, was solid throughout the short term testing. Electronic noise / whine was modest enough to be ignored. Not surprisingly, the unit ran quite hot, with the casing reaching over 80°C in spots at 400W load. At 400W output, the Coolmax has to dissipate a whipping 160W of heat, compared to just 44W for the Seasonic X-400.

The sample passed the 250W torture test without issue. OTP shutdown occurred very soon after the 400W test was started. It restarted after cool-down without any problem, but overheated and shut down again in a few minutes. The Nexus 120 fan at full speed was added to blow air out of the hot box. At that point, it ran successfully for a couple of hours, but OTP shutdown occurred when the ambient room temperature exceeded 26°C in early afternoon. The Scythe Gentle Typhoon 120mm fan was installed as the exhaust fan and run at full speed (~1500 RPM). The increased airflow kept the hotbox temperature under 43°C, and the Coolmax successfully ran at full power for 15 hours.



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