Efficiency, Differential Temperature and Noise
Efficiency is defined by the power output divided by the power input and is usually expressed as a percentage. If a PSU were a 100% efficient (which none are) 850 watts of AC power going in would result in 850 watts of DC power coming out (with no waste heat to dissipate). In the real world there are always inefficiencies and power is lost in the form of heat during the conversion process. Newer revisions to the ATX12V Power Supply Design Guide V 2.2 have continued to increase the efficiency recommendations for PC switching mode power supplies and now lists both required and recommended minimum efficiencies.
We measured the AC power input to the HX850 Platinum PSU with an Extech power analyzer while the total DC load was found by adding all the individual +3.3V, +5V, +12V, -12V and +5VSB loads together.
The overall efficiency of the HX850 power supply is excellent and easily exceeds the criteria for 80 Plus Platinum certification even while operating on 120VAC and at elevated temperatures.
80 Plus Program
Note: Tests conducted at room temperature (25°C)
Differential Temperature and Noise Levels
To simulate a demanding environment, some of the warm exhaust air from the PSU under test is recirculated back to the intake through a passive air duct, which allows the PSU air inlet temperature to increase with load, up to 40°C.
The differential temperature across the power supply was calculated by subtracting the internal case air temperature (T in) from the temperature of the warm exhaust air flowing out the back of the power supply (T out).
Thermocouples were placed at the air inlet and exhaust outlet. The ambient room air temperature was 23ºC (74ºF) +/- 0.5ºC during testing.
T out = temperature of air exhausting from power supply
T in = temperature of air entering power supply
Delta T = T out – T in
Sound pressure level readings were taken 3’ away from the rear of the case in an otherwise quiet room. The ambient noise level was ~28 dBA. The HX850 PSU was tested in Single rail mode.
*Fan not spinning
The fan did not start spinning until we hit the 50% load test. By the time we reached the 75% load test with an elevated ambient temperature, the HX850 PSU cooling fan noise was still relatively quiet. We were not able to take a SPL reading at the 100% load mark because of all the DC load cooling fans cycling on and off.
(Courtesy of Corsair)
PSU reviews are immensely
PSU reviews are immensely boring.
While the number of
While the number of spectacular PSU failures has markedly decreased, reviews such as this excellent example are incredibly important when making purchasing decisions. Have a little respect for the work that Lee has put into this review.
Maybe reviewers could spice
Maybe reviewers could spice up the format by testing PSUs to the point of failure. I would like to see what it takes to physically destroy these things. Can one take a 850W PSU to 1000W? What happens if I short an active power cable? What happens to thermals without the fan active? Can I add a waterblock to it in a custom cooling loop? There are so many interesting questions.
Virtually all enthusiast
Virtually all enthusiast grade PSUs have built in safety circuits that are designed to protect the PSU from catastrophic failure. I have only had one PSU actually explode (fireball, sparks and smoke) during testing over the last fifteen years. Over Current protection or Over Power protection should shut the PSU down if too heavy a load is applied to a particular rail or the total output power is exceeded. Short circuit protection should shut it down if a short occurs on one of the outputs. And if the cooling fan fails, Over Temperature protection should shut the PSU down before it self destructs. Boring but safe!
And water-cooling a PSU is possible (although maybe not practical). I have done this in the past by attaching several custom made water blocks to the PSU's existing aluminum heat sinks. I chose a PSU that was designed to operate fanless, removed the cover and attached three custom water blocks. Use your imagination… 🙂
Maybe I missed it but I read
Maybe I missed it but I read through the review and didn’t see any info about what the 12v real switch actually does other then switching between single rail and multi rail mode.
Does this have any impact at all on the operation? Is effeciency affected? What kind of scenarios exist in which that feature is even useful? I can’t really think of one, although I’m not a die-hard PSU junkie.