Efficiency, Differential Temperature and Noise
Efficiency
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) 750 watts of AC power going in would result in 750 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 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 Snow Silent-750 power supply is also excellent and meets the criteria for 80 Plus Platinum certification (assuming rounding error and the fact we test at elevated temperatures and the 80 Plus certification testing is done at room temperature).
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, just like it would in a real PC.
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.
*Fan not spinning (S3FC Fanless Mode)
Tests were conducted with the Fan Control switch in the “Hybrid” position (S3FC), which enables fanless mode. The fan did not start spinning until well into test #3 at 50% load, which coincides with the advertised fan profile for the Snow Silent-750. Once the fan started spinning the noise was barely noticeable through 75% load and didn’t get loud even at 100% load. The down side to being so quiet is the relatively warm operating temperatures at the higher loads.
The only thing I would like
The only thing I would like to see is 2-4 fan headers for semi-passive case fans.
Also 15-20% passive operation threshold (X-series) makes more sense then 50% as it is kind of hard to dissipate 375W out of the case without a fan.
I’m sure that you’re mistaken
I’m sure that you’re mistaken about the 375 watt dissipation. At 92% efficient, it would be something like 30 watts, before the fan kicks on.
I have had zero issues with any of the Seasonic power supplies that I’ve purchased and have an older 750 watt model in my main rig. I would definitely consider something like this for a future high-end build.
Exactly. The rest of the heat
Exactly. The rest of the heat is energy used by the PC though it would be more than 8% heat dissipated by the PSU since it would suck some heat back into the power supply.
That’s why it is also based on the temperature.
I was talking computer case
I was talking computer case not power supply case. If you deliver 375W to power your computer you need to get rid at least this amount of heat from the computer case.
Would it be easy to swap the
Would it be easy to swap the fan out for something like a Noctua? I believe some of their 140mm fans work in 120mm openings.
Why would you do that when
Why would you do that when one of the main reasons is to get the special fan? Does Noctua even make fans or do they just rebrand too?
Very nice, but why is it
Very nice, but why is it upside down? Everything is oriented as if the fan is expected to be pointing up, but in almost all cases it will be installed with the fan pointing down. Old cases put the PSU above the CPU with the fan down, and modern cases put the PSU at the bottom with the fan pointing down to pull in outside air from underneath. Why would they be expecting the fan to usually point up?
Valid question is why there
Valid question is why there are so few cases where motherboard is turned 90 degrees.
Actually, there might be more
Actually, there might be more people than you think installing the PSU with the fan up (myself included). With a PSU mounted in the bottom of an ATX case with the fan up – it adds to overall case cooling. This can help suck warm case air out of the sometimes stagnant area below the GPU card. The trade-off is causing the PSU to run a little warmer than it would with the fan down (sucking cool, outside air) but good PSUs like the Seasonic, are rated for up to 50 deg C operation. Not for everyone, but a good option for some.
The fan is sucking air in,
The fan is sucking air in, not pushing air out. It’s blowing over the internals of the psu. If it was installed on the top of a case it would act as an exhaust. Which would be optimal as heat rises.
At page 3, I think that fan
At page 3, I think that fan curve hysteresis is actually increased. Reducing hysteresis actually increasing the frequency of fan switching on-off when temperature is near equilibrium at setpoint.