Efficiency, Differential Temperature and Noise

The overall efficiency of a power supply is very important, especially when operating at higher power levels.  The less waste heat generated the better!  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) 600 watts of AC power going in would result in 600 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.

PC Power & Cooling Turbo-Cool 860W PSU Review - Cases and Cooling 39

The latest 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.

PC Power & Cooling Turbo-Cool 860W PSU Review - Cases and Cooling 40

I measured the AC power input to the Turbo-Cool 860W PSU with the Extech power analyzer while the total DC load was found by adding all the individual +3.3V, +5V, +12V, -12V and +5VSB loads together. 

PC Power & Cooling Turbo-Cool 860W PSU Review - Cases and Cooling 41

PC Power & Cooling Turbo-Cool 860W PSU Review - Cases and Cooling 42
(click to enlarge)

The overall efficiency of the Turbo-Cool 860 power supply is excellent and the efficiency appears to peak around 400W.  Note that efficiency will almost always be higher at the 240 VAC line voltage versus 115 VAC (as the voltage goes up the current goes down, and since line/component loses are proportional to current, less current means lower loses).

Note: When comparing efficiency data from one review site to another, be sure to keep in mind that several factors can have a big affect on the numbers.  First, it requires high quality, calibrated instruments to insure that both the AC and DC load measurements are accurate.  Another BIG factor is how the total DC load is distributed across all of the outputs when the power measurements are taken.  Because the +12V section will most always be more efficient than the +3.3V and +5V sections, placing a heavier load on the +12V outputs and a lighter load on the +3.3V and +5V will swing the results to show higher efficiencies.

PC Power & Cooling Turbo-Cool 860W PSU Review - Cases and Cooling 43

There is a growing awareness among users, PC manufacturers and electric utilities regarding the money and natural resources that could be saved by adopting higher efficiency power supplies.  One group that is spearheading this new movement is Ecos Consulting.  You can learn more about their efforts to promote power supplies with better than 80% efficiency by visiting the 80 Plus Program website.

Spending a little more money up front to purchase a high efficiency power supply may very well pay for itself over the lifetime of the PC, especially when you are using this much power… 🙂

Differential Temperature and Noise Levels

To simulate real world operation the Turbo-Cool 860W power supply was mounted in a modified mid tower case (Lian Li PC60) for testing.  Some of the warm exhaust air from the PSU under test is recirculated back into the case, which allows the internal case air temperature to increase with load, just like it would in a real PC.  The internal case air temperature is allowed to increase up to 40ºC and then held constant from then on at 40ºC. 

The differential temperature across the Turbo-Cool 860W 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 20ºC (68ºF) +/- 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. 

PC Power & Cooling Turbo-Cool 860W PSU Review - Cases and Cooling 44

PC Power & Cooling Turbo-Cool PSUs are not designed to be quiet.  The primary design goals are to deliver stable, clean outputs with high reliability for high-end workstations and gaming systems.  The single 80mm fan does a very good job of keeping all the internal bits cool but at the higher output levels it can get noisy. 

However, the Turbo-Cool 860W PSU unit proved to be quieter than its big brothers, especially at low to mid power levels with relatively cool ambient air temperatures.  Noise probably won’t be an issue for most high-end gaming systems but I wouldn’t use this PSU for a quiet build HTPC.  If you want a quiet power supply, then look to one of PC Power & Cooling’s Silencer series units.

I was not able to measure the SPL when the power supply was running at the higher loads because all the cooling fans on the programmable DC loads were also running at this point.

« PreviousNext »