Differential Temperature and Noise Levels

To simulate a demanding environment, some of the warm exhaust air from each 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 ~27 dBA.  The power supplies were tested with Hybrid Fan Control turned On (enabling fanless operation at low to mid power levels).

*Fan not spinning

The PRIME Titanium Series PSU cooling fan did not start spinning on any of the PSUs until we entered the 50% load test (the 650W unit fan started spinning soon after hitting the 50% load mark but the 750W and 850W unit’s fans didn’t start spinning until well into the tests). At the 75% load mark the fan noise was still relatively quiet and even at the 100% the fan noise never really became loud. Having great efficiency helps keep the waste heat and fan noise to a minimum.

(Courtesy of Seasonic)

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