How do they define 85% power efficiency and 88% power efficiency... against what standard ? What is special about 135 mm double ball-bearing fans, which can actually be more trouble than they are worth.

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Power efficiency like the 80+ rating you see applied to many psu's is calculated at different power draws - 20%, 50% and 100%

So,for example if the PSU is rated at 85% efficiency then for a 750 watt power supply it can deliver 85% of the 750 watts ( 0.85 x 750 = 637.5 watts), the remaining 15% is converted into heat ( 112.5 watts)

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The power draw is calculated at 20%, 50% and 100% of its rated power load and the lowest value is generally accepted as the power efficiency -although some manufacturers fudge the numbers by quoting only one of the three values- Hence the adoption of the 80+ certification:

80% power efficiency at 20, 50 and 100% = 80+ certification, so you need at least:

81/82% at 20% draw, 85% at 50% draw and 81/82% at 100% draw = 80+ Bronze cert.

85% at 20% draw, 88/89% at 50% draw and 85% at 100% draw = 80+ Silver cert.

87/88% at 20% draw, 90/92% at 50% draw and 87/88% at 100% draw = 80+ Gold cert.

90% at 20% draw, 94% at 50% draw and 91% at 100% draw = 80+ Platinum cert.

Fan size and capability is either an advertising ploy or because the power supply needs that much cooling (i.e. generates a lot of heat) and yes bb fans are usually noisy. Taking the PSU apart and replacing the fan with a fluid or electromagnetic drive will usually cure the problem)

I wouldn't recommend taking apart a PSU that has already been in use as the capacitors store a charge long after the power supply has laid dormant.

Sorry about the double post- hit the wrong button before- loooong day.

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You just clarified a lot about psu tech for me. Thanks man

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