Enermax EG851AX-VH - can you trust the specs?

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Enermax EG851AX-VH - can you trust the specs?

Postby Kreshna Aryaguna Nurzaman » 2018-3-13 @ 14:17

Looking for spare PSU for my PIII system, I naturally look for models with beefy +3.3v and +5v. Then I found Enermax EG851AX-VH, with the following specs:

+3.3V@38A, +5V@42A, +12V1@14A, +12V2@18A, +12V3@16A,+12V4@14A, -12V@0.8A, +5VSB@2.7A

+3.3v at 38 ampere, and +5v at 42 ampere, seriously? Its +12v amperage isn't bad either. But the PSU is described as 660 watt power supply, while those numbers above add up to more than 900 watts!

Tried another site, yet the specs are the same: +3.3V@38A, +5V@42A, +12V1@18A, +12V2@18A, +12V3@15A, -12V@0.8A, +5VSB@2.7A

Can you trust those numbers?
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Re: Enermax EG851AX-VH - can you trust the specs?

Postby PC Hoarder Patrol » 2018-3-13 @ 17:11

2005 spec sheet from Enermax USA

https://imgur.com/a/wO8y0
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Re: Enermax EG851AX-VH - can you trust the specs?

Postby Koltoroc » 2018-3-13 @ 18:45

The individual rails on most power supplies will add up to more than the rated value, however, You can only draw (safely) up to the rated power in total.

For example, in that linked data sheet, the combined power of +5 Vand +3.3V is rated at 240W, while the individual rails are rated at around 125W for 3.3V (3.3Vx38A) and 210W for 5V (5Vx42A). If you were to draw the full 42A for the 5V rail, you would only have about 30W available for the 3.3V (3.3Vx9A).

The same applies to the 12V rails and the relation between 12V and combined 5V and 3.3V power.

You can't draw the mximum rated per rail on all rails at the same time. But this setup gives the PSU a really broad range of load situations it can handle.
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Re: Enermax EG851AX-VH - can you trust the specs?

Postby Kreshna Aryaguna Nurzaman » 2018-3-13 @ 23:10

I see. Interesting. So the specs are genuine, and that's what the specs mean by "Load Range 2".

Koltoroc wrote:You can't draw the mximum rated per rail on all rails at the same time. But this setup gives the PSU a really broad range of load situations it can handle.

Obviously it's something I haven't notice before. Wonder how many PSUs are like this.
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Re: Enermax EG851AX-VH - can you trust the specs?

Postby shiva2004 » 2018-3-14 @ 00:03

In any good power supply the sum of the different rails is higher (way higher, even) than the rated power value, in fact it's one of the tests I do when looking at a power supply, if the rated power is higher than 75% of the theoretical sum (80% perhaps, but that's already a stretch) I discard this PS at once.

To me, the combination of a good theoretical/rated power values ratio, nice weight and a good selection of connectors identify a decent power supply at first glance; I've never seen a bad one that scores good in these three areas.
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Re: Enermax EG851AX-VH - can you trust the specs?

Postby Koltoroc » 2018-3-14 @ 00:27

Kreshna Aryaguna Nurzaman wrote:Obviously it's something I haven't notice before. Wonder how many PSUs are like this.


Pretty much all good ones are like that. Although with modern PSUs there is a very strong weighting towards 12V since virtually all pieces of modern hardware draw the majority of their power from the 12V rails.
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