Seasonic SS-330GB draws 11W in off modus?

PSUs: The source of DC power for all components in the PC & often a big noise source.

Moderators: NeilBlanchard, Ralf Hutter, sthayashi, Lawrence Lee, Devonavar

Post Reply
Posts: 65
Joined: Sun Dec 23, 2007 3:18 am

Seasonic SS-330GB draws 11W in off modus?

Post by oberbimbo » Sun Dec 23, 2007 3:23 am

I'm in the process of building a NAS. Figuring it would run 24/7, I decided that an efficient PSU would be tantamount and went for the 80Plus rated Seasonic SS-330GB.

However, I'm having some doubts about it's efficiency if it's drawing 11W with the machine off (inside the machine, there's a Via EPIA M6000 and right now just ONE Samsung 500GB drive). With the machine running idle, it draws about 40W (which I consider to be a lot, seeing that my Core 2 Duo laptop idles at less than that).

What am I missing?

Posts: 274
Joined: Mon May 23, 2005 12:04 am

Post by wwenze » Sun Dec 23, 2007 6:39 am

Yea u missed out something alrite...

Is your idle wattage with the HDD spinning or with it spun down? It's only a few watt difference compared to a notebook HDD, but that's quite a good part of the total 40W.

It's hard to have your Seasonic SS-330GB to be as efficient as the notebook power brick. The general knowledge is that, bricks are usually more efficient than norm ATX PSUs, and the less you use out of current-generation high-efficiency PSUs, the worse their efficiency. At 40W total, it can be that the PSU is only 70% efficient (not impossible if you see the 380W-er's review) - meaning 28W useful output and 12W heat. If The laptop idles at, say, 24W (lets say because of the 2.5" drive), but the brick is 80% efficient, power draw would be 30W after conversion loss by the PSU.

40W vs 30W looks like a lot of difference, is that why you're puzzled?

As for the 11W with machine off, I know computers need to draw a small amount of current so that you can on it by pressing switch/timer/wake-on-lan etc. For reference only, the Intel 440-era mainboards state a minimum of 720mah of +5VSB - that's 3.6W. If the PSU is only 50% efficient at <10W, that'd be 7.2W draw from the wall. Still not as high as 11W. But just add a bit more standby power and lower the efficiency more, you might get 11.

You can say the above is entirely guessing. But it's an estimated guess. You decide what to do with this guess.

Posts: 65
Joined: Sun Dec 23, 2007 3:18 am

Post by oberbimbo » Sun Dec 23, 2007 6:49 am

That's with the Samsung HD in sleep mode. I know that the PSU is not as good in ultra low load, but still, I was puzzled (especially considering that I know a guy who has a Core2 desktop that draws less than 50W). And mind you, the notebook needs to drive an LCD plus backlight (which easily eats 10 W, nearly as much power as a 3,5" disk).

Anyway, I'm most likely going to replace the Epia with a Intel D201GLY2 though, as the Epia really is too slow for anything useful. That may draw somewhat more power, but also go much further into useable territory. I was also considering going the Sempron LE 1100 route (total cost is about the same as for intel board) but I can't find any real world power consumption data for the CPU...

*Lifetime Patron*
Posts: 1304
Joined: Thu Apr 10, 2003 7:16 am

Post by nutball » Fri Dec 28, 2007 1:12 am

This is normal. As wwenze said, even when "off" computers aren't really "off" these days.

I've seen power-off figures ranging between 5W and 17W for my various builds depending on the quality of the power supply (none of the PSUs in my builds rate as "crappy" except those in my Pundit bareboneses, just that the expensive ATX form-factor PSUs seem to do a bit better than eg. those in HTPC boxes for example).

It sucks. Maybe using a picoPSU would get you closer to 0W consumption when switched "off".

Post Reply