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PSU for low power system

F

faugusztin

2[H]4U
Joined
Mar 9, 2008
Messages
2,668
Hi,

i'm having problems what PSU to use/buy for my low power system. Configuration is this :
Gigabyte GA-M85M-US2H (GeForce 8200 chipset)
AMD Sempron 140
2GB DDR2-800 RAM
4xWD10EADS (1TB), 1xSamsung HD154UI (1,5TB)
Corsair HX520

Now the question is what PSU to use ? The idle power usage of this system is 69W at wall (counting with 80% efficiency it means 55.2W power usage, about 15W of that should be the power usage of disks).

55.2W seems like a perfect number for picoPSU, but there is a problem - spinup power usage. picoPSU 150 can handle only 8A sustained and 10A peak power usage, which means drives itself will take 4x 1.6A (WD drives) + 1x 2A (Samsung) = 8.4A. So picoPSU is a no-go. Next options are the bottom models of different PSU brands - but Enermax and Corsair drives has a minimum of 425-450W for modular PSU, which is way bellow the minimal 25% power for 80Plus rating (15.3-16,2%). Then there is a option of nonmodular 350W OEM Seasonic (19%), 380W Seasonic S12-II (18%), 385W Enermax Pro82 (18%) 400W Corsair CX400 (17.25%) - still too powerfull for this setup.
The last option is a superexpensive Silverstone SST-ST30NF-GM, which is a passive PSU with a price comparable to the new Seasonic X 650.

What is your opinion ? Should i stick with my current PSU which is used just because i had it as a spare, or should i buy something else (if yes, what) ?

PS: unfortunately two Enermax Modu82-425 failed on me (one had a noisy fan, other one had a electric buzz comming out of PSU even when turned off), so i'm not really interested in Enermax if there are other options ;).
 
Too lazy to double check your math at the moment. But I can say this: If your goal is to try get increased efficiency, don't bother. The minor savings you'd get would nowhere near be enough to offset the cost of a new PSU, even a cheapy one. So I'd recommend saving your money and keep the Corsair.
 
Just stick with what you've got. There won't be any significant power savings from transitioning to something more efficient at those loads since your total power consumption is so low to begin with.
 
For me it was more about silence than the power savings :), but unfortunately there is nothing like 200-250W super silent PSU. That range is reserved for mATX and TFX PSU it seems.
 
faugusztin said:
For me it was more about silence than the power savings :), but unfortunately there is nothing like 200-250W super silent PSU. That range is reserved for mATX and TFX PSU it seems.
Click to expand...

To be expected. It seems that with PSU production, the lower wattage PSUs do not cost that much less than a higher wattage model yet have a somewhat limited market.

There are fanless PSUs out there but they cost around $125 and above. I don't think silence is worth that $125.
 
faugusztin said:
For me it was more about silence than the power savings :), but unfortunately there is nothing like 200-250W super silent PSU. That range is reserved for mATX and TFX PSU it seems.
Click to expand...
Well, the HX520 should still be effectively silent at those loads. And if you really want silence, you can always go with a Seasonic X-650 if you're willing to drop the cash, since it won't even run the fan.
 
If you hear much noise out of the HX520, then there is something wrong with the fan. (Mine started to make some noise after a couple of years.)

Since you will never use much power, you don't need much air moving through the PS. You can swap out the stock 2200 RPM fan and replace it with something like the 1200 or 1600 RPM Scythe S-Flex fans.
 
Check out my system in Sig. Both the 380W Antec and 300W Seasonic are both highly recommended!
 
faugusztin said:
picoPSU 150 can handle only 8A sustained and 10A peak power usage, which means drives itself will take 4x 1.6A (WD drives) + 1x 2A (Samsung) = 8.4A. So picoPSU is a no-go.
Click to expand...
I'd wager it will work fine. Those numbers are all going to be worst-case, including the peak load rating for the PSU - it should supply much more current than that for the few ms where that worst-case load current from the drives is needed. And I doubt the remaining 1.6A of headroom isn't enough room for the remainder of the components either. Tight, and I could be wrong, but I think it would work fine.

Efficiency claims on the picoPSU, while accurate, are a bit misleading. It might be 95% efficient at the DC-DC conversion, but the power brick is going to be much less efficient than that. For example the one recommended by mini-box is only 85% 'typical'. Still better than a typical ATX supply at these loads, but 82% or so aggregate efficiency is not the 96% they claim, and that's assuming the 85% number holds water.

Like the others I don't think it's worth it unless you want a truly silent PC.
 
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