PSU for low power NAS? 30-75w?

xrayos

n00b
Joined
May 31, 2017
Messages
54
so, I built my own NAS and with 2x 8tb WD REDS and an i5-7600 power draw is under 30w idle. Currently there's a 600w SFX PSU in the fractal 304 case. Obviously overkill, but the SFX PSU was taken from another system.

Now, I search and search, but I cannot find an efficient PSU for my NAS. What's the work around? put a cheap 300w PSU in there? but then it won't be efficient for a NAS that is on 24/7
 

nightanole

[H]ard|Gawd
Joined
Feb 16, 2003
Messages
2,013
Um, you need to look at the efficiency charts at different loads.
Take the power supply of my poweredge r720 server, for example.




I have mine rigged up to idle at 100 watt right now. so that is 20% of the 500 watt supply, so that puts it in the 90% efficiency range.
There is no point for me to upgrade to the titanium 750 watt ultra high efficiency power supply, since 100 watts is in the 13% range. So its still 90% efficient.

So you need to check the performance curve of whatever 500-750 watt power supply you are buying, is at 30 watts, about 5%. You may find a hasswell certified 500 watt model is more efficient at 30 watts(5-7% load) vs a 150-200 watt "normal" bronze atx supply(20-25% load).


Here is another comparison:
http://www.corsair.com/en-eu/vs-seriestm-vs350-350-watt-power-supply
30 watt load is only 76%

Mean while this 450 watt is at 85% for the same 30 watts:
http://www.corsair.com/en-eu/sf-ser...-plus-gold-certified-high-performance-sfx-psu
 
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xrayos

n00b
Joined
May 31, 2017
Messages
54
I have the SF600 in my NAS right now. When power draw is around 30W, the chart according to corsair is about 85%. Same for the SF450
 

nightanole

[H]ard|Gawd
Joined
Feb 16, 2003
Messages
2,013
I have the SF600 in my NAS right now. When power draw is around 30W, the chart according to corsair is about 85%. Same for the SF450

So what is the problem? Your current power supply puts out 30 watts of power and 5 watts of heat. If you get a 60-120 watt power supply so you can run at 25-50% load, odds are it will be a 75% efficient(small power supplies are never very eff), so it will put out 30 watts of power, and 10 watts of heat.

You might find a platinum/titanium 300 watt that runs at 90% eff at 10% load, but thats still 3.33 watts of heat, doesnt seem worth it vs your current 5 watts of heat.

24/7 electricity is about 1 buck per year per 10 cents per kwh. So if you are on the coast and paying a lot (20 cents) 5 watts extra cost you 10 bucks more a year.
 

xrayos

n00b
Joined
May 31, 2017
Messages
54
Lol!

Guess 86% efficiency is good enough. Would have been nice to get > 90%. For that I would need to go platinum but none of the psu come in the low wattage
 
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