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Question about UPS

post #1 of 6
Thread Starter 
Here's one for you electrical nuts out there.

What do you feel is the maximum wattage PSU or rig under normal load that a 650VA UPS can handle safely to perform a quick safe shutdown after a blackout.

Also is their anyone here running a rig similar to mine or just with a single 580 that uses a decent UPS and what size VA rating have you chosen to go for.

Cheers in advance.
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post #2 of 6
Well, I can tell you that your rig under 100% full load will be pulling around 750w - 850w (probably closer 750w)

Using this calculator http://www.csgnetwork.com/upssizecalc.html you should have around 1500va (it say's between min 1150 and recommended 1750)

So, i'm thinking that a 650VA UPS can handle probably around 350w,

Comps
post #3 of 6
It's actually pretty easy to compute. Here's how:
Notations: S-apparent power [VA] (the UPS rating); cosphi-power factor; n-efficiency;P-rated power PSU[W]

The equations is:
P=S*cosphi*n
If you have S=650VA, supposing you have active PFC cosphi~=0.95 and a 80+PSU we can consider n=0.8 ==> P=650*0.8*0.95, P=494W. You can almost use a 500W PSU that is loaded at 100%; you can also use a 1000W PSU @50%, the only limit is you can't consume more than 500W; most rigs don't come close to this unless they're based on OCed GTX 570+ SLI and heavily OCed CPUs.

If we go further and your UPS has a E=200Wh battery capacity you can compute the amount of time to shutdown for the 500W rig: t=E/P => t=0.4h or 24 minutes for this particular UPS/computer combination.

cheers

*EDIT: now I see you actually have a 500W+ rig. My advice is to get a 10$ Kill-a-Watt and measure the exact power consumption of your rig. Since the Kill-a-Watt rating contains the efficiency and power factor you only need a UPS with the VA rating equal to whatever the meter is showing. Otherwise, supposing your rig needs P=800W as Comps said, you can compute the VA rating of the UPS you need: S=P/(n*cosphi) => S=1052VA - the UPS should be a bit above that.
Edited by dragosmp - 7/27/11 at 4:13am
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post #4 of 6
Thread Starter 
Well, two very good replies, thank you for the info.

I must say that second reply was very electrician of you.

I'm actually going to take one of my 580's out and sell it to my mate so the power draw will be quite less.

I think I should be ok with this http://www.ple.com.au/ViewItem.aspx?...CategoryID=365

Let me know what you think.

Rep's for both of you.
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post #5 of 6
I am a bit of an electrician, more like a hobby

I looked at the UPS and that "capacity" rating is about as correct as measuring a bag of fries with the yardstick... both numbers represent power, not capacity (700W and 1200VA); capacity is Wh, Ah. My guess is that there's a typo and the UPS has 1.2KVA and 700Wh, which would be good for your rig even with two GTX 580s. If by any chance there isn't a typo and it can only provide 700W then it won't hold the charge with two GTX 580s fully loaded. I'd just oass a question to the tech support to make sure what is what.
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Centurion
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Corsair Force 3 TRUE Win 7 Pro x64 ACER 23" TN  
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400W Silverstone Strider Antec P182 
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post #6 of 6
Thread Starter 
Quote:
Originally Posted by dragosmp View Post
I am a bit of an electrician, more like a hobby

I looked at the UPS and that "capacity" rating is about as correct as measuring a bag of fries with the yardstick... both numbers represent power, not capacity (700W and 1200VA); capacity is Wh, Ah. My guess is that there's a typo and the UPS has 1.2KVA and 700Wh, which would be good for your rig even with two GTX 580s. If by any chance there isn't a typo and it can only provide 700W then it won't hold the charge with two GTX 580s fully loaded. I'd just oass a question to the tech support to make sure what is what.
Thanks again for looking into this, I appreciate it.

I ended up buying it on my way home from work today and i'm pretty impressed with it so far. I bought it mainly because there are some serious storms going on where I live and my old UPS couldnt handle the new rig. After about an hour of setting it up the weather got worse and we had a black out I took note of how much the UPS was under load and while the pc was idle just watching a dvd only 21% of the UPS was under load while on UPS power, that's a good sign I hope?

I should also mention I put my CPU back down to stock clocks as I have no need to run it at 4.8 since I'm not video editing for a while and just gaming. Also I only have the single 580 in now.

Should be good I hope? And thanks for the heads up about the 700W/700Wh info, I will check with their tech support to find out for peace of mind. If I could rep you again in the same thread I would, you've been helpful once again.

Cheers - Mike
My Rig
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i5 2500K ASUS P8Z68-V 2x EVGA GTX 580 SLI 8GB Ripjaws 
Hard DriveOptical DriveOSMonitor
1x WD Black 1TB 2x WD Green 2TB LITEON Sata DVD Burner Windows 7 Professional 64Bit 27" 
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MS X4 CORSAIR HX 1000W HAF932 Deathadder 3g 
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My Rig
(13 items)
 
  
CPUMotherboardGraphicsRAM
i5 2500K ASUS P8Z68-V 2x EVGA GTX 580 SLI 8GB Ripjaws 
Hard DriveOptical DriveOSMonitor
1x WD Black 1TB 2x WD Green 2TB LITEON Sata DVD Burner Windows 7 Professional 64Bit 27" 
KeyboardPowerCaseMouse
MS X4 CORSAIR HX 1000W HAF932 Deathadder 3g 
Mouse Pad
None 
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