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help with VA ratings on a UPS?

Last response: in Components
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August 19, 2008 5:38:23 PM

Ok I've been doing alot of reading and now I'm confused,lol

I want to buy a UPS of 700W which has a VA rating of 1000.
This is what is indicated in the manual:
3.3 Determining How Much Equipment You Can Connect to Your UPS
1. Make a list of all equipment that requires protection.
2. Each piece of equipment has voltage and current (VA) ratings printed on
the back label (see examples below). Your equipment may have a voltage
rating such as 88-264V. Since the standard voltage in the United States is
120V, you should use 120V in your calculations.

ViewSonic G810
120V 2.7A
50 / 60 Hz

Computer
Pentium Pro 200MHz
120V 2.0A
50/60 Hz

3. Multiply the voltage and current of each piece of equipment (VA
requirements); for example, 120V x 2.7A = 324VA, 120V x 2.0A = 240VA.
Add up the VA requirements for each device; for example, 324VA +240VA = 564VA.
4. Make sure that your UPS has at least as much VA capacity as your
equipment requires.


Now I'am confused concerning my PC's PS.
It's a 600W OCZ gamextreme
Its says its input Current is 6A @115V
So if I calculate this for lets say 120v @ 6A=720VA !!
Now this is just for calculation figures as I know my PS doesn't pull 100% at all times.
So I'm seeing that this UPS with 1000VA is NOT enough for my PC and monitor.Which I think is impossible and I'm not calculating something right.
Please can someone explain?

More about : ratings ups

August 19, 2008 5:49:38 PM

Well generally, your monitor will have its own power plug so it won't be powered from your computer power supply. Find a power calculator online and see how much your system would need. Then add about 30% to that figure and you'll know how big of a power supply you should buy.
August 19, 2008 7:22:16 PM

I don't want to know if my PS is enough, I want to know if the UPS will be sufficient for my needs, even for a 750wPS
Now I think Iam going to go buy a Kill-a-watt and verify what my computer draws and make my decision for my UPS on that.
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August 20, 2008 5:35:57 PM

The UPS calculations are using maximum numbers (you don't want it to fail when your computer is under heavy load). The PS rating is output (to the computer), but the UPS has to supply that + energy lost in converting from house current. Your OCZ is a high-power power supply, and monitors are not low-power items, so it's not unreasonable that 1000VA is not enough for your monitor + computer running at full load. The kill-a-watt is a good idea, but make sure you are running your computer at max CPU, GPU and hard drive load while measuring.


August 20, 2008 5:47:50 PM

Don't forget once you have worked this out to add extra VA's, if so desired, to the UPS to extend your up time before the batteries run down, this is your preferance. there are models that offer external battery packs which would fulfill this desire.

I use a APC UPS 650VA, the VA rating is much lower than what I would need if I desired a longer up time (time after mains has failed whereby battery backup is keeping you powered up(excuse me, forgotten the jargon:( )).

My UPS runs for about a minute after mains goes down then hibernates my PC. I have not found a setting in the UPS application which allows me to change it from hibernate to just shutdown?

My PC's current draw is higher than yours.
!