Is my UPS limiting my system's juice?

[saz]

Hi there!

I have a computer with an 750W PSU, however my UPS is only 400VA ( ), my question is:

Is my UPS limiting the amount of energy that my computer uses? I mean, if my computer is trying to use something like 500W will my UPS cut it down to its lousy 400VA?


Thanks!

 

[GhislainG]

If you exceed the UPS capabilities, it will let you know.

 

[cmashwin]

400va refers to the total backup time of the battery i think.. at the most, it might cut out sooner when ur power goes..
Since ur PC does NOT use 750w ALL the time, its safe to assume you are ok for now.. unless u r running high-end stuff like overclocked quad with dual/tri graphics and stuff..

 

[WR2]

Your UPS is not limiting the amount of house current your PSU is pulling to power your system.
But your UPS is not protecting your system like you probably think it would. Chances are your 400VA/200W UPS might support your system at low power conditions like just surfing the web. But a power loss while gaming is almost certain to bring about a system crash when the UPS overloads.
If you suspect your system is using 500W of power and you want a UPS to carry that load you should be looking at something along the lines of 1000 VA/500W.
I suspect a 750VA/450W UPS would be good enough.

 

[Zorg]

You need to be concerned about the wattage more than the volt amps. Run the eXtreme Power Supply Calculator to get a feel for the actual load, and check the UPS specs for the wattage output. Understanding that the PSU calculator gives you the recommended PSU size not actual draw, so it's a little high. Just because you have a 750W PSU doesn't mean that you are drawing 750W. I'm guessing you are using it more for protection than actual backup, so if you get 5 minutes of backup run time it's not that big of a deal, but you don't want to run the UPS at 90% load either.

 

[CompuTronix]

Zorg is correct. A UPS which is rated at 1000 VA is typically rated at about 600 Watts. Generally speaking, VA = Watts x about 0.6 which can typically vary from about 0.55 to 0.75 according to type of loads, PSU efficiency and Power Factor.

Prior to about 12 years ago, UPS manufacturers sold their PC Grade products using the more straight forward Watts rating. However, competitive marketing and sales strategies tend to be ruthless and deceptive, so some "creative" marketing whore realized that since the VA rating is a "bigger" number than the equivalent Watts rating, sales would increase if their company was the first to switch to the VA rating, because the average PC user will blindly buy at face value a similarly priced product with a "bigger" number. Consequently, all the UPS manufacturers soon followed suite, thus the confusion most PC users have today when buying a UPS.

As has been suggested, unless you're running overclocked multiple graphics cards and an overclocked quad, a quality 500 Watt PSU is plenty of power. Researching the actual full load requirements of your computer, peripherals, and the specifications of your PSU, is the key to accurately determining what size UPS you need. Backup run time is determined by load and battery Amp Hour rating, which is has nothing to do with VA or Watts, so different 1000 VA units from different manufacturers may have different battery capacities.

The bottom line? Let the buyer beware!

Comp

 

[saz]

Thanks!!

I've decided to buy a new one! (girlfriend's christmas present xD)

Again thank you very much for the quick and explanatory responses!

 

[saz]

Would a 800VA Line-Interactive be enough?

The one I'm using is an Online one, but hear that Line-Interactive aren't far behind.

The one I'm talking about has 2~6ms transfer time

 

[Zorg]

If I was asking about a particular piece of equipment I would link it, but that's just me.