Running 450W system on 500VA UPS for 2 minutes - wise?

[bippukt]

My cousin's PC has the following specs:
-Intel Core 2 Duo 2.2 GHz
-2 GB DDR2 667 MHz RAM
-LG 17" display @ 1440X900
-1 SATA HDD and 1 DVD-R
-GTS 250 512MB
-CoolerMaster Extreme 600W (recommended power supply for system = 450W)

He has a UPS rated 500VA. Now, I know that he will not be able to run his system for a long time, but is it possible to just hook up his system to the UPS so that he is able to shut down his system safely? There are power outages at least 2-3 times a day here, so it would be really helpful. On the other hand, it could also be dangerous. Please advise!

 

[MRFS]

I doubt that your cousin's PC is drawing more than 250 Watts.

Although Watts = Volts x Amps, "500VA" does not equal 500 Watts:
check the manufacturer's specifications for the official wattage rating.

For example, the APC 500VA UPS has a rated output of 300 Watts:

http://www.newegg.com/Product/Product.aspx?Item=N82E16842101122R
( thus 300/500 = VA x 0.60 )

Also, if that UPS has a USB feedback cable and software to report
the instantaneous wattage output of that UPS, you should run that
program to measure that wattage.

A good rule of thumb for powers supplies and UPS battery backups
is to target 50% of their rated capacities.

This 50% rule of thumb provides a good margin for error,
and it also increases the chances of reaching the maximum
efficiency of your PSU, which tends to peak at or near 50%
utilization.

To illustrate, if your PC is drawing 250 Watts, that demand
would be 50% of a 500 Watt rating. This APC 750VA UPS
can deliver 500 Watts:

http://www.newegg.com/Product/Product.aspx?Item=N82E16842101137R


MRFS

 

[bippukt]

Thanks for your reply

I would like more people to say if it would be ok to use the UPS. Please remember that I only wish to use the UPS for a minute or two, so that I may shut down the system safely.

 

[geofelt]

MRFS gave you a good answer.

Go ahead and use the ups. At least it willcondition the power and let you ride through momentary spikes. To test, just pull the plug on the unit to see how things work.
You will be no worse off than if you had a power failure when the pc was directly attached to the outlet.

If the ups is a APC unit with a usb attachment, download their "PowerChute personal edition" program.
It will give you stitistics on failure history, and tell you how much time you can run on battery. + more.

 

[bippukt]

Go ahead and use the ups. At least it willcondition the power and let you ride through momentary spikes. To test, just pull the plug on the unit to see how things work.
You will be no worse off than if you had a power failure when the pc was directly attached to the outlet.

This was exactly what I was hoping for. I am going to use the UPS and see. As far as I know, the output of the UPS is around 300W. It has just undergone a battery replacement, so I think it will perform close to its best. Thanks for your reply; it was very useful

 

[Orion1024]

It will work OK, but your runtime won't be very good. It will also put a larger load on the battery and likely shorten it's useful lifespan compared to a higher amp hour battery. IMO, a 500VA is the bare minimum for just about any system because the output wattage of the UPS is roughly 60% of the VA rating. Unfortunately the APC utility forces a shut down with 5mins of battery time remaining and also doesn't support hibernating, so you might want to use the Windows power management instead.

 

[bippukt]

Well, my only aim in using the UPS is ti ensure that I can safely shut down my PC. As long as it doesn't harm my PC, I am OK. I don't have the cash to buy a 750VA UPS with enough battery to run for an hour (the average time of a power outage here).