UPS won't keep my system up when line power is disconnected

[tbrowne]

I have a full tower work station running a 450 watt power supply and 19 inch monitor attached to a Belkin 800VA UPS. The Belkin unit is new and fully charged; however, when I test the unit by disconnecting from line power - the system immediately reboots. It will reboot and run on battery power - but it won't stay up when line power is lost.

I've tested this UPS with a smaller PC and it keeps that PC powered and up when line power is disconnected.

I suspect this UPS is too small for the application I'm using it with; however, I don't want to make a new purchase for a larger unit if it won't perform any better than this one.

Anyone have any experience with this problem?

 

[AlexandreAmant]

HI !

The Belkin claims 800 VA. So with a cos phi of 0.6, it can give out max. 480 watts. If you have a power supply of 450W and a 19 inches screen aside, your UPS is underdimensionned, the screen consuming more than 250 W, leaving only 200 W for you PC, which is not enough.

The UPS can't give out the power needed when the line goes off, so the PC reboots (like a small power cut), and during the reboot, the UPS can stabilise and give out enough power. This makes me think that you are just above the UPS max power limit, so when switching from line to battery it is not able to release the power needed in a timely manner.

This is most likely an off-line UPS, you don't have these problems with on-line UPS, but they are more expensive.

You should get a 1000 VA.

Hope it helps !

@lex

 

[jimbopalmer]

or only UPS the PC, not the monitor I tried to remain child-like, all I acheived was childish.

 

[tbrowne]

Thanks to everyone for the input. My new, 1200VA UPS is scheduled for delivery today. I'll post the results as soon as I have them.

 

[tbrowne]

Here's the update on the new UPS. It arrived yesterday and does hold the sytem when line power is disconnected. The new UPS is a 1200VA unit and would confirm that capacity is everything when it comes to keeping the unit up during an outage.

Thanks again for all of the input on this subject.

 

[AlexandreAmant]

For your info, I have a power cable that I have cut to insert an ammeter and check what the systems are consuming for dimensionning UPS.

 

[Slik]

Change the battery, I had a very similar problem and it turned out that even though the UPS showed no signs of a low battery it was in fact slowly draining and with a smaller load it did not show as quick but when a larger load was placed on it, the UPS would not properly shutdown the computer in the case of the line power being removed, I went through several steps including reinstalling the software several times and nothing until a new battery was put in.
Good luck