Go to my favorite PSU calculator site: eXtreme Power Supply Calculator Pro v2.5
If you have listened to me before, you already have a Pro account, so login to the member site, do your calculations and you will see the recommended wattage for your PSU, but also, and that will answer your question, the recommended UPS VA capacity.
Very nice; did not notice that before.
This is helpful, because I am getting a larger PSU than I need (for the later upgrade of the video card and other things). Their recommendation for VA on my new system (about 25% over their calclated VA) is under my current UPS. So I'm good for now.
I did find more info (sales paper on the APC site) regarding why the newer Active PFC (Power Factor Correction) power supplies create problem when using cheaper UPSs. http://www.apcmedia.com/salestools/RMUZ-7DTKRC_R1_EN.pdf
So apparently my new APC BR1500lcd
won't play well with my CM Silent Pro M 1000w PSU ?
It is not just the size of the power supply, but the actual usage. $2 for 3 days for the pro version of the calculator Harm linked above limited the guess work.
The "maybe" for me is that the problem only occurs if certain technical overwattage events occur while on or switching to battery power. The few reports of problems I saw were newer Dells, but I suspect this is because the power supplies were too low AND the UPS was being pushed to the limit.
I note that yours is a 1000 Watt PSU with a UPS rated for only 865 Watts. If you are pushing the the PSU and adding other things on that UPS (monitors etc), you might have the traditional problem of just plain overloading the UPS.
Bottom line for me: use Harm's link and pay for the Pro version.
1 person found this helpful
UPS units should exceed the total wattage rating of all devices connected to it. You cannot base it on average load. I deal with clients making this mistake constantly and they have burned out system components including PSU's and system boards because they were told to base it on the average load. Remember when hardware initializes it normally pulls the max load and if the UPS is not feeding the transformer correctly in the PSU it will cause the output on the PSU transformer to transmit out of range. This can cause intermitant problems to the system or damage over time. The load on a system is rarely constant as well. This is another reason you should always exceed the watt rating of every device plugged into the UPS.