How to Size UPS Correctly / Online tool seems wrong?

[Anonymous user]

Hi,

I currently have a fairly high-end computer and I know it's pulling some power and I'm unsure how to size up a UPS. The route I'm thinking of going is the BR1500LCD. What has me concerned is that I have two power supplies, here are the specs to my computer:

Motherboard: DFI DK X48-T2RS
Processor: Q9450 Core 2 Quad
HD1: Velociraptor 300GB SATA II // the new 2.5" model
HD2: Seagate Barracuta 500 GB 7200.11
CD/DVD: ASUS DVD+/-R/RW with Lightscribe
Video: Sapphire HD 4870 X2 ***
PSU1: Rosewill 950-S-B (950W)
PSU2: Thermaltake W0158RU (650W VGA Only PSU) - I really like this 🙂

I think max amp pull on the Rosewill is 14 AMPS and the max on the Thermaltake is 7 AMPS, yet I am only using 1/2 of that since I only have a single video card. Those are AC AMPS drawn - I know DC amps are different and I'm not sure if that is important for a UPS?

So, the BR1500LCD shows to be 900W, but 1500VA, so is that enough? I would only care to have a minute to shut down the computer, so up-time with power loss isn't critical, it's more for voltage regulation (clean power) with a little bit of time for shut down.

I wasn't planning on anything else going to the UPS, but I do have two 22" Wide Screen ACER monitors and another computer beside this one that I wasn't planning on putting on the UPS which has a 600W PSU.

Thanks in advance for your help.

-slipmat

[Erasmus_apc · Accepted solution]

I would be more concerned about what your realistic draw is from the computer. When just looking at the sizing on the power supplies, it certainly looks like you may experience an overload with that UPS. Fortunately those ratings only indicated the total real power available to the system and not what they consistently draw. Since you're only running one video card, and the Q9450 Core 2 Quad draws anywhere from the low 80s to mid 100s in terms of wattage (idle to full utilization), it doesn't look like you would be overloading the UPS even if you were spending a lot of time gaming or doing 3D rendering/art etc.

What you should do is research the sum wattage on all of those parts, see if you can come up with a idle/max. value, and then choose a UPS from there.

I would also check the specs on each power supply and check if they are Power Factor Corrected or if they have any other technical notes about sinusoidal tolerance, since ALL of our APC Back-UPS units output a step-approximated sine wave while on battery, which can cause a computer with a PFC PSU to reboot or drop during the transition. If your power supply uses PFC then you may need to look at a Smart-UPS unit.

Message was edited by: Erasmus