How to pick a UPS?

[AlexanderDomin]

Hey all,

I'm looking into an uninterruptable power supply / surge protector for my rig, and I'm not sure what rating I will need. I've done some cursory Googling and everything I can find is either a Web 1.0 calculator (how many CRT monitors do you have?) or faux-mathematical approximations. I recall nothing of Ohm's law from high school aside from the PIE thing, so I'm looking for a simple explanation here.

I have a medium-high-end gaming rig powered by a Corsair HX850. I am currently using a 32" LED TV as a monitor, but plan to upgrade to three smaller LED monitors within the year and move the TV elsewhere. What rating of UPS will I need (assuming at least 3 minutes of battery backup) and what is the math behind that decision?

Thanks again,
Alex

 

[leo2kp]

I have a CyberPower 810watt and that gives my Dell PowerEdge 2950, which has dual 750watt PSUs, dual quad-cores and 6 HDDs about 15 minutes of uptime. So far I've been very happy with it, and you can get one for about $140.

 

[boosted1g]

What you need to do is know or guess the total wattage used by your PC. If you wanted a more accurate measurement you can get a Kill-A-Watt power meter (like $20) . Hook that up to your surge protector at the wall outlet and it will measure your wattage and show you peak. You want peak when gaming not idle use.

While knowing you have a 850w psu helps, you could easily have a 850w psu and a system that does not pull more then 300w.

Without knowing any additional info on what you real wattage load is, I would tell you to get a 1000w UPS for 5-10min of battery backup. Both CyberPower and APC are good brands.

 

[americanbrian]

I don't think you will find one with only 3 mins of backup. Really what you should be looking at is peak load. Assume~40W per screen and add your PC consumption on top. Obviously your PSU is rated for 850W, but depending on your hardware I doubt you are over 500W (that would be a 125W CPU Plus say 40W for rest of platform and ~300W peak for GPU.

So ultimately a decent 750W load rated UPS is what you should go for imho. You will probably get 30min+ as a guess in a smallish UPS.

http://www.newegg.com/Product/Product.aspx?Item=N82E16842101421

This one is very cheap and quite compact from the number one brand of UPS's (that I am aware of) It has a ~15 min run time

 

[AlexanderDomin]

Thanks for the feedback. I would imagine my setup pulls around 750W at peak consumption. I haven't tested it, but these are my parts...
Mobo: ASUS M5A99FX
CPU: FX-8320 (stock)
GPU: ASUS GTX 770 (dual SLI, stock)
RAM: 16GB DDR3 (4 DIMMs)
Plus an SSD and a high-end NIC.
And however much the TV pulls.

So if I pull 750W, what VA rating would I need to get a good 15 minutes of backup time?

 

[giantbucket]

why would you assume you're pulling 750W at peak? when choosing a UPS to give you proper runtime, MEASURE, don't assume. if you're pulling 500W or if you're pulling 800W could be very different. also, if you're mid-game and the power dies, are you going to keep playing or are you going to chill and ease back on your PC? that will affect the actual load you're putting on the UPS when it has to run off the batteries.

i use a 1000VA (670W) UPS at home (PC + 8 screens), and at full load it lasts 8min and at half load it lasts 24min. why doesn't the math work? because batter capacity is NOT linear - especially at the high currents (high power) of running a computer.

find a UPS that has your desired run time at half-load, or even better one where your actual load is even less than half of the load of the UPS. that will prevent your batteries from being killed too quickly.