What size UPS needed?

CathJ

CathJ

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Does this page look accurate?

http://www.powerboxes.co.za/

They're not selling UPSs so much as inverter/battery/whatever systems, but do this figures hold for a UPS as well?

One of their examples: 500VA supplies 300W which allows for a PC, 17" screen, printer, and standing lamp for up to 8 hours. Basically they say, add up the watts of what you want to use, then choose a (UPS/whatever) that supplies just more than that (allowing that a 500VA will supply 300W or so, not 500W).

Seems very generous? I was looking at a 2000VA UPS, but maybe I just need a 650VA?
 
Those prices are heavy. What they are charging R12 000 I had built for under R6000 :/

Also, what computer with a monitor only uses 220 watts? My monitor uses more than that...
 
Well, 500VA with a efficiency rating of 60% (which isn't too great) is 300W yes.

The VA rating of the UPS however, is an indication of the maximum LOAD that the UPS can carry, not the runtime of that UPS. To run 300W for 8 Hours is 2.4kWh, which translates to 100aH (presuming the batteries runs at 24VDC, and that we can run the batteries completely flat).

So yes, it's possible. However, IMHO, 300W for a PC, 17" Screen, Lamp, and Printer (let's presume we aren't talking about a laser printer) is very much on the low side.

Also, the datasheet has some worrying specs at http://www.powerboxes.co.za/specifications Modified Sine Waves aren't a good thing at all. Personally, I would stay clear of these.
 
savage said:
Well, 500VA with a efficiency rating of 60% (which isn't too great) is 300W yes.

The VA rating of the UPS however, is an indication of the maximum LOAD that the UPS can carry, not the runtime of that UPS. To run 300W for 8 Hours is 2.4kWh, which translates to 100aH (presuming the batteries runs at 24VDC, and that we can run the batteries completely flat).

So yes, it's possible. However, IMHO, 300W for a PC, 17" Screen, Lamp, and Printer (let's presume we aren't talking about a laser printer) is very much on the low side.

Also, the datasheet has some worrying specs at http://www.powerboxes.co.za/specifications Modified Sine Waves aren't a good thing at all. Personally, I would stay clear of these.
Click to expand...

There is nothing wrong with modified sine for computer equipment. Most computer UPS`s use modified sine.
 
ghoti said:
Those prices are heavy. What they are charging R12 000 I had built for under R6000 :/
Click to expand...

For the price of their 2KVA, I can get a 10KVA Pure Sine Wave.... Yes, it's ridiculously expensive.

EDIT: So from their website too - the UPS comes with a 12V, 100aH battery. It's under spec'ed in terms of the claim of running 300W for 8 hours long. You won't get anything near 8 hours out of these units with the batteries they supply standard.
 
Yeah, it looked a bit expensive to me, but what do I know :D

The basic calculations are sound, though? So that gives me some reassurance that I don't actually need a 2000VA UPS for what I need.
 
CathJ said:
The basic calculations are sound, though? So that gives me some reassurance that I don't actually need a 2000VA UPS for what I need.
Click to expand...

It's not. "a PC, 17" screen, printer, and standing lamp" is definitely not 300W, it's more. Especially if you have a more power hungry computer used for gaming and stuff with high end graphics cards and/or loads of hard drives. Calculate the wattage of all the devices you want to connect to the UPS, and see what your total wattage is, or guess, and hopefully you don't get it wrong.

Your PC's power supply, screens, printers, even your kettle all have (or should have) a sticker on it indicating how many watts of electricity the device us. Add all of that together, convert the Watts to VA (plenty of calculators online), and then buy a UPS of the correct size, keeping in mind that generally it is not good to load a UPS more than 80% of it's absolute maximum load. Therefore, 600VA should actually only carry about 480VA of load, or +- 400 watt provided it's a good UPS with a +- 90% efficiency.

In terms of runtime (how long you can run off the UPS), that depends entirely on the batteries, and has actually very little to do with the UPS itself. Datasheets of the various UPSes would give indications of runtime under different loads (in absolutely optimal conditions) and you can work on an assumption that you'll get about 80% of what they claim their runtime is (if it's a respectable UPS brand). Chances are, you'll only get a couple of minutes most of the time. If you want extended runtimes, you will most certainly need extended (more) batteries which is normally through the purchase of an additional battery bank that you can connect to the UPS. Smaller UPSes mostly do not offer that option in order to keep the costs down.

Personally, I would recommend the biggest UPS that you can afford. There's always something else that you want to connect over time as you become accustomed to not having power disruptions (TV/entertainment for example instead of just your PC).
 
All depends on the PC config.
My home office has a media server (no screen) with 5 drives, router, 16 port switch, modem, router/Wifi and this is only 110W odd.
Then add in my dev machine (gen 4 i7, ssd, 2 screens) and it pushes it to 250W or so. No GPU at all.

Best is to get a Watt meter from builders and measure the wattage yourself. Otherwise it's just speculation.

EDIT: Get something rated much higher though. I setup a 840W pure sinewave just in case I wanted to use it for more. I have already added 3 x external 10W led spots, switch and an IP camera. Pretty sure it won't end there.
With all the above I am hovering on 300W.
 
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My I5 uses 75 watts, and 22" led monitor uses 20 watts.

Measured with meter.
 
mister said:
My I5 uses 75 watts, and 22" led monitor uses 20 watts.

Measured with meter.
Click to expand...
Ya, screens are quite low nowadays. My secondary LG is 20W and primary Dell is about 12 to 15W. Overall PC's don't really chomp a lot - unless some beast gaming setup.
 
Can someone recommend a quality affordable product to test power flowing through a power chord? I would love to see my actual watt usage.
 
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