UPS selection help

Captain Dondo

I suggest a separate UPS for each computer. It is just a lot easier for the controlled shutdown of the machines since each has a connector (serial port or USB depending on the design) that plugs into one computer. It is easy for software to shut down that computer, but if you have one big UPS and plug all your machines into it, the one receiving the power failure information has to signal all the other machines to shut down before it shuts itself down. This is by no means impossible, but a PITA.

I have not priced any UPS over 2200 VA (about 1600 watts), but I suspect a bunch of small ones may actually be cheaper due to economies of scale. Also, if you plug the small ones into separate outlets (that should be on separate breakers) you may not need to re-wire your building.

Not sufficiently. You need both the volts and the amps. Multiply them together to get VA. To get watts, you need to know the power factor of the stuff plugged in. If you must guess, allow that a 100 VA UPS can power 70 watt load.

You certainly should. Here is a true story.

A military installation had a diesel generator for backup power. It took X minutes to start the generator, so X * 1.1 minutes of UPS protected each load. Once a month they powered on the generator to test that it was still working properly, let it run 5 minutes, and returned to utility power.

When the real power failure came, the generator came on, ran for 5 minutes, and then failed due to overheating. No one had ever run it for over 5 minutes to discover this. You might wish to go to APC's web site. If you have the patience, they have a lot of useful information there, though it is not always easy to find. They have a very broad product line.

My APC Smart-UPS 2200 uses 48 volt battery (looks like four 12V motorcycle batteries).

The batteries in there would have to provide that, but that is inside the UPS. Outside, you would need to provide 3000 watts which, at 120V would be only 25 amps. You will need a dedicate circuit with a 30 amp circuit breaker, and a high-amperage outlet to plug the UPS in. I have a 20A circuit for my large computer.

Sneer if you like. In my UPS, looking through the ventilation holes, I would estimate that some of the big wires are 8 Guage, and one looks like #4 guage.

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