Hello.

I need to buy UPS (Uninterruptible Power Supply) units for several desktop computers. The computers are all Pentium 4 towers with 19" crt monitors. At the APC site, the selector recommended a UPS of around 750 VA in power.

I'm planning on buying around 10 725VA units I found on another site.
These will be used for the computers mentioned above as well for some laptops equipped with docking stations and external LCD monitors.

I just wanted to get a second opinion before making the purchase.

Thank you.

When sizing the UPS, do not take the power draw of the CRTs into consideration. The CRTs should not be on UPS, as they are not critical. Ideally, you should also exclude any printers. These devices should be plugged directly into the mains, not the UPS. Typically, this will reduce your UPS size by at least 50% (or increase your run time). Remember that the function of a UPS is to provide time for an orderly shutdown of the systems to prevent data loss, preferably in an automated fashion. Make sure that the UPS you buy will interface with apcupsd, for automated control of the systems it is powering.

Nope, UPS is needed to make sure your boxes are fully functional until your diesel generators kick in

Thanks for the suggestions. I just need the UPS to power the computers for a few minutes until either we shut them down manually (they're only on during the workday)
or until they're shut down by some program (this is not especially important to us). So, in case of the first option, the CRT will also need to draw power from the UPS. There are no peripherals that need to be attached to the UPS. Under those conditions, is 725VA sufficient?

Edit: By the way, I'm in the U.S.: 120V, 60Hz. A rough computation (volts times amps) shows 725 to be sufficient, but I'm looking for confirmation from someone experienced with these things.

In order to properly determine the current requirement, an in-line amp meter will be best, second best would be a clamp-on amp meter. If neither of these are available, add the current requirements of all the equipment you will be putting on the UPS (should be on labels on each piece of equipment) and add 20%. If the machines are networked, remember that only one CRT is needed; you can ssh in (manually or with a script) and shut them down - assuming you don't set them up to automatically do that.

I don't know if this is helpful or not, there was a (kind of) similar discussion on another forum (since closed) about UPS.

hacker_supereme: I did read about UPSs failing after a few months, but the ones we're looking at come with a 2-year warranty.

macemoneta: We don't have such facilites.

To elaborate on what I did: I multiplied volts time amps for the monitor, since that info was available on a label on the back of the monitor. The PC docs give the power in terms of Watts, which I divided by 0.6 to get an upper-bound on the max VA. Added together, I got a figure close to, but slightly less than 725. I'm hoping that's sufficient. Each UPS will also provide power for an IP phone, but I considered its power requirements to be negligible.

OK, that's as good an estimate as you're going to get then.

Okay, thank you, macemoneta. I don't think I have the 20% to play with, but I did probably give a little room by dividing by 0.6 instead of by something a little higher.

Moved: This thread is more suitable in General and has been moved accordingly to help your thread/question get the exposure it deserves.

Mod Note: Not a Linux technical question