Question about Uninterrupted Power Supplies

I was in a store earlier today looking at Uninterrupted Power Supplies (UPSs) but before I buy I have a few questions I was hoping some of you could help me with.

I saw several brands in the store, APC (American Power Conversion),CyberPower CyberPower, and Energizer. Now I know APC makes good UPSs because I have had one in the past and they come highly recommended. But does anyone know how the other two brands compare to APC? Are the quality and reliability comparable? Energizer seems to be new to the UPS scene because I’ve never seen one by them before. Mostly what I’m concerned about is if they will do what they say they will do. I’ve seen brands that claim much higher VA and on-battery run time than APC at a mere fraction of the cost, so I am a little suspicious. I’m not sure exactly what to look for, but if any of you electrical engineer types want to look through the specs and let me know what you think I would appreciate it.

My second question is about UPS power ratings. UPSs are rated in VA, but can I relate VA to anything I am familiar with? Watts or kW/h, maybe? Just trying to understand the rating.

Lastly, does anyone have any recommendations on what the minimum VA rating on the UPS I buy should be? I want my computer and 19" monitor to be on battery backup. The computer is an Athlon XP 2700+, 1 GB RAM, soundcard, Geforce Ti 4800, 1 7200 RPM HD, 2 Optical Drives, and 5 80mm case fans all on a 400W power supply. I imagine that battery run times can vary greatly depending on what you’re doing and I can’t help wondering if the run times posted on the box aren’t a little bit on the generous side. Besides, it doesn’t say what kind of activity a computer would have to be doing to get that kind of run time. I don’t need a rating for an idle computer because if I’m at the computer its probably not going to be idle.

>> UPSs are rated in VA, but can I relate VA to anything I am familiar with? Watts or kW/h, maybe? Just trying to understand the rating.

VA is the measure of the active and the reactive components. You might want to check a recent thread on this. A computer and monitor should not have significant reactive components as they both use switching power supplies so just use the watts and add a safety margin of (say) 15%.

Even though I’m SURE someone here will come along shorty with a good answer, if you go to they have a lot of discussions about UPS’s and alot of people over there have tried alot of different brands and can compare/contrast them for you.

Basically, you get what you pay for. I bought an Energizer 450VA UPS with a low price and good specs, and returned it when it couldn’t even handle the moderate load of my older system and 19" monitor, which did come out under its 200W rating. APC UPSs are generally well regarded in the industry. You might look at the Back-UPS ES 725 Broadband, which seems pretty beefy and is under $100. I think you’ll probably get around 10-15 minute runtimes on your system, depending on load level and the monitor.

One general note: you might consider not hooking up your 19" monitor up to the UPS because a) you get a less expensive UPS or a longer battery run time out of it and b) you slightly worsen your system’s reliability because in the event of a short inside the monitor the monitor’s fuse might not be selective over the UPS’s output protection, IOW the UPS’s protective circuit might trip before the monitor’s fuse blows, which leads to power loss for the PC even though the mains hadn’t failed.

You don’t need the monitor to effect a clean shutdown of your PC - that’s the job of the software that should come with the UPS. Surely you don’t need to use your PC during a power failure - or do you anticipate blackouts that last hours?

APC is the 800-lb. gorilla of the UPS industry. (I used to work for one of their competitors.) I’ve never heard of the other 2 brands. You should be able to get some info on the run times for various typical loads on the box.

And I have completely forgotten how to calculate VA from watts, for which the person who tortured me for weeks of technical training would probably want to strangle me. Any salesperson with half a clue should be able to tell you what the runtimes are for your load, and for various watts. Your various pieces of equipment should have the wattage labeled on the back; it might help to write it all down and take it to the store with you.

No, but the system won’t automatically save your work, especially if you haven’t previously saved a new document. Monitors are fairly low draws, at around 60 watts, typical (more for larger monitors, less for LCD types.) I’ve always connected the monitor to the UPS. Things like printers and other nonessential peripherals can be left off.

Watts = VA x power factor. Power factor is the ratio of real power to apparent power, and is 1 for a purely resistive load. As per sailors post, you can get by with an approximation when shopping for UPS units.

Thanks for your replies everyone. I ended up getting the Energizer unit for several reasons. 1) It has a 3 year warranty on the unit itself. 2) It has a $100,000 connected equipment warranty. (Though admittedly I’m more concerned with my gear not getting fried in the first place.) and 3) It was $59.99 with a $50 mail-in rebate. Didn’t look too bad to me. It should fit my needs. It’s rated for 400VA and 200 watts. I’ll probably end up not hooking my monitor up to the battery backup because Viewsonic says my monitor draws about 120 watts on average. That should be fine, though, because it comes with software that automatically shuts down the computer in case of a power outage.

In response to Q.E.D.'s post, a feature panel on the back of the box actually says, “When a blackout occurs, FileSaver™ software will save all open documents and programs, close all applications in use and guarantee a safe shut down for your computer and other equipment.” Perhaps I can hook everything up, create a fake Word document and see what happens when I pull the plug.

Just FYI, “pulling the plug” is not a reliable (or entirely safe) way of testing a UPS. The UPS relies on the third prong ground to assure safety and correct output. This also means you shouldn’t take a UPS camping with you as an emergency power supply. (Simple inexpensive inverters, which are not meant to protect delicate electronic gear, work just fine as remote power sources, combined with a deep discharge battery. Recharge deep discharge batteries properly ASAP after use)

When the power goes out, your ground prong is still connected via your house wiring to earth ground, so the UPS considers it a given. Bad or improper grounds can cause all sorts of problems with some UPSs in normal operation.

Having said all that, I’ve taken the chance and done both of the above, but that was back when I was young, reckless, and broke. UPSs were expensive, and my time was cheap, so I often fixed free broken UPSs -the only way I could get them at all- and abused them

Most ‘real’ UPSs have a built in test switch to disconnects the power but not the ground, but the smallest consumer UPSs may not. Trip your household circuit breaker instead. My electronics bench has GPF safety breakers on several outlets (sensitive outlet breakers that are required in all newly built or renovated bathroom or kitchen wiring in most jurisdictions these days). They have a test button on them. If you have these, you can run a heavy duty extension cord to your bathroom to test the UPS, if you don’t feel like going to your fusebox, or don’t know what each breaker in the box controls

ChronosGF: I had the 450VA 200W unit, it couldn’t power nearly that, and the phone support people admitted as much. Things to watch out for: Reboots when the UPS switches from line to battery power, short battery lifespan (I lost about 1% charge per second), and random powercuts with no alert, shutdown, or battery drain.

I’ve had nothing but good luck with APC, in every case having the unit outperform its specs. The UnaBoard can go more than 2 continuous hours on its 1200VA APC, when it appeared to me it should only be able to do 100 minutes based on the current draw.

I’ve heard that the “$100,000 warranties” and so forth are essentially a crock. I know of no one who has been able to successfully get a dime for a computer that went gump while connected to a UPS, as the burden of proof is on you to prove that the UPS failed to protect the computer, and that it could not have died by any other means whatsoever, including EM pulse from a lightning bolt. If anyone has been able to get an actual full-value payoff from one of these warranties, I’d love to be shown wrong.

I got an APC a couple of days ago used & I left it on all night & it worked fine. Then I unplugged it for a few hours but it didn’t have any charge in it when I tried it alone. I thought they would keep the charge if they weren’t plugged in. Is this how they are designed?

ChronosGF, you could always get a gas powered generator :slight_smile:

Chances are some or all of the conected equipment was drawing at least some power, even though it was “off”. A number of things, especially those powered by transformers, draw a small amount of power as long as they’re pluged in.

Thanks for the heads-up Alereon. One of the big reasons I wanted to get a UPS is some friends and I are having a get-together this weekend, and with 11+ computers all hooked up and running I was a lil bit concerned about about power lags/spikes, especially since my computer isn’t even totally paid for yet. I’m gonna hook some things up and run some pretty extensive tests and if it doesnt work like it should then its back to the store tommorow.

Also, thank you KP for that warning. There is a circuit that powers just my room so I’ll go trip the breaker and see what happens. Details at 11…


Yeah, its definitely going back. Once I got the battery charged I plugged in just my computer and started it up. It registered a 90% load just sitting at the desktop and jumped to over a 100% load when I started a game. I waited until it settled down and then tried a 10 sec self test. As soon as I clicked the ‘Test’ button the whole thing shut down. I’ll be taking it back tomorrow for a better, higher rated APC unit.