Do you know what would happen if you were to use your notebook computer while it was plugged into an outlet and charging, and a blackout were to occur? Nothing. It will probably be dark in the room, but the computer will be fine. The battery in the notebook computer will kick in and provide power until it’s completely discharged or until the AC power comes back online. At the very least, you would have enough time to save whatever you were working on and shut down the computer in an orderly fashion.
If the same thing were to happen while you were using a desktop computer, you could be in trouble. As far as a computer is concerned, a blackout is the same as pulling the plug out of the wall. At best, you might lose whatever you were working on, or at least any recent changes to it. At worst, in addition to losing what you were working on, critical system files might be corrupted, and your computer might not work properly. Unless you have a UPS, that is.
A UPS, or Uninterruptible Power Supply, is basically a big rechargeable battery pack with a built-in power inverter and AC power outlets. The unit plugs into a wall and charges and conditions its battery pack while constantly monitoring the incoming AC voltage. If it determines that the incoming AC voltage is within specified limits, it simply passes that voltage on to its AC outlets to power whatever is plugged into them. All the while, voltage spikes are suppressed, and over- and under-voltages are conditioned so that plugged-in equipment is unaffected. If the incoming voltage disappears completely, the UPS switches to battery power and anything plugged into its outlets continues to operate, unaffected by the power outage.
When a UPS switches to battery power it also sounds an alarm to let the user know that there’s a problem, while providing enough run time on battery power for the user to close files and shut down the computer in an orderly fashion. A UPS will also warn the user when the AC voltage is too low or too high, or if the batteries need replacing.
Sometimes a computer is left running 24/7 (coincidentally a comfy work chair), with no user ready and able to shut it down in the event of a power failure; servers are a perfect example. That’s why UPS’s usually come with software that runs on the protected computer, and shuts everything down when the UPS tells it to, through a serial or USB link.
UPS’s come in different capacities, or sizes, to support different current loads. They are typically rated in both watts (a DC power value) and volt amperes, or VA (an AC power value). For example, a mini tower desktop computer with a low-end processor and a single hard drive doesn’t draw nearly as much current as a workstation with an 8-core processor and twin hard drives. You would therefore need a much beefier UPS to provide the workstation with 10 minutes of run time than you would for the mini tower. And naturally, a bigger display uses more power than a small one—unless you’re still using a small CRT display, which consumes more power than a large flat panel.
When you set up a UPS, you should not use it to power non-essential items. For example, you shouldn’t plug a printer into a UPS because it’s not a big deal if a printer goes down. Laser printers in particular should never be plugged into UPS’s because they draw too much current. You also wouldn’t want to plug your speakers into a UPS because it doesn’t matter if your speakers stop working. You really just want to protect your computer and any work you stand to lose. Monitors are usually plugged into a UPS because you need them to see what you’re doing when it’s time to shut everything down. But a monitor connected to a server might not require battery backup.
Sometimes a UPS will have outlets that aren’t battery backed; they allow you to plug in such things as printers and speakers, eliminating the need for an additional power strip, but they turn off during a power outage. Also for convenience, some UPS’s feature outlets with extra space around them to accommodate large AC-to-DC power adapters that would otherwise block adjacent outlets.
A UPS is not intended to be used like a generator. In other words, it is not intended to allow you to keep working until the power comes back online. Even so, the greater the capacity of a UPS, the more run time it will provide for a given device. For example, an entry-level UPS might provide a mini tower computer with 10 minutes of run time while a monster UPS, intended for use with a big server, might be able to keep the mini tower computer running for hours. But again, that’s not how they’re used. Any system that cannot be allowed to go down must have generators in addition to UPS’s as part of their infrastructure.
Keep in mind that UPS’s can be used for anything, not just computers. While you wouldn’t want to use one for, say, a blender, it might make sense keep your VCR, DVR, alarm clock or security system plugged into one. In fact, security systems often contain a UPS to keep them functional during a power outage. But by plugging your VCR, DVR or alarm clock into a UPS, you can forever avoid lost programming information and the dreaded flashing 12:00 display that occurs when power is removed from these devices. Well, maybe not forever, but for as long as the UPS batteries are good. UPS batteries typically need replacing every 3-5 years.
B&H carries UPS’s ranging in capacity from 350VA to 6000VA, at prices ranging from less than $50 to several thousand dollars. Prices vary according to capacity, number of outlets, whether it has serial and/or USB connectivity, whether or not it has spike protection and if it protects telephone lines, network cables, TV/Internet cables and so on. Voltage spikes and surges can be harmful to any appliance, especially computers. During an electrical storm, any wire leading into a computer is a potential path for lightning to follow and possibly destroy the computer. That’s why UPS’s often provide spike protection for telephone and coaxial cable lines.
Generally, you want a UPS that can provide about 10 minutes of run time for any given system. It’s difficult to go by specs alone when buying a UPS. That’s because different combinations of computers and monitors have different current requirements, regardless of the type of processor and size of the display. Basically, though, UPS’s rated up to 500VA are ideal for entry-level systems, UPS’s rated for 500VA to 1000VA are ideal for mid-level systems and UPS’s rated for 1000VA to 2000VA are ideal for high-end systems. You’ll want to go even higher if you’re using a particularly big monitor or if your system has a lot of drives installed. UPS’s larger than 2000VA are typically intended for use with one or more servers, and many of these are rack-mount units not ideal for home use. Some of the high-end models consist of a UPS as one unit and one or more battery units; battery units can be added as current requirements increase.
Keep in mind that UPS’s are heavy. A 350VA unit might weigh between 5 and 10 pounds, while a 1500VA unit can weigh more than 30 pounds. Larger units can easily weigh between 50 and 100 pounds, while the really big units can weigh several hundred pounds. So don’t go overboard when there’s no need to. Remember that a UPS is not intended to let you continue working indefinitely. It’s there just to prevent you from losing work. And the term “work” doesn’t necessarily mean a letter you’ve been typing or a spreadsheet you’ve been compiling. Work could also mean many hours worth of HD video footage that’s being encoded or a computer simulation that takes hours or days to complete. And every minute counts when time is money.
A UPS could even pay for itself in the form of insurance. Most UPS’s come with a guarantee from the manufacturer that it will pay to replace any equipment, up to a certain value, that’s damaged by a power surge or other power event that occurs while the equipment is plugged into one of its units. Sometimes you’ll also get a data-protection warranty that provides professional data recovery services for any data lost due to the failure of the UPS.
Now that’s peace of mind.
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