Originally created 04/01/97

Shedding light on blackouts, brownouts, spikes and surges

Q. What is the difference between a UPS and a surge suppressor? Will it protect my computer from a lightning strike? How powerful a unit do I need for my computer system?

A. My apologies to all of the electrically literate, as I am about to drastically oversimplify a highly complex topic in the following four sentences.

Electrical power can either drop below or rise above the normal flow of electricity. Falling below is referred to as brownout. Rising above is called a surge. Rising quickly is called a spike, and falling all the way is a blackout.

Looking much like a box or strip that gives you several electrical outlets in exchange for the one in the wall into which it's plugged, a quality surge suppressor (over $50) should protect your equipment from most surges and spikes. However, if the equipment gets a direct hit from a lightning bolt, you can pretty much kiss everything goodbye.

A UPS is an uninterruptible power supply. As the name implies, when you lose electricity, the UPS replaces it.

A UPS consists of a lead-acid battery (the same type as in your car) and sophisticated electronics that monitor the status of your outlet's electrical power, plus surge suppression. As prices fall, UPS models will take advantage of newer battery technologies, such as lithium-ion. Today's UPS units can detect many different electrical anomalies that might occur and make sure your equipment has the current that's required for normal operation.

Every UPS has a volt/amperage or VA rating. This is directly related to how much equipment can be supported in a power-loss scenario as well as how long the total power to keep things running can be maintained. To determine how much power your computer system draws, look at the specification sticker that's usually on the back of each piece of equipment.

For example, your color monitor might draw 2.1A (amps), your computer .4A and an external modem .2A. Add up the amounts (2.7A) and multiply times 120 (volts). We get 324, so you need a UPS that's rated 324VA or higher. It's wise to add a little extra headroom, so look for a UPS rated somewhere around 400VA.

Only essential devices should be connected to a UPS. Aside from the computer, you'll need the screen to see what you're doing. The modem should also have power, in case you are in the middle of downloading a big file and you don't wish to start over. Do not hook up a printer or scanner to a UPS, since nothing critical is lost if these devices stop. Besides, laser printers draw an enormous amount of power (usually about 15A) and a small UPS couldn't handle it.

Check out the offerings from several excellent UPS manufacturers, such as Tripp Lite, SL Waber and Best Power. Best's Fortress line has a unique offering. In a blackout, the front panel displays a numerical readout indicating how many minutes you have before you run out of battery power.

Craig Crossman is a columnist for The Miami Herald. Send questions to him at Business Monday, 1 Herald Plaza, Miami, Fla. 33132. Please include a phone number.