Suppressors can save PCs from summer's sizzling surges

July 04, 2002

YUP, IT'S HOT. As in really hot. As in heat warnings, and humidity warnings, and air quality warnings. In other words, summer in Baltimore.

Along with that heat and humidity and the discomfort they pose comes another irritant - those little lightning flash icons that show up in the daily weather forecast.

They mean thunderstorms - and danger to your computer and other delicate electronic gadgets. If you haven't thought about it lately, it's time to make sure you're protected.

The first step is to learn a bit about your electronic equipment and why it needs your protection in the first place.

Computers are designed to run at very low internal voltages. The voltage is the "pressure" that a flow of electricity exerts on wiring and circuits, much like the pressure of water through a hose or the pipes of a house. A sudden increase in pressure in a hose can burst it; in your house, turning the pressure up too high can damage your dishwasher and other appliances.

PCs and other electronic equipment are even more sensitive to voltage. Typically, it only takes three to five volts to power a PC's internal chips. House wiring in the United States supplies 120 volts, so plugging a computer into a wall outlet is a bit like filling an espresso machine with a fire hose.

A transformer inside your computer reduces the voltage to the proper level, just as a reduction valve in your home can turn high-pressure flow from water mains into a flow safe for your pipes.

The voltage that emerges from your wall outlets does vary slightly, depending on your electric company, the time of day and other factors, including the normal cycling of refrigerators, washing machines and so forth.

Your computer is designed to handle these customary fluctuations. Unfortunately, it isn't designed to handle sudden, large spikes and surges in current. These can fry the innards of your computer if it doesn't have a device to protect it. Modems are particularly sensitive - not just to spikes in house current, but also to much smaller and almost undetectable surges over the phone line.

In the summer, these spikes generally have two causes. The first is a lightning strike at or near your house. Forget about protecting against a direct strike - when you're talking millions of volts, the only way to keep equipment safe is to unplug it.

In fact, if you see a thunderstorm heading your way, it's a good idea to do just that - unplug. Most storms that produce local ground lightning pass by in a half hour or less. Whatever you're doing can probably wait.

The second type of surge occurs after lightning has knocked out the power in your area, or in heat emergencies, when the power company blacks you out. When the juice returns, it's likely to do so with a real kick.

As a result, it's a good idea to protect your computer equipment and other expensive electrical gadgets such as TVs and sound systems, with a surge suppressor - or better yet, an uninterruptible power supply.

Surge suppressors, usually sold as power strips with four or more outlets, contain circuits that can sense a surge and cut off the power in a fraction of a blink - before the extra voltage can ruin your equipment. Better units also filter the power, so that small glitches and electromagnetic interference are less likely to create problems.

You don't have to pay a fortune for a good surge suppressor, but the $5 power strips in the bargain aisle aren't likely to do the job - in fact, they may have no surge protection at all.

Look for a unit that carries an Underwriters Laboratories certification of UL 1449 or is certified as a "transient voltage surge suppressor." That means it meets minimum standards.

Also, look for a "clamping voltage" (the minimum surge that will make the protection kick in) of 330 volts, and an energy absorption rating of at least 400 joules (600 is even better).

A good surge suppressor will have an indicator light that tells you whether surge protection is still active (suppressors lose effectiveness each time they're activated). More sophisticated units will also have protected jacks for a phone or cable line. These are important if you have a telephone or cable modem.

Solid, six- to eight-outlet suppressors that meet these specifications are available for $40 to $60 and can protect an entire computer system.

But for computer users, a surge suppressor solves only half the problem. If the power suddenly goes out, you'll still lose what you were working on and could wind up with a scrambled hard drive if your system was writing data at the time.

To be really safe, consider an uninterruptible power supply (UPS), which combines a surge suppressor, line filter and a battery backup that takes over instantaneously when the main power dies.

Starting at $100 or so, these are considerably more expensive than suppressors. Generally, you'll pay more money for more battery time to keep your system working longer in the case of a power outage.

An inexpensive UPS may keep a single computer and monitor running for only 5 minutes - but even that's enough time to execute an orderly shutdown if you're at your desk when the power fails.

UPS capacity is measured in volt-amps. The best way to figure out how much you need is to visit an equipment manufacturer's site and use its calculator. You'll find useful information at American Power Conversion ( and Cyberpower (

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