Lightning Strikes

The Lab Guys' work becomes particularly challenging during the summer, when northern Colorado's frequent thunderstorms can cause power problems that interrupt testing and damage equipment. Last summer, one storm caused a voltage surge that damaged network cards in six client systems. Now, we have UPSs that provide battery backup and surge protection for our servers; if our budget permitted, we'd provide UPS support for the entire Lab. Instead, we chose a less expensive solution and installed surge suppressors for our clients.

If you've shopped for a surge suppressor lately, you've probably noticed a wide price range. As you might expect, surge suppressors don't all provide the same level of protection: You could mistake some low-priced models for simple power strips. A full-featured surge suppressor might cost $60 to $70; the least-expensive models sell for $15 to $20. If you look at the innards of some of these budget-priced units, you might be shocked by the amount of empty space inside the case. How can you ensure that you're buying adequate protection?

The first thing to look for is an Underwriters Laboratories (UL) 1449 testing certification, which is usually printed on or molded into the suppressor's case. UL submits surge suppressors to a variety of transient voltage tests, and the UL 1449 certification designates the suppressor's maximum output voltage when fed voltage spikes of up to 6000 volts. (For information about UL testing, visit the UL Web site at http://www .ul.com/.) The best products limit output voltage to 330 volts or less. You might also see ratings of 400, 500, or 600 volts.

Voltage surges can take as many as three paths through your power line: line to neutral (L-N), line to ground (L-G), and neutral to ground (N-G). A quality surge suppressor will use a combination of thermal and fast-acting fuses, capacitors, and metal oxide varistors to provide protection along each path. To identify which paths a surge suppressor can handle, look on the case for UL ratings for each path. Some budget-priced surge protectors eliminate the fuses or capacitors and provide protection along only one or two paths.

Surges can also enter your system through network cabling (as happened in the Lab Guys' case), so you might want to look for units that also protect your Ethernet or Token-Ring interfaces. If you use dial-up connections, you might want a surge suppressor that also can protect your modem. (Be aware, however, that the UL test ratings apply only to the AC power-line circuitry and not to protection circuits for network or telephone interfaces.) Some models even come with an equipment-protection policy that will replace your equipment if the suppressor fails to prevent surge-related damage.

Whichever surge suppressor you choose, it won't work properly unless your electrical outlet is grounded and the outlet's neutral line is correctly wired. Some full-featured surge protectors have circuitry and indicator lights that can monitor your outlet's status (although you might need to look in the suppressor's instruction manual to find information about these features). You can also purchase a receptacle tester for less than $5 at a hardware store.

Depending on the frequency and severity of the voltage transients in your area, a surge suppressor should last for a few years. However, all these devices use metal oxide varistors that can lose their effectiveness if surges are particularly strong (e.g., when lightning strikes close to the building that houses the device) or sustained, so choose a surge suppressor with a light that signifies that the suppressor's circuitry is still effective. Whatever you do, don't leave your equipment unprotected.

End of Article