Short-circuit the shocking gremlins, By Don Gussin

Ever wonder how gremlins coming in over the power line can zap your computer, TV, microwave or refrigerator? Can surge protectors stop spikes, voltage regulators correct brownouts, and uninterruptible power supplies (UPSs) keep your equipment humming? Confused? Interested? Read on.

As you probably know, power at the wall plugs in our homes is nominally 120 volts, the same as north of the Rio Grande. Problems start when the voltage strays too far from this value, and unfortunately there are several ways that this can happen. We need to look at each separately. The clean 120-volt power can change (brownouts, overvoltages, or complete loss of power), or it can be corrupted with high-voltage spikes or surges. These gremlins may be simply annoying, or they can be downright destructive. Brownouts can unexpectedly turn off equipment or make it behave erratically, such as by causing your computer to freeze or crash. Overvoltages, or spikes, can fry sensitive equipment, and continuous low or high voltage levels can significantly reduce life expectancy (of your equipment-not you!).

So, having protection for expensive equipment is important wherever you can have one or more of these gremlins, and Mexico certainly qualifies. We'll look at three types of protective devices: surge protectors, voltage regulators, and UPSs. Some do a part of the job, and some do just about everything you need.

Power line surges are the most destructive of the gremlins. If lightning strikes even as far away as a few kilometers from your home, it can put spikes of thousands of volts not only on your power line but also on your telephone line and TV cable. Even though a spike lasts only a few thousandths of a second, it has enormous power (potentially many times more current than all of your house's needs put together), more than enough to completely burn electronic circuits.

A surge protector connected between your wall plug and your equipment diverts the spike harmlessly to ground before it reaches your equipment. A surge protector is usually provided as a power strip or box with multiple outlets, and it's as simple to use as an extension cord: just plug it into the wall and plug your equipment into it. In doing its job, however, the protector can be damaged itself. Many models have an indicator light that show they are working properly, so it's important to keep an eye on it and replace the protector if the light goes out.

Surge protectors are most appropriate for use with computers, home entertainment systems, and microwave ovens, because of all the electrical equipment in your home these are the most vulnerable to surges. Note that your computer may be connected to a phone line and/or TV cable for internet service, and that these lines can also conduct surges that have to be stopped. Some surge protectors do this, too, so when you buy a device to protect your computer be sure you get all the functions you need.

Surge protectors cost from about 100 pesos and up. Some devices are labeled with a capacity (for example, "600 joules"), but because this is not a standardized rating it cannot be used to compare devices between manufacturers. Some manufacturers provide an insurance policy with the unit that will pay for the replacement of your equipment if it's damaged while connected to their device; since I've never had to make this claim, I can't vouch for whether they pay up. There are also devices installed at your house's circuit breaker (fuse) box that protect the whole house, but it's still advisable to install the dedicated units described above for your most delicate devices.

Note that for surge protectors to work, your house has to have what is called a "grounded" electrical system, that is, one with three-prong outlets that are properly wired to ground rods outside the house. While this practice is required in construction north of the border, unfortunately it's frequently not followed in Mexico. An electrician can check your house wiring and advise you if your system is grounded, and if it is not he may be able to upgrade it appropriately.

Another gremlin comes in the form of brownouts and overvoltage (respectively, voltage below and above normal levels) that can happen momentarily or persist for a long time. Brownouts will cause electronic equipment to perform erratically: TV pictures can dim or flicker, electric ovens and microwaves won't heat properly, your PC may act peculiarly or crash, and motors (like in your fridge and washing machine) may suffer an early death. And as you would expect, overvoltage can cause an early death of just about anything using it.

Voltage regulators correct brownouts and overvoltages. They do just what their name suggests: they adjust electric utility power that's out of range to an acceptable level (usually 120 volts plus or minus 10 percent). The devices aren't perfect, though; they typically only correct utility power from 100 to 140 volts, have limited power capacity, and often provide no surge protection. It's important to make the correct choice from the several types available. Those designed for electronic devices (PCs, TV sets, etc.) provide tight voltage control but have limited power capacity, while those for use with refrigerators provide more power but with a wider range of output voltage that might not be suitable for electronics. These voltage regulators cost upward of 300 pesos. There are also units that provide voltage regulation for the whole house, but these tend to be expensive and may not work properly when you are using only a small amount of power.

Combining a surge protector and voltage regulator will clean up electric utility power and keep your house humming, at least as long as there's electric power. But nothing works when there's no power, and since it usually disappears without warning, your PC will die right in the middle of some important job. If you're concerned about this, then a UPS is for you. These contain a high-capacity battery and electronics that instantly provide 120-volt power when the utility fails so your computer keeps on running without a hitch. The battery has sufficient capacity for many minutes of operation during a power loss, giving you time to do a managed shutdown; some units are even intelligent enough so that if you're not there they will shut down your computer themselves just before the battery runs out. UPSs also usually provide voltage regulation and surge protection, giving complete protection all in one box. Good units can cost in the range of 1,500 to 2,500 pesos, depending on their power capacity; 400 VA (power c
apacity rating) is probably sufficient for use with computers with a flat panel display, while those with TV-type monitors require 600 to 800 VA.

When you're shopping, it's important to avoid bargain products because their designers may have cut corners, which can make them unreliable and even dangerous. APC, Belkin, Koblenz, Leviton, and Tripplite are some manufacturers of quality products. Now that you know all about those electrical gremlins, don't put it off until the thunderstorms start: get your protection installed now!

Don Gussin is a retired electrical engineer living part-time in San Miguel.