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Is It Grounded or Not?

The Computer Corner

All you want to know about computers by Charles Miller

Aquestion recently came to me from a reader who asked, “Since my new TV got fried, I have learned that they don’t ground here. We may have an electrician do a whole house ground, but that alone is not enough. So what do you, the guru, do to protect your equipment?” I wrote back to her with a short answer I am now going to expand upon here.

Her first observation was unfortunately correct: a lot of electrical wiring in Mexico is not properly grounded. Since protecting delicate electronics from voltage surges requires a good ground, the first thing I am going to recommend to readers is that they trot down to the nearest ferreteria where most of them sell a simple “probador de voltios” that is a small plastic box with a three-prong electrical connector on one end and three lights on the other. This tester is a simple way to determine if an electrical outlet is grounded or not, or to reveal if it is wired with reverse polarity. You will need to have a properly wired socket in order to proceed.

The first level of protection you can buy is a simple surge protector. These are often termed to be “sacrificial devices” because they are intended to burn up before the more expensive television or computer you have plugged into it does.

An Uninterruptible Power Supply (UPS), called a “nobreak” in Mexico, provides meaningful protection. These boxes contain a battery weighing several kilos and are combined with a much better quality surge protector. Briefly, your electrical supply is used to charge the battery and the battery used to power your equipment, thus providing a level of isolation. The battery also keeps your equipment powered during brief power outages.

Just how big a UPS you need is determined by the amount of current consumed by your equipment multiplied by the length of time you need the battery backup function to continue working. There are quite a few websites available to calculate how many joules you need. My favorite is “” Most other UPS manufacturers provide similar programs to aid in choosing their products.

It is important to remember that both simple surge protectors and UPS units require proper electrical grounding in order to function. And even when installed correctly, none of these measures provide absolute protection. If lightning strikes an electric service too near your house then all bets are off.

If you are experiencing strange problems with your electrical service you are probably better off calling a professional; however; there is a gadget I can recommend. P3 makes a gizmo called the “Kill-A-Watt” that can detect over/under voltage as well as off-cycle power. Kill-A-Watt can also measure how much electric current is being consumed to help you monitor your electric bill.

Finally, the answer to the question the reader asked. What I did was to have an electrician put in one properly grounded circuit; then I bought a US$500 UPS to protect my computer equipment. I also rearranged the furniture just a bit in order to be able to connect everything important to that one good circuit.

Charles Miller is a freelance computer consultant, a frequent visitor to San Miguel since 1981 and now practically a full-time resident. He may be contacted at 415 101 8528 or email FAQ8 (at)


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