03 September, 2011

A Shocking Surge--When lightning stikes

 I’ve had a long history of dodging lightning, I sometimes have a feeling that someone up there is using me for target practice. One instance back in the mid-70’s, I was sitting in my car at a gas station in Tampa, FL, a iron post about twenty feet from my front bumper was struck by lightning. I was so surprised that I jerked violently, bent the steering wheel, and rocked the whole car. The pump-jockey laughed and said, “Ya best get used to that around here, man.” That was not the first – and certainly not the last – close call I’ve had with lightning.

During a storm about a few years ago, lightning struck the service pole at the end of my property. Because my electrical service box is connected to two 8 foot-long grounding rods in the earth outside the house, the surge did not affect the house wiring or appliances. But unfortunately, there was an ineffective connection (a corroded clamp on an outdoor hose spigot) to the ground for the phone system. Because of that, the lightning was able to enter my house by way of the phone line, taking out the computer modem, answering machine, and three telephones.

Because electrical, TV cable, and phone services in my area all come in on overhead wires, they can act as an antenna for lightning. Even buried wires can be affected if the strike is near them. So, it's important to have adequate grounding capacity to dissipate the surge into the earth. If you have had a new electrical service panel installed in the past ten years, you should have one or more grounding rods installed outside. My local electrical inspector insists upon a minimum of two rods. Older panels may only be grounded by one rod – or have no outside rod at all – so you may want to add additional rods for protection.

Inside the telephone interface box, there is a lightning arrestor on the company access side. To protect your phone lines, connect a 10-gauge wire from the arrestor to the ground rods for your electrical service panel. (You may have to contact your phone provider to get into that side of the box.)
And, while you’re at it, install a coax grounding connector on the TV cable on the outside of the house, route a wire to the ground rods and clamp the wire to them. If you have outdoor TV or radio antennas, you can ground them with a coax grounding connector as well.  The whole idea here is to divert any surges directly to the earth instead of allowing them to come into the house.

Finally, you might consider a whole-house surge suppression unit that mounts onto the service panel. They are designed to protect all of your household appliances and electronics from all voltage spikes besides lightning. Some surge suppressors are one-time use ($80-100), others are resettable and retail for $120-150. Not a bad idea to get one, considering what it could cost to replace all your major electric appliances.

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