Protecting your computer hardware from Lightning

I think it was last night on the local news, they led with a story about a local family that, during a recent thunderstorm heard/saw a very close lightning hit. They had some nice film footage of a tree that had its bark completely blown away and a nice rip down the side of the tree. (My guess is the lightning hit flash heated ( vaporized) the sap or water inside the tree and the pressure of that is what blew bark around. I don’t know though.) The report talked about how North Carolina is high on the list of states with regards to lightning strikes and then they talked to Progress Energy who suggested that you buy something from them to protect your inside wiring from lightning related surges. I was a bit annoyed by their use of a story to scare people about the threat of lightning damage and then give a specific power company spokesman a chance to sell something, but that’s not the point of this post.

My point is with regards to computers. It seems that when I was little I remember everything got unplugged when it was thundering. Of course, that was before the personal computer. I still go around and unplug most things these days when there’s a storm right on top of us, but I don’t unplug the computers around here. That may be a poor choice, but I do have a few levels of protection. I guess I’m taking somewhat of a gamble.

Here’s what I’ve seen though. One that I recall very vividly was a system that had suffered a lightning related surge (not sure how close the hit was.) There was actually a divot blown out of one of the IC’s on a peripheral card. Very impressive. It seems that most of that system was unworkable. Usually what I see are power supplies that are damaged by either power surging or brown outs. The power supply is basically where the big black cable comes into your computer from the wall and converts line current (110 AC in the US) to various DC supply voltages (3.3, 5 and 12). This part usually gets hot (there’s almost always a good size fan venting here.) Power supplies are usually fairly easily swapped and run anywhere from $25-$45 and then up depending on the wattage (how much power they can supply) and the quality and these days some have LEDS and other styling.

A UPS “would be nice” to help protect the power supply. Here’s why, the battery in the UPS will help cover “brown” conditions and help ensure that there’s a constant flow of electricity to the power supply. With surges, they typically have surge suppression capabilites as well. I think APC UPS’s start from 40-50 dollars depending on where you find them.

There are a few other things to consider though. What other cables are running from the wall to your computer? Many surge suppressors (and most UPS’s now) have telephone line protection as well, so if you have a traditional phone modem, make sure that is protected by the surge protector or UPS.

Cable Modems…
My dad went through 3 cable modems in one year once from lightning. For starters the cable line wasn’t properly grounded outside (the line had broken). But, many UPS’s also have a cable line in and out to help protect that line as well.

Network cable… now I haven’t see too many devices with network cable protection. I haven’t seen any evidence of a network card being knocked out from a surge over network cable. Since the network cable is just within the building, I would think a surge suppressor on the hub or switch might be enough. But, since it is a large mass of wire, you could still get static electric buildup in the network cable from nearby lightning strikes (induced current.) I don’t know of any good solutions for this.

Of course for most of these options we’re ignoring the obvious. Unplug it. Frankly if your right under a ferocious storm, unplug _everything_ from the wall and go read a book. I think home installations are more likely to be able to follow this. If you can’t though. Most of the more expensive power strips and UPS’s will offer insurance on the equipment that’s connected. That can be comforting, but is an after the fact compensation.

Truth is, if you have a VERY close hit, it may not matter what other protections you have against it, your system will be damaged. For that reason, the best advice I can sum up with is to make sure that you backup your irreplacable data regularly and keep it in a safe place (usually another location) away from the computer. From time to time, test your ability to restore a file from a backup as well.

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