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Electrical Connection: Surge Protection for the Home
| I have written several dozen
articles on surge protection for magazines and Website in the electrical
industry. I have a long list of credentials in this area, but won't bore
you with them. Instead, I will tell what you need to know about home surge
protection. Surge protection planning really starts where the power comes into the building. For the typical home owner, this means at the meter. What most folks don't know is their homes (typically) are not wired in conformance with the National Electrical Code (specifically, Article 250: Grounding) or in accordance with the IEEE Green Book. Just because the home has passed an inspection doesn't mean it's wired right. I must stress that homes rarely are. You can see photos of an amazing incidence of protection for a home where I replaced the original illegal grounding system with a Code-compliant one, if you visit: http://www.mindconnection.com/library/electrical/groundingcasehistory01.htm. It's worth the money to hire a licensed Master Electrician to come to your home to check your grounding system. For one thing, all of those plug-in point of use surge devices require a good grounding system. This is also true of the whole-house surge protectors. What most people don't know is the small print in the contract (if you are leasing this from a utility for $4.95/month or whatever) says the utility is not responsible for damage to a home that doesn't conform to the NEC. Well, since the typical home doesn't conform to the NEC, you will have a rough time getting the utility to pony up for damaged equipment. For a home, then, do the following: 1. Install a good grounding system. Typically, this means driving several 10 foot ground rods (no closer than 10 feet to each other) and bonding them together with bare #4 wire buried below grade. You also need to tie in your "other" grounds--such as your gas pipe, water pipe, CATV, and phone. But, how you do this is critical--these must tie into the system without being on its main path. Making a mistake here can be very costly. Thus, it's economical to hire someone who knows the right way to do this rather than to guess at it and burn things up. 2. Assess for lightning protection. At www.harger.com, you can find a free tool for doing this. Most homes do not need lightning protection, but many do. If you are on top of a hill, assume you do. If lightning has struck anywhere on your property, get a system installed. 3. Install a whole-house surge protection unit. This blocks out the high-energy stuff your point of use UPS and other surge protection simply is not designed to handle. A two-stage system provides adequate protection. The point of use units are designed to work with a beefier unit at the service entrance. If it's not there, your point of use unit will be able to handle only small surges that come from incidental sources. 4. Assess your home wiring. Understand that in industrial facilities, most surges come from inside the building. In your home, sensitive equipment can also suffer from spikes generated from within. So, unplug your computer if you are going to run power tools. If you have problems with an appliance--such as your refrigerator or AC unit--you can expect large spikes to be on your system. Keep these appliances in good working order. Vacuum behind your refrigerator and--with it unplugged--clean the dust off the coils, motor, and fan at least twice a year. Have a heating and air conditioning contractor inspect your AC unit once a year for signs of problems (these can happen even to new units--for example, the starting capacitor can be failing and that means all kinds of power quality problems). 5. Going along with your excellent advice: Shut off and unplug sensitive equipment during a storm. I have visited many data centers in my time. As an officer in the 7x24 Exchange (where this kind of thing is a very big deal), I did a tour of the AOL facilities in Virginia. What they do when a storm is 10 miles away is they disconnect from the utility and go on generator power so that they aren't going to get any surges from lightning. Now, you don't need to unplug everything in your house if a storm is within 10 miles. But, you do need to unplug stuff that a storm can wipe out. Keep in mind that lightning jumps miles through the sky. It is no trick for it to jump across a surge protection device no matter what rating that device has or what the sales literature says. 6. Finally, ask your electric utility if there is a spark gap arrestor or other surge device on your incoming power line. This device takes advantage of the fact lightning jumps, and provides a path for the lightning to jump to ground rather than into your service panel. Most utilities now have these or won't install them even if you ask. I used to work for Commonwealth Edison, and I remember one home owner who lost their stereo, TV, and electronic organ about twice every summer. I advised them to work with their utility rep to get that arrestor put in. They did that. This was in 1981. Last summer, I happened to visit that house (I know the owners personally), and guess what? They had not had a single loss of any equipment in the 22 years since following this bit of advice! So, there you have it. Get your electrical infrastructure right and unplug stuff at high-risk times. Best Regards, Mark Lamendola 2002 IEEE Outstanding Member, Region 5 |
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