I need advice about lightning protection. My home has underground service, 8′ ground rod at the meter, tv cable is grounded, etc. Twice in the last 6 mos. we have been hit. Home is on a hilltop under 60 year old oaks. Should I buy high-end suppressors? (Already use garden-variety) Or what about lightning rods? Any help would be appreciated. I can’t keep paying for electronics……………
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Yes.
I am no expert and would also like to learn more about lightening protection, especially information about the ground rods and wire. I have read that reducing resistance to ground with more rods, heavier wire, and low resistance wire-to-rod connections is important.
To elaborate, you should probably get lightning rods for the house, AND get a whole-house suppressor and suppressors for incoming cable/phone wires. Valuable pieces of equipment (that 60 inch plasma panel) should have their own fairly good quality suppressors. The cheap ones should suffice for other stuff.
Make sure that the outlets you use for suppressors are properly grounded.
Definately protect your phone & cable lines too. We lost a new laptop that was plugged into a surge protector when lightening hit the wireless internet reciever on top of our house.
Mark
I have a question about this as well. In the book "wiring a house" he recommends going above code and installing 8 rods all around the house, preferable near gutter drains and link them all together with a large cable. It seems like overkill but since ground rods are not that expensive it doesn't seem like a bad idea to me. Anyone else go over board with a setup like this?John
There is nothing wrong with that, just make sure that you only have one connection point to your ground wire for your house wiring.
we get lightin storms three , four times a week. Summer everyday coming off the gulf. This weekend it was bad. Lightin with hail. Only wayto protect electronic from lightin is to unplug from wall.
John,
I had my electrican install four ground rods spaced 8 feet apart. Not the two rods at six feet as required by code. He looked at me like I was nuts but did it. The extra material cost was probably 10 bucks, labor costs I have no clue. I am sure it will be in his bill :) Our local inspector thought this was a good idea but of course not required by code.
Regards,
Dennis
I'll put a ground ring around an entire building in some industrial applications - around municipal water towers is one example, another is around cellular telephone equipment buildings (those cell phone guys go nuts over grounding their equipment.) It may be overboard for a house, but it wouldn't hurt anything.
The connection between the ground rod (or rods) and the ground cable is best done with an exothermic weld instead of a clamp - it creates a molecular bond between them that won't deteriorate over time like a clamped joint will. The weld is done with a little kit, Cadweld is probably the most common brand: http://www.erico.com/faqDetail.asp?faqid=28 It's probably not the sort of thing a homeowner should do, it's best left to the electrician.
As far as surge suppressors go, the lower priced models use something called a metal oxide varistor, or MOV. The MOV itself looks kind of like a little lollipop. The problem with MOVs is they can deteriorate over time, and they may not be able to react quickly enough to a lightning strike. There are electronic surge suppressors out there that are more expensive but may provide better protection. One brand I like is Transtector, at http://www.transtector.com/.
My overboard setup is two rods, each 30 ft deep, of 1" type K copper pipe, about 50 ft. apart (opposite corners of the house).
I'm doing it partly to play with the hydraulic rod sinking technique I learned from a guy who used to install them for the TV transmitters on Mt. Wilson. He would go 40 - 60 ft. down.
If you're going to be in Las Vegas the middle of next month, you can get a free exhibits only pass to the National Association of Broadcasters show. Somewhere there among a few football fields worth of HDTV gear there'll be a few vendors in the business of providing lightning protection to towers up to 2049 ft. tall.
Another thing to bear in mind is that electrons don't give a s--t about deeds and property lines. Your ground rods are directly connected to those of all your neighbors who are on the same utility company transformer.
-- J.S.
Edited 3/28/2005 8:11 pm ET by JOHN_SPRUNG
Is it me, or does only one 8' grounding rod sound "under minimum"?
I want to remember that recent NEC is two rods for a panel. Doesn't mean that is "right" for this install, just that I remember it that way.
I seem to also remember that the "preferred" installation is for lightning protection to use its own ground--but that may be not remembering Clifford's above spec correctly, too.
"I want to remember that recent NEC is two rods for a panel. Doesn't mean that is "right" for this install, just that I remember it that way."Not exactly.There are a series of allowed grounding electrodes that can be used.A ground rod is one of them. And if a ground rod is used then it needs to either be verified by measuring it's resistance or a second ground electrode needs to be used.That second electrode can be another ground rod (I don't remember the distance away) or another type of ground electrode.A metalic water pipe that is at least 10 ft long under ground can be used for a ground electrode. However, that type of one can not be used alone. Don't know the reason, but my guess is concern that sometime it the future that it might get replaced with plastic.So the most common residential installation is one ground rod and the metalic water pipe.But there are other ground electrodes. I think that the latest codes are pushing towards a UFER system at the first choice.That uses the rebar in footings for the ground.
A ground rod is one of them. And if a ground rod is used then it needs to either be verified by measuring it's resistance or a second ground electrode needs to be used
Yeah, ok, that's what needed jogging out of my memory. I knew somebody here would remember it right.Occupational hazard of my occupation not being around (sorry Bubba)
Speaking of whole house surge protection, my impression is that basically it is a super-sensitive circuit breaker that pops off if a surge hits it. Is this correct? Seems to me the risk of spoiling all everything in the fridge and wine cooler by being out of the house when this happens might be greater than the protection.Anyway, what other types of whole house surge protection are there?
Completely wrong.They use devices that clip off the peak of the surge and absorb it and bypass it to ground or the other line (depending on the type of surge).Much like a pressure relief valve on a water heater.
A whole-house surge protector is not a breaker. It's a surge protector that installs behind your power meter or in the breaker panel, with enough surge capacity to swallow fairly large jolts. It is true that a large surge may cause the master breaker to trip, but this would likely happen whether or not a surge protector is present. However, the nature of the beast is that a large suppressor isn't particularly fast, so having a "local" suppressor at each sensitive device is still advisable. (Interestingly, a few "local" suppressors scattered around the house actually provide some modest protection even for devices not plugged into them.)Re grounding: Any significant amounts of metal siding, roofing, metal framing, etc, should be securely grounded, especially anything that's relatively high up on the house. (Typical amounts of metal flashing need not be grounded, though.) Obviously, a TV antenna mast should be grounded, preferably with it's own ground rod separate from any used at the TV cable entrance to the house (where the cable shield ground rod should be).And, of course, major mechanical systems (plumbing, heating ducts, etc) should be grounded. Usually this is accomplished through their normal connections, but there should be jumpers around plastic water filters, eg, and across flexible vibration isolation sections in heating ducts. (Being the paranoid type, I have jumpers around water meter and water heater, and an all-copper bypass that effectively jumpers the water softener.)
That makes far more sense to me. My electrician kept saying it was like a GFCI breaker and would trip, thus shutting off electricity to the house. What ground does the CATV want? Mine actually comes into the third floor (with the phone line) into the distribution box. Keeps it out of reach of burglars, who are prone to cutting both phone and cable lines here.Anyway, the video distribution box is grounded to the electrical sub-panel, via the ground for the outlet. Does this work, or should I pull another ground wire from the CATV connector all the way back down the outside and to a ground rod?
For standard cable there should be a grounding block at the "service entrance", which is usually a plastic box outside the house. The grounding block should be tied by a #10 or better wire to a nearby solid electrical ground. In cases where the cable enters near the regular power entrance, tying to the power ground may suffice, but if the power line is susceptable to strikes then a separate ground rod may be better. Definitely don't just tie it to the ground pin in a nearby outlet.Likewise, there is a lightning arrestor in the phone service entrance that should be properly grounded.
I would suggest tying a separate ground wire from the (presumably metal) shell of the video distribution box to a good ground point. Depending on the distance between this box and the service entrance, it may make sense to use the same ground or a different one.
Damn, I brought that up with the electricians, and they said it wasn't needed, since there is an outlet bonded to the box. Now the floor is back down and refinished.
You have to have somewhere for any voltage shunted by suppression equipment to go. But don't think your on your own. To some extent the entire power grid is helping. Every transformer location has a ground rod and every second or third pole also. So getting a decent ground at your house is important but it doesn't have to do it all on its own.
The other thing to remember is that lightning isn't malevolent. Like anyone after a long day it just wants to go home. Also like most of us it is lazy. It will take the easiest path to get home. Key here is to make sure there as many easy paths as possible before it has to go through your plasma TV.
The first point depends a lot on your soil composition and mechanics. Desert sites, solid rock and sand hills are notorious for poor ground conductivity. In such cases I have seen wells sunk through sand hills all the way down to ground water, sometimes hundreds of feet, to establish a decent ground for communications towers. If your home is in one of those locations consulting an electrician in your area familiar with local grounding or even specialists might be called for. They can recommend options such as wide ground grids, chemically enhanced systems or wells.
Most people don't have this sort of problem. In most cases a couple of standard ground rods or at most a half dozen with connecting heavy conductors are more than sufficient. I hear some portions of Arizona and Colorado face sterner problems.
Once you have a decent ground, and it only needs to be better than the path offered by your valuable equipment, think layers.
A whole-house surge arrestor at the main panel or meter. Both if your hit a lot. Then install quality surge arrestor strips. One for your plasma and theater system. Another for the stereo and TV in the bedroom and another for the microwave in the kitchen. Don't forget another one for each computer.
Idea here is you want your bench to be both deep and wide. Layers and arrestors on many circuits. Also you need protection to be airtight. More computers are damaged by way of the telephone connection than through the power lines. So the power strip needs a telephone and/or coaxial line protection if the appliance your protecting uses these connections.
Once your protected you have to maintain what you have. It will vary widely how often you need to replace your suppression units. Unless your using top grade industrial grade units with very reliable indicators don't depend on those LEDs to tell you the unit is OK.
Generally whole-house units should get replaced every five or ten years. Those surge strips need replacement more often. For your much loved home theater setup you will want to replace a mid-grade unit every year. Higher end units can be allowed to remain longer. Let the price of suppressor, the replacement costs of the equipment being protected, the frequency of surges and your risk tolerance be your guide.
A trick is to use a Sharpie to note the month and year when the unit is put into service. It is easy to forget when you installed a surge strip.
Once you replace the strip protecting your most valuable equipment don't throw the strip away. Demote it. Picture a hierarchy of equipment values. When the top unit gets replaced with a new suppressor everything gets moved down one. On the end of the line expand the base. Any remaining capacity can be used to protect the portable TV in the kids room and their X-box. Eventually, after many years and demotions, they end up in the shop no longer considered surge suppressors but handy for getting power to multiple tools.
One other thing to remember about lightning is that it's essentially high frequency. For this reason, the impedance of a wire largely swamps it's resistance. To a lightning bolt even a straight wire to ground has several hundred ohms of impedance, and a crooked one much more. The size of the wire is important only with regard to current-carrying capacity (without burning out), not resistance -- whether it's a half ohm to ground or two ohms to ground doesn't matter.So the trick is to keep ground wires straight and short.
I would like to get some stuff from http://www.lightningrod.com. I've got charred trees.
I think some people are using high dollar UPS's to filter the power to their sensitive equipment. They at least claim to have high insurance for equipment replacement.
Big Macs - 99 cents
All the grounding in the world won't make a difference without supressors. The surge has to be directed to ground, preferably by a whole house supressor. The strips wont do much to a full strike.
Actually, grounding alone can make a lot of difference on some things. A grounding block for coax, eg, will eliminate about 90% of the "baddies" if there's a splitter anywhere before "real" equipment. And grounding RF amps, cable modems, and Ethernet hubs/routers will keep maybe 95% of the baddies out of downstream equipment (though the grounded device may make the ultimate sacrifice). Most of these components are on "wall warts", so they're not inherently grounded -- you have to take explicit steps.
I was poorly trying to make the same point. You have to have a good ground to make the explicit steps you mention effective. Just having a good ground available isn't enough.
I have seen weired stuff like phone wires melted together, light switches blown to smitherines, once saw a cast iron soil stack split from lightning.
All this stuff has to have arc gaps and MOVs to direct the strike to ground, as well as good grounds. Back in the Kentucky mountains in the old days there was an antenna on the tops of most mountains to pick up a tv channel. Most of us hillbillies knew to have ground blocks and good ground rods to keep our one static plagued channel alive.
I saw a wall wart that was connected to a modem and hit by lightning. It was so bad looking it was funny. Stinky too.
> once saw a cast iron soil stack split from lightning.
I've heard of -- but didn't see -- a septic tank and drain tile blown out of the ground by lightning. Sounds worse than that wall wart. ;-)
-- J.S.
Ugh...
Actually, I would like to have seen that.
from how close????
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