This post on surges is designed to answer various questions that have come up and will come up regarding this topic. Perhaps it will be a work in progress. Perhaps this is all I have to say on the matter. Call it a sort of in depth overview of things. I must state that although this post bears my name, it is as much Bill Kane's as anyone elses. It was Bill, whose strong interest in this matter, caused me to dig deeper. If you haven't read any of Bill Kane's postings, you should. They're a marvel of lucidity and directness. Spectacularly easy to understand. Bill is a decent and honorable man. Although we live on opposite coasts and have never met, to the extent I can call anyone my friend, it is my privelage to call him that. Types of Electrical Events The way I see it, there are five different scenarios that can exist. 1) Blackouts 2) Brownouts 3) Noise 4) Harmonics 5) Surges Short of having your own power generator you can never solve all the above problems. If people have a problem with a specific scenario, then they need to focus on that scenario. For the homeowner or any concern for that matter, the most deadly are surges. What Are Surges? People and especially salespeople use a very broad explanation and interpretation when defining this term. For starters, surges are not generated within your home. I realize there can be things that happen if an A/C compressor goes on or your using a circular saw that manifest themselves as a glitch on your TV or a pop sound from your stereo system, but they are not surges. If they were really surges, you'd be heading down to the store to constantly replace your lightbulbs, your clock radio, your GFI's, dimmers, microwaves, and just about everything that runs off electricity in your home. Further, if you put a plug-in surge protector on the device that you think is the culprit, you'd be replacing that surge protector in a matter of weeks if not sooner. Its not happening though, is it? Wait a minute now, I've got a 120 volt A/C and whenever it goes on I can see my lights dim or get brighter. What about that? Well you may have a problem with your neutral line and that's really something that should be checked by a qualified electrician. Not all houses are wired correctly and problems do arise. Nonetheless, let's look at this a little more closely. In order for your bulbs to dim or brighten perceptibly, very little voltage is required. If your voltage drops to say 90 volts, a 25% reduction, the the lamp's brightness will decrease by 60%. You'll be hardly getting any light at all. Conversely, if the voltage goes to 130 volts, an 8% increase, the brightness will increase by a little over 30%. Surges are well over a 100% change. The dimming you see is likely due to a much smaller voltage change than you think. Whoa now! Can't that mess up my equipment? Doubtful if your equipment is properly designed. Check your owner's manual to determine what the allowable tolerances on incoming voltages are. If you're going to agonize over that then that's your call but its not a surge. Can We Get Back to Surges Now? We've talked about what they aren't. Now let's look at what they are. In a general sense, a surge is a very short duration, high frequency, high voltage, high current event. The most disastrous are those occuring from lighting and if we can effectively deal with those, we can deal with the other causes of surges such as power station events (somebody crashing into a substation, a crew outside that dropped a transformer). There are several categories of lightning: 1) Negative lightning (cloud to ground) - this is a lightning strike from a negative cloud to a positive earth. 2) Positive lightning (cloud to ground) - this is a lightning strike from a positive cloud to a negative earth. 3) Negative lighting (ground to cloud) - this is a lightning strike from a negative ground to a positive cloud...moves upwards. 4) Positive lighting (ground to cloud) - this is a lightning strike from a positive ground to a negative cloud...moves upwards. 5) Inter-cloud lighting - this is a lightning strike between clouds. The lightning voltages are typically greater than 20 kV (20,000 volts) but voltages in the millions are not unknown. The current is in the range of 30 to 35 kA (30,000 to 35,000 amps) but 300 kA currents are not unknown. Depending upon the magnitude of the strike, it can last anywhere up to a second but generally is less. Lightning has been studied by a number of institutions and organizations in order to come up with a most likely scenario as far as what the inside of a building may experience. The Institute of Electrical and Electronics Engineers (IEEE) 587 states that "6000 volts is the largest transient that the interior of a building would experience, and that it’s harshest interior surge environment is one that would experience 100 surges of 6000 volts, 3000 amps in a years time". ANSI/IEEE C62.41 is a standard that lists the various waveforms that a surge suppresser is to be tested with. Within the standard are three categories (A, B, C) and each category has a subcategory (1, 2, 3). The categories refer to the general location in question. CATEGORY A: long branch circuits, receptacles (indoor) UL Test: Ring wave with 6,000 volt, 200 Amps CATEGORY B: major feeder, short branch circuits, service panel (indoor) UL Test: Ringwave of 6,000 volts and 500 amps plus impulse wave of 6,000 volts and 3,000 amps. CATEGORY C: outdoor overhead lines, service entrance UL Test: Ringwave of 6,000 volts and 500 amps plus impulse wave of 6,000 volts and 3,000 amps. The subcategories refer to the nature of the exposure. 1) Low exposure; geographical areas known for low lightning activity, little load switching. 2) Medium exposure: systems and geographical areas known for medium to high lightning, activity, or with significant switching transients, or both. 3) High exposure: those rare installations that have greater surge exposure than those defined as low or medium. For our purposes, the homeowner, this has resulted in an accepted standard that tests surge suppressers for the most likely transients. These transients are: 1) A 0.5 microsecond, 100 kHz ringwave 2) An 1.2 x 50 microsecond (refers to a voltage waveform which is dependant upon what's being tested) (Leading edge builds from 10% to 90% of peak in 1.2 microseconds (µs). Leading edge from 0% through peak and decrease to 50% in 50 microseconds. This is considered by many experts to be about the worst case transient a secondary surge arrester would typically experience.), 8 x 20 microsecond (refers to current which is dependant upon what's being tested) (Leading edge builds from 10% to 90% of peak in 2.0 µs. Leading edge from 0% through peak and decrease to50% in 20 µs.) OK, now that we know surges are pretty powerful, how can they get into our homes? Well, they can get into our homes via the AC lines, phone lines, and any cable or satellite lines (coax). A surge wants to do one and only one thing. That thing is that it wants to find earth ground. The path to earth ground is completely unpredictable. It might be as simple as going back down the ground wire or it might follow a multiple, tortuous path through your phone lines, an adjacent computer, really who knows. Anything else? Yes. When a surge enters the AC lines it can do so in one of two ways: Differential and Common Mode. Differential mode surges can occur between any two wires. Often you'll see this specified on various surge suppressers as (L-N or Line to Neutral), (L-G or Line to Ground), and (N-G or Neutral to Ground). The current goes down one wire and leaves on the other. Common mode surges can come down any one wire or it can come down all three simultaneously. Is one more dangerous than another? Absolutely. The common mode surge is the killer. I've got a Monster (Panamax, APC, TrippLite, stick your favorite plug in device here) unit. Won't that protect me? Not against the common mode surge. Consider the following. A common mode surge comes up the hot line. The surge protector looks to shunt (divert) the surge to the other lines. Now you've got a surge on three lines looking for earth ground. Where's it going to go? It'll jump a line if it has to or is strong enough in order to find the shortest path to earth ground. The shortest path isn't necessarily down the ground wire. I'm confused. Doesn't the ground wire go back to the breakers and isn't that in turn bonded to the grounding rod outside? Yes. The confusion lies because a surge is also a high frequency event. This means that the ground wire, which might only be a few tenths of an ohm when considering DC is going to look like quite a few ohms to a surge. Its not necessarily the shortest path. So while maybe you protected your equipment, you wound up frying something else. Maybe the garage door opener. How's it feel to have to replace that? Well what about a Brickwall (Adcom, SurgeX, etc.) device? Those are different. The government uses them. Yes they are. They work on the principle of taking a surge and then bleeding it off to the neutral through a bank of capacitors. They're spectacular at dealing with differential modes or power glitches. What happens if the surge comes up all three or just up the neutral? Also ask them what happens when you've got a miswiring situation with hot and neutral reversed. Happens you know. You think the government ONLY relies on a Brickwall type device? The facility itself is protected but they don't tell you that do they? What else is there? A whole house unit. That's installed at either the breakers or the meter. What makes it so spectacularly effective is that its located close, typically less than 10 feet from the grounding rod. No matter how the surge comes in, its diverted to earth ground. The surge itself never gets a chance to get inside the house no matter how it comes in because place there, the shortest path of least resistance is that ground wire that goes to the rod. So does that mean there's no reason to use plug in devices? Is the stuff I bought or own useless? Not at all. Plug in devices have their greatest utility when used in conjunction with a whole house approach. In fact, this is the recommended way to use them. What kind of brands are there? How should I size them? Are they expensive? There are so many brands out there that I can't begin to list them all. Just to get you going, you'll find the following as possibilities. The Intermatic EG240RC sold in Home Depot is rated at 1200 joules and about 50,000 amps. Toll free # too. http://www.dale-electric.com (do a search on surge) http://www.deltala.com/prod01.htm http://www.deltala.com/prod02.htm http://www.ditekcorp.com/ http://www.eatonelectrical.com/NASAp...7&Sec=products http://members.tripod.com/~StorminPr.../index-31.html http://www.nooutage.com/LightningSurgeProt.htm (LA-302) http://www.mimcv.com/residential.html If you live in an area prone to a lot of lightning activity with a fair amount of cloud to ground strikes, then you're most capably served by a 2000 joule unit. Otherwise, a 1000 joule unit should cover you. However, don't trust me. I cannot recommend strongly enough getting in touch with companies that you're interested in and asking to speak to an applications engineer. They'll walk you through the entire process and give you a model or models to choose from. I personally recommend that you have an electrician install this as you're talking about dealing with power at the mains. This isn't putting in a new outlet. If you're having a new house built, having electrical work done, then this is a great time to have one put in as you won't need a separate call. While electricians may have their own pet brands or the local electrical supply house may carry a particular one, it might, or might not be, the one you want. Find out who makes it and do a Google search to get a phone number and call. You see, an electrician is a talented person but he/she has one primary concern and that is human safety. While that's not to be underestimated, bear in mind that transistor safety, or protecting your electronic goods in many ways goes beyond that. That's a job for an engineer. Now he won't be the one to install the device, but he's likely the best person to specify what's needed. Ummmm...2000 joules doesn't sound like a lot. I've seen 3000+ plug in devices. What's up? First bear in mind that when you're dealing with a whole house unit, that 2000 joules is available no matter how the surge comes in. With a plug in device recall they typically specify L-N, L-G, and N-G so that 3000 joules is split across all three modes. If its split evenly, then its 1000 joules tops. Now you've got to derate that 1000 joules even further to say 700 or 600 joules because earth ground is so far away. High frequency event, right? I've looked at some of the links and I'm confused by all the different claims. Some look better than others. What do I do, what do I pick? This certainly can be confusing. First let me begin by saying even the simplest, no frills type is going to do a better job of protecting your home than any plug in device. After that, its a matter of preferences and dealing with your own paranoia and wants. You're going to pay more for units that have features like surge counters, sine wave tracking, audible or visible alarms, etc. Every company you deal with, just like when you're buying cars or a toaster, is going to highlight their advantages at the expense of their competition. That's just the nature of the beast called capitalism. Is there anything else that's important? absolutley. Any surge protector is as good as earth ground. Don't underestimate this. The question is, how good is your ground and can or should you improve it? You should have an idea what the soil is like where the rod is. If its moist or the rod is driven deep enough so that the soil is moist, this is a plus. Remember, you want good conductivity. Also the wire that's going to the ground wire should be in good shape. Do a visual inspection and replace it with the same or a thicker length of wire. Check the building code in your area to see what's required. The wire should have no kinks or bends and the contacts to the metal should be tight and not corroded. Its still summer here in the northern hemisphere. Now's the time for digging if that's what's needed. A company that is serious about facility protection will hammer over and over the importance of earth ground. That's what's going to save you. Also, just because you might have two ground rods doesn't mean you've got a superior earth ground. When electricians install two, it's generally done in soil that's of poor conductivity. After the electrician installs the first, they run a test and if its not up to snuff, a second is installed. Case closed. You see, soil resistivity testing is expensive and the purpose of the NEC is to address human safety. Transistor safety actually goes beyond the scope of the NEC. For NEC, we're just concerned about the ground wire's resistance. For transistor safety, we're worried about its impedance. Therefore, we have to improve upon and enhance matters if we're to get superior surge protection. What approaches enhance surge protection over what I have now with respect to earth grounding? The ground wire must not be grouped with other wires. This way surges can't be induced into the other wires. It should be 10 feet or less to the ground rod. No splice or kinks. The ground rod must extend past the frost line. Frozen earth is not very conductive. Anything else? Yup. House insurance. If you've got a special place in your heart for your HT setup then find out how you're covered. Is your equipment covered for full replacement or is it prorated? Is there a deductable? Sometimes there are special riders you can get or even supplemental insurance. Don't ever rely on those $25,000 or whatever amount of protected equipment warranties. They're full of holes and they're based on fair market value and that's not determined by you, but by whomever you bought your equipment from. Look at it this way. Let's say you've got full replacement value and somehow your equipment is irreperably damage. Maybe you messed up somehow and a surge did get you or there was fire or water damage or theft. Cheer up my friend. You're getting a new system. Upgrade time! Check though to see what sort of proof of purchase you've got. Get serial #'s, keep your receipts, take pictures. How do you know all this? Are you an engineer? Nope. I know a little about electricity and like most of you, I became confused and felt I was getting the run around from all those companies like Monster or Panamax or APC. I became curious how professional places protected themselves. So I spoke and visited with a local telco, internet provider, a very large satellite tracking station where I lived and asked questions. I got answers. I spoke with the ARLL and called various companies up that made facility wide protection like PolyPhaser, perhaps the industry leader in lighting protection. I also read government requirement contracts to see how and what they specified as protection when it was needed. While the means of protection differed as you'd expect since the equipment differs, the message was always the same. Stop the intruder before it gets in the door. Then use point of use devices where you think you need them. Myself, I've got a whole house plus a separate unit for a well pump. Scattered throughout the house, are various $1, yes you read it right, single device units hooked up to things like the microwave, washer, dishwasher, etc. I got them at Home Depot a while back in some discontinued products that were tossed into a wheel barrow. I've also got a $4 circuit tester from Home Depot that I used to verify the correct hookup of all my outlets and corrected or replaced any that were defective. Aren't you that f*cking a$$hole that says wire is wire? Yup, and that's Mr. F*cking A$$hole to you. Have a nice day.