surge protectors

[karsan]

It is dangerous to have more than one surge protectors in you home I have 3 surge protectors running in my home.

[professorpaul]

Not a problem. I assume that each is for a separate circuit, such as a computer, hi-fi, misc. electronics, etc.

The only problem that I've had is knowing that they have been "hit," as many of them are a "one shot" thing, and must be replace (varistor type), if a real nasty surge hits them.

I have such devices, in the form of outlet strips, on both computers in the house.

[Ralph Mowery]

If you mean the kind that plug into the wall (may be called power strips) and they are installed in seperate outlets, you can not have too many in your house. The only thing is if you have too many things using too much current plugged in to them. Then a fuse or breaker should blow or trip.

I have 4 or 5 in use right now. One on each of the TV sets, computers and my ham radio gear.

In a house I lived in before I moved , having 3 in use probably saved me a bunch of equipment. A surge during a lightning storm took out 3 of the protectors but did not get any of the electronic gear except an unprotected telephone and an internal surge supressor saved most of the electronics in the oven control.

[hallerb]

Better to have UPS on critical or sensitive equiptement.

A WHOLE HOUSE surge protector is better, and probably more reliiable and costs less than a bunch strewn all around the house

[Pete C.]

The clamping capacity (Amps) of the surge suppressers will be additive (no, not perfectly additive, but still increasing protection) so more will be able to clamp bigger surges. A surge suppresser at the main panel is best since it can clamp a surge before it gets further into the homes wiring. Additional surge suppressers further down the line, whether the little blocks or power strips with suppressers built in will just add an additional line of defense.

The surge suppressers that install at the service entrance panel are generally higher quality and capacity and more likely to use multiple technologies like MOVs and gas discharge arrestors. Nearly all the small plug in suppressers just use inexpensive MOVs.

A decent UPS is a must for computers and any other expensive items like big plasma / LCD TVs, etc. UPSes used to be expensive, but they are now quite reasonably priced for decent units. One thing to watch out for is surge suppressers on the output of a UPS. Since suppressers work by creating a short circuit across the line (briefly) they can damage a UPSes inverter if a surge gets through and they clamp. Some cheaper UPSes may generate small HV spikes that could trigger the suppresser as well and again damage the UPS output.

Nothing will protect against a direct strike on the power line near your house, so if that happens you'll have a big insurance claim no matter what. The suppressers might help clamp things enough to lessen the damage though.

Inductive pickup of nearby lightning strikes is also an issue and long wires like phone, network and CATV lines can pickup significant surges that way. Good suppressers on those lines along with good grounds will help.

Pete C.

[w_tom]

They are called shunt mode protectors. They work by earthing a destructive transient such as a direct lighting strike and then remain functional. If a 'whole house' protector could not earth that transient, then what good willl a plug-in protector do trying to earth to the same ground?

So instead some assume plug-in protectors sit between the surge and an appliance to block or stop surges. Bull. Will that silly little less than one inch component stop what 3 miles of sky could not? Effective protection was never about stopping or absorbing surges. Effective protection is about diverting - shunting - a destructive transient to earth. Divert - not stop or absorb.

Protector amperage is additive IF all protectors have a same 'low impedance' connection. And that is the problem. Things such as sharp wire bends, long distances, splices, etc all increase that wire impedance. Now a plug-in protector has too much impedance. Instead of seeking earth via safety ground wire, that transient may seek earth through an adjacent appliance and phone line. This is how modems are so easily damaged. Incoming on AC electric. Through an adjacent protector. Into comptuer motherboard and modem. Out to earth ground via phone line. Notice where most modem destructive transients come from.

Having learned this by tracing destructive surges, then what is a most typically damaged component? The path through adjacent protector, through modem (its DAA section), is often via a transistor that drives an off-hook relay. The failure message is "No Dialtone Detected". Incoming on AC. Through that transistor and off-hook relay. To earth, destructively, via phone line and phone line surge protector.

Why did damage result? A transient was not earthed BEFORE it could enter the building.

A surge protector basically shunts - connects all wires together during a transient. If that wire makes a low impedance connection to earth, then the transient is earthed. No damage. But plug-in protectors don't have a good earthing connection. Above is one example; demonstrated by tracing surges and replacing transistor. A protector too close to transistors and too far from earth ground can even contribute to damage of the adjacent (and powered off) appliance. An effective protector makes a 'less than 10 foot' connection to the building's earth ground.

Ineffective protectors (power strip and UPS) are easily identified.

1) No dedicated earthing wire. 2) Manufacturer does not even discuss earthing. Look at your protector. Does it meet these criteria for ineffective protector?

What does a telephone company do to protect their $multimillion switching computer? Its computer connects to overhead wires everywhere in town. Why do they not provide service for a whole week while replacing that computer? Because the telco installs 'whole house' type protectors on every single wire of every cable that enters the building. Tehcnology even discussed in an Oct 1960 Bell System Technical Journal article - because the technology is that old and that well proven. An effective protector is ideally 50 meters from transistors AND as close as possible to earth ground. That 50 meter separation adds to protection. But most important is what makes that 'whole house' type protectors effective. A low impedance - meaning short - connection to a building's single point *earth ground*. Not only is the connection short. Every protector is earthed to a same ground - the single point earth ground.

For residential protection, manufacturers with responsible brand names provide effective 'whole house' protectors. Siemens, Cutler-Hammer, Square D, Leviton, Intermatic, and GE all sell 'whole house' protectors that are available in Home Depot, Lowes, and electrical supply houses. These protectors have a dedicated earthing wire. These protectors costs tens of times less money per protected appliance. And these protectors are properly sized.

Why properly sized? Many plug-in protectors are so grossly undersized (MOVs undersized; too few joules) as to vaporize during a surge. Vaporized MOV provided ineffective protection. But its smoke promotes more sales. Effective protectors, instead, earth direct lightning strikes and remain functional. A human never knows that when a properly sized protector is doing protection. Grossly undersized plug-in protectors that vaporize and smoke will be recommended by the naive. So many plug-in protectors are undersized - to promote sales rather than provide effective protection.

Earthing - at minimum, the building must conform to post 1990 National Electrical Code earthing. Enhanced earthing means a protector will be even more effective. And so we say, "a protector is only as effective as its earth ground." What do those plug-in power strip and UPS protectors manufacturers not even discuss? Earthing. Where is that dedicated earthing wire? Did they just forget? Or do they hope you never learn why earthing is so essential?

Some incoming wires are earthed using a protector. Telco provides a 'whole house' protector where their wire enters your building. But again, that protector will only be as effective as its earth ground. Did you (or your builder) provide that essential earthing connection? Cable needs no protector. Its ground block must connect directly to the same earth ground - a 'less than 10 foot' connection. Every incoming wire must be earthed directly or through a 'whole house' protectors to the single point earth ground.

Ineffective protector manufactures and those who promote them hope you never learn what a shunt mode protector does: makes a low impedance connection to earth. No earth ground means no effective protection. So where is that earthing connection in a plug-in UPS? Notice that their own numerical specifications don't even define protection? How's that for a damning overlooked fact.

Appliances already contain internal protection. Protection that can be overwhelmed if destructive transients are not earthed where wires enter the building. Earthing is why 'whole house' protectors are so effective. No earth ground (such as with plug-in protectors) means no effective protection.

If you d> " [e-mail]" wrote:

[karsan]

Yes. evertying is seperated. My computer is has surge protector I have a telephone and a lamp on one surge protector and on the second one is my computer and the third one I have water cooler running.

[w_tom]

Any protector that was one shot protection was grossly undersized - ineffective. When it vaporizes, then it promotes more sales to the naive. Effective protectors do their job without vaporizing; human never knows when it is working. But effective protectors are not promoted by the naive.

Active component in a protector is the MOV. A datasheet from an MOV manufacturer provides a ballpark idea how many times a properly sized protector should work - without failing:

Does that sound like a one shot protector device? Of course not. Ineffective protectors are also grossly undersize to be promoted by the naive. Smoke rather than facts promote ineffetive plug-in protectors.

Effective 'whole house' protectors are manufactured by names recognized as responsible: Square D, Cutler-Hammer, Leviton, Intermatic, Square D, and GE. They are sold in Home Depot, Lowes, and electrical supply houses. They are not sold in Radio Shack, Sears, and grocery stores. Essential for any effective protector is earthing. A protector is not protection. Protection is what the protector connects 'less than 10 feet' to: earthing.

Meanwhile, let's look at what some grossly undersized plug-in protectors have done:

Think about it. Would you put a protector in dust balls behind a table or atop a desk of papers? There are overhyped, so called 'one shot' protectors. Properly earthed and sufficiently sized 'whole house' protectors are available. And then we have this fact demonstrated in commercial broadcasting stations and telephone switching centers everywhere in the world. The protector is nothing more than a connection to protection. That protection is a good earth ground. An effective protector is only as effective as its earth ground which is why effective protectors have a dedicated earthing wire.

[Pete C.]

The fact that they will operate in parallel. The transient will rise to the trigger point of all the suppresser devices and all will clamp the line. If there is sufficient clamping capacity the differential voltage will be substantially reduced.

As I noted, nothing is going to stop a direct strike. Most strikes aren't direct however and are primarily inductive pickup from a nearby strike and therefore reduced to a much more manageable level.

Again for a direct hit. For a surge of the level of the much more common inductively coupled strike that does not apply.

The MOVs that are located adjacent to the phone line connector on a quality modem should clamp the surge. The drive to the off hook relay is also not electrically connected to the line, nor is most of the rest of the modem. The DAA transformer, ring detect optoisolator and hook switch relay are about all that is connected to the line.

There is absolutely nothing magic about the building. The building wall is no different than the wall of an electrical panel, or the case of a computer.

One thing you do buy by clamping the surge as far out as possible is to keep the current path of the clamped surge further away from other wires which helps limit further inductive coupling.

Again, reducing the current path and the potential for further inductive coupling.

As I noted, every suppresser on the line adds some level of protection. Suppressers at the electric service entrance panel, the CATV and telco demarcs all with short connections to a proper grounding electrode are the first line of defense.

Any suppressers downstream provide further protection against inductively coupled surges which don't have to come through the service entrance conductors and residual surges past what the primary suppressers were able to clamp. Also for #1, that third pin on the power plug *is* a dedicated earthing wire.

Yes, the closer you can locate the suppressers to the grounding electrode the more effective they can be. Those grounding electrodes are also rarely a single point ground particularly in a utility application. More commonly they will be a multipoint electrode array bonded together with quite heavy conductors, often with exothermic welded connections.

The telco is also a good example since it employs multiple stages of protection from the primary suppressers at the drop entrance to the suppressers on the SLIC cards, the suppressers on the power system, etc. More is better for the most part.

Again these should be the first line of defense along with quality suppressers at the telco and CATV demarcs. This does not mean that additional suppressers are of no value as lightning can induce surges in the building wiring inside the house just as easily as outside.

I've never seen a vaporized MOV of any size. I have seen a few that have failed and cracked after being subjected to substantial surges. If you review the joule ratings of the various MOVs and gas discharge arrestors you find in typical small suppressers you'll see that their ratings are not at all far behind those of the common whole house suppressers. Some of the quite expensive service entrance suppressers intended for commercial services have higher ratings, but not the common ones.

Refer you to the dedicated grounding (earthing) conductor provided to every electrical device in a residence. The dedicated third pin on a NEMA 5-15 (or 5-20 or 5-xx, 6-xx, etc.) receptacle.

Cable is not required by any code to have anything but the ground block at the demarc, however this only grounds (earths) the shield of the coax. The coax center conductor still can and often does convey significant surges into the premises. A quality coax surge suppresser will clamp surges on the center conductor to ground as well.

Again, every single one of those suppressers has an earth ground connection. They wouldn't pass code and UL listing requirements if they didn't.

The grounding pin of the NEMA 5-15 plug on the UPS.

The specifications for my UPS indicate the clamping voltage and joule rating of the suppresser devices.

Some appliances do, many do not. Don't recall the last time I saw any suppression devices in a toaster or a blender.

Again you are 100% incorrect, any plug in suppresser with a three prong plug *does* have an earth ground. What the heck do you think NEC article

250 is all about? NEC articles 280 and 285 relate to surge arrestors and transient voltage surge suppressers BTW.

If you have a direct lightning strike on your service entrance drop or service feeder on the poles, your glorious whole house suppresser will be in pieces along with your entire service panel.

Pete C.

[Tom Horne, Electrician]

I work as a communications wireman whenever the electrical service industry gets too slow. I have built alternative powered and utility powered radio equipment shelters in remote places from Alaska to the Argentine pampas. These room sized buildings are struck quite regularly by lightning without loosing a single circuit. The inevitability of damage secondary to a direct strike is a myth. If you are willing to invest the necessary effort damage can be averted. Most home owners will not find it cost effective to install fully effective lightning protection.

[karsan]

I have a surge protector for my computer, the telephone, and our lamp. We only have one televison.

[Bud--]

The same old Bull.

The best information I have seen on surge protection is at

is a guide that was published by the Institute of Electrical and Electronic Engineers in 2005. You provided the link to this guide.

Another good source is

by the US government - National Institute of Standards and Technology.

Both guides were intended for wide distribution to the general public to explain where surges come from and how to protect against them. The IEEE guide was targeted at people who have some (not much) technical background. The NIST guide is intended for everyone.

Both the IEEE and the NIST say that plug-in surge suppressors ARE EFFECTIVE. Perhaps you are smarter than they are.

Note that if equipment, like a computer, has connections in addition to the power line, particularly phone but also possibly LAN or other, that wiring also needs to go through the plug-in surge suppressor. That also applies to equipment with power and cable TV connections. This is described in both guides.

Plug-in surge suppressors work primarily by clamping the voltage on all wires (power and signal) to the common ground at the surge suppressor. That includes the cable TV coax center conductor, as described by Pete C.

bud--

[Bob]

I have a whole house "protector" at the electrical panel and several smaller units scattered throught the house. I have had several lightning hits in the near vicinity and have never had electrical damage. But I have lost 4 TV's from lightning coming in on the cable - all damaged in the tuner sections rather than power sections. And I have had computer modems fry from surges on the telephone line. So from that, I deduce the whole house unit is doing it's job, but the others are questionable. Bob

[w_tom]

Was cable earthed before entering a building? If not, then yes, cable may be an incoming source of electricity called a surge. Cable must drop down and make a 'less than 10 foot' connection to a same earth ground used by AC electric and telephone. If cable enters house without dropping down and connecting to earth, then yes, cable can be the incoming path of a surge that was seeking earth ground destructively through tuners.

No protector is required to earth coax cable surges. But the most important component of a protector - earth ground - must connect to that cable. Connected so that a surge finds earth at the building entrance instead of via TV tuners.

Actually we don't know that any protectors were doing their job. You suffered damage. If, for example, the telephone line 'whole house' protector and AC electric 'whole house' protector were not using a same earth ground, then damage could still occur. Protection starts with and is defined by earthing - not by some protector. The effective protector makes a 'less than 10 foot' connection to same earth ground used by all other protectors.

What makes problems more complex is that plug-in protectors have a history of offering surges more destructive paths through household appliances.

Forget that protectors are protection. What was the earth ground? Earth ground is the protection. How were those protectors earthed?

Don't assume a modem was damaged by a surge from phone line. Don't think of surges as a wave crashing on a beach. Surges just don't work that way. First electricity flows in everything in a path through that modem. Everything is conducting the same electricity. Long afterwards (microseconds later), something in that path is destroyed. That path could be incoming on phone line. Or a destructive path through modem can be incoming on AC electric or cable; outgoing on phone line. Notice - first there must be both an incoming and outgoing path. Notice, the cable is not directly connected to computer. Since numerous household items may be conductors, then even a cable surge could have found a path to earth via that computer modem.

Any incoming utility could have been an incoming surge path into the computer. However most modems are damaged by surges incoming on AC electric; outgoing to earth via phone lines. No 'wave crashing on a beach'. An incoming path and an outgoing path to earth must exist to have damage.

You don't know if phone line was incoming or outgoing path based upon what was posted. You only know a modem was in a destructive path from cloud to earth. And that path existed because something was not properly earthed where it enters the building. How do you learn from and fix the problem? Start with earth ground. Is it the best earthing on the property? Does every utility make a 'less than 10 foot' connection to that one earthing electrode? IOW do all utilities enter at a same location or is that earth ground expanded to connect to all incoming utilities? We don't yet know whether cable or TV wire was the incoming source or outgoing path to earth. Analysis must start by identifying both incoming and outgoing path through that modem and those TV tuners.

How did lightning from a cloud find earth ground through those tuners and modem? Until we can answer that question, then it is only a guess why something was damaged and no idea yet how to fix this human created failure.

You cannot deduce the 'whole house' protector is doing anything effective until the most essential part of a protection system - earth ground - is verified. Did a surge enter on phone line if telco had installed a 'whole house' protector -for free? Well again, what is that protector earthed to. Protection is defined mostly by the quality of earthing.

Meanwhile, what did those plug-> I have a whole house "protector" at the electrical panel and several

[Joshua Putnam]

I've looked rather closely at my coax entrance -- only the outer conductor is grounded. The center conductor is not. (Shouldn't be too surprising, if you shorted them both to ground, it would attenuate the signal a bit, no?)

What, other than a surge protector, stops transients on the center conductor of cable TV?

[w_tom]

Numerous points that make assumptions based in a world where impedance does not exist - where only resistance exists.

First, nothing will stop a direct strike. But direct strikes routinely do no damage when they are diverted. Major difference between stopping (which plug-in protectors hope you will assume) and diverting which is standard where direct lightning strikes do not damage. Again, 25 direct strikes annually to electronics atop the Empire State Building; 40 annually to the WTC - and electronics not damaged. It is routine to earth direct strikes without damage - because we don't stop a direct strike. We divert it to earth.

Inductive transients? Well put some numbers to them. I assume this is about a nearby lightning strike to a long wire antenna. Well that nearby strike may induce a few thousand volts onto that antenna. Then we connect an NE-2 (neon glow lamp) from that antenna to earth. Because that neon glow lamp conducts only milliamps, then that thousands volts on antenna is now less than 60 volts. IOW induced transients are that trivial. So trivial as to be made irrelevant by protection inside all appliances. And yet, even industry standards of

30+ years ago (i.e. CBEMA) defined protection that was inside all electronic appliances even that long ago. It takes so little to make induced transients irrelevant. But it is the direct strike that causes damage.

You did not see protector devices inside the blender? You were not looking like an engineer? Why do you think wire was heavier gauge than necessary? You are making a classic mistake. You have assumed protector is as specific device. Protection is not necessary achieved by a protector. Protection is something in the engineering. You are instead looking for a specific device rather than first learning the design. Meanwhile, we were discussing electronics appliances - not blenders that have no electronics.

Is "drive to the off hook relay ... also not electrically connected to the line, nor is most of the rest of the modem"? First go to data sheets. That coil inside a modem off hook relay does electrically connect to its wiper as those datasheets demonstrate. Not at 100 volts. But then even floors and wall paints become conductive during these transients. Datasheet for that off-hook relay even states what voltage causes a coil to connect to relay wiper. That is how modems are so often damaged - as we also demonstrated when constructing massive relay switching drawers in test equipment to connect and disconnect those voltages. How are modems damaged? Get those datasheets. Even optocouplers have breakdown voltages. When that off-hook relay coil breakdown voltage is exceeded, then a destructive transient passes through PNP transistor, through relay, and to earth ground via phone line. Everything has a breakdown voltage. What we assume is not conductive at trivial low voltages become a perfect conductor at higher voltage.

Defined was how a modem is damaged when an AC electric line surge finds earth ground via modems DAA section, phone line, and earthed 'whole house' protector.

Try to make two ends of a fluorescent lamp conduct with an ohm meter. No connection. Then why do so few volts conduct current across that tube when tube is glowing? Same principle. That relay coil and relay wiper are electrically connected during a surge which is why we so routinely repaired modems by replacing a surge damaged PNP driver transistor. Surge incoming on AC lines and outgoing on phone line. To be damage, electronics must have both an incoming and outgoing path. Surges do not enter on phone line, ignore phone line 'whole house' protector, crash on a modem, and stop. Electricity just does not work that way.

As described in another post is wire impedance. Using Bud's citations that demonstrate how plug-in protectors can fail to provide protection: two TVs sharing a plug-in protector are at 8000 volts. How can this be when those plug-in protectors are grounded by three prong electrical connection to breaker box? Because one end of that safety ground wire is at near zero volts and the other end is at 8000 volts - wire impedance. How can one end of a wire be at 8000 volts and the other end at near zero volts? Welcome to a basic electrical principle that also explains why different parts of a transmitting antenna wire are at different voltages.

A 50 foot AC electric ground wire is maybe 0.2 ohms resistance. But that same ground wire is maybe 120 ohms impedance to a surge. A trivial 100 amp surge enters wall receptacle. 120 ohms times 100 amps is a voltage somewhere below 12,000 volts. Same reason why those two TVs can be at 8000 volts during a surge. Same reason why earthing must be 'less than 10 feet' to single point earth ground. But then this is old and well proven concepts - wire impedance.

More reasons why that 50 foot AC electric wire has even higher impedance and creates other surge related problems. Sharp bends. Splices. Bundled with other wires thereby induced transients on those other wires. Wall receptacle is not an earth ground. Wall receptacle is a safety ground. Wire impedance is why that wall receptacle is not sufficient for earthing.

Yes appliances do have internal protection as required by industry standards. Once some appliances (ie Apple II) installed those protectors. No longer. MOVs inside the computer were as not effective as they would be on its power cord - for so many reasons - including too far from earth ground.

You have not seen MOVs vaporize? Get 30+ years experience with this technology to see it. Some vaporized MOVs looked ominously ghostly. Only left were two leads. Nothing left of its carbon material or red paint.

Meanwhile, learn what joules really mean in a plug-in protector.

1000 joules in a plug-in protector is maybe equivalent to a 333 joule 'whole house' protector. And that assumes none of those joules are used on other ports such as telephone or cable. Furthermore, as joules increase, then protector life expectancy increases exponentially. To be equivalent to a minimal 1000 joule 'whole house' protector, the plug-in protector must be at least 3000 joules. Too often, UPSes and power strips were only 345 or 900 joules - grossly undersized. Only recently have some plug-in protectors sold 'still too small' 2000 joules products.

You have never seen a grossly undersized protector vaporize? View what was too unacceptably common with so many plug-in protectors:

what these would do in dust balls on a rug behind the table or on a desktop covered in papers. Does not matter if your desktop does not have papers. Other's do which is but another reason why plug-in protectors can also cause human safety problems.

But again, some principles to grasp before understanding surge protection. Ever touch a doorknob to cause a static discharge? What was the electrical connection from that finger to charges below your shoes? Notice how many of those items are normally not considered conductive. And yet electricity flowed from that finger tip, through door, through floor to bottom of your shoes. Welcome to surge protection where concrete and linoleum become excellent conductors of electricity. Where a coil and wiper inside a relay become electrically connected. Just more examples of why surges cannot be stopped - and therefore why effective protection has always been about diverting before a surge can enter a building. Diverting via low impedance - not just low resistance - connections to a single point electrode.

[w_tom]

Generally all protectors attentuate signals. In earlier days, I always wondered why center core connection was not performed. Some experienced professionals in the rec.radio.amateur.antenna newsgroup confirmed what I had been told. Leakage from the center conductor to a well earthed outer conductor provides sufficient protection. A capacitive protector on center core would only attentuate signals; provide little protection advantage. But then some legendary manufacturers do make protectors that include that center core.

You are not earthing a 200,000 amp direct strike - which you probably will never see in your lifetime. Using a ground block to earth the outer braid is a massive protection improvement. If you still need better, then visit some expensive and superior protector manufacturers such as

.

Nothing 'stops transients on the ... conductor'. Anything that stops or blocks such transients is not effective. Effective protection is diverting. Destructive transients seek earth. Therefore the sooner that transient is diverted / earthed (meaning a shorter connection to earth and farther from transistors), then the better that protection.

[Bud--]

Plug-in surge suppressors for cable TV need to have a port to include both the power and cable TV. The multi-port surge suppressor will clamp all voltages on power and signal wires to the common ground at the suppressor. The IEEE guide at

this quite well. It says the cable center conductor can be 4000 volts with respect to the shield. A plug-in suppressor will clamp this, likely with a gas discharge tube. A bigger problem is if the cable entrance ground block is not near, and connected with a short wire, to the power service earthing conductor. That is also protected by a multi-port plug-in surge suppressor and is illustrated in the IEEE guide.

Similarly, a plug-in suppressor for a computer with phone connection has to have ports for both power and phone line.

bud--

[Rob Mills]

have 3 surge protectors running in my home.

[Pete C.]

You sure do like to babble, too bad 99.9% of what you say is either total nonsense, pseudo-science, or hopelessly misapplied scientific principles. Your links to claimed "vaporized" MOVs show no such thing either.

Pete C.