"chain" surge suppressers?

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Does anyone know if surge suppresser protection can be increased by "chaining" two or more together?
For example, I have two power strips that have surge suppresser outlets. If I plug one of the strips into the protected outlet of the other suppresser will the down-stream strip offer more protection than the up-stream one?
Thanks,
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Tripp Light told me it works that way. I use two in some areas. But only unplugging in a storm is 100% guarnteed.
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Buy a UPS, far better design and protection.
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snipped-for-privacy@aol.com wrote:

. I would get a single suppressor with high ratings. They are readily available at rather low cost.
The division of the protection between the suppressors depends on the clamp voltage of the MOVs in the suppressors.
If chained, I would plug-in only to the most downstream suppressor.
Any manufacturer with a protected equipment warranty is likely to say the warranty is void.
UL does not intend for any plug strips to be chained.
Everything that is interconnected needs to be plugged into the same suppressor. External wires, like phone and cable, also need to go through the suppressor. .

. UPSs, of the kind commonly used, do not intrinsically provide any surge protection. The surge protection included in a plug-in suppressor is commonly added.
Compare surge ratings.
And in the US get a UPS that includes UL1449 listing (surge suppressors). Many (most?) UPSs don't.
--
bud--


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Actually, if you think about it, it really doesn't matter. All the protection elements end up in parallel even though the plugins are in "series". With one plugged into the other it won't make a bit of difference. A "big" one and a "small" one will result in the small one always being the guy to fail first anyway since it'll be the first to go under fault cases. So, a second one does add some protection, but not as much as one would expect. Two identical units would not result in twice the juoles of protection because one's components will always fire first and clamp first, leaving the other one to sit there nice and cool. They won't both clamp most of the time except under long, sustained faults and then one will try to source it all, blow, and leave the other one to take its place. It's really better to have one larger, better designed unit than multiple smaller ones. The conduction points, knees, and clamp times/voltages are not very closely controled, especially in the cheap units. All they're really there for are a few short duration spikes in excess of about 600V, then once fired, try to pull that voltage down to something lower until it burns itself out or the voltage goes away.
Do a Google for "how to's" & designs on surge supression; it's pretty interesting stuff. I used to do safety testing on them for UL certifications & componentry.

Right; they're good protectors on the regulated side, but not on the unregulated outputs. The batteries, caps & xfrms provide a lot of surge protection just by having to be there for the design. And yes, I'm including switching supplies.
Cheers,

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TWayne wrote:

. The plug-ins are in "parallel". .

. Depends on the actual clamp voltage of the MOVs in the 2 units. If the "bigger" one has a lower clamp voltage it will take most of the hit and may well fail first. .

. MOVs dont work by "firing".
If they have the same nominal clamp voltage and a strong surge, one will take more of the hit (unless the MOVs have been matched). The voltage across that MOV goes up with the current through the MOV. That can allow the parallel MOV to start conducting. .

. Anytime MOVs are paralleled in a suppressor by a competent manufacturer they will be "matched". .

. MOVs dont fire. The current goes up rapidly as the voltage rises. Below a characteristic voltage the current is negligible. They dont pull the voltage down. They try to prevent it from going up. .

. The type most commonly used are good protectors on the regulated side only while in back-up mode. That is after an event.
In normal operation the "regulated side" is connected to the incoming line and there is no intrinsic protection.

. Switch mode power supplies provide some surge protection on the line side depending on how big the DC side caps are.
An insurance company, a power utility, Martzloff and others did a very limited examination of equipment allegedly damaged by surges. A number of computer power supplies had input side diodes burned out (surge current to the caps). There were a few blown fuses. Some power supplies worked after fuses/diodes were replaced.
--
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Same diff.

Something's silly there; you don't get different specs on bars to vary that widely. Nearly every power strip sold uses the same design levels, which are very minimal anyway w/r to protecting equipment from more than in-home surges and spikes. There may be something to what you say, but it would be more accurate to say that the one that reaches the clamp voltage first will be the first one to be damaged. I actually shouldn't has said it WILL be the cheapie, although odds are it almost always will be.
The "actual" clamp voltage etc. are never identical between components. You're not likely to find different clamp voltages of much variation and tolerances almost always negate them anyway. It isn't the clamp voltage, it's the shape of the knee curve and how quickly one does or doesn't get to the point where it begins to clamp. The clamp voltage is not the voltage at which the component begins to conduct: It is the voltage level the component tries to maintain after it has begin conducting. It may take 600V to start the clamping action, and then if current remains high enough it will try to clamp it down to 300V or whatever the clamp voltage spec happens to be.

Call it what you want. To "fire" would be to move up the power knee until the component begins to conduct, and then it will try to pull the voltage down to its design clamp voltage whle the current remains within its range of capabilities. I consider that firing. You can play with syntax and semantics all you want, but it's a stupid point and makes me wonder what your real point is. Also, MOVs have fallen from favor for any but the cheapest power strips anymore. That happened years ago when better components became price competitive.

No, they specifically will NOT be. They will have the same specs, but they will not be matched within those specs to make th em nearly identical to each other. There is no reason to. It would drive their costs up very quickly. MOVs, which seem to be the only component you understand, are much like fuses; you cannot test them reliably enough to pick matched components.

There's your semantic lunacy again. Take a closer look; the clamp voltage is NOT the voltage at which they begin to conduct current. Go to any mfr and take a look at the specs and you'll even note "fire" points on several of them. MOVs are NOT linear devices and it's far from as simple as you're trying to make it out to be.

Wrong. Don't be so lazy; go do some of your own research. And a UPS only comes on after a power loss of greater than xx mS or brownout conditions as measured by the UPS itself. You're mixed up apparently between line conditioners and uninterruptable power supplies. You can get line conditioning WITH a UPS, but you're going to pay for it. But line conditioning has almost nothing to do with this subject.

Well, sorry to tell you ths, but there is. The defunct unit at my feet here contains exactly 9 surge/spike components, 3 inductors and a fusible link used as a resistor. The one I am running off at this moment carries several thousand joules of protection on the unregulated outputs, but that's not the norm. The norm is approximately the same as a decent power strip not from an Aisan country.

lol, really? The DC side caps, which is actually mostly accomplished by the battery, are NOT the surge protection. The surge protection in that area is actually very SMALL capacitors, often in the nanoFarad range, and probably a couple of tiny inductors in most of them. Large DC capacitors are INDUCTORS to high frequencies. Spikes will have very fast wavefronts which will skip right across large caps.
I'm slowly coming to the conclusion that you are not educated but rather have done some reading and made many mistakes in your comprehension of what little you have read of you wouldn't be making the statments you're making.

And? Is there a point to that? I've routinely seen such components replaced and the item put back into service. It's not necessarily a good idea, because if something has blown spike protection components, chances are extremely good that semiconductor materials, especially CMOS input types of just plain CMOS, have had their input diodes/capacitances/trace inductors blown too, meaning those components are, assuming they are still working, primed and ready to blow at the first hint of an extraneous voltage. They are there to protect the CMOS, say, from normal PSU transients above the rails or below their ground reference, so without them they often don't last much longer.
When you get more than a few buzzwords and some primer type reading under your belt, we can talk again, but until then I don't think I have much use for you or your so called knowledge. Suffice to say you are a dangerous person around electronics gear. I'll bet you even think that because you didn't see of feel an arc, you never transferred any static electricity to what you touched either. I hope your'e young because you have an awful lot to learn.
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TWayne wrote:

. Engineers everywhere will be glad to find out there is no difference. .

. Stated unit clamp voltages are set by UL and are very gross steps - 330, 400, ... IIRC.
MOVs have more voltage levels. Characteristic voltages for a MOV depend on action at a huge number of grain boundaries throughout the volume of the device. Even MOVs with the same nominal characteristic voltage will have different real world voltages because of the impossibility of exactly matching manufacturing. Because of the very non-linear characteristic of MOVs, small differences can result in large differences in current at the same voltage. .

. Plug-in suppressors with very high ratings are readily available.
Still missing - your response to another thread where investigations from Martzloff indicate a very strong lightning strike to a utility pole behind a house results in 34Joules or less to a plug-in suppressor. .

>

. You are describing a device that "fires". Neon lights, gas discharge tubes, SCRs all "fire". Conduction starts after a trigger.
MOVs do not "fire". Conduction is on a continuous curve, increasing rapidly as the voltage goes up. They do not "clamp down to 300V". Source current will drag them up to 300V on a continuous curve.
[MOVs have a reaction time far faster than a surge.] .

. The point is how MOVs work. You show no evidence of knowing, as in the "take 600V" paragraph above. .

. The IEEE published an excellent guide on surges and surge protection: <http://www.mikeholt.com/files/PDF/LightningGuide_FINALpublishedversion_May051.pdf
The IEEE says: "The vast majority (>90%) of both hard-wired and plug-in protectors use MOVs to perform the voltage-limiting function. In most AC protectors, they are the only significant voltage limiters."
MOVs are very attractive, with high current ratings and high energy dissipation ratings in a small package.
"Better components" are not specified. .

. MOVs from the same manufacturing lot may be sufficiently similar. From different lots they will not be. As I wrote above "because of the very non-linear characteristic of MOVs, small differences can result in large differences in current at the same voltage." Paralleling MOVs from different lots will result in current not being shared equally which will negate a significant part of the advantage of paralleling them. . It would drive their

. MOVs, which seem to be a device you do not understand, certainly can be "matched". .

. I said just above "the current goes up rapidly as the voltage rises". That describes a non-linear device - a Varistior, as in moV.
"May take 600V to start the clamping action, and then if current remains high enough it will try to clamp it down to 300V" does not describe MOVs. MOVs have a smooth, though non-linear characteristic I-V curve. .

. That is what I just said. .

. I agree. You shouldnt have introduced line conditioning. .

. Well, sorry to tell you but the "9 surge/spike components" are not "intrinsically" part of the UPS. The UPS worked fine without them. They are added to the basic UPS to provide surge protection. .

. Surge protection can be added to anything. Surge protection is not "intrinsically" a part of the type of UPS commonly in use. UPSs can easily be made without the surge protection components. Surge protection is function added to a basic UPS. .

. Switch mode power supplies, the subject of the sentence above, do not have batteries. .

. Manufacturers will be glad to know they can dump the MOVs and just use nanoFarad caps and tiny inductors. .

. In the investigation below, the real world, burned out diodes were found on the input/DC side of the switch mode power supplies. The diodes were burned out by surge current to the filter caps, which acted as snubbers. .

. I'm slowly coming to the conclusion that you are educated beyond your intelligence. .

. Switch mode power supplies provide 'some' surge protection. Do you want a direct reference from Martzloff? .

. When you
- learn how MOVs work - learn the difference between series and parallel - learn that the type of UPS commonly used does not *intrinsically* provide surge protection - explain why it is illegal to sell a UPS without safety compliance - explain where Martzloff was in error that a strong lightning strike produces 34Joules or less to a plug-in suppressor
we can talk again.
--
bud--

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Caesar Romano wrote:

It will give you more current sinking ability but it wont give you faster response times. So you could take a longer charge, but not a faster one. In essence, based on the way they rate these products, it will increase protection. I don't know how useful it will be in practicality though.
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Yes it surge protectors work as less responsible companies would imply. Since protectors stop or absorb surges, then more damns should help.
Problem: protectors don't work that way. Same protection is also achieved by plugging both each power strips directly into the same duplex receptacle.
Protectors do not work by absorbing or blocking surge energy. Will those silly little parts in a power strip stop what three miles of sky could not? That is also what they imply. Why does your telco not use plug-in protectors? Telcos need protection.
Protectors are not protection. Protectors work by connecting surge energy to protection. Those power strips accomplish much more if plugged into receptacles attached to the breaker box. Now the protector is closer to earth ground and farther from protected appliances. Yes, separation between protector and appliance increases protection. But most important, the effective protector connects surge energy very short into earth.
Tripplite does not sell 'whole house' protectors. No obscene profits found in protectors that actually do effective protection. To install an effective protector, see products from far more responsible companies such as Square D, GE, Siemens, Intermatic, Cutler Hammer, Intermatic, Keison, Leviton, etc. Effective protector has a short (ie 'less than 10 feet') connection to earth. Why? Protection is what absorbs all that surge energy. Protection is always about what dissipated that surge energy. Protector is woefully too tiny. But the protector can connect massive energy into earth. However it must have that short connection to earth.
One who promotes for plug-in protectors (and will not admit it) will post citations that show what protectors must do:

You somehow assumed protectors are blocking, stopping, or energy absorbing devices. If true, then chaining protectors together would make better protection. But protectors are 'diverting' devices. How well do they divert? How far is that distance to earth?
Each protection layer is defined by what provides protection. This post discussed secondary protection as defined by the breaker box earth ground. Also inspect the primary protection layer: http://www.tvtower.com/fpl.html
Does your earthing meet and exceed post 1990 National Electrical Code requirements? That is where effective protection begins. Every wire that enters the building (including telephone, cable, satellite dish) must connect to that one earthing electrode before entering a building. Did you know all telephones have a 'whole house' protector provided for free? But again, the telco 'installed for free' protector is only as effective as the quality of and connection to earth ground. Earth ground defines protection. Effective protectors connect 'less than 10 foot' to the earthing rod. Power strips may do something effective if attached closer to earth ground. But then you might buy a 'whole house' protector (from responsible companies) that provide effective protection at tens or 100 times less money per protected appliance.
One earthed whole house protector does more protection than 100 chained plug-in protectors. Thats why your telco does not waste money on them. That is why your telco is fanatic about earthing every protector. That is why your telco can suffer maybe 100 surges to their switching computer and no damage. A protector is only as effective as its earth ground where that surge energy must be dissipated.
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w_tom wrote:

. The best information on surges and surge protection I have seen is at: <http://www.mikeholt.com/files/PDF/LightningGuide_FINALpublishedversion_May051.pdf - "How to protect your house and its contents from lightning: IEEE guide for surge protection of equipment connected to AC power and communication circuits" published by the IEEE in 2005 (the IEEE is the dominant organization of electrical and electronic engineers in the US). And also: http://www.nist.gov/public_affairs/practiceguides/surgesfnl.pdf - "NIST recommended practice guide: Surges Happen!: how to protect the appliances in your home" published by the US National Institute of Standards and Technology in 2001
The IEEE guide is aimed at those with some technical background. The NIST guide is aimed at the unwashed masses. .

. Only w_ talks about absorbing, blocking and stopping. .

. Apparently airplanes cant have "effective protectors".
w_ has a religious belief (immune from challenge) that surge protection must use earthing. Thus in his view plug-in suppressors (which are not well earthed) can not possibly work. The IEEE guide explains plug-in suppressors work by CLAMPING (limiting) the voltage on all wires (signal and power) to the common ground at the suppressor. Plug-in suppressors do not work primarily by earthing (or stopping or blocking or absorbing). The guide explains earthing occurs elsewhere. (Read the guide starting pdf page 40).
Being evangelical in his belief in earthing, w_ trolls google-groups for "surge" to paste in his religious tract to convert the heathens. This is at least the 5th time he has been to this newsgroup in the last 2 months. .

. As dpb has pointed out several times, all of these "responsible companies" except SquareD make plug-in suppressors.
SquareD, for its "best" service panel suppressor, says "electronic equipment may need additional protection by installing plug-in [suppressors] at the point of use." .

. Poor w_ has to try to discredit anyone who exposes his drivel. To quote w_ "It is an old political trick. When facts cannot be challenged technically, then attack the messenger." My only association with surge protectors is I have some. .

. What does the NIST guide really say about plug-in suppressors? They are "the easiest solution". .

. If w_ was not impaired by religious blinders he could read in the IEEE guide that plug-in suppressors do not work by blocking, stopping or absorbing. .

. Service panel suppressors are a good idea. What does the NIST guide say? "Q - Will a surge protector installed at the service entrance be sufficient for the whole house? A - There are two answers to than question: Yes for one-link appliances [electronic equipment], No for two-link appliances [equipment connected to power AND phone or cable or....]. Since most homes today have some kind of two-link appliances, the prudent answer to the question would be NO - but that does not mean that a surge protector installed at the service entrance is useless."
Never seen - a link to a source that agrees with w_ that plug-in suppressors are NOT effective.
Never answered - embarrassing questions: - Why do the only 2 examples of protection in the IEEE guide use plug-in suppressors? - Why does the NIST guide says plug-in suppressors are "the easiest solution"? Why does SquareD say "electronic equipment may need additional protection by installing plug-in [suppressors] at the point of use."
For real science read the IEEE and NIST guides. Both say plug-in suppressors are effective.
--
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One thing I don't agree with is the notion that the protection is poorer because the protection device is further from ground. This works both ways. The device being protected is also further from ground so its a less attractive target if you will.
The protection is more influenced by the difference in the quality of ground between the ground pin and the neutral pin the protector device is plugged into. So being farther away from the house ground does not negatively affect protection based on the way these devices operate.
CL
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Again you are assuming the protector somehow absorbs or blocks surges. They don't work that way. The typically destructive surge is never blocked or absorbed by anything in the house. Surge voltage will rise as high as necessary to obtain earth ground. No protector will stop or absorb what three miles of the worlds best insulator could not stop - air.
Any voltage differentially between two AC wires is not a typically destructive surge. That surge is made irrelevant by protection inside all appliances. A simplified example: you have assumed a surge as a positive voltage on the black wire and a negative voltage on white. But the destructive surge does not work that way. The destructive surge is a positive on black, white, and green wire. Negative is in earth. Voltage will increase as necessary to find earth ground. Conductors through that computer include wall paint, concrete floors, the telephone wire, linoleum tile, network cable, baseboard heater, etc.
Another possibility is surge positive on black wire, nothing on green or white wire, and negative surge voltage in earth. What does an adjacent plug-in protector adjacent do? Now a positive surge is on black, white, and green wires - and still seeking earth ground. That is the point of Page 42 Figure 8 where the surge found earth ground 8000 volts destructively through the TV.
What does your telco do to have better protection from about 100 surges during every thunderstorm? They don't use any plug-in protectors adjacent to equipment. They put every 'whole house' protector where each wire enters the building, as close to earth ground as is practicable, and protectors up to 50 meters distant from electronics. Why 50 meters? Because separation increases protection.
That connection to earth ground must be as short as practicable. Having said that, Polyphaser make a surge protector without an earth ground wire. That protector mounts directly on earth ground to provide even better protection. Polyphaser is a highly respected industry benchmark.
If thinking a protector is protection, then a protector near to an appliance is protection. Again, stop falling for 'Saddam WMD' type reasoning. The protection is earth ground. The protector is nothing more than a connecting device to protection. If any wire enters the building and connects directly to appliances (ie black AC electric wire), then a surge may find earth ground via that appliance. However, if the surge is earthed before entering the building, then the surge need not seek earth through any appliances. That's right. Do you protect 100 devices with one properly earthed protector, or buy 100 plug-in protectors that cannot connect surges to earth?
Again, if the surge is not connected to earth, then wires, pipe, floors, wood inside wall, etc all will give surges potentially destructive paths to earth. You read that correctly. Why did Franklin put lightning rods on church steeples? Those wooden steeples were an electrical conductor to what surges seek - earth ground.
You are assuming surges are voltages. See that above simplified example. I never said positive surge voltage. Surges are currents. Voltage will increase as necessary so that the same current will flow. Give that current a short path to earth and near zero voltage results. Attempt to shunt (clamp, connect) all wires adjacent to the appliance and that current will still seek earth ground - unfortunately inside the house. Current of the typically destructive surge must get to earth. Either it gets earth at the service entrance (near zero volts) OR it gets earth 8000 volts destructively via the adjacent TV (Page 42 Figure 8).
Why does Franklin's lightning rod work? Either surge is electrically conducted by the wooden church steeple. Same current with a high voltage means destructive power. Or surge is connected to earth via metallic wire. Same current with trivial voltage means no destructive power AND all surge energy gets dissipated in earth. Same principle applies to surge protectors. Your surge protector must do what that metallic wire did for Franklin.
Stop thinking of surges as voltages. Stop thinking of surges as voltages between wires. Stop thinking that wires shunted (merged, clamped, connected) together makes surge energy disappear. Do you have protection? Then you can say where surge energy gets dissipated (without currents inside the house). An effective surge protection 'system' makes a short connection to earth. Even sharp wire bends will only subvert that connection to earth. Where does surge energy get harmlessly dissipated? No plug-in protector will answer that. Instead, they hope you *assume* wires shunted together means energy magically disappears. That energy does not disappear and is not absorbed by the protector.
As the NIST also says it:

An ineffective protector has no earth ground AND pretends that surge energy just magically disappears. If connecting black, white, and green wires together, does that surge energy disappear? No. It has more wires to find earth ground destructively via adjacent appliances. Your protection 'system' (and yes, protection is a 'system') must include something to dissipate surge energy. A protector is only as effective as its earth ground. No plug-in protector even claims protection from the typically destructive surge. Why? The answer is obvious. No effective earth ground. Where is that surge energy dissipated? Adjust your definition of a typically destructive surge that can overwhelm protection already inside all electronics.
Why does your telco not use plug-in protectors? Too far from earth ground. Too close to electronics. Both only subvert effective protection. But these facts get ignored to hype obscenely profitable plug-in protectors.
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w_tom wrote:

No, I am not assuming that at all. Surge voltage will rise as high as necessary to obtain earth ground. I (loosely) agree. As an electrical engineer I could explain it better but why complicate things that are already misunderstood.

That's incorrect. Equal voltage surge on all contacts is effectively 0 volts (with respect to the component in question) and will not hurt the component outside of the effects of noise in the circuit. Voltage is the difference in potential. If there is no difference in potential, there is no voltage.
A surge is most certainly additional positive voltage on the black wire. Anything else might be considered a potentially harmful event, but it would not be called a "surge."

No such thing as a negative earth surge. Are you talking about reverse polarity?
If you are trying to differentiate between a surge that seeks to return to the power company and a surge that seeks to return simply to earth ground, than I agree there is somewhat of a difference. But not much since the power company's ground is tied to earth as well.

This is not because the ground is "better" where it enters the house. This is for different reasons. The phone company would not want to add several protection devices throughout your house. Its easier for them to add just one. In addition, if the phone line gets a direct hit by lightning, they don't want it entering your home to seek ground. Thus, they are "grounded" before they enter the home. Like all other metal of any kind.

Dude, you have a misunderstanding of the fundamentals. You must have cut-pasted this because its too long of a rant for you to have just come up with it. Anyway its based on flawed understanding.
Current takes the path of lease resistance. I think you know this much. What makes a protection device work is that it can provide a path of lower resistance than the device it is trying to protect. That is all. The protection is directly proportional to the difference in resistance of the path to ground through the protected device vs. the path to ground the protection device can offer a surge. The key here is "difference" in resistance.
A quality device by a reputable company will not protect better because its installed by your fuse panel as opposed to by your computer. If that were the case then there would be one big surge suppressor installed at the power company.
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On Fri, 11 Jul 2008 10:35:14 -0400, "CL \\"dnoyeB\\" Gilbert"
[snip]

A common error. Current takes ALL possible paths. Relative resistance affects how it's divided.
[snip]
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Gary H wrote:

Yes, I did misspeak. I am used to saying it that way. In fact its this relative resistance division that makes local protectors just as good as remote ones.
The only thing worth mentioning is that the device protects everything downstream of it. So a fuse panel protector will protect a lot more devices. But it still wont protect the better.
CL
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Power plant surges don't create consumer surges for numerous reasons. But lightning and other surges such as those created by utility switching may be destructive and do seek earth. Also install one 'whole house' protector for typically non-destructive surges. We install and earth one 'whole house' protector to protect from all types of surges. The word *all* does not apply to plug-in protectors.
Install only four plug-in protectors around the house. If a plug-in protector works as claimed, then we need maybe 100 plug-in protectors including one at the furnace, one at the dishwasher, and one for every far more critical appliance such as bathroom GFCIs and smoke detectors. That is the kind of protection obtained from one 'whole house' protector. Meanwhile, plug-in protectors do not even claim to protect from the typically destructive surge and can even provide that surge with more destructive paths through appliances (Page 42 Figure 8).
Instead of 100 plug-in protectors selling at $25 or $150, the informed consumer installs superior protection from all types of surges using only one properly earthed 'whole house' protector. Superior protection for only $1 per appliance. Yes, you agree. But this post is for many - not just you. Four protectors scatter around the house does not even approach being sufficient or effective. Four protectors - and not one provides a manufacturer spec for protection from typically destructive surges? What kind of protection is that? Profitable. Ineffective.
I don't know what your 'relevant impedance' is. But wire impedance is why effective protectors are located close to earth AND separated from appliances. Wire impedance for earthing concerns industry professionals. A 'top of the front page' article in Electrical Engineering Times entitled "Protecting Electrical Devices from Lightning Transients" discusses what is required for surge protection: http://www.planetanalog.com/showArticle.jhtml?articleID=201807830

The article is about surge protection. Therefore it describes what is essential - a low impedance earth connection. It is about effective protection. So it does not discuss plug-in protectors.
Any facility that requires effective protection earths surges at the service entrance, worries about connection impedance. and addresse grounding issues should damage not be averted. A plug-in protector cannot protect from typically destructive surges. Its manufacturer makes no such claims. Obvious: plug-in protectors are not used inside telephone switching centers where damage must not occur and therefore 'whole house' protectors are used.
Protection inside appliances makes most surges irrelevant. A typically destructive surge can overwhelm that existing protection. So we install and better earth one 'whole house' protector to make a typically destructive surge irrelevant AND to make other surges also irrelevant.
Where does the US Air Force demand that protectors be located? Not inside:

Why at the service entrance? Any surge that might be stopped or absorbed inside a building will simply find many other (some potentially destructive) paths inside that building. A surge earthed before entering the building means protection inside *all* (not just four) appliances is not overwhelmed. A surge earthed at the service entrance (ie breaker box) means a low impedance connection into earth AND a high impedance path to appliances. Essential to effective surge protection is that low impedance earth connection. Then surge energy gets dissipated in earth; not inside the building. Routine is to have direct lightning strikes and no damage.
A 'whole house' protector also makes that other typically non- destructive surge irrelevant for tens or 100 times more money.
Of course this is not 100% protection. From the IEEE Green Book entitled 'Static and Lightning Protection Grounding' :

Where does a plug-in protector costing tens or 100 times more money per appliance make any such claim? It doesn't. One glaring reason - no low impedance connection to earth.
Surge created by a high voltage transmission line falling onto local distribution is energy from the power plant (actually transformer that is sourcing power) seeking a path back to that power plant via earth. A surge so violent as to literally explode hundreds of electric meters 10 meters off buildings did not cause any appliance damage when one 'whole house' protector (and no plug-in protectors) was properly earthed.
A surge that entered a building of powered off and networked computers was simply earthed, destructively, by two plug-in protectors through those adjacent computers and through the network. We traced that surge by literally replacing ICs. What kind of protection from two plug-in protectors? Completely ineffective as demonstrated on Page 42 Figure 8 - 8000 volts earthed through the adjacent TV.
Why spend so much money on protectors that cannot and do not claim to protect from the typically destructive surge? Why waste money on plug-in protectors? Because it is the popular thing to do. Facilities that must have protection don't waste money on plug-in protectors. Instead 'whole house' protectors AND short (low impedance) connections to a single point earth ground are installed. Earthing is critical for protection from all typically destructive surges. Same protection 'system' also protects from all other surges. No plug-in protector can or does make that claim.
Effective protection protects from all types of surges including the type that is typically destructive. Where does any plug-in manufacturer make that protection claim?
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Re Re: "chain" surge suppressers?:

I have a Delta LA302R lightning arrestor
http://www.deltala.com/prod01.htm#LA302R
installed at my meter. How effective can I expect that to be?
Thanks
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LA302R is called a single phase protector. That means it connects one AC hot wire to earth. The other phase would not have protection. However it also uses the number 125/250 and phrase 'per pole' implying this is really a two phase protector.
First, joules define a protector's life expectancy. As joules increase, a protector's life expectancy increases exponentially. This protector has an above average life expectancy. Being larger, it would also earth more surge energy - absorb less. For others, this protector to protect maybe 100 household appliances is listed at $42 or about $0.42 per protected appliance. Compare that to $150 per appliance for Monster Cable plug-in protector that does not even claim to provide this protection.
Above is about protector life expectancy - a long duration consideration measured in years. Another consideration involves short duration operation - what the protector does during microseconds. This is defined by how that protector connects to and the quality of earthing. A protector is as effective as its earthing. Nothing in that Delta spec will provide information on its short term quality - how well it will earth a surge.
For example, does the breaker box wire go up over the foundation, then down to an earth ground rod? How to make that Delta protector even better? Reroute that earthing wire through the foundation and down to a single point earthing electrode. Having made a shorter wire with less bends, now the Delta is an even better protector. If that rerouted ground wire is separated from other wires, protection further improves. Not only should that earthing wire be as short as possible, no sharp bends, no splices, etc. It must also attach to the same earth ground used by telephone, cable, and satellite dish. Another factor that makes that Delta protector and equivalent protectors more effective.
Delta's specs only discuss something long term - life expectancy. What determines how well the Delta will perform during microseconds of surge? Well, the Delta has above average joules meaning it is conductive. But what really determines its short term performance is how the Delta is earthed.
Whereas a plug-in protector would be promoted as a complete solution; effective protection is a 'system'. The Delta is only one 'system' component. Only component always required in a protection 'system' is the earthing electrode. How good is that earthing electrode and connections to that electrode? Earthing is a defining parameter for Delta effectiveness. A protector is only as effective as its earth ground.
Above discusses a 'secondary' protection system. Also inspect your 'primary' protection system: http://www.tvtower.com/fpl.html Again, notice what defines whether that protection layer will be effective. I cannot stress how often utility install grounding is left compromised as if it was never needed. After all, the lights work. Therefore earth ground for the primary protection layer also is not required?
The Delta protector appears to have specs significantly above minimum. How effective is it? Well does its earthing meet and exceed post 1990 code requirements?
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Re Re: "chain" surge suppressers?:

Thanks for the info.

I don't know. How is the quality of an "earthing" determined or measured?
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