MOVs and surge suppressors

Many surge suppressors on the market (I'm only talking about the MOV type here, not the fancy induction style) have little indicator lights to tell you if the thing is still providing protection. How do they do this? I thought the only way to test a MOV was to send a surge through it, and then you will only know what condition it was in before you sent in the surge. What is the circuit diagram for one of these indicator LEDs, and is this a way to test any MOV or MOV device?

Thanks.

Reply to
grizdog
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** There is a fuse wire link in series with the MOV.

If the MOV blows all to hell, then so does the fuse.

The light ( usually neon ) indicates that the fuse is blown.

.......... Phil

Reply to
Phil Allison

You're right, there's no way to test an MOV, and any indicator that claims to indicate the status of the MOV is nothing but marketing hype.

Cheers! Rich

Reply to
Rich Grise

A typical MOV has a capacitance of 100-2000 pF, which is an impedance of about 1.3 - 26 Megohms at 60 Hz. This is barely enough to light a neon lamp at 120 VAC. But it could provide enough current to drive a transistor and indicator lamp. However, a failing MOV gradually increases its leakage, and it would take a sophisticated circuit to analyze that.

I think Phil is right, except that the indicator is probably across the MOV, so it lights if the fuse is OK. I know *my* surge suppressor has a green light that indicates "protection", so I think that's how it must work. I don't really want to take it apart (unless it goes bad).

Paul

Reply to
Paul E. Schoen

In some failures, the indicator light can indicate that the MOV is bad, but it can never indicate that the MOV is good. So if the light tells you it is bad, believe it. If the light tells you the MOV is good, it could be lying to you.

Ed

Reply to
ehsjr

"Paul E. Schoen"

** The light can be made to work in the opposite sense - ie as a warning the MOV has been damaged - by having a resistor ( say 50 kohms) across the MOV and the neon plus 100 kohms wired across the fuse link.

This will operate the neon in both open and shorted MOV conditions, if the link goes open.

....... Phil

Reply to
Phil Allison

As others have noted, an MOV is 'protected' by a thermal fuse. If a surge is so large as to cause MOV to vaporize, then a major human safety threat exist (see scary pictures). A thermal fuse is placed in series with MOVs in a desperate hope to disconnect an MOV before it vaporizes Vaporizing MOV is a complete violation of MOV manufacturer specs AND a human safety threat.

Think about it a minute. MOV is so grossly undersized as to vaporize or be disconnected. It leaves the appliance to fend for itself from surges? Yes, the fuse does not disconnect appliances. Fuse leaves the appliance to protect itself from a surge.

So why is that appliance working while the protector failed? Surge was too small to overwhelm protection inside the appliance. But MOV protector was so grossly undersized as to be permanently destroyed.

By undersizing it, a plug-in protector manufacturer gets the naive to recommend a grossly undersized protector. Effective protectors earth surges AND remain functional - do not blow the fuse. Any properly sized protector remains functional after a surge. So that 'failed' protector light says what about the protector? Grossly undersized?

Another problem when that fuse does not disconnect fast enough:

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IOW many plug-in protectors will fail even on smaller surges to avoid those scary pictures. Failure also promotes sales among the naive.

How to test an MOV? Apply a 1 ma current source to it and measure its voltage. Remember, a vaporized MOV is a complete violation of manufacturer specifications. MOVs must degrade; never vaporize. When has an MOV degraded excessively? When that voltage during a 1 ma current is more than 10% of its rated voltage. See the datasheet. A fully degraded MOV remains functional - does not vaporize.

So again, if a surge was so large as to trip that indicator lamp, then the protector was grossly undersized - completely ineffective. If a power strip protector is reported defective by its indicator light, then you have no business buying more of those grossly undersized devices. Otherwise even the house is a risk per those scary pictures. See the Gaston County Fire Marshall report to appreciate the threat - the fifth citation.

Reply to
w_tom

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Notice that all MOVs are remove and indicator light says protector is good. Its not good. All MOVs are removed. Lights can only report a catastrophic failure; not report the protector as good.

Reply to
w_tom

Thanks, everyone.

Reply to
grizdog

Vaporizing is a scare tactic.

MOVs have an energy (Joule) rating. They do not protect by absorbing surge energy, but in the process of protecting they absorb enengy. When they have absorbed an energy equal to their rating, they will conduct at successively lower voltages, eventually conducting at 'normal' voltages and overheating. UL has, since 1998, required disconnects for overheating MOVs. Plug-in suppressors have their current limited by the significant impedance of the branch circuit.

For w_, all plug-in surge suppressors are "grossly undersized". In fact suppressors with very high ratings are readily available at rather low cost. And apparently a surge that can destroy a MOV won't damage protection inside an appliance? Hallucination.

"Grossly undersized" red herring again.

The hanford link describes overheating as being a problem with "some older model" power strips and says overheating was fixed with a revision to UL1449 that requires thermal disconnects. Overheating was fixed, for UL listed suppressors, in 1998.

Competently manufactured suppressors engineer the fuses/thermal disconnects to open only when the MOVs fail. (They fail by conducting at too low a voltage and overheating.) w_, apparently, buys only cheap no-brand Chinese suppressors.

I agree this is the way to test a MOV.

The "grossly undersized" red herring again. Grossly undersized applies equally to service panel suppressors, which will also be disconnected if their ratings are exceeded.

w_ believes that plug-in suppressors to not work. Instead of using technical arguments, he doesn't have any, he is using scare tactics.

For accurate information on surges and surge protection read:

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- "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:

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- "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.

The author of the NIST guide, who was the surge guru at the NIST, has said "in fact, the major cause of TVSS [surge suppressor] failures is a temporary overvoltage, rather than an unusually large surge."

-- bud--

Reply to
bud--

This link is an anti-MOV propaganda piece by a manufacturer whose suppressors do not use MOVs.

But removed MOVs are indeed a problem in areas where MOV theft rings are active. Check with your local police to see if there is a ring active in your area.

Lights indicate MOVs have been disconnected. Because MOVs have been disconnected there is no "catastrophic failure".

It is very unlikely the light would be on and the suppressor would not be functioning. (Provide an example of how.)

-- bud--

Reply to
bud--

Bud will not admit the only reason he is here. He promotes for plug- in protectors manufacturers, follows me everywhere posting replies, and now makes a comment that is completely irrelevant to the discussion.

Demonstrated was that lights did not even report missing protection. MOV protectors are removed and light still says protector is OK. The picture demonstrates exactly what we are discussing here. Lights report a failure so catastrophic due to protector being undersized.

The picture demonstrates that the lights will not report all failure conditions. They created a failure and lights said protector was OK. Demonstrated is that lights report only one type of failure - that should not happen and that is too common when plug-in protectors are grossly undersized.

Bud fears you might learn this major problem with plug-in protectors

- undersizing. He will post replies incessantly to confuse you - so that you will also ignore these scary pictures.

These pictures come from sources who are not selling anything - a contradiction to what Bud is doing. Indicator lamps also will not warn of this failure. These scary pictures of current technology plug- in protectors are too common. Threat is not because MOVs are bad. Effective protectors are designed to provide protection; not located in fire risky locations and not to maximize profits:

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Notice the last 'scary picture' - a recent report from the Gaston County Fire Marshall. Why would anyone place these things on a rug or adjacent to desktop papers?

Of course Bud will reply incessantly to get the last word. He must say anything so that your eyes will glaze over; so that you will not remember which MOVs protectors are so ineffective. The indicator light only reports failure when the protector was so grossly undersized that those "scary pictures" were more probable.

Reply to
w_tom

Yes.

1) The mechanism by which they change from high resistance to low resistance requires absorbing energy. 2) Staying in the low resistance mode requires energy absorbtion. 3) Any energy they absorb cannot reach the device(s) they are protecting.

Absorbing surge energy is the only way an MOV can work. It cannot provide protection without absorbing surge energy. That does not mean it absorbs the entire surge energy. Where does the surge energy go? Some is absorbed and dissipated in the source path, some in the MOV and some in the return path.

This is a point w_tom has missed in the past when he insists that point of use MOV's don't absorb surge energy. They most assuredly do. If they did not absorb, they would not switch to low resistance. When they do switch, they absorb I^2R, per ohms law. They clamp the voltage that the device "sees" to some level by absorbing energy. They do not absorb the entire energy that the surge contains - just the amount of energy they "see" that falls into their operating specs.

Nicely stated.

Ed

Reply to
ehsjr

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.

But with no valid technical arguments, w_ has to discredit those that oppose him.

w_ uses google-groups to search for "surge" so he can spread his wisdom, as ehsjr has seen. Unfortunately his wisdom about plug-in suppressors is wrong - read the IEEE and/or NIST guides.

My comment was entirely about the link w_ posted and the point w_ made in his post. My comment was entirely relevant to w_?s post.

It is true. If you cut MOVs out of the suppressor the light will not report the theft. Check for a MOV theft ring in your area.

In the real world, MOVs fail by starting to clamp at line voltage, overheating and being disconnected as required by UL1449 since 1998. The lights indicate a disconnect.

In w_?s mind, plug-in suppressors have miniscule ratings. But plug-in suppressors are readily available with very high ratings for relatively low cost.

The current to a plug-in suppressor is limited by the branch circuit ratings. The energy hit a plug-in suppressor takes from a surge is similarly greatly limited. High ratings mean a suppressor can take a very large number of hits without failing, likely more hits than the suppressor will experience. This allows manufacturers to have a warrantee on the suppressor, and some manufacturers also have a warrantee on connected equipment.

Note that suppressor has to be connected properly. In particular, all interconnected equipment needs to be connected to the same plug-in suppressor, or interconnecting wires need to go through the suppressor. External connections, like phone, also need to go through the suppressor. Connecting all wiring through the suppressor prevents damaging voltages between power and signal wires. These multiport suppressors are described in both guides.

w_?s propaganda picture demonstrates MOVs being deliberately cut out of the suppressor.

In the real world, the lights indicate the MOVs are connected and still providing protection.

The undersized red herring. Buy suppressors with adequate ratings.

The ?old political trick? #2. And zerosurge is selling something and provides propaganda against competing MOV technology.

They warn of a failure unless you have a MOV theft ring in your area.

The lie repeated. The hanford link says overheating was fixed by a revision to UL 1449. That was 1998. w_ has posted no link that says his scare tactics apply to ?current technology plug-in protectors.?

Recent? It is not dated. And does not say there are problems with suppressors produced since 1998.

I recommend people interested in accurate information read the IEEE and/or NIST guides. Both say plug-in suppressors are effective. Neither guide includes w_?s scary pictures. The only 2 examples of surge protection in the IEEE guide use plug-in suppressors.

-- bud--

Reply to
bud--

So let's quote that IEEE guide that shows how plug-in protectors might work AND what happens when it is not properly earthed. Page 42 Figure 8 in

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shows what happens when the plug-in protector does not earth a surge. Due to a plug-in protector too far from earth ground and too close to the TV, therefore the TV earths that surge - 8000 volts destructively.

The effective protector earths surges. The effective protector is not protection. Protection is earth ground. Numbers are posted in reply to above ehsjr's 27 Aug post. In that example, earth may dissipates (absorbs) 60 million or 100 million watts. But what happens to that energy when the protector does not have that 'less than 10 foot' earthing connection. Where is that surge energy absorbed? Bud conveniently forgets that fact.

The protector without properly earthing - on Page 42 Figure 8 - it earths that surge 8000 volts destructively through an adjacent TV. That is effective protection? Bud hopes you ignore what his IEEE and NIST citations state. Protectors work by earthing. No earth ground wire? How then does it earth that surge? It does not. Plug-in protectors don't even claim to provide protection in numerical spec sheets. What kind of protection is that? Ineffective - but so profitable.

Reply to
w_tom

w_tom never said "MOVs do not absorb energy". Even wire absorbs energy - which is what I post everytime in response to ehsjr's intentional misquotes. What are functions of an MOV and of wire? Both are shunt mode devices. Both operate by shunting (diverting, connecting, clamping, conducting) electrical current (and energy) elsewhere. Both absorb energy when performing their job. But neither function is to absorb all energy - as ehsjr repeatedly claimed.

If we increase MOV joules, then MOV absorbs more energy? Of course not. If we increase the gauge of wire, then it absorbs more energy? No. In both cases: as MOV joules and wire gauge increase, then the device absorbs less energy - because that is what we want it to do. The function of wire and MOVs: absorb less energy and shunt more energy.

If MOVs are grossly undersized, then absorbed surge energy increases massively. That unacceptable operation causes an MOV to vaporize. A vaporized MOV exceed manufacturer acceptable ratings. Undersized protectors - too few joules - can also create these scary pictures:

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When too much current passes through an MOV, then its voltage increases. That unacceptable voltage increase is when an MOV is grossly undersized - has too few joules. We increase MOV joules so that an MOV does not absorb more energy; just as we increase wire diameter.

From manufacturer data sheet: An MOV for 120 volt operation rated at 25 joules (241KD09 is an 11 mm MOV disk) see voltage climb quickly past 800 volts during a 2500 amp surge because it is undersized - too few joules. That peak 2 million watt surge dissipated in that MOV means its life expectancy is 1 surge (does not vaporize). If we increase to a 72 joules MOV (241KD18 is a 22 mm disk)). Then a 2500 amp surge creates an MOV voltage of 550; only 1.4 million watts dissipated in that MOV. Larger MOV means increased life expectancy and less energy absorbed by the MOV. Better protectors (more joules) absorb less energy.

What happens if we use five 72 joule MOVs? 110 amps through each MOV means each MOV voltage is 320 volts - 35,000 watts per MOV or

0.175 million watts total. Increasing from 25 joules to 360 joules means MOV absorbs 11.5 times less energy. Meanwhile, the 360 joule protector is now rated for about 3000 surges. Increases joules also means life expectancy increases exponentially.

Why do some foolishly claim a protector is only for one surge? Why did a plug-in protector manufacturer charge so much for so few joules?

When joules increase, MOV absorbs less energy AND MOV life expectancy increases massively. The purpose of an MOV is not to absorb 'more' surge as ehsjr claimed. More joules means the MOV absorbs 'less' energy AND lasts longer - just like increasing wire size.

ehsjr and this poster have argued this for maybe seven years. ehsjr insisted MOVs provide protection by absorbing the entire surge. MOVs do not. Is ehsjr finally backing off that claim?

MOVs are shunt mode devices. Like wires, MOVs are not perfect conductors; absorb a minority of a surge. Whereas that large MOV might dissipate 1.4 million peak watts, a same surge may also dissipate 60 or 100 million peak watts into earth. What makes an MOV effective? Earth ground is the protection. Earth ground is where maybe 40 or 70 times more energy is dissipated.

A protector without earth ground means no effective protection. Earth is where the brunt of a surge energy is absorbed; not inside an MOV as ehsjr once repeatedly claimed.

What makes an MOV effective? MOV resistance drops so that a surge is shunted to and dissipated by earth ground. Demonstrated above is how the 72 joule MOV absorbs 30% less energy compared to a 25 joule MOV. As MOV joules increase, then absorbed MOV energy decreases.

Where is most all surge energy dissipated? Not inside an MOV. Above numbers make that obvious. Effective protection means most surge energy is dissipated in earth. But since MOVs are not perfect, then MOVs (like wires) absorb some of that energy. I was posting this to ehsjr seven years ago. ehsjr still misrepresents what w_tom has posted.

Reply to
w_tom

You most certainly did:

Quoting what you wrote on 15 Apr 2006 00:04:07 -0700 under the subject "Re: surge protector question" in the alt.engineering.electrical newsgroup:

"Shunt mode protectors do not to suppress, absorb, dissipate, or arrest energy as ehsjr repeatedly claims over so many years. "

The full post, including header data, is shown at the bottom, between the lines of asterisks.

You've gone too far with your accusations this time.

You are the master of intentional misquotes. I have never intentionally misquoted you, and I doubt that I have ever done it unintentionally. You have done it often, intentionally.

I have *NEVER* stated that the MOV function is to absorb *all* energy. That is a blatant lie.

What I *have* said, consistently, is that an MOV will absorb whatever surge energy it "sees" at its leads that is within the MOV's specs, until it dies or until the voltage drops below the spec.

Blatant lie. I have *NEVER* said "MOVs provide protection by absorbing the entire surge".

The post I quoted from you at the begining of my reply proves you are the one who misrepresents what you have said. You've hoisted yourself on your own petard.

Ed

***************************************************************************** Subject: Re: surge protector question From: "w_tom" Date: 15 Apr 2006 00:04:07 -0700 Newsgroups: alt.engineering.electrical Path: nwrdny02.gnilink.net!cycny02.gnilink.net!gnilink.net!

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Because "energy will be absorbed & dissipated when current flows through a resistance" then the purpose of wire is to absorb and dissipate electrical energy. Surge protectors, like wire, will dissipate some energy when performing their function: to conduct, shunt, divert, transport that electricity. Shunt mode protectors do not to suppress, absorb, dissipate, or arrest energy as ehsjr repeatedly claims over so many years. Although some energy is dissipated (neither wire nor protectors are perfect conductors), well, a one hundred joule protector will absorb how many joules in a lightning strike? (One joule is one volt and one amp for one second: how many in lightning?) How many joules will that 100 joule protector suppress, absord, or arrest?

A wire diverts (conducts) energy to my vacuum cleaner. How many joules has its power cord suppressed, absorbed, dissipated, or arrested? About 3700 joules. Well that proves it. The purpose of a power cord is to absorb electricity. Meanwhile the power cord carries another 3,456,000 joules into the vacuum cleaner. Irrelevant. That wire dissipated / absorbed energy. Absorbing enery must be its purpose.

When ehsjr posts this same refrain, a credible source is cited in reply. This time the National Institute of Science and Technology is quoted from in their publication 960-6 entitled "Surges Happen! How to Protect the Appliances in your Home.":

ehsjr wrote:

*****************************************************************************

Reply to
ehsjr

Yes - let's cite it *accurately*, and note that when you read all of the information,the IEEE guide clearly indicates that point of use protectors can be of value in protecting your gear. First, figure 8 is on page 33, not on page 42 as you indicated. The last line in the text description for figure 8 says: "A second multi-port protector as shown in figure 7 is required to protect TV2." The last line in the text description under figure 7 says: "The multiport protector shown at the TV set can greatly decrease the voltage between the AC ground and the coax cable, preventing damage to the set."

That is from the IEEE guide you are recommending, and it clearly shows that point of use protectors can be of value in protecting your equipment.

Why don't you read the whole thing? It *plainly* tells you that a second multi-port protector is *REQUIRED*.

Where do you get off stating what Bud hopes?

Again, you bash plug-in protectors, when the very guide you cite says: "The multiport protector shown at the TV set can greatly decrease the voltage between the AC ground and the coax cable, preventing damage to the set." See figure 7, page 32.

Quoting Section 5.1 page 38:

"Most plug-in AC protectors use MOVs rated for 130 V AC RMS, and have a surge limiting voltage of ~330 V peak for the 500A test pulse. So, plug-in protectors tend to provide lower limiting voltages (better protection for equipment) for moderate incoming surges. The gap widens when more realistic surges, and the effects of wiring, are considered."

Repeating for emphasis: *better protection for equipment*.

Continuing the quote: "Section 2.3.2 pointed out how rapidly the lead length raises the effective limiting voltage of hard-wired protectors for large current impulses. For a typical installation with 20 inches (50 cm) leads, the effective limiting voltage at the panel would be ~1160 V for a

10 kA impulse (see Table 1). In a well-constructed plug-in protector, the load is connected directly across the MOVs (Figure 6B), and there should be negligible voltage drop in the MOV leads. So for the same 10,000 A surge current, the load can actually see a ~400?500 V effective limiting voltage (with 130 V MOVs), much smaller than allowed by the hard-wired protector, and much more protective for the equipment."

Repeating for emphasis: *much more protective for the equipment*

Continuing the quote: "Well-designed and well-built plug-in protectors will actually withstand the 10,000 A (8x20 ?s) surge current, and that is rating required by NFPA 780-2004 for plug-in protectors. However, the UL 1449 Standard only requires plug-in protectors to withstand, without damage, ~20 500 A surges. Inexpensive protectors using the 6C type of circuit are designed to respond to overload by opening the protective fusing shown in Figure 6C, sometimes at surge currents barely over the 500 A limit. Because the UL 500 A surge withstand requirements are relatively weak, it is important to have both a hard-wired protector at the service entrance and a plug-in protector at the critical loads."

Repeating for emphasis: *it is important to have a hard-wired*

*protector for the service panel and a plug-in protector at* *the critical loads*

Tom, the guide you cited *clearly* recommends plug-in protectors. It states thay provide better protection. If you are honest with yourself, you will stop bashing them, and perhaps recommend them, as the IEEE guide does, in conjunction with the ideas you have put forward about a single point grounding system with a short, straight connection to an effective electrode grounding system.

Ed

Reply to
ehsjr

Trying to not duplicate Ed?s post -

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 the voltage on all wires (signal and power) to the common ground at the suppressor. Plug-in suppressors do not work primarily by earthing. The guide explains earthing occurs elsewhere. (Read the guide starting pdf page 40).

The illustration in the IEEE guide has a surge coming in on a CATV drop. There are 2 TVs, one is on a plug-in suppressor. The plug-in suppressor protects TV1, connected to it.

Without the plug-in suppressor the surge voltage at TV2 is 10,000V. With the suppressor at TV1 the voltage at TV2 is 8,000V. It is simply a *lie* that the plug-in suppressor at TV1 in any way contributes to the damage at TV2.

The point of the illustration for the IEEE, Ed, and anyone else who can think, is "to protect TV2, a second multiport protector located at TV2 is required."

Because plug-in suppressors violate w_'s religious belief in earthing he has to twist what the IEEE guide says about them.

w_ says suppressors must only be at the service panel. In this example a service panel protector would provide absolutely *NO* protection. The problem is the wire connecting the CATV entry block to the power service is too long, as is the case in many houses. The IEEE guide says in that case "the only effective way of protecting the equipment is to use a multiport protector."

Note that a critical feature of a ?single point ground? is that entrance protectors for CATV, phone, ... connected with a *short* wire to the earth electrode conductor at the power panel. This was violated in the IEEE example above. With a large surge, the house ground will always rise above `absolute' ground. The goal is for the power and CATV and phone 'grounds' to rise together.

According to NIST guide, US insurance information indicates equipment most frequently damaged by lightning is computers with a modem connection TVs, VCRs and similar equipment (presumably with cable TV connections). All can be damaged by high voltages between power and signal wires.

I hope people will read the guides - excellent sources.

w_ has never explained:

- 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"?

The required statement of religious belief in earthing.

The question is not earthing - everyone is for it. The only question is whether plug-in suppressors work. Both the IEEE and NIST guides say plug-in suppressors are effective. Read the sources.

There are 98,615,938 other web sites, including 13,843,032 by lunatics, and w_ can't find another lunatic that says plug-in suppressors are NOT effective. All you have is w_'s opinions based on his religious belief in earthing.

-- bud--

Reply to
bud--

That right. It's important to have hard-wired protector at the service entrance that has that short connection to earth ground. And $2000 or $4000 worth of plug-in protectors? Remember we must install them on dishwasher electronics, dimmer switches, and most critical appliances such as bathroom GFCIs and smoke detectors. Or maybe those critical devices are best protected by a 'whole house' protector that is properly earthed.

As the guide says repeatedly, a protector works by earthing. If the earthing is not sufficient, then how does a plug-in protector put more current into an earth ground what would not accept that current initially? It does not.

How do we make better protection? We enhance what provides the protection. We upgrade the earthing.

Without that 'whole house' protector, then those supplemental protection - plug-in protectors - are not sufficient. How insufficient? Again the scary pictures demonstrate the problem of grossly undersized plug-in protectors you are recommending:

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And that is what the guide is also noting. Plug-in protectors alone are not effective. The guide says plug-in protectors can work IF massive cautions are taken. Meanwhile what does your telco do to operate during every thunderstorm? Do they disconnect their switching computers to protect them from lightning? Of course not. Those computers are connected to overhead wires all over town and must not suffer damage.

They use properly earthed 'whole house' protectors on every incoming wire - and no plug-in protectors. To have effective protection without spending massively, the telco uses a 'whole house' protector AND better earthing.

How did the Orange County FL emergency response center stop damage? They also did not waste money on plug-in protectors that are also a fire hazard. Instead they upgraded the earthing. Why upgrade the earthing? Even the IEEE guide says it. Protectors don't stop or absorb surges as ehsjr had claimed even on 29 May 2005. Earthing provides the protection. Orange County stopped surge damage by not using plug-in protectors AND by enhancing the earthing. They spend money where money would be useful which meant upgrading earthing:

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Why do you recommend protectors that the guide even warns as poor? Meanwhile the IEEE defines the only thing that provides protection in their Red Book (Standard 141) and in many other standards. No they don't recommend plug-in protectors. IEEE recommends the only thing that provides protection - earth ground: :> In actual practice, lightning protection is achieve by the

Yes one can supplement protection with grossly undersized and massively more expensive plug-in protectors. And then the guide also shows why plug-in protectors will fail to provide protection.

Meanwhile Page 42 Figure 8 of the other citation also shows what telcos know. A protector too close to appliances and too far from earth ground many even earth the surge 8000 volts destructively through an adjacent TV. Therefore telcos that operate without damage during every thunderstorm put the protector within feet of earth ground AND up to 50 meters distant from electronics. Why 50 meters? That separation also makes the earthed protector more effective. The protector adjacent to an appliance may even earth that surge destructively through that appliance. How curious. We engineers saw this happen even 20 years ago.

We engineers also knew that protectors do not work by absorbing all the surge energy - as ehsjr repeatedly claimed seven years ago.

Reply to
w_tom

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