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MOVs and surge suppressors

Discussion in 'Electronic Basics' started by [email protected], Aug 22, 2007.

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  1. Guest

    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?

  2. Phil Allison

    Phil Allison Guest

    ** 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
  3. Rich Grise

    Rich Grise Guest

    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.

  4. 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).

  5. ehsjr

    ehsjr Guest

    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.

  6. Phil Allison

    Phil Allison Guest

    "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
  7. w_tom

    w_tom Guest

    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

    Another problem when that fuse does not disconnect fast enough: Protectors.pdf or SURGE SUPPRESSOR FIRES.doc

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

    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.
  8. w_tom

    w_tom Guest
    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.
  9. Guest

    Thanks, everyone.
  10. bud--

    bud-- Guest

    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: Guide_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:
    - "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."
  11. bud--

    bud-- Guest

    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.)
  12. w_tom

    w_tom Guest

    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

    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

    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: Protectors.pdf
    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.
  13. ehsjr

    ehsjr Guest

    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.

  14. bud--

    bud-- Guest

    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.
  15. w_tom

    w_tom Guest

    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 Guide_FINALpublishedversion_May051.pdf
    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
  16. w_tom

    w_tom Guest

    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

    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: Protectors.pdf or SURGE SUPPRESSOR FIRES.doc

    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

    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

    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
  17. ehsjr

    ehsjr Guest

    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 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.


    Re: surge protector question
    "w_tom" <>
    15 Apr 2006 00:04:07 -0700


    <> <[email protected]>



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    X-Trace: 1145084652 7683 (15 Apr 2006 07:04:12 GMT)

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    Sat, 15 Apr 2006 03:04:12 EDT (

    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

    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.":

  18. ehsjr

    ehsjr Guest

    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

    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 μs) 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.

  19. bud--

    bud-- Guest

    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
    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
    - Why does the NIST guide says plug-in suppressors are "the easiest
    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.
  20. w_tom

    w_tom Guest

    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: Protectors.pdf or SURGE SUPPRESSOR FIRES.doc

    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:

    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.
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