1. This forum section is a read-only archive which contains old newsgroup posts. If you wish to post a query, please do so in one of our main forum sections (here). This way you will get a faster, better response from the members on Motherboard Point.

Is it safe to use computer during lightning/thunder storm?

Discussion in 'Laptops' started by Guest, Sep 21, 2004.

  1. Guest

    Guest Guest

    Here in New York City (Manhattan) where I live, I usually use a laptop
    computer running on an AC adapter, and get online via a dial-up modem
    (phone line plugged into computer's built-in modem).

    When it's merely raining outside, it's usually of no concern to me.
    But when there's lightning or thunder, I quickly get offline, turn off
    the computer, and literally unplug the AC adapter from the outlet, and
    unplug the phone line from the computer.

    This is done to avoid the possibility of the AC adapter or the modem
    suffering damage from a voltage spike carried through either the AC
    power line or the phone line (because of a lightning strike).

    Does all this sound sensible to you, or am I being
    overly/unneccesarily cautious?
    Guest, Sep 21, 2004
    1. Advertisements

  2. Guest

    Ron Reaugh Guest

    Not dumb.
    I always do it too.
    Ron Reaugh, Sep 21, 2004
    1. Advertisements

  3. Your precautions are very sensible. Not only is the computer, modem
    and power supply at risk, if you happen to be near a ground
    connection, your body is at some risk, also.

    However, there is a simple precaution you can take that makes it much
    safer to use your computer during a rain storm. Get a filtered, surge
    suppressed power strip that has both receptacles and phone line
    sockets. The surge suppressers help limit the voltage peaks between
    any of the incoming power lines, which protects the supply, but also
    limits the peak voltage between the phone lines and the power ground,
    protecting both the modem and you from anything but a very close
    strike. I still wouldn't use it in the bath tub, though.

    Here is an example of one without a low pass filter (just surge
    And a bigger unit that includes the RFI filter (that improves the
    operation of the surge suppression a bit).

    I am not endorsing these particular products, just using them as
    examples of what I am talking about.
    John Popelish, Sep 21, 2004
  4. Guest

    Odd Bob Guest

    Very wise. A couple years back I had a modem fried by a nearby
    lightning strike and I'm grateful that's all that was fried. These days
    if I even think I hear thunder I pull all the plugs and go read a good
    book. My suggestion, anyway...

    -- Bob
    Odd Bob, Sep 21, 2004
  5. Guest

    Sporkman Guest

    The greatest danger is from your modem. Surges coming in through
    telephone lines can do quite a bit of damage. In fact, I've had
    desktops almost completely smoked via the modem. Fried the motherboard,
    video, AND drives (both CD and HDD). Spared the RAM and the power
    supply and not much else. And yes, it is absolutely certain that it was
    through the telephone line, not through the power line. Surge
    suppressors and uninterruptible power supplies MAY protect from
    telephone line surges well enough, or they may not. After having a
    computer smoked and having seen my neighbor's computer smoked in the
    same way I stopped using internal modems altogether, but of course
    external modems are seldom used with a laptop. Your computer power
    supply will possibly protect your laptop well enough from power surges
    with sacrificial diodes in the rectifier circuit, but it's a better bet
    to unplug and run off the battery. I'm sure you don't want to even have
    to buy a new AC supply for your laptop. Those can be expensive,
    although Radio Shack carries AC supplies that MAY be enough for your
    computer (mine actually requires more amperage than the RS model can
    supply on startup, and if the battery is down the thing won't boot).

    Mark 'Sporky' Stapleton
    Watermark Design, LLC
    Sporkman, Sep 21, 2004
  6. Guest

    Bigbazza Guest

    How about 'Cable Broadband ' delivery...Obviously a 'Telephone' is not
    used..But cable is !...So do I need to turn my Cable Modem off as well ..or

    Bigbazza, Sep 21, 2004
  7. Turning it off would help. but _very_ little. Unplugging it would be the
    correct thing to do. I"ve had more analog modems fried by lightning (4) then
    cable modems (2) but you can see, it happens. Personally I don't bother with
    unplugging the cable modem as Brighthouse really does not have a problem
    replaceing them with no charge.
    Todd Copeland, Sep 21, 2004
  8. If you live in a densely populated city and all these cables come through
    underground cables there is very little risk for damage from lightning.

    The high voltages from a lightning must then travel long distances
    through underground cable systems, and the power is distributed among
    thousands of end users connections.

    There is probably also good protection systems in place to protect
    against overvoltage conditions.

    Earlier I lived in a small old house on top of a mountain, with
    electricity and phone lines coming through the air, wires on poles.

    Now that was a risky place to live at during lightning storms!

    And there was often lightning hits even on clear days,
    without any warning signals in the weather at all.

    I have had my telephone practically explode a few feet from my head, and
    I have had lots of equipment destroyed.
    Mainly modems and tv sets but also other stuff.

    Then I installed some protection components, spark gap devices, on both
    the electricity and phone lines. Where the lines enter the house and
    inside the house, close to the computer and tv set too. I also increased
    the lightning protection for the house with lightning rods and lots of
    wires in the ground around the house to absorb the power better.

    That helped a lot, and I had no equipment destroyed for those 6 years
    I lived there when I had the protection components installed.

    Compared to my house on a mountain you are very well protected in a
    densely populated city with underground cable systems for electricity,
    phone lines, cable tv and cable internet.

    A lot of people have a situation somewhere between these two extremes,
    big city or mountain top, and may want to take necessary precautions.

    The easiest way to add protection to vital equipment is to put all of it
    on an extension cord with multiple outlets and add protection circuits to
    that extension cord system. Make sure that both phone connection and
    electricity connection are protected where they enter that extension cord
    Roger Johansson, Sep 21, 2004
  9. No, very sensible!

    About a year ago, we had a thunder storm where a bolt of lightening actually
    struck our back garden. The PC in the office was protected by a UPS /
    filter, but the DSL connection through the phone line and the external
    modem/router weren't protected. The lightening fried the modem and the
    network card in the PC! Fortunately the rest of the PC was ok.

    Now, the PC is protected by a UPS, and the modem/router's phone connection
    is filtered through a surge protection device.

    Code Developer, Sep 21, 2004
  10. Sounds sensible to me. You could also try getting a good surge protector.
    Then you won't have to unplug everything. I would make sure that the phone
    cable also runs through the surge protector or unplug it.
    Alex Rodriguez, Sep 21, 2004
  11. There are 3 potential failures here:
    o Data-corruption from power failure
    ---- for a laptop this risk is removed (usefully :)
    o Modem is damaged thro telco system
    ---- not impossible even in NYC, not uncommon in rural or elsewhere
    ---- for an onboard modem you 1) lose your modem or 2) lose the laptop
    ---- both of which involve downtime & expense
    o Computer is damaged through mains system
    ---- lightning will happily hit buildings, then run thro mains systems

    It's not uncommon for lightning some distance away to cause line-drops,
    as well as major power dips (brownouts/sags) and surges. Computer PSU
    are switched-mode PSUs so tolerant of large variations in power, but that
    is not a guarantee where lightning is concerned.

    Telephone cables often run outside a building, along walls, which can be
    interesting re picking up voltage from lightning or attraction.

    When lightning appears to have gone, remember it can still strike some
    distance from the originating storm - even in blue-sky. That is how most
    people are struck by lightning, and potentially buildings, power poles etc.

    If your power comes in thro a pole transformer, and same for telco, then
    local lightning can pose a serious risk to both power & telephone services.
    Colleague lost the corner of their tiny sub-let warehouse last year due to
    a lightning strike - what wasn't burnt was electrically damaged.

    So whilst it may seem old-fashiooned, it's not a bad idea.
    Certainly unplugging the telco connection. In the UK the master telco socket
    has a GDT, gas discharge tube, but if lightning is close they're a bit useless.
    If something nearby is hit, the surge protectors can save a modem etc,
    but a direct or very close strike will generally take out anything re energy.
    Dorothy Bradbury, Sep 21, 2004
  12. Guest

    w_tom Guest

    A wide variety of good responses and outright myths. Some
    just post answers without even providing a single reasons
    why. Those posters are particularly insidious and typically
    respond with insults.

    Turning something off will not help. Destructive surges
    were not stopped or absorbed by 3 miles of air. Why then will
    millimeters inside a switch do what miles of air could not?

    In the early days of ham radio, equipment would suffer
    lightning damage. Antenna lead was disconnected and even put
    inside a mason jar. Damage finally stopped when the antenna
    lead was connected to earth ground. They only rediscovered
    what Ben Franklin demonstrated in 1752. Lightning seeks earth
    ground. If not earthed before entering a building, then
    lightning will seek earth ground, destructively through

    Some will claim that a plug-in protector would help. Again,
    plug-in protector will stop or block what miles of air could
    not? So very quietly, those plug-in manufacturers forget to
    mention they don't even claim to protect from that destructive
    type of surge. Obviously. No dedicated earth ground. They
    just let others assume all surges are the same type.

    Industry professionals demonstrate how protection is
    installed as it was proven before WWII on the Empire State

    Two structures each with their own single point earth ground.
    Any wire entering each structure first makes a connection to
    that earth ground. Connection either by a hardwire or via a
    surge protector. Notice what an effective surge protector
    does. Makes a temporary and short connection to earth ground
    during a surge.

    Also notice the buried phone wire in that figure. Even
    underground wires must first connect to that single point
    earth ground. Yes even underground wires will carry
    destructive surges inside a building.

    So what can you do? Protection is a building wide
    solution. However if your circuit breaker box is 'earthed'
    (connected) to building steel, then it already has an
    excellent single point ground. Breaker box then gets a 'whole
    house' protector so that surges entering on AC mains are
    immediately earthed long before they can get to your
    computer. Most destructive surges - especially to modems and
    portable phone base stations - are incoming on AC electric.

    Same applies to phone line. But phone line already has an
    effective protector provided free by the telco because 'whole
    house' protectors are so effective and so inexpensive. Cable
    company is also required to bond to earth ground where cable
    enters the building. Cable requires no surge protector
    because cable can make a direct (hardwired) connection to
    earth ground.

    All electronics contains internal protection. Anything that
    is effective on an appliance power cord would already be
    inside the appliance. But that internal protection assumes
    destructive transients are earthed before entering a
    building. Earthed transients will not overwhelm protection
    already installed in appliances. Again, protection that has
    been proven repeated in virtually every town for so many
    decades. Protection that does not use plug-in protectors.

    Do not fall for urban myths that a UPS or power strip will
    filter or stop surges. Again, a 1 inch component will stop
    what miles of sky could not? Of course not. A UPS will stop
    or filter a surge? Franklin did not stop or absorb
    lightning. He shunted (diverted, connected) an electrical
    transient to earth so that it did not seek earth ground via a
    church steeple. Effective protection inside telephone
    switching centers, 911 emergency response centers, and even in
    grocery stores do same.

    A telephone switching center connected to overhead wires
    everywhere in town does not unplug during thunderstorms. And
    yet that is what your are being told. They simply connect
    every incoming wire to single point earth ground where wires
    enter the building. Protection that is best located 50 meters
    from computers.

    The plug-in protector does not even claim to protect from
    the destructive type of surge. It claims to protect from
    surges that don't typically exist. Myth purveyors then assume
    protector protects from all kinds of surges - not knowing that
    different types of surges exist.

    Plug-in manufacturer encourages others to play word games as
    if it was technical fact. Surge protector and surge
    protection are same? No. All protection 'systems' require
    surge protection - earth ground. Only some incoming utilities
    require a surge protector to connect to surge protection. A
    surge protector is only as effective as its earth ground.
    Plug-in protector manufacturers even avoid discussing earth
    ground. Telling the 'whole truth' would only hurt profits.
    Effective protection is a 'whole house' protector. Therefore
    internal appliance protection will not be overwhelmed. A
    surge protector is only as effective as its earth ground.

    Recommended is a 'whole house' protector at AC mains
    electric box. That is effective protection for about $1 per
    protected appliance.
    w_tom, Sep 21, 2004
  13. A good surge protector contains one or more of these components:

    A spark gap device, also called ComGap, which allows overvoltage, charge,
    to jump to the earth connection.

    A VDR which is slower than the Comgap, but it lowers the voltage to zero,
    which protects the Comgap, this is needed if we are talking about a mains
    wire, because mains delivers current until the mains cycle reaches the
    zero crossing, and this current hurts the Comgap device.

    A Comgap needs to be used in series with a resistor, a big mass type
    resistor, value 20 Ohm or so. The VDR is used in parallell with this
    Comgap-resistor combination.

    To make the protection better one can use small coils in the signal/mains
    way, after the comgap. The coils stop fast voltage changes and make the
    comgaps take the charge instead.

    The comgaps and the VDR:s need to have the right voltage, 450Volt for a
    240Volt mains wire, a 140Volt for the phone line.

    It doesn't hurt the computer and other devices if the voltage is raised a
    thousand volts for a short moment, as long as all connections to it are
    raised together. So the surge protector only has to keep all connections
    at fairly the same voltage, even if they all are raised momentarily. What
    really hurts the equipment is if one of the connections moves far away
    from the other connections, because then there is a surge inside that
    piece of equipment, burning some component to pieces.

    That is why the extension with outlets protected by a surge protector
    works. It creates a subsystem which is kept together at virtually the
    same potential for all connections to that subsystem.

    When a modem is hurt by the lightning it is because the mains connection
    to it and the phone connection to it are pulled apart by thousands of
    volts, and that creates a damaging surge inside the modem.

    If both the mains and phone line connections to the modem first have to
    pass through a protector box, where they are prevented from moving apart
    too much, voltage-wise, the modem is protected.
    Roger Johansson, Sep 22, 2004
  14. Guest

    w_tom Guest

    An adjacent surge protector contains a device that does not
    stop surges. It simply shunts all wires together during that
    surge. A surge shunted from one wire to all others goes
    where? Remember, the destructive surge seeks earth ground.
    It now has more paths to find earth ground, destructively, via
    the adjacent computer. What kind of protection is that
    adjacent protector? Ineffective.

    Telcos prefer their protectors located 50 meters from a
    $multimillion switching computer. Protectors adjacent to the
    computer might only shunt the surge to earth through that
    computer. Many cable companies now add additional
    restrictions to how cable is installed. Connection from cable
    to earth ground must be significantly shorter than connection
    from same point to TV or cable modem. Why? Effective
    protector is distant from transistor and adjacent to earth

    A surge protector is only as effective as its earth ground.
    Effective protectors make a 'less than 10 foot' connection to
    earth. No plug-in protector will make that connection. Just
    another reason why plug-in protectors are so ineffective.
    Just another reason why plug-in protector manufacturers avoid
    all discussion about earthing. They don't claim to protect
    from that type of surge.

    Your example of an adjacent power strip protector works IF
    destructive surges are normal mode. Destructive surges are
    longitudinal mode. That means a surge shunted by the power
    strip will seek many paths back to earth ground - including
    destructively through a computer modem. The resulting error
    message may be 'No Dialtone Detected'.

    Damage you demonstrate inside a modem is classic of a surge
    that enters on AC electric. Remember primary school science.
    First electricity must flow through everything in that
    circuit. Only later does something fail. A complete circuit
    from cloud to earth is fully energized. Then the modem
    fails. Classic modem damage is a surge that enters on AC
    electric, passes through modem, then outgoing to earth ground
    on phone line. This surge often damages the modem's DAA
    section - the phone wire side of modem.

    Many assume surges act like ocean waves. The surge destroys
    the first component encountered? Of course not. Surge first
    travels through everything in the circuit. Only then does
    something fail. A failed DAA section does not say where surge
    comes from. But many will tell us the surge ignored a telco
    installed 'whole house' protector to enter modem via that
    phone line. Why does surge completely ignore the phone line
    'whole house' protector? Because many don't even know the
    protector exists.

    Surge enters on utility wire that has no 'whole house'
    protector - AC electric. It then leaves (makes a complete
    electrical circuit) by leaving - going to earth ground - via
    phone line.

    How does the phone line surge completely ignore a telephone
    company installed 'whole house' protector? It must to enter
    on phone line.

    Your theory is good IF surge is normal mode.
    Manufacturer's specifications claim to protect from normal
    mode transients. Problem is that destructive surges are not
    normal mode. So manufacturer forgets to mention two things:
    1) plug-in protectors don't provide protection from the
    typically destructive type of surge and 2) earth ground. By
    forgetting to mention other types of surges, they have
    promoted protection myths. Many then *assume* it protects
    from all types of surges.

    Destructive surges must be earthed before entering a
    building. Then protection internal to all household
    appliances will not be overwhelmed.

    Let's see. We spend $15 or $50 to protect only one
    appliance. What protects smoke detectors, intercom,
    dishwasher, etc? Effective 'whole house' protector costs
    about $1 per protected appliance. Furthermore it provides
    protection from all types of surges. Plug-in protectors don't
    make such claims.

    Your example only demonstrate that plug-in protectors work
    as speced. Your example forgets to discuss the type of surge
    that typically damages electronics. All appliances contain
    any protection that is effective adjacent to appliance.
    Internal protection that requires 'whole house' protection on
    every utility wire where that wire enters building.

    Why are plug-in protectors often so undersized - have so few
    joules? They are not really selling effective protection.
    Why waste good money on more parts - more joules? Profit -
    not protection - is the agenda with plug-in protectors.

    Those who know surge protection do not speak of Tripplite,
    Panamax, Belkin, or APC. They discuss a benchmark in surge
    protection - Polyphaser. Polyphaser application notes are
    legendary. Polyphaser makes a protector that has no
    connection to earth ground. Distance to earth ground is so
    critical that the Polyphaser protector sits directly ON earth
    ground. That is zero feet to earth ground. Distance to earth
    ground is that critical to effective protection. No earth
    ground means no effective protection. So plug-in
    manufacturers avoid the whole earthing topic all together to
    sell their ineffective products. A surge protector is only as
    effective as its earth ground.
    w_tom, Sep 22, 2004
  15. Guest

    Shawn Hearn Guest

    The odds of a lightning strike doing any damage in a densely populated
    region such as Manhattan are astronomically slim. If I lived in that
    area I wouldn't worry about it. There are so many tall buildings in
    Manhattan to attract lightning and the majority of them probably have
    lightning rods on them.

    The situation in a rural area is different. I once had some electronic
    equipment fried by a nearby lightning strike a few years ago in a
    suburban Philadelphia home.
    Shawn Hearn, Sep 22, 2004
  16. Guest

    Shawn Hearn Guest

    The average person does not have a "good surge protector."
    Shawn Hearn, Sep 22, 2004
  17. I feel like I am discussing loudspeaker cables with an audio hi fidelity

    You obviously do not understand what I am saying, but you have a lot to
    say about special modes, earth connections and special brands, which
    doesn't make sense from a scientific point of view.

    You do not have an education in electronics, but you have a brain filled
    with blurb from advertisements.
    Roger Johansson, Sep 22, 2004
  18. Guest

    w_tom Guest

    If you don't understand normal and longitudinal mode, then
    you do not even have first year engineering knowledge. People
    with insufficient knowledge that can promote myths about
    plug-in protectors. If you think that power strip surge
    protector provides more than normal mode protection, then
    simply cite the manufacturer's spec. I state this knowing
    full well there is no such spec. Manufacturer does not even
    claim to provide that protection. Why then would you? You
    are confusing normal mode with longitudinal mode.

    Lets put numbers to your previous example. Lets say a small
    (100 amp) transient approaches your power strip surge
    protector. Let's say the wall receptacle connects to breaker
    box with 50 feet of 12 AWG wire inside walls. Now let's
    assume your power strip protector shunts all 100 amps to wall
    receptacle safety ground. That 50 foot wire is less than 0.2
    ohms resistance. But to the transient, it is something on the
    order of 130 ohms impedance. Basic engineering. Wire has
    impedance. 100 amps times 130 ohms puts the power strip
    protector at something less than 13,000 volts. Will that
    13,000 volts try to obtain earth ground via 50' safety ground
    wire? Of course not. It will seek many other paths to earth
    ground. One destructive path is via computer modem and
    telephone wire.

    So what has that power strip surge protector done? Again,
    nothing complex here. The concepts only require first year
    engineering. That power strip has shunted the 100 amp surge
    from black hot wire onto all other wires. It has contributed
    to damage of an adjacent and powered off computer.

    I don't understand why you have so much difficulty with the
    concept; assuming you have engineering training. These
    numbers only demonstrate what has been well understood for
    generations. Surge protection has always been about earthing
    a surge before it can enter a building. Need I again cite how
    telephone switching centers are constructed so as to not
    suffer surge damage. Need I again cite the legendary
    application notes of Polyphaser? What advertisement? Anyone
    familiar with real surge protector knows this name as an
    industry benchmark:

    Or maybe the National Institute of Science and Technology
    might help. They are not advertising. Their figure is used
    to demonstrate how a fax machine is protected or may be
    damaged. Again 'whole house' protector and the all so
    critical single point earth ground:

    Yes, you made a good case for normal mode protection. But
    that is not the type of surge that typically damages
    electronics. How many industry professional citations need I
    provide? A surge protector is only as effective as its earth
    ground. A fact well proven even before WWII.
    w_tom, Sep 22, 2004
  19. Guest

    Rich Grise Guest

    An apartment I was living in once took a direct hit. It's pure dumb
    luck that I had unplugged the modem - it took out the answering machine
    and a desk phone. It also blew out a couple of exit lights - the
    manager said there was a total of about $7,000 damage from that one

    So, if it's actively lightninging, you're not being overly/unneccesarily
    cautious to unplug stuff. It also took out the on/off transistor in
    the TV, so the remote wouldn't turn it off any more. I had to get up
    and walk to the TV, until I got it fixed, of course. I took it to
    the shop, and asked how much a diagnosis was, which was about $35.00,
    and the repair would have been about $85.00, so I just asked the tech
    to mark the transistor so I could replace it myself. I had to rearrange
    the leads on a plastic 2222, but it fixed it. :)

    Rich Grise, Sep 22, 2004
  20. A lot of useful information in these links, but you still need an
    education in electronics to fully understand that information.

    Like Henri Poincare said: Facts are just the building blocks of science,
    you need to know how to build them together, you need models and
    theories, that is real science.
    "Ground Potential Rise (GPR)", is used a lot on the Polyphaser web site.
    If you understood what it means you would not write about "sitting ON
    earth", as you did in your earlier message, because no point can be
    exactly "on earth" during a thunder storm. All points are moving
    voltage-wise, so you have to choose a suitable moving point and use it in
    a proper way.

    As I stated earlier, the important thing is not to keep everything
    exactly at earth potential, because that is impossible, read about GPR,
    the important thing is to prevent different parts of the system from
    moving too far apart voltage-wise.
    And that is what we use spark gaps and other devices for.
    This can be done for a whole building or for subsystems within a building.
    Roger Johansson, Sep 22, 2004
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.