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PCs plugged into power strip into ungrounded GFCI?

Discussion in 'Electronic Basics' started by jim, Jun 19, 2006.

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  1. jim

    jim Guest

    This is an electronics basic noob question to be sure.

    I'm moving into a place that only has two pronged (presumably
    ungrounded) outlets.
    I'm trying to figure out if I will have to go back to the stone ages or
    if I can run my PC's and router/firewall in this home?

    My thinking is that I can replace the two pronged outlets with
    ground-fault circuit interrupters and then plug power strips into
    those.

    Is this a sensible solution or am I asking to burn the house down
    around a fried motherboard?

    If it is the later could anyone advise me on a way to work in an older
    home?

    jim
     
  2. Ralph Mowery

    Ralph Mowery Guest

    Sure you can run the computer. The surge supresser/power strips will not be
    as effective as if you had a third wire ground. YOu could install a whole
    house protector at the fuse/braker box. A UPS would go a long way toward
    protecting the computer and other electronic equipment that is plugged into
    it.
    You really need a 3 wire system for the GFI to add much protection to the
    electronics, and that is not going to do much either way for equipment
    protection.
     
  3. jim

    jim Guest

    Huh?

    This is a rental and tearing up the walls to add a third wire earth
    ground isn't an option.
    As I understand it the danger of running a PC off an ungrounded outlet
    is that any voltage leaks in an unbalanced system will try to find a
    place to go and a metal PC (power supply, case frame, case) are the
    nearest place to hang out, causing anyone who touches the case to catch
    the volt - not to mention frying the innards of the PC.

    So sans a ground in the outlet will a GFCI protect the PC from getting
    fried? I thought that if there was a voltage difference between the
    neutral and the hot wire the GFCI would trip and shut down.

    Furthermore the surge protector would be a second line of defense for
    the PC.

    Is this correct?
    I'm not thinking worst case scenario here where my PC is hit by
    lightning or anything like that so a UPS seems over the top (read, I
    can't afford one).

    Jim
     
  4. w_tom

    w_tom Guest

    Tearing up the walls is only for safety ground. Earth ground is
    another connection from breaker box to earth.

    They are called shunt mode protectors. They protect by shunting
    (diverting, connecting) destructive transients to earth. But if no
    earth ground exists, then no effective protection. Furthermore, a
    shorter path to earth (and farther from appliances), then enhanced
    protection. Responsible manufacturers such as Leviton, Siemens, GE,
    Cutler-Hammer, Intermatic, and Square D make those more effective
    'whole house' protectors. What makes them effective? Breaker box
    should meet and exceed post 1990 National Electrical Code earthing
    requirements. And all other incoming utilities should also connect to
    this same earthing electrode.

    Notice that superior protection is provided with two wire or three
    wire wall receptacles. It does not care because the destructive
    transient is shunted to earth before getting to those wires. Notice
    what the plug-in protector quietly forgot to mention - earth ground.

    'Whole house' protector is so effective and so inexpensive as to even
    be installed on pone lines. But again, that protector will only be
    effective if also connected 'less than 10 feet' to the same earth
    ground that also conforms to post 1990 code.

    Earthing is your line of defense. Each layer of protection is
    defined by earthing and how each utility wire connects to earth (ie via
    the 'whole house' protector). Above defines secondary protection.
    Primary protection should also be inspected:
    http://www.tvtower.com/fpl.html

    Inspect the primary layer protection. Inspect or install earthing
    for the secondary protection layer. BTW, the reason protection is
    installed is so that lightning damage is made irrelevant. What does
    lightning seek? Earth ground. Why are Ben Franklin rods struck,
    suffer no damage, and provide effective protection? Again, they are
    only as effective as their earth ground. Earthing defines the
    protection even from direct lightning strikes. Look at numbers on
    those 'whole house' protectors - those are numbers for earthing
    lightning.
     
  5. Ralph Mowery

    Ralph Mowery Guest

    I think I understand what you are asking now. Without the ground wire going
    to the case, a short from the hot wire to the case could be dangerous to
    you. Unless there is a current unbalance such as if you have the
    router/cable modem connected to the earth by the coax comming into it, the
    GFCI will not trip to save the computer as the current going out the hot
    wire is the same as the current comming back down the neutral wire. The
    GFCI will protect you if the hot wire shorts to the case and you touch the
    case while you are grounded.
     
  6. jim

    jim Guest

    So now I am more confused.
    I thought that two pronged outlets were ungrounded.
    But you say that they might be grounded; either through an earth ground
    at the breaker box or some other form of ground fault circuit
    interrupter at the breaker box.

    How do I tell if these two pronged outlets are in fact grounded and if
    they are how should I best plug in a PC or a surge protector - by
    replacing the outlet with...What?
    If there isn't a ground wire running through the walls putting in a
    regular three pronged outlet would be useless, except that the PC power
    cable would fit.

    Jim.
     
  7. ehsjr

    ehsjr Guest

    1) The operation of a GFCI does not depend on the GFCI being
    connected to ground.
    2) A GFCI is intended to protect people, not equipment. It is
    used for *your* safety, not the safety of the attached equipment.
    3) The installation of a GFCI receptacle on an ungrounded
    circuit is permitted, and is a good way to enable the use
    of 3 prong plugs. It does not provide the same electrical
    function as grounding.


    I thought that if there was a voltage difference between the
    No - if there is a *current* difference greater than ~ 5mA
    the GFCI will trip. There is always a voltage difference
    between neutral and hot of ~ 120 volts (in the US) in a
    properly operating circuit.
    You seem to think the GFCI is a first line of
    defense for the PC - that is wrong. The GFCI
    provides no defense for the PC - it allows
    you to plug in the 3 wire PC cord, and protects
    you from a fault current should the PC case
    become electrically "hot".
    And since it is an apartment, you can't put in a whole
    house surger protector or re-wire. So the only thing
    you can do for PC protection is install point of use
    surge protectors.

    Ed
     
  8. w_tom

    w_tom Guest

    I never said those wall receptacles are grounded. I said, to have an
    effective protector, the breaker box must be earthed so that a 'whole
    house' protector has an earth ground. An earth ground, not to be
    confused with safety ground that does not exist in two wire
    receptacles.

    To protect appliances from being fried (from transients), breaker
    box must be earthed. Then a 'whole house' protector will have an
    earthed connection so that computer, et al is not fried. Surge
    protectors earth a transient. Obviously wall receptacles have no
    ground whatsoever. Therefore how can they earth transients? They
    cannot.

    Ground fault interrupter was implied as a type of ground. It is not.
    GFCI is for human safety and can provide that safety even if safety
    ground does not exist in that wall receptacle. Notice a difference
    between safety ground and earth ground; and different functions of
    those grounds: human safety and transistor safety. Function of a
    safety ground is human safety. But a GFCI without safety ground may
    also provide that function.

    The only way to convert a wall receptacle to three prong is to either
    route a ground wire to that receptacle OR install a GFCI (with
    appropriate warning label that says No Equipment Ground).

    GFCI (like fuses) does nothing for transistor safety. In fact, such
    devices (such as fuses) will blow after transistor damage so that the
    damage does not threaten human life (ie create a fire).
     
  9. jim

    jim Guest

    So
    So without the whole house protector (the ground wire running through
    the house to each outlet) There is no way to achieve computer or
    transister protection. Correct?

    This will not protect a computer correct?

    Jim
     
  10. w_tom

    w_tom Guest

    Again wire running to wall receptacles has no relationship - is
    irrelevant to - a 'whole house' protection system. There is a
    protector. Where is it located? At breaker box. OK. A shunt mode
    protector needs a short connection to earth. Fine. Post 1990 NEC
    requires an earthing connection adjacent to breaker box. Now that
    protector is earthed - is made effective.

    What does a shunt mode protectors do? It either connects a transient
    to earth or it provides ineffective protection. Do you have earthing
    wires in wall receptacles? No. Is that earthing connection short (ie
    'less than 10 feet'). No. Two reasons why shunt mode protector are
    ineffective when plugged into wall receptacles.

    There are series mode protectors. But again, that means building
    earthing must be upgreaded to post 1990 code requirements. Even if
    wall receptacles remain two wire, still, effective protection even
    using series mode protectors means earthing at service entrance must be
    upgrade. Must meet and exceed post 1990 requirements AND all other
    incoming utilities must also connect short (ie 'less than 10 foot') to
    that same earth ground.

    Earthing is where all transient protection starts. Does this exactly
    answer your question? No, because your question is chock full of
    assumptions. However where do you start with electronics protection?
    Earthing. Don't worry about interior wires for transient protection.
    Transient protection is where utilities enter a building (secondary
    protection) AND where utility also earths (primary protection as
    demonstrated in www.tvtower.com citation).

    The other issues include human safety. That issue completely
    different from transistor safety and answered previously - including a
    GFCI option.
     
  11. Bud--

    Bud-- Guest

    That is what w_tom says, but the IEEE and the NIST both say plug-in
    surge protectors are effective.

    The best information I have seen on surge protection is at
    http://www.mikeholt.com/files/PDF/LightningGuide_FINALpublishedversion_May051.pdf--
    - w_tom provided the link to this guide
    - the title is "How to protect your house and its contents from
    lightning: IEEE guide for surge protection of equipment connected to AC
    power and communication circuits"
    - it was published by the IEEE in 2005
    - the IEEE is the dominant organization of electrical and electronic
    engineers in the US
    - the 5 authors have broad experience with surge suppression

    Another reference is
    http://www.nist.gov/public_affairs/practiceguides/surgesfnl.pdf
    - this is the "NIST recommended practice guide: Surges Happen!: how to
    protect the appliances in your home"
    - it is published by the National Institute of Standards and Technology,
    the US government agency formerly called the Bureau of Standards
    - it was published in 2001
    - it was writen by Francois Martzloff - the NIST guru on surges and
    lightning

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

    Both say plug-in surge suppressors are effective.

    Plug-in surge suppressors clamp the voltage between the wires. Earthing
    is secondary. This is clearly described in the IEEE guide. Without a
    ground wire, some earthing will still occur on the neutral back to the
    service panel. Not desirable, but you work with what you have or change
    it. As ehsjr said "the only thing you can do for PC protection is
    install point of use surge protectors". With no ground you still need a
    GFCI.

    A phone line connection to a computer can be a surge entry point if the
    ground reference between the power connection and the phone diverge. The
    best solution is a surge reference equalizer, described in the IEEE
    guide (multi-port protector in NIST). These would be unwise without a
    power ground wire. Unplugging the phone line when not in use would be a
    good idea. Or unplug phone AND power.


    bud--
     
  12. w_tom

    w_tom Guest

    IEEE and NIST 'introduce' various types of protectors. A plug-in
    protector may be effective IF all six ports area integrated into 'SRE
    protection'. You don't know what SRE is? Important if plug-in
    protector is to be effective. But another fact that Bud would have you
    believe you need not know.

    Details in Bud's citations demonstrate again and again why plug-in
    protectors don't provide effective protection. For example, two TVs at
    8000 volts because a transient was not earthed? Somehow that will
    never create damage? Nonsense. Instead everything in that room must
    be part of a faraday cage so that 8000 volts is not destructive. Do
    you know how to reconstruct a room to be a faraday cage? If so, then
    the plug-in protector could be effective. Show me a layman who knows
    how to reconstruct each room to be a faraday cage? Bud may call that
    effective. But I call a protector that requires room reconstruction
    and advanced engineering knowledge to be ineffective. Ineffective
    especially since those same dollar bills can install the effective
    'whole house' protector. Especially when those same dollar bills can
    make a 'whole house' protector even better by enhancing / expanding a
    critical and essential earthing system.

    NIST / IEEE does not recommend as Bud assumes. Those papers define
    various protector methods. Those same papers also include paragraphs
    that define superior protection methods such as:
    And this quote directly from Francois Martzloff - Bud just forgets to
    tell whole truths:
    Meanwhile, Bud cut and pastes this same claim everywhere. He ignores
    the many reasons why plug-in protectors fail - in his own citations.
    Some above quotes are from his citations. They demonstrate significant
    electrical engineering caution necessary when the plug-in protector has
    no short (ie 'less than 10 foot') connection to earth.

    They are called shunt mode protectors. They are effective when they
    shunt the surge into earth. So plug-in protector manufacturers don't
    discuss earthing. You might learn why those plug-in protectors are not
    effective. They don't even claim to provide protection from typically
    destructive surges in their own numerical specs. Why would they be
    effective when even the manufacturer does not make that claim? Bud
    knows why. It's in is own IEEE / NIST citations that also
    demonstrate why plug-in protectors are not effective; can even
    contribute to damage of the adjacent appliance.

    Effective protection earths before those destructive transients can
    enter the building. That also defined by Bud's own citations.

    Meanwhile effective protectors are sold by more responsible
    manufacturers such as Leviton, Intermatic, Square D, Cutler-Hammer, GE,
    and Siemens. These even include what is missing with plug-in
    protectors - the earthing wire. A shunt mode protector is only as
    effective as its earth ground. That is what they do - connect
    destructive transients close to earth AND distant from electronics.
    Bud would hope you ignore those facts. Even IEEE papers demonstrate
    that short connections to earthing are essential to effective
    protection. Those effective protectors (that cost so much less money
    per protected appliance) are sold in Lowes, Home Depot, and electric
    supply houses. A protector is a temporary connection to earth. Earth
    ground - quality of and connection to - determines the effectiveness of
    a protector. Don't be mislead by Bud who has a relationship to plug-in
    protector manufacturers - and will then post insults rather than deny
    it.
     
  13. Bud--

    Bud-- Guest


    IEEE guide - chapter 6 provides examples protection using surge suppressors.

    "SPECIFIC PROTECTION EXAMPLES
    "The previous sections have shown, in general, how to protect electronic
    systems in houses:
    "1) Proper grounding and bonding, especially at the service entrance.
    "2) AC panel and primary signal surge protection at or near the service
    entrance.
    "3) Multi-port plug-in protectors near the equipment to be protected."
    #3 explicitly recognizes plug-in surge suppressors as effective. As is
    clearly described, these devices work primarily by clamping all wires to
    a common ground at the surge suppressor.

    Why do both examples of surge protection in this chapter use multi-port
    plug-in surge suppressors??
    If you have trouble figuring out the text look at the nice pictures of
    multi-port plug-in surge suppressors.

    ----------------------
    NIST guide

    page 12 discussing protection of 2-port equipment:
    "A simple solution to the problems of voltage differences for two-link
    appliances is to install a special surge protector that incorporates, in
    the same package, a combination fo input/output connections for the two
    systems. Each link, power and communications, is fed through the
    protector which is then inserted between the wall receptacles and the
    input of the appliance [electronic device] to be protected. This type of
    surge protector is readily available in computer and electronics stores,
    and the electrical section of home building stores."
    If you have trouble figuring out the text look at the nice pictures of
    multi-port plug-in surge suppressors.

    page 16 - questions and answers:
    "Q - Will a surge suppressor installed at the service entrance be
    sufficient for the whole house?
    "A - There are two answers to that question: Yes for one-link appliances
    [electronic devices], No for two-link appliances. Since most homes today
    have some kind of two-link appliances, the prudent answer to the
    question would be No - but that does not mean that a surge protector
    installed at the service entrance is useless. ...."

    Page 17 - surge suppressor installation hints:
    "Plug-in (with cord or directly into receptacle)
    The easiest of all for anyone to do. The only question is "Which to choose?"

    -------------
    Another paper writen by Martzloff, the NIST guru on surges, describes
    surge reference equalizers.

    "CONCLUSIONS
    "The rapid expansion of smart electronics involving power and
    communications connections creates the potential for disappointing
    performance under surge conditions if adequate, coordinated protection
    is not provided. Separate, uncoordinated surge protection of each of the
    two ports still leaves the possibility of damage or upset.
    "A new type of device, the 'Surge Reference Equalizer', offers a
    solution to the problem, provided that the performance characteristics
    of the device will be coordinated with the environmental stress and with
    other surge-protective devices that may be installed on the
    systems."

    -----------------------------
    It takes willfull stupidity to claim the IEEE guide, the NIST guide, and
    Martzloff do not say plug-in protectors are effective.

    They do not operate primarily in shunt mode. The IEEE guide clearly
    describes, to anyone who can read and think, the action as clamping
    wires to a common ground at the plug-in surge suppressors. Your
    reading/thinking disability is unfortunate.

    The IEEE and NIST guides clearly say plug-in surge suppressors are
    effective.

    And you have never provided a link to a reputble source that says
    plug-in suppressors are not effective. It is you against the world.

    bud--
     
  14. w_tom

    w_tom Guest

    And then we add missing parts to that sentence, that Bud routinely
    forgets. He misrepresents IEEE papers. 'Effective' if one with
    advanced technical knowledge can carefully eliminate all six ports of
    failure in that room - construct a farady cage. The six ports as
    described in Bud's SRE paper. And what is found in conventional rooms?
    Items and materials that violate those six ports - compromise
    protection as defined by that IEEE paper. Any one of the six ports
    makes an adjacent plug-in protector ineffective as detailed in those
    IEEE papers.

    That and other papers cited by Bud note, a plug-in protector can
    contribute to damage of an adjacent appliance: "even when or perhaps
    because, surge protective devices are" adjacent to that appliance. Why
    does he repeatedly ignore that conclusion from his own citations? Who
    does he represent?

    "High-current surges ... are best diverted at the service entrance of
    the premises." - also from Bud's own citations.

    What does another citation define as an effective protector?His company's products don't have that earthing wire.

    Others are encouraged to locate claimed protection in numerical
    specifications for a plug-in protector. Such numbers do not exist.
    They don't even define protection for each type of transient? Why?
    Ask what Bud hopes you don't ask. Ask why a surge that seeks earth
    ground destructively via an appliance is not listed in those numerical
    specs? Why mention a transient that plug-in protectors don't protect
    from? No earth ground means no effective protection. They are shunt
    mode protectors - only as effective as their earth ground. Earth
    ground? Plug-in protectors don't even discuss earthing in a hope that
    you don't ask such embarrassing questions.
     
  15. Bud--

    Bud-- Guest

    If you could read and think you could see the point of the SRE paper is
    that SREs protect the six ports:

    "The surge reference equalizer combines the protective function for both
    system ports in the same enclosure. A common, single grounding
    connection equalizes the voltages of the two paths that return the surge
    through the grounding connection of the 3-prong power line plug... Such
    a solution is particularly attractive as an element of 'whole-house
    protection'..."
    Apparently you can't argue on the science. I have no interests in surge
    suppressors.

    Stated numerous times and clear from the IEEE guide: plug-in surge
    suppressors work by clamping wires to the common ground at the surge
    suppressor. They work primarily by clamping, not earthing. It is
    embarrassing you can't read the description - clamping is the primary
    protection.

    The IEEE and NIST guides clearly say plug-in surge suppressors are
    effective.

    You have still never provided a link to a reputble source that says
    plug-in suppressors are not effective. No one agrees with you.

    bud--
     
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