Why is PC chasis put on voltage when earth/ground wire is missing ?!?

Discussion in 'Asus' started by Skybuck Flying, May 14, 2011.

  1. Hello,

    Apperently PC's have "incoming netfilters/powerfilters" in the Netherlands
    possibly Europe which filter out fluctuations caused by other equipment on
    power lines.

    One design which seems to be in use is a netfilter which tries to use the
    earth/grounding wire to get rid of the excessive fluctuations... however if
    the earth wire is not available it seems to dump the additional voltage to
    the chasis, or it puts the chasis under/on voltage for some other reason ?!?

    So my question is:

    Does the netfilter indeed output excessive voltages onto the chasis ?

    If so why does it do this ?

    Can it not simply dump the excessive fluctuations to the other wire ?

    Perhaps it does not know which wire to use because of the way plugs can be
    plugged in ?
    (+ - versus - +)

    If so then that could explain why it can't dump additional voltage to the
    2-wire system and instead choses to dump it to the chasis.

    Can this voltage on the chasis slowly build up over time ? Does it become
    like a battery or something ?

    However if these are not the reasons to put the chasis under/on voltage then
    what is the real reason to put the chasis on voltage in case there is no
    earth wire ?!?

    Skybuck Flying, May 14, 2011
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  2. Skybuck Flying

    Paul Guest

    There are some example schematics here. The first one is a schematic of the ATX
    supply. You can see the details of the input filter, and C2 and C3 would be
    the things making leakage current.


    Now, for this link, when you click, please be patient. It can take a couple minutes
    for this server to respond. The "metal box" described in this PDF, is a professional
    filter for equipment, used to perform the same function as the simpler circuit inside
    the ATX supply. The wording in the description states the purpose -


    "designed to provide superior common-mode and differential-mode attenuation"

    For one of the two types of attenuation, a capacitor needs to be connected to
    ground, to form a filter. The filter is designed to trap signals at "Megahertz".
    But an accidental side effect, is the capacitor also shunts a small amount of
    50Hz or 60Hz current, into the ground.

    If the appropriate capacitors were disconnected, then you'd stop getting a shock,
    but then, more switching noise from the ATX supply, would flow backwards into
    your supply mains, disrupting your ability to view over-the-air television

    The electrical code in your country, will state how to safely handle this
    situation. An electrician can advise you on what to do next (you don't even
    have to pay him for a visit - describe your problem over the phone to him).
    I cannot offer any "home solutions", because if I told you what to do next,
    you could hurt someone. Your electrician can solve the problem safely,
    or at least give a cost estimate as to how expensive it would be to

    Paul, May 15, 2011
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  3. Skybuck Flying

    tuinkabouter Guest

    Op 5/15/2011 12:29 AM, Skybuck Flying schreef:
    hey moron,

    This is already answered in another group you posted too.
    Besides that YOU mentioned a website with the answers.
    tuinkabouter, May 15, 2011
  4. Skybuck Flying

    Hal Guest

    Simply: regular netfilters contains two capacitors of the same value (the so
    called Y-capacitors). The midpoint (fig. 1
    http://www.ce-mag.com/archive/2001/janfeb/Georgerian36.html ) is connected
    to the chassis. These capacitors carry about 0.25 -0.5 mA ~ current. Both
    the ~ terminals in the PC are floting. As the mains outside the PC is
    grounded, and in case the chassis of the PC is not connected to ground, the
    chassis will, because of voltage dividing, end up at a potential of half the
    mains voltage, capable of delivering 0.5 mA. So you can get a shock when
    touching a not grounded PC. Especially care is needed if more than one
    device with such a filter is connected to the same outlet. Currents add up
    an can become hazardes.
    So don't use your lips to sense the temperature somewere in the PC as I
    sometimes did :).

    Hal, May 15, 2011
  5. Hey Moron,
    No LOL.

    These websites explained why there was a voltage on the chasis from a
    reverse enginering point of view.

    My question is from a design point of view.

    Why was it designed like this in the first place ?! ;)

    Skybuck Flying, May 15, 2011
  6. This was already discussed, this is looking at it from an reverse enginering
    point of view.

    Now the question is:

    Why was it designed this way ?!?

    Cannot it now be designed in a different way so that the chasis does not
    need to be under/on voltage ?!?

    Skybuck Flying, May 15, 2011
  7. Skybuck Flying

    Ben Guest

    Read the fucking manual.

    This apparatus MUST BE EARTHED !

    So, connecting to a Non Earthed AC source is totally on your own risk.
    Ben, May 15, 2011
  8. It's not in the fucking manual:

    Seasonic S12 600 watt manual:

    Why does it need to be earthed ? Why does it need a third earth wire ?

    Why cannot it not simply use two wires without earth and without putting the
    chasis under voltage ?!?

    Why does it need to put the chasis under voltage when it's not earthed ?

    You have not answered any of my questions and seem to think that these
    questions are documented somewhere which so far appears not to be the case.

    Skybuck Flying, May 15, 2011
  9. Antec 1200 case does not mention it as well:

    http://www.antec.com/pdf/manuals/1200_EN manual.pdf

    I am starting to get a little pissed off right about now.

    There is no way I could have known that first of all earthing is required
    and second of all what would happen if it's not earthed... -> chasis under

    Seems to me these companies might be sueable... only thing which is in doubt
    if it was in the law by the time I bought and assembled and damage the PC...
    (laws might have been updated in 2001 however might not apply to every home
    build before that time).

    Perhaps law says: "it's required to earth computers"... in that case the
    companies might get away with it.
    However law also says what to do when not earthed, though to difficult for
    me to tell.

    But perhaps not because I did not know what would happen if it was not
    earthed and that if I would connect my devices that there would be a voltage
    on the chasis:

    Thus negleance of critical information and thus perhaps sueable for
    withholding critical information which could lead to damage.

    Skybuck Flying, May 15, 2011
  10. Skybuck Flying

    Dave Platt Guest

    The filters are intended to create a connection between each side of
    the power line, and ground, which has a low impedance at high (RF)
    frequencies. This connection is created with a capacitor, connected
    between the power line conductor(s) and ground. By presenting a low
    impedance at RF, the capacitor creates what one might call a
    "preferred" path for the RF noise... it's "easier" for the noise to
    flow to ground, than it is for it to flow back onto the power line (if
    it was created inside the equipment) or into the equipment (if it was
    coming in from the power line).

    Noise can be present on either or both of the power-line conductors,
    (and if it's on both, it can be in the same polarity or the opposite
    polarity). This means that you need a capacitor from each conductor
    to ground.

    The capacitors do allow a small amount of power-line current to flow
    through them... their impedance at 50 or 60 Hz is quite high, so only
    a small amount of current leaks through.

    If you disconnect the equipment chassis from ground, this leaves the
    chassis connected to the two sides of the power line by capacitors of
    equal value (usually). If you're using "non-balanced" power (with one
    side being "neutral" and close to ground voltage), this capacitive
    "voltage divider" will leave the chassis sitting at around half of the
    power-line voltage. However, this will usually not present any sort
    of safety/shock hazard if you touch the chassia and are grounded,
    because the high impedance of the capacitors at 50 or 60 Hz limits the
    current to well below the shock limit.

    If you're in a country which uses symmetrical, "balanced" power, then
    the chassis will remain at nearly ground voltage even if you
    disconnect it from ground.

    I believe it's *not* a good idea to run this sort of equipment (three
    wires, with one wire connected to the chassis and to earth-ground) in a
    non-grounded mode. Even if doing so doesn't create a safety hazard,
    it defeats much of the benefit of the noise-filtering components, and
    it may create hum/buzz problems (if e.g. you connect it to another
    component, via a simple non-balanced audio or video cable with RCA
    plugs/jacks, and the other component *is* properly grounded).

    Here in the U.S., I believe it's considered to be unsafe to run such
    components this way... "defeating the ground prong" on a 3-wire plug
    is generally considered to be a hazardous or improper installation,
    and might void the warranty. That's part of what I meant by "grossly
    defective" in my earlier message.

    Appliances which are designed with a 2-wire (non-grounded) power cord
    and plug are built differently... they don't connect RF filtering
    capacitors to the chassis, and they are usually "double-insulated" so
    that a fault in the wire insulation can't bring it into contact with a
    metal chassis that someone could touch.
    Dave Platt, May 15, 2011
  11. Skybuck Flying

    Dave Platt Guest

    If you do that, it becomes impossible to filter out "common mode"
    electrical noise.
    Dave Platt, May 15, 2011
  12. Care to explain why ?

    To me these all seem wires... perhaps one or two wires with some kind of
    voltage on them.

    Let's suppose one wire with voltage on them and the other being zero/nul

    What's the difference with a ground wire ?!? Some even say at nul wire could
    be grounded as well.

    So it seems to make little difference/sense... unless there is something
    else going on like confusion about
    wires/impossible to tell cheaply how they wired electronically and so

    What makes the earth wire so special compared to the other wires ?!? ;)

    Skybuck Flying, May 16, 2011
  13. Perhaps it's like a traffic jam.

    The + is where the traffic comes from.

    The - is where the traffic would go to.

    The PC wants to consume some of the traffic and
    wants to shed the rest so it would have to divert
    traffic to the -.

    However becomes other devices might also try to shed traffic to the -, the -
    gets flooded and can't handle the traffic, so the traffic backsup back into
    the pc and the pc gets into trouble.

    Perhaps this is where the ground wire comes into play.

    The ground wire is like an additional lane, which is at least as big as the
    + maybe even bigger so it can easily divert extra traffic.

    At first this might not seem to make much sense since how could the - be
    bigger than the + ?

    Well that's where batteries/capacitators come into play... they store some
    of the + insight them... and then suddenly it's all released at once...
    flooding the -.

    Just like people parking their cars at work/parking garage... then all
    leaving at the same time ! ;) =D

    Just another whacky theory/hypothesis of mine, does it make any sense ? ;)

    Skybuck Flying, May 16, 2011
  14. Skybuck Flying

    Dave Platt Guest

    Care to explain why ?[/QUOTE]

    Not really, because ...
    .... you've just demonstrated that you don't currently understand
    enough about electricity, or mains-type wiring conventions, to make
    much sense out of the answer.
    There is a real difference. You're going to have to figure this one
    out for yourself.

    Simply apply one of the most fundamental laws of electricity - Ohm's

    E = I * R

    Consider the fact that there are often many amperes of current (I)
    flowing through both the hot and neutral ("nul") wires.

    Also consider that the safety-ground wire is *not* carrying any
    current under normal circumstances.

    Finally, consider the fact that all wires have resistance.

    Now, answer it for yourself: what's different between the ground-wire
    connection and the neutral-wire connection when they reach your PC?
    Dave Platt, May 16, 2011
  15. Not really, because ...
    ... you've just demonstrated that you don't currently understand
    enough about electricity, or mains-type wiring conventions, to make
    much sense out of the answer.
    There is a real difference. You're going to have to figure this one
    out for yourself.

    Simply apply one of the most fundamental laws of electricity - Ohm's

    E = I * R

    Consider the fact that there are often many amperes of current (I)
    flowing through both the hot and neutral ("nul") wires.[/QUOTE]

    Flowing in what direction ? ;)
    I don't agree with that simply because all pc's attached to it are "leaking"
    even if it's just a little bit.

    So if this is compared with a nul-wire which some say has little to no
    current as well I see little difference.

    At least from the wire perspective... perhaps the Earth is a big sucking
    device sucking all the electricity harder
    on the ground wire then on the other wires but I don't know that for sure ;)
    I'd figure all wires made of same material and same thickness ultimately so
    perhaps little difference ? ;)

    At least the wires directly on the socket... the ground pin does seem a bit
    Depends on situation... neutral wire could be 0 or -120 volts, ground should
    be 0 or something... but can also contain some... perhaps 120 volts leaking
    from pc ! ;)

    The neutral wire probably has more ampere flowing because of the pc... and
    the ground wire has little ampere flowing...

    But why can't excessive ampere not simply flow out the neutral wire ?!? why
    most it go through ground wire ?!?

    Why would ground wire have less fluctuations ? Partially answered already
    because leak is only very little...

    But why would leaking to neutral cause fluctuations ?! ;) Seem my traffic
    reasoning... perhaps that has something to do with it...

    Eletricity does flow in a certain direction... from + to - ?!?

    So big + goes to PC... which goes to -.

    Little + is leak and why can't it also go to - ?!?

    Perhaps use eletricity consuming component to get rid of it, instead of
    going via ground wire ?!? So ground no longer necessary.

    Don't bother with formula's and such... nature don't work with formula's...

    Nature work with electrons... so you try explaining it with little
    electronics as if they were cars...

    Maybe then I will understand it a bit better ! ;)

    Skybuck Flying, May 16, 2011
  16. Skybuck Flying

    John G Guest

    Skybuck Flying explained on 16/05/2011 :
    At your current ignorance and inability to be told you will never
    understand anyting electrical.
    So why don't you go to a real college and learn the basics before
    demonstrating how stupid you are.

    For starters current flows both ways in any domestic supply circuit and
    barring error leaks and very minor currents from noise suppresion
    capacitors, the current in the Neautral is EQUAL to the current in the
    The Ground is a safety and must be capable of carrying the full current
    possible in this particular circuit if a fault occurs.
    John G, May 16, 2011
  17. Skybuck Flying

    Hal Guest

    You need an EMI expert to answer this question. But I am shure that if there
    are ways, they will be (much) more costly then the presently choosen
    solution. So the second question is: "Are most customers willing to pay
    extra for something, almost nobody (except you) is intersted in."

    Hal, May 16, 2011
  18. Skybuck Flying

    Bob F Guest

    It's AC, so it flow both directions.

    In some cases, the ground wire is somewhat smaller than the power conductors.

    Neutral carries almost exactly the same current as the hot lead.
    Remember, this is AC (alternating current). It goes one way, then the other,
    ovewr and over.
    Ground is there to carry minor leakage (to get rid of electrical noise) and
    contain major fault currents, thus keeping the chassis at a safe voltage level
    even if something goes wrong, so you don't get electrocuted. The chassis stays
    at ground voltage, the same as your house pipes, floor, etc.
    Try googleing a few basic electronics sites and learning. The formulas show
    exactly how electricity works - don't put them down. When you understand them,
    you will understand how it works. Argueing with people here ("don't bother with
    formulas") just shows an unwillingness to study and learn. You seem to want us
    to do all the work for you to learn.
    Bob F, May 16, 2011
  19. Skybuck Flying

    Joel Koltner Guest

    Formulae give you a means to predict what nature's going to do, which is quite
    useful in that -- as your thread here shows -- it's not always intuitively
    obvious to the casual observer.
    The ground path is kinda like a "high occupancy vehicle" (HOV) lane (do they
    have those in your country?) -- the idea is that, compared to the main roads,
    it's relatively clean and has little if any traffic on it. Those filter
    capacitors' jobs is to essentially take the trucks that are hauling toxic
    sludge and route them off of the main road and into the HOV lane, since there
    are various restrictions on how much slude is allowed to go through, e.g., the
    central business district (that is, how much noise your PC is allowed to
    inject into other devices, or other devices are allowed to inject into it).

    Cutting the ground lead is somewhat like blowing up the bridges in the HOV
    lane: The sludge trucks can no longer use it, and therefore it renders the
    filter capacitors ineffective. It also means that if one of the "hot"
    vehicles (say, a fuel truck that's been set on fire) inadvertently enters the
    HOV lane, since it can no longer return to base via the intended route (since
    you blew up the bridges), it'll instead try to climb onto your fingers when
    you touch the case, burning/shocking you.
    Which grade did you say you're in? Are you/have you gone to college in a
    field related to electronics?

    Joel Koltner, May 16, 2011
  20. Hmm interesting point... I'll look into this to make sure it's true... but
    it sounds believable ! ;) :)

    But how such a large distance can swing/move both ways remains weird to
    me... then again there are transformer
    houses and other stuff in between... and how stuff can swing both ways
    between multiple homes also seems a bit weird.

    Then it must be flucuating a lot me thinks... like multiple waves right
    behind each other... otherwise if it was a single super large wave it would
    surely get disturbed ;)
    This is assuming the grounding from the chasis to the earth is the shortest

    But if I touch my pc and the path through me is shorter will it still go
    through me ?!?

    Or does it depend on the "most" resistance... if I offer more resistance
    then electricity would go via wires ?!?

    Or does "literally" shortest distance win... hmmm...

    And does electricity care about my resistance anyway ?! ;) probably not up
    to a certain point, probably depends on current.
    I am trying to learn, but I want to learn it from a practical and
    conceptually point... not from a theoretical point... that's more for people
    wanting to do real designs and such... Perhaps later I will look into
    formula's a little bit more... but don't count on it ! ;) =D

    Skybuck Flying, May 16, 2011
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