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Grounding

Discussion in 'Electronic Repair' started by Rodney Kelp, Nov 12, 2004.

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  1. Rodney Kelp

    Rodney Kelp Guest

    If you have a 2 wire house electrical system what's the difference between a
    3 wire system and installing a 3wire plug and jumping the ground pin to the
    white return line. I see no electrical difference between that and running a
    green wire all the way to the box and connecting it to the same place as the
    return line ground. If you know what I mean.
     
  2. If the neutral wire ever comes loose then the appliance becomes
    electrified. Don't do it, it is very dangerous.
     
  3. CJT

    CJT Guest

    Consider the possible failure modes. It's called a "safety ground"
    for a reason.
     
  4. NSM

    NSM Guest

    | If you have a 2 wire house electrical system what's the difference between
    a
    | 3 wire system and installing a 3wire plug and jumping the ground pin to
    the
    | white return line. I see no electrical difference between that and running
    a
    | green wire all the way to the box and connecting it to the same place as
    the
    | return line ground. If you know what I mean.

    The difference is that it violates code and can result in your insurance
    being voided in case of fire or accident. See if the box is grounded, and if
    so you can use that as the ground.

    N
     
  5. Functionally, there is little difference. However, safety-wise, they
    are a world apart.

    Nothing a user can come in contact with should ever be attached to
    Hot or Neutral.

    --- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
    Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
    +Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
    | Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

    Note: These links are hopefully temporary until we can sort out the excessive
    traffic on Repairfaq.org.

    Important: Anything sent to the email address in the message header is ignored.
    To contact me, please use the feedback form on the S.E.R FAQ Web sites.
     
  6. Rodney Kelp

    Rodney Kelp Guest

    If you look inside some power panels the white neutral is connected to the
    same terminal block as the green ground wires.
    What's the diff?
     
  7. CJT

    CJT Guest

    That connection is on the power panel end of the wire is the difference.

    There's also a connection to earth ground at that same point.

    Consider the possible failure modes at the appliance end of the wire.

    It's a _safety_ issue.
     
  8. NSM

    NSM Guest

    | If you look inside some power panels the white neutral is connected to the
    | same terminal block as the green ground wires.
    | What's the diff?

    The difference is that it violates code and can result in your insurance
    being voided in case of fire or accident. You may also be liable for death
    or injury to other persons or loss of property.

    This is called a multiple earthed (grounded) neutral system. It is carefully
    designed to provide maximum safety for persons and property. The rules are
    not arbitrary, not pointless, they are there for a reason. Ask 100
    electricians - or 100,000 - and they will all tell you what you are
    suggesting is wrong, dangerous and stupid. The neutral is grounded in very
    specific places according to very specific rules.

    I am a registered electrician as well as an electronics technician (in more
    than one country) and I understand this system as well as anyone. You have
    been told not to try this and given several reasons why. You have also been
    told the right way to proceed. Believe those who advise you - they are
    correct. Ask your local electrical inspector if you don't believe us.

    If you insist on this foolish procedure, I suggest you practice first by
    checking the level of gas in your tank with a lighted match.

    NM
     
  9. Ross Herbert

    Ross Herbert Guest

    Perhaps you should do some reading on the MEN system. Here is an
    publication from Australia which illustrates the hazards and reasons
    for using it.

    http://www.eso.qld.gov.au/publicat/men/men1.pdf

    No matter where you live, if your electrical supply uses the MEN
    system it will be very similar even for 115V.
     
  10. RonKZ650

    RonKZ650 Guest

    If you look inside some power panels the white neutral is connected to the
    OK there's been 100 explanations now how grounding to the white wire will "kill
    you, start a fire, cause a neuclier explosion ect." I'm still in the dark too.
    If ground is on the white and also on the green, what the heck does it matter?
    Not trying to be a moron, but these electrical codes are beyond me, living in a
    house built in 1898, I'd be surprised if there's even a hint of *code* here,
    but no problems.
     
  11. NSM

    NSM Guest

    | >If you look inside some power panels the white neutral is connected to
    the
    | >same terminal block as the green ground wires.
    | >What's the diff?
    |
    | OK there's been 100 explanations now how grounding to the white wire will
    "kill
    | you, start a fire, cause a neuclier explosion ect." I'm still in the dark
    too.
    | If ground is on the white and also on the green, what the heck does it
    matter?
    | Not trying to be a moron, but these electrical codes are beyond me, living
    in a
    | house built in 1898, I'd be surprised if there's even a hint of *code*
    here,
    | but no problems.

    Even in the days of knob and tube wiring (the earliest type) there was a
    code at least of sorts. Learning from every accident and fire has produced
    the code we have today which aims to minimize those problems.

    Hey, I feel I can drive perfectly safely at 120 MPH while the rest of the
    traffic is doing 70 MPH. So why shouldn't I? It's only a rule, right? And if
    you feel the same way why shouldn't you do whatever you please? After all,
    red light, green light, they're just colors. Go when you feel like it. No
    problem. And who says you need to drive on the right hand side of the road?

    And anyone can be a doctor too. Why waste time at medical school? How hard
    can it be?

    Right.

    N
     
  12. OK there's been 100 explanations now how grounding to the white wire will
    "kill
    you, start a fire, cause a neuclier explosion ect." I'm still in the dark
    too.
    If ground is on the white and also on the green, what the heck does it
    matter?
    Not trying to be a moron, but these electrical codes are beyond me, living in
    a
    house built in 1898, I'd be surprised if there's even a hint of *code* here,
    but no problems.[/QUOTE]

    Yes, it would be nice if someone would undertake to answer your question
    by explaining. a little about electrical wiring conventions in general
    and grounding in particular. I know something about electronics, but
    I've never found a good (short) explanation of even the basics of house
    wiring and grounding.

    Leonard
     
  13. NSM

    NSM Guest

    | Yes, it would be nice if someone would undertake to answer your question
    | by explaining. a little about electrical wiring conventions in general
    | and grounding in particular. I know something about electronics, but
    | I've never found a good (short) explanation of even the basics of house
    | wiring and grounding.

    See the previously mentioned http://www.eso.qld.gov.au/publicat/men/men1.pdf

    Here are a couple of cases I know of:

    1) The city replaces the wires to the house, but accidentally connects the
    hot to the neutral and the neutral to the hot. Now all of your 'grounded'
    appliances have 120 volts on each metal surface. I know the people this
    happened to. They put an old fashioned metal bucket in the kitchen sink and
    dropped the metal handle across the hot and cold taps. It promptly welded
    itself to them.

    2) A 15,000 volt overhead wire breaks and drops on the 120 volt wires
    feeding your house. You still want to take your chances? This also happened.

    The MEN system is the safest we have been able to come up with, but the
    rules must be followed.

    N
     
  14. Rodney Kelp

    Rodney Kelp Guest

    It seems to me that if a 15,000 volt line falls across your house feed it
    will probably connect to the bare neutral and make all the little green
    wires in your house 15k volts also.
     
  15. Rodney Kelp

    Rodney Kelp Guest

    The greatest danger would be as you say, someone connecting the feed lines
    backwards putting the neutral and hot lines in reverse. That kind of mistake
    from a licenced electrician though, would be a grave violation of code and a
    powerful demonstration of stupidity.
     
  16. Rodney Kelp

    Rodney Kelp Guest

    The original question was " is it electrically the same" Not is it legally
    the same.
     
  17. But the real point is that it is not electrically the same in the case of a
    failure of the neutral line.

    Leonard
     
  18. CJT

    CJT Guest

    It's not even electrically the same, because the wires are not ideal.

    So neutral won't be at the same potential as safety ground.

    However, from the point of view of an appliance, that shouldn't matter.
     
  19. Here's one example:

    Consider the 'appliance' below:

    +-----------------+
    | | Open Fault
    Hot o---------o-o----/\/\---------+------ X -----o Neutral
    | Switch Load | |
    | (On) |----+ Case should be G but is connected to N
    +-----------------+


    With the appliance 'on', current passes through the internal
    wiring/motor/etc. of the appliance to the N but this is now connected
    to the case as well. If the house wiring opens (or even if the plug is
    loose, it is possible to have line voltage on the case.

    The 'appliance' can actually be *all* loads on the circuit upstream of
    the the Open Fault - all those with a grounded cabinet have it then
    become live! Testing installed GFCIs

    --- sam | Sci.Electronics.Repair FAQ Mirror: http://repairfaq.ece.drexel.edu/
    Repair | Main Table of Contents: http://repairfaq.ece.drexel.edu/REPAIR/
    +Lasers | Sam's Laser FAQ: http://repairfaq.ece.drexel.edu/sam/lasersam.htm
    | Mirror Sites: http://repairfaq.ece.drexel.edu/REPAIR/F_mirror.html

    Note: These links are hopefully temporary until we can sort out the excessive
    traffic on Repairfaq.org.

    Important: Anything sent to the email address in the message header is ignored.
    To contact me, please use the feedback form on the S.E.R FAQ Web sites.
     
  20. NSM

    NSM Guest

    | The greatest danger would be as you say, someone connecting the feed lines
    | backwards putting the neutral and hot lines in reverse. That kind of
    mistake
    | from a licenced electrician though, would be a grave violation of code and
    a
    | powerful demonstration of stupidity.

    But as they say, shit happens. In each case the occupants survived, as they
    have in other cases. We don't have time to analyse each possible result from
    each possible combination of faults or errors. We follow the code because
    that represents the accumulated wisdom gained from all previous occurrences.
    If we didn't need the code it wouldn't exist.

    If the homeowner (or anyone else) doesn't follow the code, god help the next
    poor bastard who tries to work on the electrical system. There is a very
    popular show on TV in Canada called "Holmes on Homes" which shows some of
    the nightmare results of not following all codes, electrical, plumbing and
    building. Some of the stuff he has found could loosen the bowels of a
    granite rock.

    N
     
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