Colored Electrical Outlets

Discussion in 'Misc DIY' started by William Munny, Aug 14, 2009.

  1. In some hospitals and office buildings, I see some electrical outlets that
    are red or orange (not the outlets cover plates, the outlet itself).

    What's that all about?
    William Munny, Aug 14, 2009
    #1
  2. William Munny

    charlie Guest

    "William Munny" <> wrote in message
    news:h646uo$42i$...
    > In some hospitals and office buildings, I see some electrical outlets that
    > are red or orange (not the outlets cover plates, the outlet itself).
    >
    > What's that all about?


    they are on a ups for safety critical use during blackouts.
    charlie, Aug 14, 2009
    #2
  3. William Munny

    dpb Guest

    charlie wrote:
    > "William Munny" <> wrote in message
    > news:h646uo$42i$...
    >> In some hospitals and office buildings, I see some electrical outlets that
    >> are red or orange (not the outlets cover plates, the outlet itself).
    >>
    >> What's that all about?

    >
    > they are on a ups for safety critical use during blackouts.


    And orange is isolated ground for computer equipment/instrumentation
    that requires it.

    --
    dpb, Aug 14, 2009
    #3
  4. On 8/14/2009 10:29 AM William Munny spake thus:

    > In some hospitals and office buildings, I see some electrical outlets that
    > are red or orange (not the outlets cover plates, the outlet itself).
    >
    > What's that all about?


    Special sanitary electricity. They run it through an autoclave to
    disinfect it.


    --
    Found--the gene that causes belief in genetic determinism
    David Nebenzahl, Aug 14, 2009
    #4
  5. "charlie" <> wrote:

    >> What's that all about?

    >
    >they are on a ups for safety critical use during blackouts.


    Or they are on an isolated ground.
    Robert Neville, Aug 14, 2009
    #5
  6. "William Munny" <> wrote in message
    news:h646uo$42i$...
    > In some hospitals and office buildings, I see some electrical outlets that
    > are red or orange (not the outlets cover plates, the outlet itself).
    >
    > What's that all about?
    >


    Cool, thanks...
    William Munny, Aug 14, 2009
    #6
  7. But, that's before the centrifuge, to settle out the heavy
    electrons.

    --
    Christopher A. Young
    Learn more about Jesus
    www.lds.org
    ..


    "David Nebenzahl" <> wrote in message
    news:4a85a4c0$0$7469$...
    On 8/14/2009 10:29 AM William Munny spake thus:

    > In some hospitals and office buildings, I see some
    > electrical outlets that
    > are red or orange (not the outlets cover plates, the
    > outlet itself).
    >
    > What's that all about?


    Special sanitary electricity. They run it through an
    autoclave to
    disinfect it.


    --
    Found--the gene that causes belief in genetic determinism
    Stormin Mormon, Aug 15, 2009
    #7
  8. William Munny

    Doug Miller Guest

    In article <h646uo$42i$>, "William Munny" <> wrote:
    >In some hospitals and office buildings, I see some electrical outlets that
    >are red or orange (not the outlets cover plates, the outlet itself).
    >
    >What's that all about?


    Red = connected to emergency power (nearly all hospitals, and many office
    buildings, have backup generators in case utility power fails)

    Orange = isolated ground (used for sensitive electronic equipment, usually
    medical or laboratory instruments, or high-end computer gear)
    Doug Miller, Aug 15, 2009
    #8
  9. William Munny

    Perry Aynum Guest

    "William Munny" <> wrote in message
    news:h646uo$42i$...
    > In some hospitals and office buildings, I see some electrical outlets that
    > are red or orange (not the outlets cover plates, the outlet itself).
    >
    > What's that all about?
    >


    How's the hired gun business working out?
    Perry Aynum, Aug 15, 2009
    #9
  10. William Munny

    Guest

    On Sat, 15 Aug 2009 09:49:15 -0400, "Perry Aynum" <>
    wrote:

    >
    >"William Munny" <> wrote in message
    >news:h646uo$42i$...
    >> In some hospitals and office buildings, I see some electrical outlets that
    >> are red or orange (not the outlets cover plates, the outlet itself).
    >>
    >> What's that all about?
    >>

    >
    >How's the hired gun business working out?
    >

    ORANGE receptacles are "isolated ground" (used to be - not necessarity
    true any more) meaning the "U" ground was not connected to the
    mounting tab.
    , Aug 16, 2009
    #10
  11. On Sat, 15 Aug 2009 08:33:57 GMT, (Doug Miller)
    wrote:

    >In article <h646uo$42i$>, "William Munny" <> wrote:
    >>In some hospitals and office buildings, I see some electrical outlets that
    >>are red or orange (not the outlets cover plates, the outlet itself).
    >>
    >>What's that all about?

    >
    >Red = connected to emergency power (nearly all hospitals, and many office
    >buildings, have backup generators in case utility power fails)
    >
    >Orange = isolated ground (used for sensitive electronic equipment, usually
    >medical or laboratory instruments, or high-end computer gear)



    How is isolated ground different then "regular" ground?
    Ashton Crusher, Aug 18, 2009
    #11
  12. William Munny

    stan Guest

    On Aug 18, 9:43 pm, (Doug Miller) wrote:
    > In article <>, Ashton Crusher <> wrote:
    > >On Sat, 15 Aug 2009 08:33:57 GMT, (Doug Miller)
    > >wrote:

    >
    > >>Orange = isolated ground (used for sensitive electronic equipment, usually
    > >>medical or laboratory instruments, or high-end computer gear)

    >
    > >How is isolated ground different then "regular" ground?

    >
    > http://tinyurl.com/n937l4


    Thanks to all posters. Learned something. And made one think. Thank-
    you.

    Sounds like 'Isolated' Ground might also be called an 'Individual'
    Ground!
    In other words the grounding wire from this type of outlet (orange!)
    is run individually to the grounding point; not using the ground used
    for a 'run' or group of 'regular' outlets.

    Have only used an orange outlet once, connected to the output of a UPS
    located in our basement and wired up stairs to the room with the main
    PC etc. AFIK took the ground back to the output of the UPS.

    But as one poster pointed out if we have other computer type gear (say
    printers or scanners etc. plugged into regular outlets) their grounds
    may inadvertently be connected via the various cables connecting them
    to the main computer with its isolated ground. Thus possibly defeating
    the purpose of the individual ground?

    The < http://tinyurl.com/n937l4 > was a useful explanatory.
    stan, Aug 18, 2009
    #12
  13. William Munny

    JIMMIE Guest

    On Aug 14, 1:29 pm, "William Munny" <> wrote:
    > In some hospitals and office buildings, I see some electrical outlets that
    > are red or orange (not the outlets cover plates, the outlet itself).
    >
    > What's that all about?


    Many building have three types of circuits.
    Commercial: Same old stuff you got at your house.
    Essential: These are backed up by generator.
    Critical: These are backed up by both a generator and an
    Uninterruptable Power Supply similar to the battery backup you may
    have for your PC.
    The critical circuits are marked so people will not know not to plug
    things into them they shouldn't like blow dryers, personal heaters,
    and janitorial equipment. Also it lets them know you could plug in a
    heart-lung machine there. There may also be rules about what you can
    use on essential circuits so they may also be marked.

    Jimmie
    JIMMIE, Aug 18, 2009
    #13
  14. William Munny

    Chip C Guest

    On Aug 18, 8:31 am, stan <> wrote:
    > On Aug 18, 9:43 pm, (Doug Miller) wrote:
    >
    > > In article <>, Ashton Crusher<> wrote:
    > > >On Sat, 15 Aug 2009 08:33:57 GMT, (Doug Miller)
    > > >wrote:

    >
    > > >>Orange = isolated ground (used for sensitive electronic equipment, usually
    > > >>medical or laboratory instruments, or high-end computer gear)

    >
    > > >How is isolated ground different then "regular" ground?

    >
    > >http://tinyurl.com/n937l4

    >
    > Thanks to all posters. Learned something. And made one think. Thank-
    > you.
    >
    > Sounds like 'Isolated' Ground might also be called an 'Individual'
    > Ground!
    > In other words the grounding wire from this type of outlet (orange!)
    > is run individually to the grounding point; not using the ground used
    > for a 'run' or group of 'regular' outlets.
    >
    > Have only used an orange outlet once, connected to the output of a UPS
    > located in our basement and wired up stairs to the room with the main
    > PC etc. AFIK took the ground back to the output of the UPS.
    >
    > But as one poster pointed out if we have other computer type gear (say
    > printers or scanners etc. plugged into regular outlets) their grounds
    > may inadvertently be connected via the various cables connecting them
    > to the main computer with its isolated ground. Thus possibly defeating
    > the purpose of the individual ground?
    >
    > The <http://tinyurl.com/n937l4> was a useful explanatory.


    That's a good article about the hoo-hah surrounding isolated ground.
    I'm convinced that architects put them in out of rote habit. I've
    personally never seen a computer with documentation that requires
    them.

    I believe that audio and signal processing equipment might benefit
    from them, since in some places (at some time) I hear was ok to use
    the metallic conduit as the circuit's ground, and not pull a bare or
    green wire. The conduit picks up a lot of noise, so it causes problems
    for equipment that uses the ground as a signal reference level. The
    orange outlet at least guarantees you a real copper ground all the way
    back to something earthed. As others have said, today's codes,
    especially for hospitals, now guarantee this for all outlets.

    I am also told that the orange outlets can indicate a circuit fed by a
    (nearby) isolation transformer, on the output side of which the
    neutral is re-referenced (ie, tied) to ground. This guarantees that at
    the outlet, ground and neutral are close together in voltage.
    Otherwise, in large commercial buildings, as you get further from the
    point of grounding you can find that ground and neutral not only have
    noise relative to each other but are far apart in DC levels.

    As others have said, the read outlets are on circuits that can be fed
    by the generators if the utility power cuts out. (And yes, the
    breakers for these circuits are in bright read service panels.) But be
    warned, a lot of places do generator and cutover tests at some regular
    schedule, usually at some early morning hour, which cause outages of a
    second or so. Much hospital equipment (fridges, lighting, elevators,
    plus patient support equipment that has internal batteries) ride
    through these fine, but computers don't. And of course, when a utility
    outage happens, it takes time for the generators to ramp up (the
    nominal standard is generally 15 seconds, in the real world can be
    longer). Bottom line: don't plug a computer in to a hospital red
    outlet without a UPS.

    Chip C
    Chip C, Aug 18, 2009
    #14
  15. William Munny

    Guest

    On Tue, 18 Aug 2009 07:07:06 -0700 (PDT), Chip C
    <> wrote:

    >On Aug 18, 8:31 am, stan <> wrote:
    >> On Aug 18, 9:43 pm, (Doug Miller) wrote:
    >>
    >> > In article <>, Ashton Crusher <> wrote:
    >> > >On Sat, 15 Aug 2009 08:33:57 GMT, (Doug Miller)
    >> > >wrote:

    >>
    >> > >>Orange = isolated ground (used for sensitive electronic equipment, usually
    >> > >>medical or laboratory instruments, or high-end computer gear)

    >>
    >> > >How is isolated ground different then "regular" ground?

    >>
    >> >http://tinyurl.com/n937l4

    >>
    >> Thanks to all posters. Learned something. And made one think. Thank-
    >> you.
    >>
    >> Sounds like 'Isolated' Ground might also be called an 'Individual'
    >> Ground!
    >> In other words the grounding wire from this type of outlet (orange!)
    >> is run individually to the grounding point; not using the ground used
    >> for a 'run' or group of 'regular' outlets.
    >>
    >> Have only used an orange outlet once, connected to the output of a UPS
    >> located in our basement and wired up stairs to the room with the main
    >> PC etc. AFIK took the ground back to the output of the UPS.
    >>
    >> But as one poster pointed out if we have other computer type gear (say
    >> printers or scanners etc. plugged into regular outlets) their grounds
    >> may inadvertently be connected via the various cables connecting them
    >> to the main computer with its isolated ground. Thus possibly defeating
    >> the purpose of the individual ground?
    >>
    >> The <http://tinyurl.com/n937l4> was a useful explanatory.

    >
    >That's a good article about the hoo-hah surrounding isolated ground.
    >I'm convinced that architects put them in out of rote habit. I've
    >personally never seen a computer with documentation that requires
    >them.
    >
    >I believe that audio and signal processing equipment might benefit
    >from them, since in some places (at some time) I hear was ok to use
    >the metallic conduit as the circuit's ground, and not pull a bare or
    >green wire. The conduit picks up a lot of noise, so it causes problems
    >for equipment that uses the ground as a signal reference level. The
    >orange outlet at least guarantees you a real copper ground all the way
    >back to something earthed. As others have said, today's codes,
    >especially for hospitals, now guarantee this for all outlets.
    >
    >I am also told that the orange outlets can indicate a circuit fed by a
    >(nearby) isolation transformer, on the output side of which the
    >neutral is re-referenced (ie, tied) to ground. This guarantees that at
    >the outlet, ground and neutral are close together in voltage.
    >Otherwise, in large commercial buildings, as you get further from the
    >point of grounding you can find that ground and neutral not only have
    >noise relative to each other but are far apart in DC levels.
    >
    >As others have said, the read outlets are on circuits that can be fed
    >by the generators if the utility power cuts out. (And yes, the
    >breakers for these circuits are in bright read service panels.) But be
    >warned, a lot of places do generator and cutover tests at some regular
    >schedule, usually at some early morning hour, which cause outages of a
    >second or so. Much hospital equipment (fridges, lighting, elevators,
    >plus patient support equipment that has internal batteries) ride
    >through these fine, but computers don't. And of course, when a utility
    >outage happens, it takes time for the generators to ramp up (the
    >nominal standard is generally 15 seconds, in the real world can be
    >longer). Bottom line: don't plug a computer in to a hospital red
    >outlet without a UPS.
    >
    >Chip C


    Isolation transformer is there for safety.
    , Aug 18, 2009
    #15
  16. William Munny

    Chip C Guest

    On Aug 18, 10:12 am, wrote:
    > On Tue, 18 Aug 2009 07:07:06 -0700 (PDT), Chip C
    >
    >
    >
    > <> wrote:
    > >On Aug 18, 8:31 am, stan <> wrote:
    > >> On Aug 18, 9:43 pm, (Doug Miller) wrote:

    >
    > >> > In article <>, Ashton Crusher <> wrote:
    > >> > >On Sat, 15 Aug 2009 08:33:57 GMT, (Doug Miller)
    > >> > >wrote:

    >
    > >> > >>Orange = isolated ground (used for sensitive electronic equipment, usually
    > >> > >>medical or laboratory instruments, or high-end computer gear)

    >
    > >> > >How is isolated ground different then "regular" ground?

    >
    > >> >http://tinyurl.com/n937l4

    >
    > >> Thanks to all posters. Learned something. And made one think. Thank-
    > >> you.

    >
    > >> Sounds like 'Isolated' Ground might also be called an 'Individual'
    > >> Ground!
    > >> In other words the grounding wire from this type of outlet (orange!)
    > >> is run individually to the grounding point; not using the ground used
    > >> for a 'run' or group of 'regular' outlets.

    >
    > >> Have only used an orange outlet once, connected to the output of a UPS
    > >> located in our basement and wired up stairs to the room with the main
    > >> PC etc. AFIK took the ground back to the output of the UPS.

    >
    > >> But as one poster pointed out if we have other computer type gear (say
    > >> printers or scanners etc. plugged into regular outlets) their grounds
    > >> may inadvertently be connected via the various cables connecting them
    > >> to the main computer with its isolated ground. Thus possibly defeating
    > >> the purpose of the individual ground?

    >
    > >> The <http://tinyurl.com/n937l4> was a useful explanatory.

    >
    > >That's a good article about the hoo-hah surrounding isolated ground.
    > >I'm convinced that architects put them in out of rote habit. I've
    > >personally never seen a computer with documentation that requires
    > >them.

    >
    > >I believe that audio and signal processing equipment might benefit
    > >from them, since in some places (at some time) I hear was ok to use
    > >the metallic conduit as the circuit's ground, and not pull a bare or
    > >green wire. The conduit picks up a lot of noise, so it causes problems
    > >for equipment that uses the ground as a signal reference level. The
    > >orange outlet at least guarantees you a real copper ground all the way
    > >back to something earthed. As others have said, today's codes,
    > >especially for hospitals, now guarantee this for all outlets.

    >
    > >I am also told that the orange outlets can indicate a circuit fed by a
    > >(nearby) isolation transformer, on the output side of which the
    > >neutral is re-referenced (ie, tied) to ground. This guarantees that at
    > >the outlet, ground and neutral are close together in voltage.
    > >Otherwise, in large commercial buildings, as you get further from the
    > >point of grounding you can find that ground and neutral not only have
    > >noise relative to each other but are far apart in DC levels.

    >
    > >As others have said, the read outlets are on circuits that can be fed
    > >by the generators if the utility power cuts out. (And yes, the
    > >breakers for these circuits are in bright read service panels.) But be
    > >warned, a lot of places do generator and cutover tests at some regular
    > >schedule, usually at some early morning hour, which cause outages of a
    > >second or so. Much hospital equipment (fridges, lighting, elevators,
    > >plus patient support equipment that has internal batteries) ride
    > >through these fine, but computers don't. And of course, when a utility
    > >outage happens, it takes time for the generators to ramp up (the
    > >nominal standard is generally 15 seconds, in the real world can be
    > >longer). Bottom line: don't plug a computer in to a hospital red
    > >outlet without a UPS.

    >
    > >Chip C

    >
    > Isolation transformer is there for safety.


    Yes, in cases where its output is not referenced to earth. The two-
    prong shaver outlets that used to be in bathroom light fixtures were
    like this. Also I hear that in the UK (and other 240V places??) they
    use 120V isolated power on outdoor construction sites.

    If the one of the transformer output legs is tied to earth, then I
    don't see the safety benefit.

    Chip C
    Chip C, Aug 18, 2009
    #16
  17. William Munny

    Guest

    On Tue, 18 Aug 2009 07:22:52 -0700 (PDT), Chip C
    <> wrote:

    >On Aug 18, 10:12 am, wrote:
    >> On Tue, 18 Aug 2009 07:07:06 -0700 (PDT), Chip C
    >>
    >>
    >>
    >> <> wrote:
    >> >On Aug 18, 8:31 am, stan <> wrote:
    >> >> On Aug 18, 9:43 pm, (Doug Miller) wrote:

    >>
    >> >> > In article <>, Ashton Crusher <> wrote:
    >> >> > >On Sat, 15 Aug 2009 08:33:57 GMT, (Doug Miller)
    >> >> > >wrote:

    >>
    >> >> > >>Orange = isolated ground (used for sensitive electronic equipment, usually
    >> >> > >>medical or laboratory instruments, or high-end computer gear)

    >>
    >> >> > >How is isolated ground different then "regular" ground?

    >>
    >> >> >http://tinyurl.com/n937l4

    >>
    >> >> Thanks to all posters. Learned something. And made one think. Thank-
    >> >> you.

    >>
    >> >> Sounds like 'Isolated' Ground might also be called an 'Individual'
    >> >> Ground!
    >> >> In other words the grounding wire from this type of outlet (orange!)
    >> >> is run individually to the grounding point; not using the ground used
    >> >> for a 'run' or group of 'regular' outlets.

    >>
    >> >> Have only used an orange outlet once, connected to the output of a UPS
    >> >> located in our basement and wired up stairs to the room with the main
    >> >> PC etc. AFIK took the ground back to the output of the UPS.

    >>
    >> >> But as one poster pointed out if we have other computer type gear (say
    >> >> printers or scanners etc. plugged into regular outlets) their grounds
    >> >> may inadvertently be connected via the various cables connecting them
    >> >> to the main computer with its isolated ground. Thus possibly defeating
    >> >> the purpose of the individual ground?

    >>
    >> >> The <http://tinyurl.com/n937l4> was a useful explanatory.

    >>
    >> >That's a good article about the hoo-hah surrounding isolated ground.
    >> >I'm convinced that architects put them in out of rote habit. I've
    >> >personally never seen a computer with documentation that requires
    >> >them.

    >>
    >> >I believe that audio and signal processing equipment might benefit
    >> >from them, since in some places (at some time) I hear was ok to use
    >> >the metallic conduit as the circuit's ground, and not pull a bare or
    >> >green wire. The conduit picks up a lot of noise, so it causes problems
    >> >for equipment that uses the ground as a signal reference level. The
    >> >orange outlet at least guarantees you a real copper ground all the way
    >> >back to something earthed. As others have said, today's codes,
    >> >especially for hospitals, now guarantee this for all outlets.

    >>
    >> >I am also told that the orange outlets can indicate a circuit fed by a
    >> >(nearby) isolation transformer, on the output side of which the
    >> >neutral is re-referenced (ie, tied) to ground. This guarantees that at
    >> >the outlet, ground and neutral are close together in voltage.
    >> >Otherwise, in large commercial buildings, as you get further from the
    >> >point of grounding you can find that ground and neutral not only have
    >> >noise relative to each other but are far apart in DC levels.

    >>
    >> >As others have said, the read outlets are on circuits that can be fed
    >> >by the generators if the utility power cuts out. (And yes, the
    >> >breakers for these circuits are in bright read service panels.) But be
    >> >warned, a lot of places do generator and cutover tests at some regular
    >> >schedule, usually at some early morning hour, which cause outages of a
    >> >second or so. Much hospital equipment (fridges, lighting, elevators,
    >> >plus patient support equipment that has internal batteries) ride
    >> >through these fine, but computers don't. And of course, when a utility
    >> >outage happens, it takes time for the generators to ramp up (the
    >> >nominal standard is generally 15 seconds, in the real world can be
    >> >longer). Bottom line: don't plug a computer in to a hospital red
    >> >outlet without a UPS.

    >>
    >> >Chip C

    >>
    >> Isolation transformer is there for safety.

    >
    >Yes, in cases where its output is not referenced to earth. The two-
    >prong shaver outlets that used to be in bathroom light fixtures were
    >like this. Also I hear that in the UK (and other 240V places??) they
    >use 120V isolated power on outdoor construction sites.
    >
    >If the one of the transformer output legs is tied to earth, then I
    >don't see the safety benefit.
    >
    >Chip C


    Isolation transformer is for human safety.
    , Aug 18, 2009
    #17
  18. William Munny

    Doug Miller Guest

    In article <>, wrote:
    >On Wed, 19 Aug 2009 03:48:21 GMT, (Doug Miller)
    >wrote:
    >
    >>In article

    > <>, Chip C
    > <> wrote:
    >>
    >>>I believe that audio and signal processing equipment might benefit
    >>>from them, since in some places (at some time) I hear was ok to use
    >>>the metallic conduit as the circuit's ground, and not pull a bare or
    >>>green wire.

    >>
    >>Not "in some places" -- anywhere that has adopted the U.S. National Electrical

    >
    >>Code.
    >>
    >>Not "at some time" -- always.
    >>
    >>Not "was ok" -- still is ok.
    >>
    >>The NEC specifically permits the use of metal conduit of various types to be
    >>used as the equipment grounding conductor. Bare or green wires are not
    >>necessary.
    >>
    >>> The conduit picks up a lot of noise, so it causes problems
    >>>for equipment that uses the ground as a signal reference level.

    >>
    >>Not if it's properly grounded, it doesn't.

    >
    >"proerly grounded" and EMT as ground is an oxymoron.


    Not according to publishers of the NEC, it isn't.

    "The equipment grounding conductor ... shall be one or more ... of the
    following: ... Electrical metallic tubing...." [2008 NEC, Article 250.118]

    I imagine they know a little more about it than you do.
    Doug Miller, Aug 18, 2009
    #18
  19. William Munny

    JIMMIE Guest

    On Aug 18, 1:12 pm, wrote:
    > On Tue, 18 Aug 2009 05:31:40 -0700 (PDT), stan
    >
    > <> wrote:
    > >But as one poster pointed out if we have other computer type gear (say
    > >printers or scanners etc. plugged into regular outlets) their grounds
    > >may inadvertently be connected via the various cables connecting them
    > >to the main computer with its isolated ground. Thus possibly defeating
    > >the purpose of the individual ground?

    >
    > IBM decided IG was snake oil on the late 70s and removed the
    > recommendation from the Physical Planning Manual. You are right, as
    > soon as you connect equipment on different circuits together IG is
    > meaningless, or worse a source of additional problems. Your bonding
    > path becomes longer than the signal path so the line driver/receiver
    > becomes your surge protection. We went the other way and added
    > additional bonding, connecting machine frames directly together.


    I used to work on a mainframe computer system that was updated to
    isolated grounding. There were a few pieces of hardware on which it
    was impossible to isolate the grounds but the engineers decided this
    was OK. I have never seen so much blue smoke in my life as when they
    applied power. This happened nearly 20 years ago and the essence of
    ohms still lingers in the air. A few years ago all the equipment wa
    upgraded and it was all designed for IG and the appropriate IG system
    was installed. A few months ago the equipment was expanded and it was
    decide that IG was not needed so now we have bare ground wires laying
    in bare metal cable trays attached to IG ground points, cable trays
    are fastened to earth ground.

    Jimmie
    JIMMIE, Aug 18, 2009
    #19
  20. William Munny

    bud-- Guest

    Chip C wrote:
    > On Aug 18, 10:12 am, wrote:
    >> On Tue, 18 Aug 2009 07:07:06 -0700 (PDT), Chip C
    >>
    >>
    >>
    >> <> wrote:
    >>> On Aug 18, 8:31 am, stan <> wrote:
    >>>> On Aug 18, 9:43 pm, (Doug Miller) wrote:
    >>>>> In article <>, Ashton Crusher <> wrote:
    >>>>>> On Sat, 15 Aug 2009 08:33:57 GMT, (Doug Miller)
    >>>>>> wrote:
    >>>>>>> Orange = isolated ground (used for sensitive electronic equipment, usually
    >>>>>>> medical or laboratory instruments, or high-end computer gear)
    >>>>>> How is isolated ground different then "regular" ground?
    >>>>> http://tinyurl.com/n937l4
    >>>> Thanks to all posters. Learned something. And made one think. Thank-
    >>>> you.
    >>>> Sounds like 'Isolated' Ground might also be called an 'Individual'
    >>>> Ground!
    >>>> In other words the grounding wire from this type of outlet (orange!)
    >>>> is run individually to the grounding point; not using the ground used
    >>>> for a 'run' or group of 'regular' outlets.
    >>>> Have only used an orange outlet once, connected to the output of a UPS
    >>>> located in our basement and wired up stairs to the room with the main
    >>>> PC etc. AFIK took the ground back to the output of the UPS.
    >>>> But as one poster pointed out if we have other computer type gear (say
    >>>> printers or scanners etc. plugged into regular outlets) their grounds
    >>>> may inadvertently be connected via the various cables connecting them
    >>>> to the main computer with its isolated ground. Thus possibly defeating
    >>>> the purpose of the individual ground?
    >>>> The <http://tinyurl.com/n937l4> was a useful explanatory.
    >>> That's a good article about the hoo-hah surrounding isolated ground.
    >>> I'm convinced that architects put them in out of rote habit. I've
    >>> personally never seen a computer with documentation that requires
    >>> them.
    >>> I believe that audio and signal processing equipment might benefit
    >> >from them, since in some places (at some time) I hear was ok to use
    >>> the metallic conduit as the circuit's ground, and not pull a bare or
    >>> green wire. The conduit picks up a lot of noise, so it causes problems
    >>> for equipment that uses the ground as a signal reference level. The
    >>> orange outlet at least guarantees you a real copper ground all the way
    >>> back to something earthed. As others have said, today's codes,
    >>> especially for hospitals, now guarantee this for all outlets.
    >>> I am also told that the orange outlets can indicate a circuit fed by a
    >>> (nearby) isolation transformer, on the output side of which the
    >>> neutral is re-referenced (ie, tied) to ground. This guarantees that at
    >>> the outlet, ground and neutral are close together in voltage.
    >>> Otherwise, in large commercial buildings, as you get further from the
    >>> point of grounding you can find that ground and neutral not only have
    >>> noise relative to each other but are far apart in DC levels.
    >>> As others have said, the read outlets are on circuits that can be fed
    >>> by the generators if the utility power cuts out. (And yes, the
    >>> breakers for these circuits are in bright read service panels.) But be
    >>> warned, a lot of places do generator and cutover tests at some regular
    >>> schedule, usually at some early morning hour, which cause outages of a
    >>> second or so. Much hospital equipment (fridges, lighting, elevators,
    >>> plus patient support equipment that has internal batteries) ride
    >>> through these fine, but computers don't. And of course, when a utility
    >>> outage happens, it takes time for the generators to ramp up (the
    >>> nominal standard is generally 15 seconds, in the real world can be
    >>> longer). Bottom line: don't plug a computer in to a hospital red
    >>> outlet without a UPS.
    >>> Chip C


    >> Isolation transformer is there for safety.

    >
    > Yes, in cases where its output is not referenced to earth. The two-
    > prong shaver outlets that used to be in bathroom light fixtures were
    > like this. Also I hear that in the UK (and other 240V places??) they
    > use 120V isolated power on outdoor construction sites.


    The UK transformer has a centertap that is earthed. The hot wires are
    60V from earth potential.

    >
    > If the one of the transformer output legs is tied to earth, then I
    > don't see the safety benefit.
    >


    It keeps the hot wires from being at 2000V with respect to earth. Or
    with 120V primary and secondary one secondary wire could be at 240V with
    respect to the earth. When servicing electronic equipment an isolation
    transformer with a completely floating secondary may be used. There can
    be significant hazards working on equipment with the DC power system
    tied to the neutral.

    Almost all systems are earthed.

    --
    bud--
    bud--, Aug 18, 2009
    #20

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