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AC Power Line Color Conventions

Discussion in 'Electronic Design' started by Chris Carlen, Aug 18, 2006.

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  1. Chris Carlen

    Chris Carlen Guest


    I see a US 120V chassis wired:

    AC line hot BLACK --> switched AC hot BROWN
    AC line neutral WHITE (1) --> switched neutral LIGHT BLUE

    I think I've seen the same arrangement in universal 120-240VAC equipment.

    I'm wondering if it would be considered bad form to substitute gray for
    the lt. blue for switched neutral, since lt. blue is harder to get, and
    gray is mentioned in NEC as an acceptable "grounded conductor" (ie.,
    neutral) color.

    The trouble is that in USA neutral is expected to be at 0V, while in
    Euro and other 220VAC areas, what is the lt. blue conductor?

    Are euro and other countries with 220VAC a single phase w/ respect to
    ground (one hot and a grounded neutral)? Or are they two 110VAC w/
    respect to ground but antiphase w/ respect to each other as in USA?

    But things get more complicated then with 240VAC in the USA which is
    usually black and red hot conductors. What then would be a good pair of
    colors for the switched 240VAC hots? Just stick with brown and blue?

    There is a problem creating consistency here if the 220VAC wiring in
    Euro and 220VAC regions is different from USA with it's anti-phase setup.

    (1) or BLACK + WHITE stripe

    Good day!

    Christopher R. Carlen
    Principal Laser&Electronics Technologist
    Sandia National Laboratories CA USA

    NOTE, delete texts: "RemoveThis" and
    "BOGUS" from email address to reply.
  2. Phil Allison

    Phil Allison Guest

    "Chris Carlen"

    ** There is no real distinction ( in terms of electrical safety) between
    Active & Neutral wires when dealing with the INSIDES of portable
    appliances. All wires which attached to the incoming AC supply must be
    treated as potentially LIVE and dangerous - whether nominally Neutral
    conductors or not.

    NEVER get the damn silly idea in your head that the Neutral colour wires
    inside an appliance are different from the Active ones and hence safe to

    It would be CRIMINAL to suggest that same idea to another.

    ........ Phil
  3. DJ Delorie

    DJ Delorie Guest

    Be careful about the distinction between "grounded conductor" and
    "grounding conductor". The latter is usually green or bare.
  4. Here you are talking about wiring pre-~1970 when for years the "old
    good" tradition was implemented partly to get rid of manufactured wires
    Are your chromosomes XY? If yes then you are part of the human male
    population which includes 40% of 'color blind' (partially/totally)
    members. The 'old' AC wiring was line-red, neutral-black, ground-white.
    So a color-blind person (like a B/W film) was perceiving the black AND
    red in the same way. So mistakes happened till the standards
    organisation issued a new coloring scheme which is recognised by
    differences on the gray scale so the three wires can be connected by
    anyone. Brown- line, light blue- neutral and green(with or without
    yellow stripe)- ground.

    Ideal ground is considered zero, neutral is only cirquit completion
    connection to the source and its voltage to ground can be anything.
    The 220-240AC are single phase 'active-neutral', no ground involved.


    Slack user from Ulladulla.
  5. Eeyore

    Eeyore Guest

    230V actually.

    Blue ( light blue ) is neutral. However many European countries have unpolarised
    plugs that allow appliances to be 'reverse connected'.

    I would.

    We don't have '2 phase' here.

  6. Eeyore

    Eeyore Guest

    It would indeed.

    Only Ground ( green/yellow ) is 'safe'.

    However it's far from unknown to find outlets with no ground in some parts of
    Europe AIUI. In which case, adopt design as for Class II equipment ( double
    insulated ).

  7. Eeyore

    Eeyore Guest

    Not green any more ( for a long time actually ). Green with a yellow stripe.

  8. Ben Jackson

    Ben Jackson Guest

    I know you mean 0V vs 120V or so, but remember that neutral must
    only be bonded to ground at the panel. In an appliance, there may
    be a small potential between neutral and ground. Or if there's a
    loose neutral in the panel, a LARGE potential...
  9. DJ Delorie

    DJ Delorie Guest

    Er, no. I know a couple of color blind people, and used to work on
    accessibility testing for color blindness in software.

    What color blind people can't tell the difference between is various
    shades of (for example) red and green. Bold colors can usually be
    discriminated (by brightness, or by weak color reception), and
    certainly they can tell colors from black and white.

    To simulate red-green color blindness, modify your color palette so
    that all red and green channels are replaced with a yellow of similar
    brightness (leave blue alone). This gives you black, white, blue,
    yellow, and blends.

    One of my subjects joked that he was going to paint his house pink and
    cyan, because *he* couldn't tell the difference.

    They also have trouble with red and green street lights at night; not
    enough visual clues to tell which light is on.
  10. Phil Allison

    Phil Allison Guest

    "Ben Jackson"

    ** This is VERY dangerous crapology.

    In a portable appliance, nominal neutral conductors must be assumed to beat
    LIVE at *full line voltage* - anytime.

    The legal requirements for insulation type and thickness, clearances and
    creepage distances are the SAME for all AC supply current carrying

    ....... Phil
  11. Eeyore

    Eeyore Guest

    See also the IEC requirements for 'double insulated' AC conductors in equipment.

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