Article 200 covers the identification of terminals, grounded conductors in premises wiring systems, and identification of grounded conductors.
The wiring systems of all premises must have a grounded conductor that is identified as stated in Section 200.6. Exceptions to this are noted in Sections 210.10, 215.7, 250.21, 250.22, 250.162, 503.13, 517.63, 668.11, 668.21, and 690.41 Exception. When the grounded conductor is insulated, the insulation must be suitable for ungrounded conductors in the same circuits where the voltage is less than 1 kV or on impedance grounded neutral systems of 1 kV and over or for solidly grounded neutral systems of 1 kV or more [Section 250.184(a)], the insulation rating must be 600 V or more.
Connection to Grounded Systems
Premises Wiring. When the premises wiring system has a grounded conductor, it must be connected to a supply system which also has a grounded conductor.
Means of Identifying Grounded Conductors
(A) Sizes 6 AWG or Smaller. A white or gray covering or insulation or one with three continuous white stripes on other than green insulation is required on insulated grounded conductors of size 6 AWG or smaller. MI cable must have distinctive marking at the terminations. There are requirements for conductors in photovoltaic power systems, fixture wire, and aerial cable.
(B) Sizes Larger than 6 AWG. In this case it can be identified by a continuous white or gray finish on the outside, three continuous white stripes on the entire length on all but the green insulation, or a distinctive white or gray marking at the terminations at the time of installation. The marking must encircle the insulation or the conductor.
(C) Flexible Cords. When the grounded conductor is in a flexible cord it shall also have a white or gray outer finish or in acccordance with Section 400.22.
(D) Grounded Conductors of Different Systems.
(E) Grounded Conductors of Multiconductor Cables. There are two exceptions.
Use of Insulation of a White or Gray Color or with Three Continuous White Stripes
White or gray continuous coverings on a conductor, white or gray markings at terminations, or three continuous white stripes other than green insulation can be used only to identify the grounded circuit conductor. There are noted conditions where white or gray may be used for other than the grounded conductor.
Means of Identification of Terminals
Identification of Terminals
When conductors are to be attached to more than "one side" of a circuit, they must have the device terminals identified. This is not necessary when the connection to the grounded conductor is evident, and in panelboards, and in devices rated over 30 Aother than polarized attachment plugs and receptacles. Polarized attachment plugs and receptacles must have the terminal for the grounded conductor marked white. Refer to Section 215.126 for equipment grounding terminals. The terminal for the grounded conductor in screw-shell devices is the one connected to the screw shell. If there is a lead connected to the screw shell, it must be white or gray.
Polarity of Connections
Article 90 Introduction
Wiring and Protection
Wiring Methods and Materials
Equipment for General Use
Annex C. Conduit and Tubing Fill Tables for Conductors and Fixture Wires of the Same Size
Annex D. Examples
Annex E. Types of Construction