Grounded conductors must meet identification requirements, to avoid confusion with ungrounded conductors. The requirements are a bit confusing, because the NEC has two sets of them depending upon whether the conductor is smaller than 4 AWG or larger than 6 AWG [200.6]. These three are common to both size ranges:
1. Continuous white outer finish.
2. Continuous gray outer finish.
3. Three continuous white or gray stripes along the conductor’s entire length on other than green insulation.
For conductors sizes 4 AWG or larger, there’s a fourth way to identify the ungrounded conductor: encircle it with a distinctive white or gray marking at its termination.
For conductors 6 AWG or smaller, you have five additional methods:
1. The outer covering of the wire is finished to show a white or gray color and there are tracer threads in the braid identifying the source of manufacture.
2. It’s MI Cable and you give the grounded conductor a distinctive marking at its terminations when installing.
3. It’s a single-conductor photovoltaic system cable permitted by Sec. 690.31, and you install it with distinctive white markings at all terminations.
4. It’s fixture wire that complies with the marking requirements of Sec. 402.8.
5. It’s aerial cable with a ridge on the cable exterior; any of the preceding methods are also OK.