Identification of the Grounded (Neutral) Conductor

White or gray means grounded conductor, always. On larger wire you can re-identify with tape or marking at the ends, but the point never changes: the neutral looks like a neutral everywhere it lands.

In a remodel I run into old cloth wiring where somebody used white as a switch loop hot. If you do that today it has to be re-marked so the next person is not fooled.

When it applies

Any grounded conductor in your system needs consistent identification. For smaller conductors that usually means white or gray insulation; larger conductors can be re-identified with marking at the terminations.

Common mistakes

• Re-purposing a white conductor as a hot in a switch loop without re-identifying it. That white wire has to be marked to show it is not a neutral.
• Mixing white and gray in the same system so nobody can tell which neutral belongs where.
• Forgetting that with multiple systems in one building, each grounded conductor needs its own distinct marking.

In the field

I opened a box once and found a white wire feeding a light switch with no marking at all. The next person would assume it was a neutral and get a surprise. A wrap of colored tape at both ends takes ten seconds and tells the truth about what that wire really does.