How neutral wires must be identified

What the code requires

Under 200.6(A), the insulation of a grounded conductor, usually called the neutral, sized 6 AWG or smaller must be identified by a continuous white outer finish, a continuous gray outer finish, or three continuous white or gray stripes running its entire length on insulation other than green. White or gray insulation with colored tracer threads that identify the manufacturer also qualifies.

Special cases in 200.6(A) cover single-conductor outdoor PV cable marked at its terminations, Type MI cable marked with an encircling white or gray marking at its terminations, fixture wire under 402.8, and aerial cable, which may be identified by a ridge.

Under 200.6(E), insulated neutrals inside multiconductor cables must be continuous white or gray, or have three white or gray stripes. Conductors 4 AWG and larger in cables may instead be identified as 200.6(B) allows. By exception, a conductor in a multiconductor cable may be re-identified as the neutral at its terminations, at the time of installation, with a distinctive white or gray marking or another equally effective means. An informational note warns that gray insulation may have been used for ungrounded (hot) conductors in older installations.

On the job

• In existing buildings, a gray wire may be a hot conductor, so an electrician should verify it rather than assume it is a neutral.
• Where a white or gray conductor in a cable is used as a hot, it must be re-identified as described in 200.7.

Related sections

• NEC 200.7: Using a white or gray wire as a hot conductor
• NEC 200.4(B)
• NEC 210.5(A)
• NEC 250.119
• NEC 402.8

Where this comes from

• NFPA: NFPA 70 2026-cycle First Draft, CMP-5 (2023 baseline text)
• Mike Holt: Summary of the 2023 Changes to the NEC
• Read the official NEC free at NFPA