White and gray identify grounded conductors, including the neutral in common building circuits. 2020 NEC 200.6 sets the identification rules. Gray does not automatically mean 277 volts, and white does not automatically mean 120 volts. Identify the circuit and system before drawing that conclusion.
Watch JCR explain two grounded-conductor rules
Victor reviews Article 200, including insulation and identification when conductors from different systems occupy the same enclosure.
Watch JCR explain two grounded-conductor rulesWatch the existing JCR lesson on YouTubeWhite and gray serve the same basic purpose
Either color can identify a grounded conductor. The NEC does not assign white exclusively to one voltage and gray exclusively to another. A job may use that scheme to distinguish systems, but you must verify the documented identification.
The grounded conductor and equipment grounding conductor are different. White or gray is grounded-conductor identification. Green, green with yellow stripes, or bare conductors serve equipment-grounding functions where permitted. Review our equipment grounding conductor guide.
What if two systems share a box or raceway?
Under 200.6(D), grounded conductors from different systems in the same raceway, cable, box, auxiliary gutter or other enclosure must be distinguishable by system. White for one and gray for the other is one permitted approach. Other permitted identification includes a distinguishing colored stripe on white or gray insulation, other than green.
Make the identification method available to the people installing and maintaining the system, or permanently post it at the origin of each branch-circuit system. A color scheme only helps when the next electrician can determine what it means.
Find conductor-identification answers faster
Turn lessons like this into test-day skills. Find the rule, work the calculation and practice with JCR’s mock exam questions.
Live classes teach the 2020 NEC. Check your state’s exam requirements before choosing a course. NC prep includes NC business and law. For another state, also study any business-and-law material required for your license. JCR also carries the 2020 NEC (NFPA 70) code book.
Already licensed? Earn your CE with JCR
Choose in-person classes, live Zoom or recorded courses. Review NEC navigation, grounding and bonding, and other electrical topics. Check the course’s NEC edition, state approval and credit hours before enrolling.
See CE courses and class datesCan you mark black wire with white tape?
For an insulated grounded conductor 4 AWG or larger, 200.6(B) permits a distinctive white or gray marking at its terminations. The marking must encircle the conductor or insulation.
For 6 AWG and smaller, start with 200.6(A). The usual methods are continuous white or gray insulation, or three continuous white or gray stripes along the insulation, on a color other than green. Specific exceptions exist. The large-wire tape rule is not a general permission to tape every small black conductor white.
Practice question
A junction box contains grounded conductors from two systems. Both are plain white, with no distinguishing identification. Is white insulation alone enough?
No. It identifies their grounded-conductor function but does not distinguish the two systems as required by 200.6(D). Identify each system using a permitted method and provide the identification information.
Common questions
Is every gray wire a power-circuit neutral?
No. Older lighting controls may have gray control conductors. 2020 NEC 410.69 addresses control-conductor identification where control and branch-circuit wires share a luminaire or enclosure. Determine the wire’s function from the circuit and equipment documentation.
Are neutral and ground interchangeable?
No. A neutral normally carries load current. An equipment grounding conductor provides the fault-current path. Review the main bonding jumper rules to understand where the systems connect.
Can color tell me whether a conductor is safe to touch?
No. Identification is not a voltage test. Follow the required safe-work procedure and verify the circuit condition.
Keep practicing
Try our most-missed NEC mock exam questions and 2020 NEC practice questions. For each missed answer, find the section in your code book, read the rule and work the question again.
Reviewed October 25, 2026, for the 2020 NEC. Use the edition required by your licensing exam. Follow the adopted code and local amendments on the job.
