U.S. Wire Color Codes and Identification
Distinguish grounded and equipment grounding conductor identification from common phase-color conventions for U.S. electrical systems.
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Identification versus convention
Color communicates an intended conductor function. It does not establish voltage, phase sequence, continuity, or a safe state. Distinguish identification requirements from the phase-color scheme chosen for a project.
| Function | Typical identification | Boundary |
|---|---|---|
| Grounded conductor, often a neutral | White or gray identification | A grounded conductor is not an equipment grounding conductor. Applicable rules govern full-length marking and permitted re-identification. |
| Equipment grounding conductor | Green, green with yellow stripes, or bare where permitted | The conductor is for equipment grounding/bonding; it is not a normal load-current return. Installation and size affect permitted identification methods. |
| Ungrounded conductor | Project-specific identification excluding reserved identification | Check the adopted rules, system documentation, and conductor function. No single black/red/blue scheme proves voltage. |
| Existing re-identified conductor | An allowed permanent identification applied for the particular use | A tape color alone does not establish that re-identification is permitted in that wiring method. |
OSHA 1910.304(a) addresses distinguishable grounded and equipment grounding conductors and identification of terminals. The adopted NEC and project conditions supply additional detail; this summary is not a complete re-identification rule.
Common phase conventions
| System description | Often-used phase colors | Neutral / equipment ground | Use condition |
|---|---|---|---|
| 120/240 V single-phase | Black and red | White / green or bare as permitted | Verify the actual conductors and circuit function. |
| 120/208 V three-phase wye | Black, red, blue | White / green or bare as permitted | A common project convention; confirm the drawing legend. |
| 277/480 V three-phase wye | Brown, orange, yellow | Gray often used / green or bare as permitted | A common convention. Orange has other specific identification uses; context matters. |
A project may use another valid scheme or more than one voltage system in the same building. A high-leg delta system is not interchangeable with a wye-system color chart. Confirm its special identification and system data instead of applying the table by appearance.
Use written phase names or circuit identifiers alongside color in documentation. Printed grayscale copies and color-vision differences can make color-only drawings ambiguous.
Verify an existing installation
- Start with the panel/source identification and the project’s wiring legend.
- Check conductor markings and terminations; record discrepancies rather than silently replacing the documented scheme.
- Use qualified electrical work practices, appropriate isolation, and verification procedures. Do not touch or test conductors solely because a color appears familiar.
- Update the circuit record after an authorized correction so later work uses the same identifiers.
Use the panel directory and matching labels for circuit descriptions, or wire and cable markings to interpret insulation and cable type.