Standard control cabinet wiring colors

In control cabinets, green-yellow is used for protective earth, light blue for neutral, and other colors like black, red, or blue are used for AC/DC power and control circuits depending on the standard.

Protective Earth and Neutral

Protective Earth (PE): Always green-and-yellow, reserved exclusively for earth conductors, with a 70/30 stripe distribution over any 15mm length if insulated, or applied at accessible points if wiring is concealed (EN 60204-1, IEC 60445). Neutral (N): Light blue throughout the conductor length, or marked with a 15–100mm stripe if in a concealed location.

AC and D

C Power ConductorsAC main power: Typically black for non-earthed conductors (IEC recommendations).

A

C control circuits: Often red.

D

C control circuits: Usually blue or dark blue. Power chains not requiring separation: Orange may be used for live circuits that remain energized when the main switch is off.

U

L 508A Specifics (North America)Non-earthed internal main circuit wires: black. Grounded AC-carrying conductors: white or gray, or marked with three white stripes if insulation is a different color. Protective conductors: green, with or without yellow stripes.

Minimum wire size for control circuits: 18 AWG, with sizing based on overcurrent protection or power supply ratings.

Additional Notes

Avoid using green or yellow alone to prevent confusion with protective earth. Alternative identification methods such as terminal numbering, wire markers, or functional labels are allowed under IEC 60445 if color coding is not feasible. Tri-rated cables (BS 6231) are commonly used in control panels for high-temperature and fire-retardant applications.

By following these color conventions, control cabinet wiring remains safe, traceable, and compliant with international standards, while minimizing the risk of misidentification during installation or maintenance.