Yellow green and red wires in the distribution box

In a distribution box, red and yellow wires typically indicate live or phase conductors, while green (often with a yellow stripe) is used for earth/ground for safety.

Wire Color Functions

Red Wire: In many AC systems, especially older UK/EU installations, red is used as a line or live conductor in single-phase circuits, or as Phase 1 in three-phase systems. It carries current from the power source to the load and is potentially dangerous if touched. Yellow Wire: Yellow is often used as Phase 2 in three-phase AC systems or as a secondary live wire in certain installations.

It may also indicate a high-voltage line in some older European wiring. Green Wire (with or without yellow stripe): This is universally used as the earth or ground wire, providing a safe path for fault currents to prevent electric shock and protect equipment. Regional StandardsIEC (Europe, UK): Follows IEC 60446 standards.

For three-phase AC, red, yellow, and blue are used for the three line conductors, black for neutral, and green/yellow for earth.

US NE

C: Red and black are typically used for live wires, white for neutral, and green or bare copper for ground. Yellow may be used for switch legs or other live conductors in certain installations.

Safety Tips

Always verify with a multimeter before touching any wire, as older installations may not follow current color codes. Label wires when mixing old and new wiring to avoid confusion. Never assume color alone indicates function; testing and proper identification are essential for safety.

Understanding these color codes ensures safe installation, maintenance, and troubleshooting in distribution boxes, preventing electrical hazards and equipment damage.