1) Generally, the incoming line of power distribution box adopts five wire system, that is, a, B and C three-way phase line (the general color is yellow, green and red), one way zero line (the color is light blue) and one way ground line (the color is yellow with. 1) Generally, the incoming line of power distribution box adopts five wire system, that is, a, B and C three-way phase line (the general color is yellow, green and red), one way zero line (the color is light blue) and one way ground line (the color is yellow with. The wiring color codes are the standard safety language of electricity. They make it easy to identify immediately which wires are live, neutral, or grounded (avoiding costly mistakes and hazardous accidents). This guide describes wiring color codes, international standards, and main rules to keep. The IEC 60446 standard, “Basic and Safety Principles for Man-Machine Interface, Marking, and Identification,” establishes global guidelines for identifying electrical equipment terminals, conductors, and wiring colors. Outgoing line. What do numbers like “20A” or “15A” mean on breaker labels? It is normal to feel unsure about your distribution box. The labels might look confusing at first. You can learn what they mean with some help. Yet, one of the most overlooked steps in electrical safety and convenience is correctly labeling each circuit breaker. Too often, homeowners open their panel and. Share This Story, Choose Your Platform!.