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 green. 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 green. The requirements for the distribution box can be based on the power consumption plan of the project, and if not, you can go to a sample construction site to see (such as large projects, which are usually very formal). The information provided in this document contains general descriptions, technical characteristics and/or recommendations related to products/solutions. This document is not intended as a substitute for a detailed study or operational and site-specific development or schematic plan. Neither the main distribution board nor the distribution boards shall be directly connected to any other equipment; otherwise, the. Electrical power enters a distribution box through the incoming lines using what we call a five-wire system. Each of these wires has a specific, non-negotiable purpose: The Phase Lines : You've got three of these bad boys – A, B, and C phases. By convention, we use yellow for A phase, green for B. In this guide, we'll break down everything you need to know to install a distribution box correctly and confidently. Check for proper IP/NEMA ratings and material quality. Although the greatest of care has been taken in the compilation and preparation of this document, GTC respectfully accepts no responsibility for.