Connect the input and output wires to the corresponding terminals of the distribution box. Whether in a home or an industrial facility, this box keeps your electrical setup organized, functional, and efficient. However, the key to. That cable running from your main service entrance to your distribution box isn't just another wire – it's the critical link that determines how safely and efficiently power flows through your entire building. three phase lines a, B and C (generally yellow, green and red), one zero line (light blue) and one ground line (yellow with green stripes). Follow this guide for a clear and safe connection process: Before starting, always ensure the main power is turned off to avoid electrical shock.