Live (L) Wire Connection: In a distribution box setup, the incoming live wire (also known as phase or hot wire, denoted as L or Line) connects to the line terminal of the circuit breaker. This serves as the primary source of electrical energy from the mains supply. Learn how to install a distribution box safely and correctly. Covers wiring, placement, standards, and expert tips for a compliant setup. A distribution box, also known as a distribution board, electrical panel, or breaker box, is an enclosure that houses electrical components responsible for distributing electricity throughout a building.