Relationship between distribution box and main cable

The main cable in a distribution box is the incoming feeder cable that carries the total electrical load to the main MCB, from which power is distributed to all sub-circuits.Purpose of the Main CableThe main cable, also called the feeder cable, brings electrical power from the utility supply or main service panel into the distribution box. It connects directly to the Main MCB (Miniature Circuit Breaker) or main switch, which controls and protects the entire distribution board. When the main MCB is turned on, power flows through the main cable to the internal bus bars, RCCBs, and individual circuit breakers, supplying all connected sub-circuits safely .Cable SpecificationsCurrent Rating: The main cable must handle the total anticipated load of all sub-circuits. For example, a 60A single-phase distribution board typically uses a 16mm² cross-sectional area copper cable for both phase and neutral wires .Insulation and Type: Use cables rated for the system voltage (e.g., 230V for single-phase domestic systems) and with proper insulation to prevent overheating and short circuits .Connection: The main cable is connected to the input terminals of the Main MCB, which then feeds the RCCB (if installed) and subsequently the branch MCBs for individual circuits .Installation ConsiderationsEnsure the cable is securely fastened and routed neatly to avoid mechanical damage and maintain proper ventilation inside the distribution box .Follow local electrical codes and standards (e.g., NEC, IEC, or British Standards) for cable sizing, protection, and grounding .Perform visual inspections and continuity tests before powering the system to ensure safe operation .SummaryThe main cable is the backbone of a distribution box, carrying the full electrical load to the main protective device. Proper sizing, insulation, and secure installation are critical to ensure safety, prevent overloads, and maintain reliable power distribution throughout the building .