A main distribution box is wired by connecting the incoming supply to a double-pole main MCB, then to an RCD/RCCB, followed by single-pole MCBs for individual circuits, with neutral and earth links distributing return and grounding connections.

Components and Layout

1. Main MCB (Double Pole): Acts as the main isolator or switch, controlling the entire electrical supply. Typically rated at 63A for domestic installations. The incoming phase and neutral wires from the utility meter are connected here .
2. RCD/RCCB (Residual Current Device): Provides protection against leakage currents, electric shocks, and insulation faults. The output of the main MCB feeds into the RCD, which then supplies the downstream MCBs. A 30mA rating is common for domestic single-phase systems .
3. Single-Pole MCBs: These protect individual circuits such as lighting, sockets, and appliances. Each MCB is connected to the output of the RCD, and the live wire of each circuit is routed through its respective MCB .
4. Neutral Link: A copper bus bar that distributes the neutral wire to all output circuits. The neutral from the main supply and from each MCB is connected here .
5. Earth Link: A separate bus bar connecting all earth wires from circuits and the main supply to the grounding electrode, ensuring safety against electrical faults .
6. Bus Bars and DIN Rail: MCBs and RCDs are mounted on a DIN rail. Copper bus bars link the MCBs to the main supply and ensure proper current distribution .

Wiring Sequence

1. Connect the incoming phase and neutral from the meter to the main double-pole MCB.
2. Connect the output of the main MCB to the input of the RCD/RCCB.
3. Connect the output of the RCD to the single-pole MCBs for each circuit.
4. Connect all neutral wires from the circuits to the neutral bus bar.
5. Connect all earth wires to the earth bus bar.
6. Ensure proper labeling of each MCB for the corresponding circuit.

Wire Sizing and Safety

• Main feeder cables are typically 16mm² for a 60A load in single-phase systems .
• Use color-coded wires: Red for live, Black for neutral, Green/Yellow for earth (IEC standard).
• Always turn off the main supply before installation and follow local electrical codes. This setup ensures safe distribution of electricity, protection against overloads, and compliance with domestic wiring standards .