The minimum size of the incoming line to the distribution box is

For a standard household lighting or small power distribution box, the minimum incoming line size is 10 square millimeters.Detailed ExplanationFor lighting circuits or small power loads, the incoming wire to the distribution box should be at least 10 mm² if the number of circuit switches is fewer than 20 . This ensures safe current handling and prevents overheating. If the number of switches exceeds 20, the distribution box may require two rows of switches, but the minimum incoming line size remains the same . For power distribution boxes handling larger loads, the incoming wire size may exceed 10 mm². In such cases, additional considerations include:Bending radius: Ensure sufficient space for the wire to bend without stress .Terminal connections: Adequate space must be reserved for secure connections at the primary terminals .Two-row switch arrangements: Wiring layout should accommodate multiple rows of switches if needed .Installation ConsiderationsThe distribution box should be mounted securely on the wall using expansion bolts or embedded supports .Maintain proper clearance in front of the box (typically 0.8–1.2 meters) for safe access during maintenance .Ensure the incoming line is connected to the correct terminals: phase lines, neutral, and ground, following standard color codes and safety practices .SummaryMinimum incoming line for small household distribution box: 10 mm².For larger power loads: Use wires larger than 10 mm², considering bending radius and terminal space.Safety and installation: Proper mounting, clearance, and adherence to wiring standards are essential for safe operation .