Calculate the required miniature circuit breaker (MCB/OCPD) rating in Amps, trip curve (B, C, D) and minimum wire size from wattage and voltage.
Regulatory Rule (NEC Art. 240 & IEC 60364-4-43): The breaker rating (In) must always be greater than or equal to the design load current (Ib) and never exceed the conductor's allowable ampacity (Iz).
| Circuit | Application | Breaker (MCB) | Wire Size | RCD / GFCI |
|---|---|---|---|---|
| C1 | Lighting circuits | 10 A (Curve C) | 1.5 mm² | 40A / 30mA |
| C2 | General purpose outlets | 16 A (Curve C) | 2.5 mm² | 40A / 30mA |
| C3 | Electric range & oven | 25 A (Curve C) | 6.0 mm² | 40A / 30mA |
| C4 | Washer, dishwasher & water heater | 20 A (Curve C) | 4.0 mm² | 40A / 30mA |
| C5 | Bathroom & kitchen countertop outlets | 16 A (Curve C) | 2.5 mm² | 40A / 30mA |
Apply the coordination rule Ib ≤ In ≤ Iz: the breaker rating (In) must be at least the design load current (Ib) and never exceed the wire's thermal ampacity (Iz).
Curve C (5–10× In magnetic trip) is standard for residential outlets and appliances; Curve B (3–5× In) protects electronics and long cable runs; Curve D (10–20× In) handles high-inrush motors.