An RCCB (Residual Current Circuit Breaker), sometimes called an ELCB, is a life-safety device that constantly compares the current flowing out and back in a circuit. If even a small amount leaks — for example through a person touching a live part, or through damaged insulation — it cuts the power in milliseconds, fast enough to prevent a fatal shock.
An MCB protects the wiring from overload and short circuit; an RCCB protects people from electric shock and earth leakage. They do different jobs, so modern homes are advised to have both, especially for circuits in wet areas like bathrooms and kitchens.
An RCCB is strongly recommended for any home, particularly with children or elderly members. Have a licensed electrician fit the right type and rating, and pair it with sound house wiring and proper earthing.