KY60NL Residual Current Circuit Breaker The KY60NL RCCB incorporates a residual current operated electromagnetic release which operates without any auxiliay source of supply to open a circuit automatically in the case of an earth leakage fault between phase and earth greater than or equal to I????n. The KY60NL combined MCB & RCCB provides: 1. protection against indirect contact. 2. complementary protection against direct contact 3. protection for the installation against insulation faults