4.3 MINIATURE CIRCUIT BREAKERS
Unless otherwise indicated in the Drawings and/or Bill of Quantities, miniature circuit breakers (mcb) shall have breaking capacity not less than 6 kA (rms) and of B-type with Class 3 energy limiting characteristics. However, C-type instantaneous trip with Class 3 energy limiting characteristics shall be used for motor circuit.
They shall comply with IEC 60898, fully tropicalised and suitable for use on a 240/415 V, 50 Hz. a.c. system and up to an ambient temperature of 40 0C. They shall be quick-make, quick-break and trip free type complete with de-ion arc interrupters. The tripping elements shall be of thermal magnetic type withinverse time delay overcurrent and instantaneous short circuit characteristic.
The respond to overload shall be independent of variations in ambient temperature. They shall be manually operated by means of toggle type handles having visual indication of whether the breaker is opened, closed or tripped. Multipole mcb shall be of all pole protected type and provided with common-trip mechanism for simultaneous operation of all the poles.