The range of Miniture Circuit Breakers, MCB, help to protect equipment & cables from overloads & short circuit faults. The rated / nominal current of the device i.e. 6A will protect against overloads, this should be lower than the rating of the cable but higher than the load on the circuit. The type of device should be selected by the type of load connected to the cable: B type are rated 3 / 5 times the rated current - Domestic low starting loads. C type rated 5 / 10 times the rated current - Motors and high starting loads; D type rated 10 / 20 times the rated current - large inrush current load i.e. welders. The device should also be able to isolate large short circuit currents in the thousands of Amps so a 6KA or 6 Thousand Amps for domestic & small circuits & 10KA or higher for large city & industrial circuits. The length of circuit & BS 7671 should be considered at all times in circuit design.