Miniature circuit breakers (MCBs) are fitted in newer consumer units in place of fuses. Application of Miniature circuit breakers (MCBs) take necessary part in house wiring .They have the advantage that they can be manually reset without having to replace wire as in the case of the traditional fuse. The MCBs have either a button or lever that can be flicked to reset it. Rated current not more than 100 A in Miniature circuit breakers (MCBs). Trip characteristics normally not adjustable. Thermal or thermal-magnetic operation. Breakers illustrated above are in this category.

Miniature circuit breaker

The MCB tripping is an indication either that the circuit has been overloaded or that a short circuit has occurred somewhere in the system. Before resetting the MCB it is important to identify what has caused it to trip. Switch off all the appliances connected to the circuit to ensure it is not overloading.
 If you find any fault in MCB First switch off the main switch on the consumer unit, this is very important. Reset the MCB by either pushing the button or by flicking the lever. Finally flick the main switch of the consumer unit back on. If the MCB immediately resets itself once power is restored, then a fault is still occurring, see Identifying a faulty circuit to try to identify the fault.