MCB stands for miniature circuit breaker.
Located in the switchboard, An MCB is an isolator which automatically disconnects power to a circuit when there is a fault, such as a short circuit or overload.
MCB’s are designed to operate within a specified time frame which is typically 0.4 seconds. This is determined as enough time to clear a fault before a fire is caused.
An electricians job is to ensure that the right MCB is installed for the circuit it is protecting.
MCB’s have a current rating, curve rating (B,C,D), and prospective short circuit current rating (usually 6000 amps), all of these need to be taken into account when installing the right one.
An MCB is known as a close protection device.
Previous to MCB’s, re-wirable fuses were used which are now illegal. (Electrical Safety Regulations 2010)
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