MCBs are typically connected before RCCBs in a distribution board for several reasons:
1. Protection Coordination: The MCB provides protection against overcurrent, overload, and short circuits. By placing the MCB before the RCCB, it ensures that these faults are cleared first, preventing potential damage to the RCCB.
2. Prevention of Nuisance Tripping: If an overload or short circuit occurs, the MCB will trip before the RCCB. This prevents the RCCB from tripping unnecessarily, which can cause inconvenience and potential safety issues if the entire circuit loses power.
3. Selective Tripping: In case of an overload or short circuit, the MCB will isolate only the affected circuit, while the RCCB will remain operational. This allows other circuits protected by the RCCB to continue functioning, ensuring minimal disruption.
4. Equipment Protection: Placing the MCB first helps protect the RCCB and other downstream devices from the high currents associated with short circuits and overloads.
5. Simplified Fault Diagnosis: When an MCB trips first, it is easier to identify and locate the specific circuit with the fault. If the RCCB tripped first, it would disconnect all the circuits it protects, making fault diagnosis more complex.
By connecting the MCB before the RCCB, the overall safety, reliability, and functionality of the electrical system are enhanced.
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