Say you have a supply rated at 63A coming into a property, directly from the overhead wires.
Through the meter - and into the consumer unit.
The consumer unit has a 100A rated isolator switch.
The load consists of 4 circuits each protected by 16A MCB's, and one circuit protected by a 32A MCB.
What happens if each of the 4 circuits draw say, 14A each (56A) and at the same time the 32A rated circuit draws 20A.
That's a grand total of 76A, which exceeds the supply rating.
What is there to protect the supply cable coming into the house from overcurrent if there is no master fuse fitted before the consumer unit?
None of the circuits are exceeding their maximum rated value.
Through the meter - and into the consumer unit.
The consumer unit has a 100A rated isolator switch.
The load consists of 4 circuits each protected by 16A MCB's, and one circuit protected by a 32A MCB.
What happens if each of the 4 circuits draw say, 14A each (56A) and at the same time the 32A rated circuit draws 20A.
That's a grand total of 76A, which exceeds the supply rating.
What is there to protect the supply cable coming into the house from overcurrent if there is no master fuse fitted before the consumer unit?
None of the circuits are exceeding their maximum rated value.