ABSTRACT
The final outlets of the electrical system in a building are lighting points, socket outlets and fixed equipment. The wiring to each of these comes from an excess current protection device (fuse or circuit breaker) in a distribution board, but one fuse or CB can serve several outlets. If the circuit supplies current using equipment, wiring from one fuse or CB is known as the final circuit, and all the outlets fed from the same fuse or CB are on the same final circuit. The fuse or CB must be large enough to carry the largest steady current ever taken at any one instant by the whole of the equipment on that final circuit. Since the fuse or CB protects the cables, no cable forming part of the circuit may have a current carrying capacity less than that of the fuse, unless the characteristics of the load or supply are such that an overcurrent cannot occur. The size of both the fuse or CB and cable is, therefore, governed by the number and type of outlets on the circuit.
