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 a fuse in a distribution board, but one fuse can serve several outlets. The wiring from one fuse is known as the final sub-circuit, and all the outlets fed from the same fuse are on the same sub-circuit. The fuse must be large enough to carry the largest current ever taken at any one instant by the whole of the equipment on that sub-circuit. Since the fuse protects the cables, no cable forming part of the circuit may have a current carrying capacity less than that of the fuse. The size of both fuse and cable is, therefore, governed by the number and type of outlets on the circuit.
