ABSTRACT
It is important that all electrical installations and all parts of the installation can be isolated safely. The requirement of BS 7671 is that isolation must be possible at the origin of the installation, each circuit, every item of equipment and every motor. Isolators can be various devices such as, a disconnector, load switch, and switch disconnector; it is important that the function of each of these is understood. Apart from the origin of the larger installations there may well be more than one distribution board or consumer unit; these boards must be able to be isolated without interrupting the supply to other boards or circuits. Isolation of circuits can be achieved by using circuit breakers and fuses. Functional switching is used where parts of a circuit or parts of the installation need to be able to be controlled independently of the rest of the installation.
