Always have a card of fuse-wire available, these cover the most popular current ratings: 5, 15 and 30 amps. Make sure you rewire a fuse with the correct size fuse wire using the colour code as a guide to the size required. For cartridge fuses, always have at least two spares of each current rating in the consumer unit. Locate the ‘blown’ fuse and remove the fuse holder. Take out the bits of old fuse wire or the old cartridge and insert the new one, taking care not to stretch the fuse wire on tightening the terminal screw, as this would decrease the current rating, lead to heating of the wire and premature failure. Before replacing the fuse holder in the consumer unit try and find out why the fuse ‘blew’. If the new fuse blows immediately there is a fault in the circuit which requires attention.
Miniature circuit breakers
(MCBs) An MCB is simply a single pole switch which automatically trips (switches-off) when there is a fault in the circuit or serious overloading. To restore the current you simply switch on the MCB but if there is a fault in the circuit it is impossible to close the circuit breaker until the fault is rectified. MCBs can also be used to switch off individual circuits when required, or leave a circuit supplying a freezer or refrigerator switched on when leaving the house for an extended period.