Electrical Fuses: How to Change a Fuse

Fuses are safety devices inserted in electrical lighting, heating and power circuits. When a circuit becomes overloaded or shorted, the fuse wire, which is thinner and softer than the main circuit wires, heats and melts, automatically cutting off the electrical supply to the circuit affected — thus minimizing risks of fire and shock. Repair necessities used to be a card of fuse wire and a small insulated screwdriver – nowadays you just need a pack of the relevant amperage fuses together with the screwdriver; these should be stored near the fuse-boxes together with a torch or candles and matches.

Before opening the fuse-box, the current must be switched off at the main.

repairing a household fuseExamine all the fuses in the box; the burnt one can usually be identified by a sooty smudge on the white porcelain holder. Loosen the screws in the holder (see image) and remove every piece of the old wire; wipe off the sooty deposit before replacing burnt wire with a new piece of correct strength. The amperage is usually stamped on the side of the porcelain holder-5 amp. for lighting, 10 amp. for heating, and 15 amp. for power. It is dangerous to use wire stronger than the specified amperage, and only fuse wire should be used — not hairpins or old bits of any odd wire.

Coil the ends of the new length of wire round the securing screws in the porcelain holder and under the washers, snip off the surplus ends of wire and tighten the screws. The wires should be slightly slack between the two terminals to permit normal cooling contraction after the wire becomes hot — tight wires snap easily. Replace the fuse-holders in the box and switch the current on at the main.


Modern power fittings now incorporate fuses in the actual plug. These will prevent the overloading being transferred to the full circuit. Consisting of a small, metal-ended, cylinder, they are held between spring clips. It is a simple matter to pull one out and push another into place.

If the fuse blows again immediately the current is switched on, it is necessary to find the reason. This may be due to overloading the circuit by using more appliances at one time than the circuit can take, especially if additional wiring has been added to the original circuit. Other reasons for fuse failure are faulty connections where the lead is joined to the appliance; the insulation covering the flex wires may have rubbed bare — causing a short circuit. A fault may have developed in a socket, plug or switch, or the circuit may have been shorted by a faulty lamp or breakdown in a radio set. If no apparent fault can be traced, and the fuse continues to blow every time it is replaced, it will be advisable to call in your local Electricity Board or an electrician to trace the fault.

04. July 2011 by admin
Categories: Electricity, Mains Services | Tags: | Comments Off on Electrical Fuses: How to Change a Fuse


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