All About Fuses

A fuse is there to break the circuit if a fault develops in an appliance which has caused too much current flow.

The fuse itself contains a piece of wire which can easily melt. If the current flowing through the fuse is too great, the wire will heat up until it melts, thus breaking the circuit.

Fuses in UK plugs are generally fitted with either a 3A or 13A fuse. Any appliance up to 700w will require a 3A fuse to be fitted. Whilst any appliance which is over 700w will need a 13A fuse to be fitted.

Although manufacturers have now standardised plug fuse ratings to be either 3A or 13A, it is still possible to find a 5A fuse in some older appliances and can still be bought.

Some loads use a 5A fuse rather than the normal 3A. For instance, in the case of a 500w halogen floodlight a 5A fuse could be used even though a 3A fuse would carry normal operating current. This is due to the large current the halogen light will draw as the cold resistance is lower than the resistance at operating temperature.

In the case of other appliances it is usual to find either a 3A or 13A fuse fitted to each one. Here are some examples of equipment which would typically use each type: