The term 'fuse' is short for fusible link, and protects against overcurrent within a circuit.
The fuse contains a metal strip or wire that will melt when heated by an overcurrent and therefore break the circuit, preventing the circuit from working and causing damage.
The BS 1363 13 A plug has a BS 1362 cartridge fuse inside. This allows the use of 30 A or 32 A (32 A is the closest European harmonized size) socket circuits safely. In order to keep cable sizes manageable these are usually wired in ring mains.
Three types of fuses are used in the home:
Main Fuse – This is sealed in by the Electricity Board and can only be accessed by them. It needn’t concern a householder in their electrical maintenance as it rarely blows.
Consumer Unit Fuse – This is located next to the meter.
In older houses the consumer unit either has a wire fuse or cartridge system. In both of these the fuse carrier is removable.
In new homes are miniature circuit breakers. These consist of mini switches or buttons, as opposed to the wire, that trip is they are overloaded with current.
• Cartridge Fuse – This can be found in the rectangular pin plugs with an amp of 3 or 13. The plug fuse trips an appliance rather than an entire circuit, so a single fault can be isolated and not affect the whole electrical ring.
Fuses are always colour coded and have the amp on them:
- Appliances using up to 700 watts: 3 amp fuse
- Appliances using 700 to 1000 watts: 5 amp fuse
- Appliance using 1000+ watts: 13 amp fuse