Cartridge fuses are available in several sizes and Ampages, and are designed for several different applications. It is important to always use the correct fuse for a specific electrical circuit to avoid damage to the circuit or worse. Here is a guide to the different fuses and their main uses.
5A Fuse
Used mainly for lighting curcuits.
15A Fuse
Generally used in a Storage Heater or Immersion Heater circuit.
20A Fuse
Used in a 20amp radial power circuit and sometimes in storage heater circuits.
30A Fuse
A 30amp fuse will be used in a ring main circuit and sometimes in a radial power circuit(30amp).
45A Fuse
These large fuses are used in cooker circuits and shower circuits.
Remember that fuses are a safety device, designed to blow out and cut off an electrical circuit in the event of a power surge or electrical malfunction. Replacing fuses with any other metal object just to get the circuit running again is very dangerous!
Testing Fuses
The easiest way to test if a fuse is blown is to use a handheld fuse tester. You can buy these devices very cheaply and most types include the ability to test lightbulb and batteries as well as cartridge fuses.
Fuse Wire
Some circuits in older houses might contain Fuse Wire instead of Fuses. If this is the case in your house, you should use 5amp wire for a lighting circuit, 15amp for an immersion heater circuit, 30amp wire for a ring main or cooker circuit (for cookers up to 12kw).
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