Replacing a Circuit Fuse

There are two types of circuit fuse - cartridge and rewirable.

Cartridge Fuses

Cartridge fuses use enclosed fuses - like those in modern fused plugs, but larger - which clip into the fuseholder or are held in place by its pins. To replace a blown cartridge fuse, turn off the power at the main switch, remove the affected fuseholder, and insert a replacement fuse of the same rating. Cartridge fuses are colour-coded according to their current rating:

• white is 5 amps
• blue is 15 amps
• yellow is 20 amps
• red is 30 amps
• green is 45 amps

All are different sizes (except the 15- and 20-amp fuses, which are effectively interchangeable) making it impossible to fit the wrong fuse in the fuseholder. Replace the fuseholder and restore the power.

Rewirable Fuses

Rewirable fuses have a length of wire fitted between two terminals and running across or through a ceramic block inside the fuseholder. In these, the wire itself needs replacing if the fuse is blown. Fuse wire is sold on cards holding wire of three current ratings - 5, 15, and 30 amps - and it's essential to use the correct wire for the circuit concerned.

• Match the rating stamped on the fuseholder to the size of fuse wire printed on the card it's wrapped around.
• Loosen the terminals of the fuse so you can release the old fuse wire.
• Replace it with a new piece of wire, leaving the wire a little slack between the terminals. You will probably need about 50 mm (2in) length - the wire has to be long enough to reach from terminal to terminal and to be wrapped around each.