What is a fuse cartridge?
A fuse cartridge is a replaceable protective device containing a thin wire or strip that melts when too much current flows through a circuit, breaking the circuit before the cables overheat. In Dutch it is called a smeltpatroon, or simply a stop or zekering. Older Dutch and German homes typically use screw-in Diazed (D-type) cartridges; in the UK the familiar equivalents are cartridge fuses in older fuse boards and the small fuse inside every 13 A plug.
Features
- Fuse element. A wire or strip of copper, silver or copper alloy, packed in sand inside a ceramic body. Under overload or short circuit it heats up and melts.
- Screw-in D-type. The cartridge sits in a screw cap on a fuse base. Once it has blown, the cartridge is replaced.
- Colour code. A coloured indicator shows the rating and drops out when the fuse blows, for example red 10 A, grey 16 A, blue 20 A, yellow 25 A.
- Gauge ring. A matching coloured gauge ring in the base stops a higher-rated cartridge from being fitted.
- Fast or time-delay. Time-delay types tolerate short start-up currents, such as from motors.
Application
- Find the cause first. Unplug the appliances on the circuit before replacing the fuse, or it will blow again straight away.
- Same rating, same type. Always fit an identical cartridge; the gauge ring colour tells you the rating.
- Isolate first. Switch off the main switch before unscrewing the cap where possible.
- Keep spares. Store a few spare cartridges of each rating near the meter cupboard.
- Consider an upgrade. During renovation, fuses are usually replaced with circuit breakers and residual current devices. Leave work on the distribution board to a qualified electrician.
Common mistake: bridging a blown fuse with wire or forcing in a higher rating. The cables are then unprotected, creating a real fire risk.
Related terms
- Meter cupboard
- Residual current device
- Overcurrent
- Electrical wires
- Direct current
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