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Fuses

A fuse protects a circuit or appliance by melting and breaking the circuit when the current rises above its rating. This collection has Mercury glass fuses in 5 x 20mm and 6 x 32mm sizes, in quick-blow and slow-blow types with ratings from milliamps up to 20A, Knightsbridge BS 1362 cartridge fuses for plugs and fused spurs, and an Elmdene fuse kit for fire and security equipment.

Choosing Fuses

Replace a fuse with one of the same size, type and current rating; the old fuse or the equipment label shows what is needed.

Glass fuses in two sizes

Mercury glass fuses come in the two common sizes for equipment fuse holders: 5 x 20mm, such as the 787.010UK 1A slow blow, and 6 x 32mm, such as the 787.329UK 1A quick blow. Many state a 250V rating and compliance with IEC 127, sheets 1 and 11.

Quick blow or slow blow

A quick-blow fuse breaks as soon as the current passes its rating, which suits sensitive electronics, while a slow-blow (time-delay) fuse rides out the short surge when a motor, transformer or power supply switches on. The 787.021UK slow blow fuse suits applications that need a time delay for heavy start-up currents. Fit the same type as the original: a quick-blow fuse in place of a slow-blow one may blow at switch-on.

Plug and spur fuses

Knightsbridge BS 1362 cartridge fuses fit plugs and fused connection units: the SN13AFUSE is a 13A fuse 25.4mm long, the SN3AFUSE is 3A, and the SNMIXEDFUSE set mixes 3A, 5A and 13A fuses.

FuseExampleRating
5 x 20mm slow blowMercury 787.013UK2A
5 x 20mm quick blowMercury 787.263UK2A
6 x 32mm slow blowMercury 787.140UK2A
6 x 32mm quick blowMercury 787.332UK2A
BS 1362 cartridgeKnightsbridge SN13AFUSE13A
Fuse kitElmdene ELM-FUSE-KIT45 fuses, quick and slow blow

Brands we stock in Fuses

Elmdene, Haydon, Knightsbridge and Mercury.

Mercury makes most of the fuses here, in glass 5 x 20mm and 6 x 32mm sizes.

Related categories

Fitting a spur or panel? See our fused connection units and spurs or the wider wiring accessories range. See also Mercury Fuses.

Frequently asked questions

What is a cartridge fuse?

A cartridge fuse is a small cylinder with metal end caps and a thin fuse wire inside, which melts and breaks the circuit if too much current flows. Ceramic cartridge fuses sit in UK plugs and fused spurs, while glass cartridge fuses usually protect equipment such as amplifiers and power supplies. The range here includes plug fuses and glass equipment fuses.

What is the BS number for a cartridge fuse?

The BS number for UK plug-top cartridge fuses is usually BS 1362, the standard for fuses in 13A plugs and fused connection units. Look for the BS 1362 marking and an approval such as ASTA when choosing a replacement. Common ratings include 3A, 5A and 13A. The range here includes plug fuses in single ratings and a mixed set.

How do I know if a fuse is blown?

A blown glass fuse usually shows a broken wire or blackened, cloudy glass, so you can often see the fault. A ceramic plug fuse hides its wire, so test it with a multimeter set to continuity: a good fuse reads close to zero ohms, while a blown one shows an open circuit. Switch off and unplug before removing any fuse.

What is a fuse?

A fuse is a safety device with a thin metal link that melts when current rises above its rating, cutting the supply before cables or equipment overheat. Fuses come in quick-acting and time-delay types to suit different loads. Always replace a fuse with the same size, type and rating. The range here includes glass fuses, plug fuses and fuse kits.

  • Established 1975
  • Birmingham trade counter
  • UK-only supply

Written by the West Midlands Electrics technical team

Updated

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