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Mercury Fuses

Mercury glass cartridge fuses fit equipment fuse holders, in the two common body sizes, 5 x 20mm and 6 x 32mm, and in slow blow and quick blow versions. The single fuses come ten to a pack, and ratings include 100mA on the 787.000UK and 20A on the 787.273UK. The page also carries an assortment of 160 quick blow fuses in a storage case and in-line fuse holders.

Choosing Mercury Fuses

Replace a fuse with one that matches the old one on three points: body size, blow speed and current rating.

Body size

The fuse holder decides the size. The 787.017UK is a 5 x 20mm slow blow fuse rated 5A, and the 787.144UK is the same rating in the longer 6 x 32mm body. Measure the old fuse or read the marking on the equipment before you order, because one size will not fit the other holder.

Slow blow or quick blow

A slow blow fuse tolerates the short surge when equipment switches on. The 787.021UK suits circuits that need a time delay for heavy start-up currents, and the 787.143UK is made to handle inrush currents without blowing. A quick blow fuse such as the 787.255UK is designed to blow quickly in the event of an overload. Fit the type the equipment was built with.

Current rating

Use the rating printed on the old fuse or in the equipment manual, never a higher one. Ratings in 5 x 20mm slow blow include 315mA, 1.6A, 3.15A and 16A. Less common values are here too: the 787.271UK is a 12.5A quick blow fuse, the 787.334UK a 3A and the 787.337UK a 6A quick blow fuse in 6 x 32mm.

Standard and packs

The 787.263UK quick blow and 787.012UK slow blow glass fuses comply with IEC 127, sheets 1 and 11. The 799.050UK holds 160 quick blow 5 x 20mm fuses in eight ratings, 0.5 to 10A, in a plastic storage case, for DIY or professional use.

TypeExampleRating
5 x 20mm slow blow787.007UK500mA
6 x 32mm slow blow787.147UK10A
5 x 20mm quick blow787.266UK4A
6 x 32mm quick blow787.339UK10A
Quick blow assortment799.050UK160 fuses
In-line fuse holder787.408UK2.5A, 18cm wire

Related categories

Browse the wider Mercury range, plug fuses from other makers in fuses, plugs, sockets and wiring accessories, Mercury extension leads and fused connection units.

Frequently asked questions

What is a Mercury fuse?

A Mercury fuse is a small cartridge fuse sold under the Mercury brand to protect electronic equipment and appliances. Its thin element melts and breaks the circuit when current rises above the fuse rating for long enough. A blown glass fuse can often be spotted by a broken or blackened element inside. The range here includes glass fuses, an in-line fuse holder pack and a fuse assortment kit.

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

Written by the West Midlands Electrics technical team

Updated

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