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Recognising devices by their BS EN numberWhich BS EN number is an RCBO?

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It's worth handling actual devices and matching them to standard numbers, because on test paperwork you have to write the BS EN number of the device in, and the exam will ask you which number belongs to what.

StandardDevice
BS 88 seriesCartridge fuses — 88-2, 88-3, 88-6 and so on. Replaced BS 1361 in 2010
BS 1361The old type, including the supplier's cut-out fuse in the DNO head
BS 1362The plug-top fuse — also a cartridge fuse
BS 3036Rewireable semi-enclosed fuse — the old fuse-wire carrier
BS EN 60898Circuit breaker
BS EN 60947-3Main switch (switch-disconnector)
BS EN 61008RCD — note it is not an overcurrent device, which is why it doesn't appear in the overcurrent tables
BS EN 61009RCBO
BS EN 62423Type F or type B RCD — for example a type F built into an RCBO
✋The sticker inside the consumer unit will catch you out. Boards come with a sheet of BS EN stickers, and the one people habitually stick on the main switch row is the number for the consumer unit itself, not the main switch. Your main switch is 60947-3, and that number is usually printed on the side or the front of the switch body. Read it off the device, not off the sticker sheet.

Telling a rewireable fuse apart by eye

A BS 3036 fuse carrier has two screw contacts, one at each end, with the fuse wire caught under the screw, and the centre contact connecting through. When it blows you unscrew it and replace the wire. If you can see screw terminals with wire trapped under them, it's a fuse base — not a breaker, not an RCBO, not a main switch.

≡Fuse wire is copper, and it may be tinned or annealed. Table 533.1 gives you the fuse rating against the diameter of the wire — a 15 A element is 0.5 mm diameter. Barely anywhere sells fuse wire any more, so this is museum knowledge that still turns up in exams.
Where the RCD type symbols live. The pictograms are in Guidance Note 3, Figure 2.32 (p.97). BS 7671 lists the types (AC, A, F and B) at 531.3.3 (pp.165–166) in words only, with no symbols on that page. Tab the GN3 figure.

Chapter 53 · devices for protection, isolation and switching Table 533.1 · fuse rating against fuse-wire diameter Guidance Note 3 · Figure 2.32 · p.97 · RCD type symbols

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