Free notes
Exposed vs extraneous conductive partsDoes a radiator need bonding?
Free from the notes: Sparky’s video on it, the section word for word as members see it, and a PDF to keep.
The notes
Exactly as they are on the site.
A metal part of the electrical installation that you installed and that someone can touch. It isn't normally live, but could become live under a fault.
Examples: metal conduit, a metal-clad socket or switch, a metal consumer unit, a metal shower case, a metal light fitting.
Metalwork that is not part of the electrical installation (you didn't install it) and that comes into the building from the ground, so it can introduce earth potential.
Examples: metal water and gas pipes, oil pipes, central heating and air-conditioning pipework, exposed metal structural parts (beams, steel studs), lightning protection.
Rule of thumb: metal and you installed it means exposed. Metal and you didn't install it (it comes in from outside) means extraneous. If it's plastic it isn't conductive, so it's neither.
BS 7671 · Part 2 Definitions · "Extraneous-conductive-part" and "Exposed-conductive-part" Highlight both definitions. They're also in the Electrician's Guide and the On-Site Guide.
Myth: radiators don't automatically need bonding. They aren't something you install, and they don't come in from the ground. An electric towel rail is different: it's part of the installation, so it's an exposed conductive part.
Free section from Sparky Study Notes. The full Level 3 notes, 1,463 practice questions and the video lessons: sparkystudynotes.co.uk
Test yourself on it
The tests are in the members’ area. Get one wrong and it shows you why, and where to revise.
Get new notes and exam tips from Sparky
About one email a fortnight. Unsubscribe any time. Privacy noticeThat was one section. There are 583.
Sparky Study Notes is the whole Level 3 syllabus written up like this: the explanation, the worked example, and where it is in your book. With a video lesson for every part and a practice paper for every exam.
- 583sections of written notes
- 35video lessons
- 1,463practice questions
- 146diagrams, redrawn
- 18th Edition
- Building Regs
- PAT
- Fundamental Inspection & Testing
- Initial Verification
- Periodic Inspection & Testing