Free notes
Diversity: why the two tables differ, and the 5 A socketIs everything on at once?
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.
Table A1 and Table A2 — the same sum
| Table A1 — assumed demand | Table A2 — diversity | |
|---|---|---|
| Design current | 23.91 A | 23.91 A |
| First 10 A | Set aside | Set aside |
| 30% of | the load above the first 10 A — 13.91 × 0.3 | the full load in excess of 10 A — 13.91 × 0.3 |
| = | 4.17 A | 4.17 A |
| + 10 A back, + 5 A socket | 19.17 A | 19.17 A |
The same 19.17 A either way. On-Site Guide · Table A2 · p.151 reads: “10 A + 30% f.l. of connected cooking appliances in excess of 10 A + 5 A if a socket-outlet is incorporated in the control unit”. The trap is stopping at “30% f.l.” and taking 30% of the whole full load: 23.91 × 0.3 = 7.17 A, giving 22.17 A — about 3 A too high. The words “in excess of 10 A” are worth highlighting.
Why 5 A, and the honest answer
Nobody gives a derivation. The reasoning offered: a socket next to a cooker is unlikely to be carrying much — a phone charger rather than a kettle — so 5 A is a reasonable allowance.
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