SPARKY STUDY NOTES sparkystudynotes.co.uk/learn/rcd-testing-both-halves-of-the-waveform
Free notes
RCD testing: both halves of the waveform18.2 and 11.2 milliseconds. Which do you write down?
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.
- Press the RCD’s own test button first. It should trip. That shows it’s working, and avoids danger if it didn’t respond during the test. Reset it.
- Set the instrument to Type AC — whatever type the RCD is. Guidance Note 3’s recommended tests are Type AC for every RCD.
- Set the rating (30 mA) and ½×. Test at 0°, then at 180°: it should not trip on either.
- 1×, on the 0° half of the waveform. It trips; note the time.
- Reset the RCD. 1× again on the 180° half. Note the time.
- Record the slower of the two 1× times, in column 28 of the schedule of test results.
Example
1 × IΔn at 0° 18.2 ms 1 × IΔn at 180° 11.2 ms Record: 18.2 ms (the slower) ≤ 300 ms ✓
The two halves often differ, sometimes by a lot. That’s normal. An RCBO with an AFDD built in can read slower than a plain RCD and still pass — and may need resetting a particular way after it trips. Read its instructions.
Type A, F and B settings are optional extras. Guidance Note 3 Table 2.18(b) lists the pulsed-DC tests for those types as optional, for fault-finding. Five times is in there too. The symbol on the device tells you its type (Figure 2.32, p.97).
An auto test on many meters runs the whole set — ½× and 1× at both 0° and 180°, often 5× too — in one go. It’s still the same tests.
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