SPARKY STUDY NOTES sparkystudynotes.co.uk/learn/two-leads-or-three-which-ze-test-to-run
Free notes
Two leads or three: which Ze test to runLoop high or loop no trip?
Free from the notes: the section word for word as members see it, and a PDF to keep.
The notes
Exactly as they are on the site.
Which test you use depends on whether there is an RCD in the way — an RCD in its own enclosure somewhere upstream of where you are testing.
| Situation | Setting | Leads |
|---|---|---|
| No RCD upstream | Loop high — high current | Two |
| RCD upstream | Loop no trip | Three |
How the two-lead test is actually made up
The green and blue leads are combined into one, and clamped onto the disconnected earthing conductor. The brown goes on the incoming line terminal of the main switch (usually the top; check the board in front of you).
✋The brown lead is never combined. Under live conditions it always stays on its own.
Your leads are versatile. You can conjoin two into one, or split one into two, depending on the instrument and the test. Not every tester offers the two-lead arrangement — check yours. If you cannot tell whether there is an RCD upstream, use the three-lead no-trip test.
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