SPARKYSTUDY NOTES
SPARKY STUDY NOTES sparkystudynotes.co.uk/learn/zs-the-preferred-way-add-it-up

Free notes

Zs: the preferred way, add it upMeasure Zs, or add it up?

Free from the notes: Sparky’s video on it, the section word for word as members see it, and a PDF to keep.

From Sparky’s full video lesson. Members get the whole lesson on every notes page.

The notes

Exactly as they are on the site.

Download these notesPDF · free to keep

Guidance Note 3 gives two methods: measure Zs with a loop impedance tester, where it’s safe to do so, or add the measured R1 + R2 to the measured Ze. It says the second is preferred for final and distribution circuits.

So for most circuits, Zs on the schedule is a sum: your R1 + R2 for that circuit, plus Ze.

Ze in the exam, Zdb on a sub-board. Exam questions add R1 + R2 to Ze, and so does the book. But on a sub-board — a garage board fed from the house board, say — adding to Ze leaves out the distribution circuit in between. There, add to that board’s Zdb. At a single main board, Ze and Zdb are usually almost the same anyway.

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 access

Get new notes and exam tips from Sparky

About one email a fortnight. Unsubscribe any time. Privacy notice

That 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
Get access — £100 12 months. One payment. See what’s inside