SPARKYSTUDY NOTES
SPARKY STUDY NOTES sparkystudynotes.co.uk/learn/r1-r2-link-line-and-cpc-at-the-board

Free notes

R1 + R2: link line and CPC at the boardWhy not just put the line in the earth bar?

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

With the circuit isolated, disconnect the line from its protective device and the CPC from the earth bar, and join the two together. A connector block, a lever connector or a pair of small crocodile clips all do the job. You have now made a temporary loop: out on the line, back on the CPC.

Board line and CPC disconnected linked R₁ · line conductor R₂ · CPC a point: light, switch, socket ohmmeter reading = R₁ + R₂
Joined at the board, the line and CPC make one loop. Put the meter across the line and CPC terminals at a point, and you measure the whole loop out and back: R1 + R2.
Disconnect both, then join them. On an initial verification, take the line and the CPC out and join them to each other, so you are working on that circuit alone. The quick alternative — putting the circuit’s line into the earth bar — leaves every other CPC on the bar in parallel with yours, and can flatter the reading.

On a periodic it isn’t always that simple. In an installation wired in singles and badly marked up, you may not know which CPC belongs to which circuit. Linking the line into the earth bar is then the practical answer — with the parallel-path caveat in mind.

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