Originally Posted by Malcg

Hi
R1+R2 is only available at light drop / ceiling rose (also much easier to do).

Switch off main switch. Temp short MCB live to earth. at furthest rose, test using two or three leads (as L, N & E available).

Record result and remove temp link.

As shown on page 217/218 NICEIC Inspection, Testing, Certification and Reporting.

Hi

Also if you want to include switch drop, still test at ceiling rose with light switch on. Use Switch live, Neutral and earth. Then you get longest path of Live.