You ask: One of my colleagues has been using an R2 lead for years, and he says he finds it very useful. I’m not really sure what these leads are used for and whether I should invest in one. Can you help?
We answer: A so-called R2 lead is used to check bonding and earthing conductors for continuity and can also be used as an aid to directly measuring the continuity resistance of the circuit protective conductor (CPC) – which is, of course, R2 – using Test Method 2 from IET Guidance Note 3: Inspection and Testing. Working on a dead system, disconnect equipotential bonding to eliminate parallel paths. Next, connect one end of the R2 lead to the Earth terminal at the distribution board and connect the other end to your continuity tester.
Then probe the circuit CPC test points to confirm continuity and to make direct R2 measurements. This method is particularly useful for checking switches and roses in lighting circuits, where the usual R1 + R2 method can’t be used. An R2 lead is well worth having, but we strongly recommend that you buy a purpose-made lead on a compact cable reel, such as the Megger XTL30, which is 30m long, or XTL50, which is 50m long. You’ll find either of these leads to be fast, easy and convenient to use.