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Live-live, live-earth, and the global methodTwo insulation tests per circuit, or three?

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The certificate gives you two boxes, not three. That tells you something.

BoxWhat it means
Live – liveLine to neutral
Lives – earthLine and neutral joined together, tested to the CPC
✋Not line-to-earth and neutral-to-earth as two separate tests. Note the s on "live conductors". You join the line and neutral and test the pair against the protective conductor. That's two tests per circuit, not three.

Three ways to do it, in ascending order of sanity

  1. Pull the conductors out. Disconnect line and neutral from the board and clip your leads onto them. On a ring, remember there are two of each — clamp both, on clean copper, not on the insulation. Slow, and every disconnection is another chance to make a mistake or drop something.
  2. Piggyback leads. A lead with a socket in one end so a second lead can plug into it — turns one lead into two, so you can join line and neutral without pulling them out.
  3. A link lead. A magnetic bridge that sits across the line terminal of the breaker and the neutral, linking them into one test lead. Nothing gets disconnected at all.
The link lead on different devices. On an RCBO the line and neutral are both at the front, so it bridges straight across. On a plain circuit breaker you go from the breaker's line terminal to the neutral bar position serving that circuit. Brass works fine — it's a conductor.

Global insulation resistance

🌐Clip onto the earth bar (or the neutral bar) and the load (busbar) side of the main switch, with all breakers on and the main switch off. You test every circuit at once.

Ten circuits individually means ten rounds of disconnecting, testing and reconnecting. Global does the lot in one. It's a very quick test — the only limit is your battery.

✋All loads must be removed first — and not by you. This is a liability point, not a pedantic one. If you unplug a client's heater and drop it, you are paying for it. Get the client to remove them. That includes lamps — leave a bulb in and the test will show you a fault that isn't there.

GN3 · 2.6.7 · p.68 · insulation resistance figures · global method ★

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