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The safe isolation drill, unbrokenEight steps. Which one do people drop?

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Eight steps. This is the movement you are being marked on.

  1. Identify. The client tells you the problem. You locate the circuit on the board. Read the chart — then prove which breaker it actually is.
  2. Switch off in order. Individual breakers and RCBOs first. Then the RCD serving them. Then the next group, then their RCD. Main switch last.
  3. Lock off. Lock-off device in, padlock through it, key in your pocket. Your name and number on the lock.
  4. Warning sign on, where anyone coming to the board will see it.
  5. Prove the AVI — proving unit, or a known live supply.
  6. Test. Three on single phase, ten on three phase. Section 6.
  7. Re-prove the AVI on the same source.
  8. Barriers, if the public can reach you. Before or after, but they go up.

Only now is it safe to work.

✋Step 7 is not optional, and it is the one people drop. Getting no reading proves nothing on its own — a dead tester gives you exactly the same result as a dead circuit. You only know the system is dead once you have shown the instrument still works afterwards.
Why circuit by circuit, rather than just hitting the main switch? You can switch a main switch on load — that is what it is for. Dropping every circuit individually first is better practice, and it is what you are assessed on.
Labels lie. A lighting circuit is not always where the label says it is. Read the labels, then prove which breaker it actually is.

Safe isolation does not go on the certificate. There is no box for it. It is not one of your recorded tests — it is what you do before you fill anything in.

Electrician’s Guide · Section 7 · the full procedure Guidance Note 3 · safe isolation

1 Identify — read the chart, then PROVE it 2 Breakers/RCBOs → their RCD → next group — MAIN SWITCH LAST 3 Lock off — key in your pocket, not the lock 4 Warning sign on 5 PROVE the AVI on a known source 6 TEST — 3 readings single phase, 10 three phase 7 RE-PROVE the AVI 8 Barriers if the public can reach it THE SANDWICH
Steps 5 to 7 are one movement, not three. Proving the tester before and after the readings is what makes the readings mean anything — without the second prove, a tester that failed mid-test gives you the same comforting nothing as a dead circuit. Step 7 is the one people drop.

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