Free guide · Safe isolation
Safe isolation procedure, step by step
Safe isolation is how you make sure a circuit is dead before you work on it, and that it stays dead while you do. It's the first thing every electrician learns and the one step you never skip.
Practise the order in the interactive visualisation below, then read the steps. The Kitchen radial sim lets you do it all on a full consumer unit with a tester, a voltage indicator and a proving unit.
Before you startSafe isolation, step by stepRead first
What this shows
This interactive visualisation is a practice run of the safe isolation procedure. The drawing shows a consumer unit, the cable to the point of work, a proving unit and a two-pole voltage indicator.
Under the drawing, you tap the steps in the order you would carry them out. Each correct step changes the drawing: the circuit is ringed when identified, the device switches off, the lock and notice appear, and the voltage indicator moves between the proving unit and the point of work.
Some of the choices are unsafe short cuts. Tapping one explains why the short cut is not safe.
Key words
- Isolation
- Disconnecting a circuit from every source of supply so that the circuit cannot be switched back on by accident.
- Point of isolation
- The device you switch off and lock off: a circuit-breaker, fuse carrier or isolator, not a functional switch.
- Lock off
- Fitting a lock to the isolating device and keeping the key on you.
- Voltage indicator (GS38)
- An approved two-pole tester with fused leads and shrouded probes, used to prove dead.
- Proving unit
- A small unit that makes a known voltage, used to check the voltage indicator works.
- Prove dead
- Testing between every pair of conductors (L–N, L–E and N–E) at the point of work and finding no voltage.
What to look for
- Try tapping Switch off at the light switch first. The explanation says why a functional switch is not isolation.
- Tap the steps in order. After each correct step, read “What goes wrong if you skip this step”.
- Watch the voltage indicator: the indicator lights LIVE on the proving unit, shows 0 V at the point of work, then lights LIVE on the proving unit again.
- Tap Show all names to see every part named, or tap one part to read about that part.
On the job
- Follow the same order every time: identify, select your kit, isolate, lock off, prove the tester, prove dead, re-prove the tester. The Kitchen Radial sim marks you on this order in Assessment mode, and a skipped or out-of-order step is an automatic fail.
- Prove dead at the point of work, between every pair of conductors, not just at the board. Wrongly labelled circuits, borrowed neutrals and second supplies (solar PV, batteries, generators) are common.
- Never rely on a non-contact detector or a multimeter to prove dead. Use an approved two-pole voltage indicator to GS38 and prove the indicator before and after.
- Keep your own lock and key. If more than one person is working, each person fits their own lock (a multi-lock hasp).
Step by step
- 1Get permissionTell the people who use the installation, and get permission to switch the circuit off.
- 2Identify and isolateIdentify the right circuit and switch off its protective device or isolator.
- 3Lock offLock the device off with your own padlock and fit a warning notice, so nobody can switch it back on.
- 4Prove your testerProve your two-pole voltage indicator works on a proving unit or a known live supply.
- 5Test for deadAt the point of work, test between every pair of conductors: line to neutral, line to earth and neutral to earth.
- 6Prove your tester againProve the voltage indicator again, to show it didn't fail during the test. Only then is the circuit proved dead.
Always follow the current edition of BS 7671 and its guidance notes.
Practise it in the sim
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