Foundation · Unit 3
Safe isolation and the earth
In short
Why we work dead; prove dead with the two-pole tester - prove, confirm live, isolate, test every pair, prove again; the CPC and earth continuity to every load; an earth core misused, found by test; then the practical with no hints. Assessed: its check earns Safe Isolation (simulator).
Comes after Electricity for heating controls.
In this unit
Why we work dead
Why the law asks for dead working, and what dead means: isolated, locked off and proved dead with a proved two-pole tester. The tester, and its proving unit.
How it opensThis unit is about keeping safe while you work on wiring. An electric shock from the mains, at 230 volts (230 V), can kill. It can also burn.
Prove dead
Prove the tester, confirm the supply is live, isolate, test every pair at the boiler, prove the tester again.
The CPC and earth continuity
The earth's proper name, the circuit protective conductor (CPC), tested dead by continuity from the supply to every load. A pump with no earth path, found and put right.
An earth core misused
A green-and-yellow core carrying the switched live: found by test, not by colour, then isolated, proved dead and put right.
The practical: prove dead
Prove the boiler's circuit dead in the right order, with no help. Every step is recorded.
The practical · recorded, no hints
You will learn to
- Say why work is done dead and what dead means: isolated, locked off, proved
- Prove a two-pole tester on its proving unit before and after a test
- Prove a circuit dead: confirm live, isolate, test every pair, prove again
- Test earth continuity dead from the supply to every load and find a lost earth
- Find a green-and-yellow core misused as a live by test, and put it right
Checks and credit
- A timed check at the end of the unit, its questions drawn at random. The score goes on your record.
- A practical with no hints, every step recorded.
- The unit earns the credential Safe Isolation (simulator).
- Also a short course on its own, Safe Isolation, with credit both ways.
Where it connects
The parts it uses
Foundation
- Electricity for heating controls
Unit 2, before this one
- The parts
Unit 4, next
Back to the Programme.
Read the explanation
- Safe isolation in five steps: prove, confirm live, isolate, test every pair, prove again
Heating wiring is done dead. Prove the tester, confirm the supply is live, isolate and lock off, test every pair, prove the tester again. Why each step matters.
Practise it in the simulator.
Runs in the browser on a laptop or desktop. Cancel any time.