Skill: Check for Dead Before Any 230V Electrical Work
Skill level: 2
Wiring
Learning Objective:
Understand and apply the safety-critical procedure of proving isolation before working on any 230V electrical system — to prevent electrocution, damage, or serious injury.
1. Overview
Working with 230V AC power is dangerous and potentially fatal. The prove dead procedure ensures circuits are safe before any work begins.
Isolation is a legal requirement under UK electrical safety law.
Never assume a circuit is dead just because an isolator is off.
Always lock off, label, and test before handling live parts.
⚠️ 230V AC is lethal — always follow procedure.
⚠️ Many injuries occur when isolation is skipped or assumed.
2. Tools and Materials Required
Two-pole voltage tester (e.g. Martindale, Fluke T-series)
Proving unit (or known live supply for tester verification)
Lock-off kit or labelled warning tags
Insulated screwdriver (for covers)
PPE: insulated gloves, safety glasses
3. Before You Start
Identify correct isolation point (breaker, FCU, or main switch).
Ensure system may have multiple supplies (e.g. battery backup, secondary PSU).
Prepare lock-off kit or warning tags.
Wear appropriate PPE.
4. Procedure
4.A Isolate the Circuit
Switch off circuit at FCU, breaker, or main isolator.
Lock off and label to prevent accidental re-energisation.
4.B Prove Tester Works (Before)
Connect tester to proving unit or known live supply.
Confirm expected reading (lights/buzzer).
This confirms tester is functional.
4.C Test All Terminals
Carefully test between:
L & N
L & E
N & EAll results should read 0V/dead.
Test all exposed/accessible conductors.
4.D Prove Tester Works (After)
Recheck tester on proving unit or live source.
Confirm expected reading again.
📌 If tester fails at this point, test is invalid — repeat with new tester.
5. Best Practices
✅ Always isolate, lock off, and label before starting.
✅ Prove tester before and after every test.
✅ Test all conductor combinations (L–N, L–E, N–E).
✅ Isolate all possible supplies (mains, backup PSU, batteries).
✅ Keep lock-off tag visible for other workers.
6. Common Mistakes to Avoid
🚫 Assuming circuit is dead without testing.
🚫 Testing only L–N, forgetting L–E or N–E.
🚫 Using a faulty or unverified tester.
🚫 Forgetting to isolate battery backups or secondary PSUs.
🚫 Removing covers without PPE.
7. Safety Information
Relevant SSOW References:
SSOW-01: Electrical Isolation & Lock-off
SSOW-04: Working With Mains Voltage (230V AC)
SSOW-05: Safe Use of Multimeters/Testers
SSOW-11: PPE (gloves, boots, safety glasses)
⚠️ FCUs may isolate only one pole — always check both L and N.
⚠️ Gate systems may have multiple feeds — always isolate all sources.
⚠️ If tester fails at the end check, repeat the procedure with a new tester.
