Safe Isolation: Proving a Circuit Dead under the EAWR 1989

Legal basis

The Electricity at Work Regulations 1989 require suitable isolation and precautions against equipment becoming charged during work. Work on or near live conductors is permitted only when all three Regulation 14 conditions are met:

• it is unreasonable for the conductors to be dead
• it is reasonable in all the circumstances to work on or near them live
• suitable precautions are taken to prevent injury

Speed or convenience alone does not justify live work. Safe isolation establishes and secures dead working conditions at the actual work point.

Safe isolation

1. Identify the circuit, work location and every source that can energise it.
2. Switch off and isolate using suitable devices.
3. Secure isolation with lock-off, retain the key and display a caution notice.
4. Check an appropriate two-pole voltage indicator on a suitable proving unit or known live source.
5. Test the relevant conductor combinations at the point of work. On a single-phase line/neutral/protective-conductor circuit, check line–neutral, line–earth and neutral–earth. Other arrangements need all their relevant combinations checked.
6. Recheck the indicator immediately afterwards on the proving unit or known source.

The checks before and after the dead test help detect a failed indicator. Use the correct instrument and method; they do not guarantee that every possible instrument or connection fault is impossible.

Instruments and GS38

Use a suitable purpose-designed two-pole voltage indicator, not a non-contact volt-stick alone or an ordinary multimeter for proving dead. GS38 is HSE guidance, not a product approval mark.

Probes need finger guards and minimal exposed metal: normally no more than 4 mm, preferably 2 mm or suitably shrouded. Leads and instruments must have appropriate protection for their intended use. Some test equipment needs correctly specified high-breaking-capacity fuses; suitable voltage indicators can provide internal current limitation instead. Separate fused leads are not required on every indicator.

Securing the work

A lock prevents operation of the isolation device; a notice tells other people why it is secured. Keep personal control of the key. Where several workers share an isolation, use an appropriate multi-lock arrangement so each person controls their own lock. Notices and switch positions do not replace proving dead.

Choose an isolation point that removes every source relevant to the work. A suitable individual circuit-breaker may isolate downstream work on an assessed single-source TN circuit, but this does not make the consumer unit's other parts dead. Shared neutrals, additional supplies and work inside the board require their own assessment. Keep isolation devices accessible.

Distributor equipment and additional supplies

The service cut-out is sealed distributor equipment. Do not withdraw its fuse without the distributor's authority; authorised procedures vary. Fuse removal alone does not prove all conductors dead.

PV, batteries, generators and island-mode inverters can provide another supply. Identify the actual arrangement, isolate and secure every relevant source, and prove dead at the work point. For a generator designed for non-parallel standby operation, the changeover must prevent connection to the public supply and dangerous backfeed. Systems designed for parallel generation need the appropriate connection and protection arrangements.