Safe isolation on an installation with PV and battery storage

What is still live

• The PV array: the DC side is a current source and stays live whenever there is light. The DC isolators do not make the roof wiring dead.
• The battery: unless it has been shut down, the inverter can energise the AC side, and on a hybrid system with a backup supply it can hold up circuits inside the consumer unit with the main switch off. The neutral can also be at a potential.
• Anything fed from the garage board via the 40 A MCB is isolated by the main switch - that part is fine.

The errors

1. He isolated only the DNO supply. Every source must be identified and isolated, not just the incoming mains.
2. Proving the indicator on the live side only proves the indicator works. He has not proved the outgoing conductors dead at the point of work.
3. No proving unit, so there is no second check that the indicator still reads correctly after the test.
4. He has not tested line–neutral, line–earth and neutral–earth at the point of work.
5. Removing a cover and reaching for the neutral bar without a caution notice or a second person aware of the isolation.

He should stop now. The neutral bar and the PV/battery connections may be live.

1. Identify every source - DNO supply, PV inverter AC, battery, and confirm whether the battery has a backup/EPS output feeding a separate board or circuit.

2. Notify and prepare - tell the occupier, agree the shutdown, know what the battery/inverter shutdown procedure is from the manufacturer's instructions before you touch anything.

3. Shut down the generation in the correct order - inverter off, battery off per its procedure, DC isolators off, AC isolator off, then the DNO main switch off.

4. Lock off - a personal lock and tag at every point of isolation (main switch, AC isolator, battery isolator, DC isolators) on a multi-lock hasp. A padlock that only you hold; not a switch in a cupboard with tape over it.

5. Prove dead at the point of work - prove the voltage indicator on a proving unit, test L–N, L–E and N–E at the conductors you are about to touch, then re-prove the indicator on the proving unit. The reading that matters is at the point of work, not at the main switch.

6. Caution notice - fit it at the point of isolation with your name and the date.

7. Confirm the DC side - treat the array and its wiring as live throughout; cover or isolate per the manufacturer's method if you must work on it, which a periodic inspection does not normally require.

Scope

• The AC side of the PV and battery system is part of the installation and must be in the report - its own circuit, isolators, labelling and protection.
• If the battery has a backup/EPS output supplying a dedicated circuit or board that remains live with the main switch off, that is a separate source and must be inspected and scheduled, not treated as the client's equipment.
• If the client will not permit the battery system to be shut down for dead testing, that is a limitation: record it, say which circuits were inspected only, and say that the results do not cover them.
• The DC array wiring is not dead-tested as part of an EICR; confirm in writing that it is outside the agreed extent.

Notices and records

• A permanent warning at the origin and at the consumer unit that the installation has more than one source of supply.
• A diagram or label identifying the PV circuit, the battery circuit and the backup circuits; check that the circuit chart matches what is actually installed.
• On the report, list the additional sources in the supply characteristics and record the extent of the installation covered.

The wider point This is a safety-management issue before it is a testing issue. The scope agreed in writing has to acknowledge that two sources exist, or the report will describe an installation that is not the one in the house.