The order and purpose of initial verification, the dead and live test sequences, and which certificate or EICR code applies.
Initial verification
Every new installation, addition or alteration must be verified before it is put into service. Initial verification is carried out in two stages: inspection first, then testing. Inspection is a visual check that equipment is correctly selected, erected, undamaged and suitable for the location.
Dead test sequence
With the installation safely isolated, tests are carried out in this order so that each result is valid:
- continuity of protective conductors, including main and supplementary bonding
- continuity of ring final circuit conductors
- insulation resistance, minimum 1 MOhm at 500 V DC for a 230/400 V circuit
- polarity
Live tests
With the supply restored:
- earth fault loop impedance, where Zs = Ze + (R1 + R2)
- operation of residual current devices
Ze is the external earth fault loop impedance and (R1 + R2) is the combined resistance of the line and protective conductors of the circuit.
Certificates
- EIC, the Electrical Installation Certificate, for a new installation or any work that adds a new circuit
- MEIWC, the Minor Electrical Installation Works Certificate, for minor work that does not add a new circuit
- EICR, the Electrical Installation Condition Report, for periodic inspection of an existing installation
EICR classification codes
- C1: danger present, risk of injury, immediate action required
- C2: potentially dangerous, urgent remedial action required
- C3: improvement recommended, not a failure on its own
- FI: further investigation is advised (BS 7671:2018+A4:2026)
Under Amendment 4, an EICR is unsatisfactory if any C1 or C2 is present; C3 and FI are recommendations and do not make the report unsatisfactory on their own. Amendment 3 forms, valid until 15 October 2026, worded FI as further investigation required without delay and treated it as unsatisfactory.
Why the order and the instruments matter
- Inspection comes before testing because it finds what no meter reports: equipment wrong for its location, missing covers or barriers, unsupported cables and damaged accessories. Some of these would make testing dangerous. Equipment unsuitable for its environment is a defect even when every reading passes.
- Continuity of protective conductors proves the fault path is intact. It is measured with a low-resistance ohmmeter, because the resistances are fractions of an ohm.
- The ring final circuit test proves the line, neutral and protective conductor each form a complete ring. A ring with a break may still supply appliances, so normal operation does not establish that the ring or its protection remains sound.
- SELV and PELV circuits are insulation-tested at 250 V DC with a minimum of 0.5 megohm; the 500 V test could damage the equipment on them.
- Polarity confirms that single-pole switches and protective devices are in the line conductor, and that socket-outlets and the centre contact of lampholders are correctly connected.
- Prospective fault current is measured to confirm each protective device can safely interrupt the largest fault current at its position.
- An RCD's own test button checks only its tripping mechanism; an instrument test is still needed to verify its operating times.
Certificates, schedules and reports
- Initial verification shows a new installation or circuit was inspected and tested and is safe to put into service. The certificate and its schedule of test results become the baseline later reports are compared against.
- A Building Regulations compliance notice serves a different purpose and does not replace a BS 7671 electrical certificate.
- Before connecting an addition to an existing circuit, confirm the existing circuit is sound and suitable for the altered load, since the addition inherits its protective device, cable and earthing.
- Record any limitation precisely. A broad limitation hides the parts most likely to hold defects while the report still reads as complete.
- For a battery installation, record the stored energy and every isolation point. Identify a functional earth on ICT equipment rather than removing it as redundant, and inspect powered data cabling for support and damage as well as connectivity.
- A borrowed neutral keeps one circuit's neutral connected to a live circuit, so it can be energised even with its own breaker off. A circuit schedule helps find the right circuit, but it is not proof of dead.