Inspection and Testing: Initial Verification, Dead and Live Tests

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 includes appropriate visual and physical checks of selection, erection and condition. Correct defects that would make a test unsafe before proceeding; do not continue testing regardless of what inspection finds.

Dead test sequence

With the installation safely isolated, the normal dead-test order is:

• continuity of protective conductors, including main and supplementary bonding
• continuity of ring final circuit conductors
• insulation resistance, normally at least 1 megohm at 500 V DC for a 230/400 V circuit, with sensitive equipment disconnected or protected as required
• polarity

Loop impedance and live tests

Direct earth fault loop measurement and RCD operating tests require an energised supply. Zs may instead be determined by an appropriate calculation using Ze and the dead-test value R1 + R2, reducing unnecessary live testing. Ze is the external loop impedance; R1 and R2 are the circuit line and protective-conductor resistances. The familiar Zs = Ze + (R1 + R2) is a resistive approximation: account for temperature and any significant reactance when assessing disconnection. Complete inspection and the necessary dead tests before energising.

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, may be used for an addition or alteration that creates no new circuit; a full EIC is also valid
• 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.
• Use a low-resistance ohmmeter or suitable multifunction-tester mode for protective-conductor continuity. Compare the result with the expected resistance for the conductor length, size and connections; it need not always be below one 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/PELV insulation tests use 250 V DC and a 0.5 megohm minimum. This does not make 250 V safe for every connected device: disconnect or protect equipment as required. For an LV circuit where specified equipment such as an SPD cannot reasonably be disconnected, the permitted reduced test is 250 V DC, still with a 1 megohm minimum.
• Polarity checks conductor connections, including single-pole switches and protection in line. The Edison-screw centre-contact rule has an exception for E14/E27 lampholders complying with BS EN 60238. Correct polarity is not safe isolation.
• Determine prospective fault current by an appropriate method and check device breaking capacity, including any valid manufacturer-supported backup arrangement.
• An RCD's test button exercises its functional trip operation; it does not measure operating time or verify the installation earthing. It does not replace the required instrument test.

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.
• Agree the inspection extent and foreseeable limitations beforehand. Record operational constraints encountered during the work as well, with their effects on the assessment. Do not use a limitation to conceal a known defect.
• 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 may carry another circuit's load current after the local breaker is off. It can be near earth potential while connected and become dangerously live on disconnection. Investigate shared conductors and isolate every relevant source; a schedule or single initial reading is not proof that an unidentified conductor is safe to disturb.