C&G 2391-52 study guide
C&G 2391-52 · Work through your exam, one topic at a time.
The City & Guilds 2391-52 is a Level 3 qualification in initial and periodic inspection and testing of electrical installations, aimed at practising electricians who already hold a Level 3 installation qualification and now need to verify, certify and report on existing and new work to BS 7671. It is the combined route: candidates are assessed on both the verification of a new installation (the electrical installation certificate) and the periodic inspection and condition report of an existing one. The C&G 2391-52 study guide has 10 sections and about 3,778 words.
01Statutory and non-statutory requirements, BS 7671 and associated guidance
Statute is law: the Health and Safety at Work etc. Act 1974, the Electricity at Work Regulations 1989 (EAWR) and, for dwellings in England and Wales, the Building Regulations (Part P).
609 words, about 3 min02Safe isolation, preparation for inspection and testing, safe working practices
Safe isolation is a sequence, not a single action: identify the circuit and its point of isolation; obtain permission and agree the shutdown with the duty holder; assess the risk; isolate all live conductors at the correct point; secure the device with a lock and warning notice; prove the tester on a proving unit; test the conductors at the point of work; prove the tester again; then begin work. Use a two-pole voltage indicator to GS38 with fused leads, finger guards and exposed tips no longer than 4 mm.
858 words, about 4 min03Inspection (initial verification and periodic inspection)
Inspection is the visual part of verification - supported by limited dismantling and by the tests - and it is recorded on the Schedule of Inspections. It covers the origin and intake, the earthing arrangement and conductor, main protective bonding, cable routes and supports, enclosures and IP ratings, fire sealing, identification and warning notices, diagrams and records, protective device selection and rating, isolation and switching, and the connection of every accessory.
279 words, about 1 min04Continuity and resistance testing of protective and bonding conductors
Low-resistance ohmmeter, reading to 0.01 Ω, leads nulled or zeroed before use - including any wander lead. Measure protective conductor continuity as R1+R2 with the circuit isolated and line and neutral linked at the board, or measure R2 alone with a long lead.
301 words, about 2 min05Insulation resistance testing
Insulation resistance is measured with a DC tester: 500 V DC for circuits rated up to and including 500 V, and 250 V DC for SELV and PELV. The minimum acceptable value is 1.0 MΩ for the 500 V test and 0.5 MΩ for the 250 V test.
294 words, about 1 min06Earth fault loop impedance and earth electrode resistance testing
Ze is measured at the origin with the supply isolated and the main earthing conductor disconnected from the MET, so that parallel paths do not mask a poor earth. Zs is measured live at the furthest point of each circuit, or calculated as Ze + R1+R2 (parallel paths usually make the measured value lower).
288 words, about 1 min07RCD testing and functional verification
The RCD must operate within the required time at its rated residual current, must not operate at half that current, must operate quickly at five times, and must operate on both half-cycles. Types AC, A, F and B respond to different residual current waveforms; type A is the usual choice for socket outlets and circuits with electronic equipment, and type B is needed where smooth DC residual current can occur, such as some EV chargers and PV inverters.
327 words, about 2 min08Periodic inspection, sampling and condition reporting (EICR)
A periodic inspection determines whether an installation is safe for continued use and produces an Electrical Installation Condition Report. Agree the extent and limitations with the client before starting: what will be inspected, what will be sampled, what cannot be accessed, and what will be isolated.
268 words, about 1 min09Certification, schedules and reporting documentation
An Electrical Installation Certificate covers new installations, new circuits, and additions or alterations that involve a new circuit. A Minor Electrical Installation Works Certificate covers minor work with no new circuit and no change to the characteristics of an existing circuit.
281 words, about 1 min10Interpretation of test results, defect classification and client communication
Check polarity at every point. Check ring continuity against the expected ratios.
273 words, about 1 min