Method Statement for Electrical Fault Finding — UK Procedure

This method statement covers diagnostic fault-finding work on UK fixed electrical installations — domestic, commercial and light industrial — up to 1000 V AC. It applies to circuits supplied from a TN-S, TN-C-S (PNB) or TT system. It does not cover utility-side faults, HV work, or work on equipment where the manufacturer mandates a specific procedure.

Fault finding carries a different risk profile to a planned installation or a routine EICR. Five hazards dominate the method statement:

Fault finding sits inside a tight set of UK legal and standards obligations. The method statement must reference all of them so that any live diagnostic step has a documented justification.

Fault finding shall only be carried out by an electrically competent person — typically a qualified electrician with current C&G 2391 (or equivalent) Inspection and Testing experience, registered with a Part P scheme provider (NICEIC, NAPIT, ELECSA, SELECT or equivalent). A second competent person is required where the assessed risk warrants it.

The method follows the IET GN3 / On-Site Guide diagnostic order: information, inspection, isolation, dead testing, then — only where justified — live testing. Working through this sequence in order minimises the time spent in proximity to live parts.

1. Gather symptoms from the duty holder / occupier — when the fault appeared, what was happening at the time, what has been switched, whether the RCD/MCB tripped or the circuit just stopped working, whether the fault is intermittent.
2. Review available documentation — previous EICR, last EIC or Minor Works for the affected circuit, schedule of test results, any known modifications. An old EICR observation often points straight at the defect.
3. Conduct a non-intrusive visual inspection of the consumer unit, accessible accessories on the affected circuit and any visible cable runs. Look for: discolouration, scorch marks, melted plastic, water staining, rodent damage, missing covers, exposed conductors, evidence of DIY work.
4. Plan isolation — identify the correct point of isolation, agree with the occupier what circuits will be affected and for how long, and assess any safety-critical loads (fire alarms, medical equipment, ICT, refrigeration). Issue advance notice where reasonably practicable.
5. Isolate at the lowest practicable level (single MCB, RCBO, or whole circuit) and prove dead following the full safe isolation sequence: test voltage indicator on known live, test point of work, test voltage indicator on known live again. Lock off and label.
6. Conduct dead tests in the BS 7671 / GN3 order: (a) continuity of protective conductors (R1 + R2 or R2), (b) ring final circuit end-to-end continuity if applicable, (c) insulation resistance line-to-line, line-to-neutral, lines-to-earth at 500 V DC (250 V where electronics are present), (d) polarity. Record every reading.
7. Compare readings against design data and previous certificate values. Anomalies (an R2 that has doubled, an IR that has dropped from >299 MΩ to 0.2 MΩ) localise the fault.
8. If the fault is now diagnosed dead, restore as much of the installation as can safely be energised, complete the make-good work under safe isolation, and re-test.
9. If — and only if — the fault cannot be diagnosed dead, document the EAWR 1989 Regulation 14 justification, brief the second person where required, energise the supply under controlled conditions and carry out live tests: voltage, prospective fault current, earth fault loop impedance, RCD operating times.
10. Capture all readings, photographs of the defect, and the diagnosis on the digital report. Issue a remedial quote or, where the work has been completed during the visit, issue a Minor Works Certificate or EIC for the new/altered circuit.

Some diagnostic results — earth fault loop impedance (Zs), prospective fault current (PFC), RCD operating times under in-service conditions, supply voltage measurement at the point of utilisation — can only be obtained with the circuit energised. EAWR 1989 Regulation 14 accepts this in principle, but every live test must be justified, recorded and time-boxed.

Almost all UK domestic and small commercial fault finding happens with the occupier present. The method statement must address occupier safety, business continuity and consent to isolate.

A fault-finding visit produces one or more of: a Minor Works Certificate (where a defect is repaired during the visit), an Electrical Installation Certificate (where a circuit has been replaced), an EICR observation (where the wider installation has been assessed) or an FI flag (where the diagnosis is incomplete). Whichever the outcome, the operative records the diagnostic findings against the customer record.