Preparation for periodic inspection: documentation, extent, sampling and limitations
Before you start
The period before the inspection determines whether the report is defensible. Gather previous certificates and reports (EIC, EICR, minor works certificates, schedules of test results), distribution board charts, drawings and as-fitted layouts, design data, maintenance records including alterations and repairs, and details of how the installation is used and why the inspection has been requested.
Agree the scope with the client: the purpose, the extent (the whole installation or a named part) and the limitations. Limitations are recorded where access is not possible, where a shutdown is not permitted, or where equipment cannot be isolated. Everything outside the agreed extent is excluded, and the report must say so.
Sampling. You cannot dismantle every accessory. Guidance permits a sample - commonly at least 10% of items - spread across each distribution board and a range of circuit types, with a representative number of accessories and joints. If a sampled item shows a defect, the sample is enlarged, up to 100%.
Traps. Reusing the previous report's results as though they were current; failing to record limitations, since a report is only valid within its stated extent; assuming the client's requested extent is adequate, when the inspector may recommend a wider one; and using test equipment without a current calibration certificate, typically within 12 months.
Rule of thumb. Sample 10%; find a fault and expand the sample; a report without recorded limitations is a report you cannot defend.