Inspection (initial verification and periodic inspection)
Inspection is not optional
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.
Initial verification
The installation is inspected throughout, on completion and before it is energised. Every circuit, every accessory and every termination is checked - 100% inspection with 100% testing. The design is verified as well as the construction.
Periodic inspection
The installation is assessed in its working condition: its age, use, environment, maintenance history and previous reports drive the extent. It is more intrusive - covers are removed, terminations are checked, samples of accessories are opened - and limitations are agreed and recorded. Sampling is normal, increased where defects are found.
Trap: confusing the Schedule of Inspections with the Schedule of Test Results. They are different documents.
Trap: assuming a fixed legal percentage for sampling in a periodic inspection - BS 7671 does not specify one.
Rule of thumb: initial verification - inspect everything; periodic inspection - inspect a sample, then let the findings set the sample size.