Second Fix Electrical: Completion, Testing, and Certification

• Socket outlets — strip the cable sheath back to just inside the back box. Strip individual cores to the correct length for the terminal. Connect brown to L, blue to N, green/yellow to E. Tighten terminals to the manufacturer's specified torque. Earth the metal back box with a flying earth lead from the accessory earth terminal to the back box earth terminal.
• Switches — for one-way switching, connect the permanent live (brown) to the COM terminal and the switched live to L1. For two-way switching, connect COM and the two strappers (L1, L2) correctly at both switch positions. Sleeve the blue core brown where it is used as a switched live.
• Light fittings — ensure the fitting is suitable for the location (IP rating for bathrooms, fire-rated for fire barriers). Connect using the correct terminal block — do not rely on wagos in ceiling voids unless they are accessible for inspection. Downlights through fire barriers must use fire-rated housings.
• Cooker connection units and fused spurs — size the cable and fuse correctly for the appliance. A 45A cooker switch with a 6.0mm2 cable is standard for most domestic cookers. A fused spur with a 3A or 13A fuse protects fixed appliances such as boilers, extractor fans, and towel rails.

• Circuit chart — must be durable, legible, and fixed inside or adjacent to the consumer unit. Handwritten charts are acceptable under BS 7671 but printed charts look more professional and are easier to update.
• Warning labels — include labels for dual supply (if applicable), mixed earthing (if applicable), RCD test reminder ("This installation, or part of it, is protected by a device which automatically switches off the supply if an earth fault develops. Test quarterly by pressing the button marked 'T' or 'Test'.").
• Periodic inspection label — "IMPORTANT — This installation should be periodically inspected and tested" with the recommended date of next inspection.

Dead Tests (Supply Isolated)

1. Continuity of protective conductors (R1+R2) — verify the CPC is continuous from the distribution board to the furthest point of every circuit.
2. Continuity of ring final circuits — the figure-of-eight test on every ring circuit. Cross-connect L-L, N-N, and E-E at the distribution board end and measure at every socket. The readings should be consistent.
3. Insulation resistance — test at 500V DC between all live conductors and earth. Minimum acceptable reading is 1 megohm. Disconnect surge protection devices (SPDs) and any electronic equipment before testing.
4. Polarity — confirm all single-pole switching devices are in the line conductor. Confirm the connections at every accessory are correct.

Live Tests (Supply Energised)

5. Earth fault loop impedance (Zs) — measure at the furthest point of every circuit. Compare against the maximum Zs for the protective device (from BS 7671 Table 41.2, 41.3, or 41.4).
6. Prospective fault current (PSCC) — measure at the origin. This value determines the required breaking capacity of the protective devices.
7. RCD operation — test every RCD at 1x rated residual current (trip within 300ms) and 5x rated residual current (trip within 40ms for Type AC/A).

• Part 1: Details of the client and installation — client name, installation address, description of the work, and the extent of the installation covered by the certificate.
• Part 2-4: Designer, installer, and inspector declarations — each signatory confirms their role and that the work complies with BS 7671.
• Part 5: Supply characteristics and earthing — supply type (TN-S, TN-C-S, TT), voltage, frequency, prospective fault current, and external earth fault loop impedance (Ze).
• Schedule of items inspected — a checklist covering every aspect of the installation from connections to accessories, cable selection, and protective devices.
• Schedule of test results — the full test results for every circuit in the installation. This is the most time-consuming section to complete manually.

• Walk the customer through the consumer unit — explain the main switch, show them how to reset a tripped MCB or RCD, and demonstrate the RCD test button.
• Hand over the EIC, the schedule of test results, and the schedule of items inspected. Explain that these documents should be kept safely — they will be needed for future inspections, property sales, and insurance claims.
• Explain the recommended date of next periodic inspection (typically 5 years for domestic, 3 years for commercial). Write this on the periodic inspection label at the consumer unit.
• If the installation includes AFDDs or an SPD, explain what they do and what the customer should do if they trip.