Guidance Note 3: Inspection & Testing is a fundamental guidance book for all those involved with the testing and inspection of electrical installations. It also contains essential guidance for those studying for inspection and testing qualifications and has been fully updated to BS 7671:2018+A4:2026, including identification of conductors, Stationary Secondary Batteries, Prosumers Electrical Installations, Recommended initial frequencies of inspection of electrical installations and Maximum permissible measured earth fault loop impedance (EFLI).

• Cooperating organizations
• Acknowledgements
• Preface
• Introduction
• Chapter 1: General requirements
• Chapter 2: Initial verification
• Chapter 3: Periodic inspection and testing
• Chapter 4: Test instruments and equipment
• Chapter 5: Forms
• Appendix A: Maximum permissible measured earth fault loop impedance (EFLI)
• Appendix B: Resistance of copper and aluminium conductors
• Appendix C: Use of an earth leakage current clamp meter to provide an indication of the state of insulation
• Appendix D: Safety check for neutral current diversion
• Index