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BS 7671 Guide

The 18th Edition Wiring Regulations, Amendment 4, explained in plain English for working electricians. Practical, up to date and written by Tradefox.

Section 1What's new in BS 7671 Amendment 4 (2026)BS 7671:2018+A4:2026 explained for UK electricians: key dates, what to cite on certificates, and the changes that affect everyday work on site.Section 2Before you start: supply, earthing and demandWhat to find out before you design or alter an installation: supply characteristics, Ze and PFC, earthing systems, PME limits, diversity and Part P.Section 3Protection Against Electric Shock: BS 7671 A4:2026 GuideBasic and fault protection, ADS disconnection times, max Zs and the 80% check, 30 mA RCD rules, RCD types and blinding under BS 7671:2018+A4:2026.Section 4Fire, arc fault and surge protection under BS 7671 A4:2026AFDDs, cable supports in fire, escape routes, firefighter's switches and SPDs under BS 7671:2018+A4:2026, explained for UK electricians working on site.Section 5Choosing and sizing cables under BS 7671 A4:2026Cable sizing under BS 7671:2018+A4:2026: Ib, In and Iz, correction factors, voltage drop, adiabatic CPC checks, concealed cables, terminations and buried runs.Section 6Earthing and bonding under BS 7671:2018+A4:2026Earthing vs bonding, main and supplementary bonding sizes, PME, TT electrodes, CPC sizing and the new A4 Section 545, explained for UK electricians.Section 7Special Locations in BS 7671 Part 7: Bathrooms, Pools, Sites and MorePart 7 of BS 7671:2018+A4:2026 for working electricians: bathrooms, hot tubs, construction sites, outdoor lighting, PoE and other special locations.Section 8EV charging, solar PV, batteries and heat pumps under BS 7671 A4EV charge points, solar PV, home batteries and heat pumps under BS 7671:2018+A4:2026: PME options, RCD types, Chapter 57, multiple sources and DNO notification.Section 9Inspection and testing to BS 7671 A4:2026A practical guide to Part 6 of BS 7671:2018+A4:2026: safe isolation, dead and live tests, RCD checks, correcting Zs and recording results.Section 10Certificates, reports and EICR codesEIC, minor works and EICR paperwork under BS 7671:2018+A4:2026: which form to use, C1/C2/C3/FI coding with examples, and landlord inspection deadlines.Section 11BS 7671 quick reference: key values and site checklistsBS 7671:2018+A4:2026 cheat sheet for electricians: key dates, disconnection times, RCD and AFDD rules, test values, bonding sizes and EICR codes.

Important. This guide is written by Tradefox to help qualified electricians understand BS 7671:2018+A4:2026. It is a plain-English summary for learning and reference only. It is not the standard, it does not reproduce it, and it is not professional advice. Always work to the current edition of BS 7671, the IET guidance notes, manufacturers’ instructions, Building Regulations and your scheme provider’s requirements. Electrical work must be carried out by a competent person.

To the extent permitted by law, Tradefox accepts no liability for loss or damage arising from use of this guide. BS 7671 is published by the IET and BSI; Tradefox is not affiliated with or endorsed by either. See our Terms of Use. Spotted something out of date? Email info@tradefoxapp.com.

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