BS 7671:2018 + A4:2026 · The Orange Book
Amendment 4 — the complete deep-dive
Every material change from A3:2024 to A4:2026, with regulation numbers, what has actually changed on paper, why it matters on site and worked examples. This is the reference version — the shorter cross-amendment summary lives on the BS 7671 Amendments page.
Published
15 April 2026
Mandatory
15 October 2026
Applies to
New work + alterations
Why A4 is a bigger deal than A3
A3:2024 was a short free corrigendum — mostly housekeeping and the new bidirectional-protection definitions. A4:2026 is a paid, fully consolidated second edition (the Orange Book) — it absorbs A1, A2 and A3, adds two brand-new chapters (57 and 81), adds two new sections (545 and 716), rewrites Section 710 in full, tightens Section 551, and introduces individual competence rules that close the QS-sign-off loophole for high-risk work.
New chapter · headline change
Chapter 57 — Stationary secondary battery installations
The first dedicated battery chapter in BS 7671 history. Applies to permanently installed secondary batteries whose primary purpose is electrical energy storage — domestic BESS paired with solar PV, commercial storage, grid-connected arrays and V2H / V2G configurations. It does not apply to pluggable UPS units, BS 5839 fire-alarm batteries, BS 5266 emergency-lighting batteries, or central safety power supplies.
A3:2024 position
No dedicated chapter existed. Designers relied on PAS 63100, MCS guidance, manufacturer instructions and scattered rules in Section 551 (LV generating sets). Bidirectional protection was recognised in A3 through new definitions, but the installation rules sat outside BS 7671.
A4:2026 change
A new Chapter 57 gathers all stationary-battery requirements in one place. The previous Regulation Group 551.8 is deleted and its content migrated into Chapter 57. Batteries are now formally classified as generating sets under 551.7.2.1, not loads.
Regulations affected
- 570.6.7.203 — battery installations in dwellings must comply with PAS 63100. Non-domestic siting must be justified by fire risk assessment.
- 551.7.1 (redrafted) — a suitable protective device is required wherever bidirectional energy flow is possible; new prohibition on connecting a source to the load side of an RCD under certain conditions.
- 551.7.2.1 — stationary secondary batteries reclassified as generating sets rather than loads.
- Chapter 57 (new) — location, ventilation, fire risk, thermal-runaway mitigation, isolation, labelling, DC/AC protection coordination.
What this changes on site
- Every protective device on a battery circuit must be rated for bidirectional flow — many legacy MCBs and RCDs are not.
- Loft installs common in retrofits from 2020–2024 may need revisiting: batteries must not compromise the means of escape.
- Isolation procedures now assume the BESS is a continuous energy source. Provide a dedicated, labelled DC isolator plus AC isolator, and document safe-isolation steps for maintainers.
- Ventilation must match the chemistry — Li-ion needs thermal management; lead-acid needs hydrogen dispersal.
- Chapter 57 items become inspectable on any EICR carried out after 15 October 2026 — expect C2/C3 coding for missing isolation, poor location or absent PAS 63100 compliance evidence.
Worked example
Retrofit example — 5 kWh Li-ion battery added to a domestic solar PV system
Under A3 you sized DC and AC protection, provided a battery isolator, and referenced PAS 63100 informally. Under A4 you must: (1) confirm the location is not on an escape route or in a habitable-room ceiling void; (2) install bidirectional-rated OCPDs on the AC side; (3) provide labelled DC and AC means of isolation adjacent to the battery; (4) record PAS 63100 compliance on the EIC under Chapter 57; (5) hand the client an isolation and emergency-response note.
Watch out
Bidirectional RCD trap
A common A3-era mistake is connecting a battery inverter to the load side of a household RCD. A4 explicitly restricts this — the RCD may not correctly detect residual current when energy flows from the battery back toward the source. Feed battery circuits from their own dedicated protective device.
New section
Section 716 — Power over Ethernet (PoE) and ELV DC distribution
PoE has become the standard delivery mechanism for LED lighting drivers, IP cameras, access control, BMS sensors and small appliances. Until A4, BS 7671 was silent on it.
A3:2024 position
PoE installations were covered only by the generic SELV / PELV limits (50 V AC, 120 V DC), BS EN 50174 structured-cabling standards and BS EN 62368-3 for the power source. Cable bundle heating in dense patch-panel installs was left to designer discretion.
A4:2026 change
Section 716 introduces PoE-specific voltage limits, cable and connector requirements and mandates suitability assessment when re-using existing telecoms cabling.
Regulations affected
- 716 (new) — voltage limits: 60 V ripple-free DC in dry locations, 15 V ripple-free DC in all other locations (damp, outdoor, etc.).
- 716 — all PoE electrical connections shall comply with BS ISO/IEC 11801-1 and support a continuous operating current of 750 mA per contact.
- 716 — power sourcing equipment (PoE switches, injectors) shall comply with BS EN 62368-3.
- 716 — PoE systems must be tested for both data performance and electrical safety compliance.
What this changes on site
- PoE++ (IEEE 802.3bt Type 4) delivers up to 90 W per port — the 60 V dry-location limit is set to accommodate it.
- Bundled cable derating matters: a rack of 24 patch cords all carrying 90 W runs hot. Space the bundles or upsize conductor CSA.
- Re-using existing Cat 5e panels for PoE++? Assess conductor CSA, connector plating and patch-panel terminal ratings before energising.
- Commercial EICRs after October 2026 must include PoE assessment: voltage, cable suitability, PSE compliance and bundle temperature.
Background
Why the 15 V limit outside dry locations?
DC produces sustained-arc conditions that AC does not (no zero crossing). In damp or outdoor environments the shock and arc hazard rises sharply, so PELV limits are pulled down well below the SELV 120 V DC ceiling.
New section
Section 545 — Functional earthing for ICT systems
Modern ICT infrastructure needs both protective earthing (shock protection) and functional earthing (signal integrity and EMC). Before A4 there was no dedicated BS 7671 framework, which caused disputes over separate ICT earth electrodes, dirty-earth conductors and their interaction with PE.
A3:2024 position
Only generic Chapter 54 rules on protective earthing plus BS EN 50310 for telecoms bonding. FE / PE distinction was inconsistently applied on site.
A4:2026 change
Section 545 formalises functional earthing terminology, sets a minimum CSA for FE bonding conductors and mandates identification so FE conductors cannot be confused with PE conductors.
Regulations affected
- 545 — interruption of functional earthing shall not compromise or affect the protective earthing under any circumstance.
- 545 — minimum CSA specified for functional bonding conductors.
- 545 — FE conductors shall be clearly distinguishable from PE conductors.
- 545 — introduces the main functional earthing terminal (MFET), the ICT counterpart of the MET.
- 545 — equipotential bonding ring conductors permitted for data centres and broadcast environments.
- 545 — combined PE/FE conductors permitted with specific CSA and identification requirements.
What this changes on site
- Never lift the FE to chase a hum without knowing whether PE integrity depends on it — with combined PE/FE conductors it does.
- Data centres and broadcast facilities can use ring conductors to hold a consistent reference potential across racks.
- Green-and-yellow is still reserved for PE — FE conductors need a distinct identifier (e.g. cream or labelled sleeving) agreed at design stage.
- School and hospital installs with structured cabling co-located with LV panels benefit most: MFET provides a defined interface between the two systems.
Major revision
Section 710 — Medical locations
The most substantive revision of any existing section in A4. Fully aligned with IEC 60364-7-710:2021 and its CENELEC adoption.
A3:2024 position
Group classifications existed but were less prescriptive; medical IT system rules were present but the supplementary bonding test schedule was implicit rather than mandated.
A4:2026 change
Revised Group 0/1/2 classifications; Group 2 requirements sharpened around medical IT systems, insulation monitoring devices (IMDs), dual supplies, UPS placement and a new supplementary bonding resistance test schedule.
Regulations affected
- 710 — Group 0: no medical electrical equipment used on patients (waiting rooms, offices).
- 710 — Group 1: equipment used on intact skin or in non-cardiac procedures (examination, physio, minor treatment).
- 710 — Group 2: interruption of supply could be immediately life-threatening (operating theatres, ICU, cardiac catheterisation, angiography).
- 710 — Group 2 must be fed via a medical IT system with an IMD alerting on the first fault and disconnecting only on a second fault.
- 710 — two independent supplies mandatory for Group 2 to eliminate single-point failure.
- 710 — UPS to be positioned as close as possible to the equipment it supports.
- 710 — supplementary bonding resistance measurements must be recorded in commissioning and every periodic report.
What this changes on site
- Re-survey existing hospital areas: a room previously classified Group 1 may become Group 2 if the procedures carried out there have changed.
- Every commissioning pack for a Group 2 room now needs a signed schedule of supplementary bonding resistance values, not just a tick-box.
- Move UPS units out of remote plant rooms and into the theatre-suite envelope where practical.
New chapter · framework
Chapter 81 — Energy efficiency (introductory)
A new introductory framework aligning LV installation design with the UK's net-zero trajectory. Advisory today, but signals direction of travel for future editions.
A3:2024 position
Energy efficiency guidance sat in Appendix 17 only, and was rarely used as a design input.
A4:2026 change
Chapter 81 is added as an advisory framework covering load profiling, transformer sizing, power factor correction, conductor selection and circuit layout for efficiency.
Regulations affected
- Chapter 81 (new) — framework for assessing energy efficiency at design stage. Not mandatory in A4.
- Appendix 17 — expanded guidance referenced by Chapter 81.
What this changes on site
- Not enforceable today, but start recording power-factor and cable-loss assumptions on your design paperwork.
- Future Homes Standard and Part L developments will likely reference Chapter 81 in due course — early adoption avoids rework.
Clarification
Regulation 521.5.1 — Ferromagnetic enclosures
Clarifies grouping of line, neutral and PE conductors through steel enclosures to prevent eddy-current heating.
A3:2024 position
The general rule required all live conductors of the same circuit to pass through the same aperture. Practical exceptions for large busbar assemblies were unclear.
A4:2026 change
A note is added: for switchgear and controlgear complying with BS EN IEC 61439, conductors carrying up to 200 A may pass through separate apertures. Above 200 A through separate holes, a temperature-rise test must confirm safe operation.
Regulations affected
- 521.5.1 (note added) — 200 A threshold for BS EN IEC 61439 assemblies with separate apertures.
What this changes on site
- Panel builders no longer need to bend geometry to force >100 A conductors through the same hole — provided the assembly is BS EN IEC 61439 compliant.
- Above 200 A per separate aperture, obtain and file the temperature-rise test evidence with the O&M pack.
Clarification
Regulation 521.10.202 — Cable support in fire conditions
Widely misapplied since A2. A4 clarifies the intent.
A3:2024 position
Some inspectors read 521.10.202 as demanding fire-survival cable support on every circuit — even outside escape routes — which was never the intent.
A4:2026 change
A note is added: the regulation exists to stop collapsed cables blocking escape or impeding firefighting. It is not a requirement for circuit integrity of general wiring. Circuit-integrity requirements for safety services remain in Chapter 56, BS 5839, BS 5266 and BS 8519.
Regulations affected
- 521.10.202 (note added) — clarifies scope: escape and firefighting, not general circuit integrity.
What this changes on site
- Plastic cable clips are still not adequate on cables running along escape routes or above them.
- Standard PVC / clip fixings remain acceptable inside voids that are not on escape routes, provided fire strategy does not classify them as such.
Revision
Section 537 — Firefighter's switches
Formalises collaboration between electrical designers and fire engineers.
A3:2024 position
537.4.2 gave general siting rules; 537.4.2.1 added supplementary detail.
A4:2026 change
537.4.2 now requires firefighter's switches to be located in positions identified by the fire engineer as part of the building's fire strategy. 537.4.2.1 is deleted.
Regulations affected
- 537.4.2 (revised) — location determined by fire engineer within the fire strategy.
- 537.4.2.1 — deleted.
What this changes on site
- Get the fire engineer to sign off switch locations before first fix — retrofitting is expensive.
- Document the fire-strategy reference on the EIC.
Revision
Section 551 — Low-voltage generating sets
Reflects the reality of bidirectional energy systems and connects with the new Chapter 57.
A3:2024 position
A3 introduced bidirectional definitions but left the protection wording ambiguous.
A4:2026 change
551.7.1 is redrafted to require a suitable protective device wherever bidirectional flow is possible, with a new prohibition on connecting a source to the load side of an RCD under certain conditions. 551.7.2 is split into two separate regulations. 551.8 is deleted and its content moved to Chapter 57.
Regulations affected
- 551.7.1 — redrafted for bidirectional protection.
- 551.7.2 — split into two regulations.
- 551.8 — deleted (content migrated to Chapter 57).
What this changes on site
- Any inverter capable of exporting must be considered a source — protection must be evaluated in both directions.
- Update template designs for solar PV + battery to reference Chapter 57 alongside 551.
Revision · affects every EICR
Chapter 65 — Inspection & testing (EICR)
Direct impact on every electrician issuing periodic inspection reports.
A3:2024 position
Photographic evidence was widely used but not formally acknowledged. Different scheme providers had different rules about whether an FI code forces an Unsatisfactory outcome.
A4:2026 change
Photographic and thermographic images may be appended as supporting evidence. Recipient guidance based on the Appendix 6 model must be included. Signatures required from both inspector and authoriser. An FI code does not automatically cause an Unsatisfactory outcome — overall condition must be assessed on its merits.
Regulations affected
- Chapter 65 — EICRs must include recipient guidance based on the Appendix 6 model.
- Chapter 65 — photographic and thermographic evidence formally permitted.
- Chapter 65 — dual signatures (inspector + authoriser) required.
- Chapter 65 — FI code does not automatically drive an Unsatisfactory result.
What this changes on site
- Update EICR report templates to include recipient guidance and a dual-signature block.
- Keep thermal-imaging camera stills alongside written observations — they are now formal evidence.
- If issuing an FI code, record the reasoning for the overall Satisfactory / Unsatisfactory decision separately.
Worked example
FI example — worn socket outlet on ring final
Under A3 an FI on a worn socket outlet on an otherwise sound ring final could tip the report to Unsatisfactory in some scheme interpretations. Under A4 the inspector may issue the FI, document the further investigation required, and still declare the installation Satisfactory overall if the FI does not represent an immediate or potential danger.
Data update
Appendix updates — buried cables in ducts
New current-carrying capacity and volt-drop data for cables installed in buried ducts.
A3:2024 position
Designers had to use conservative reference-method assumptions for buried ducted cables, often oversizing conductors.
A4:2026 change
Dedicated tables added for buried-in-duct installation methods, enabling more accurate sizing and volt-drop calculations.
Regulations affected
- Appendix 4 — new tables for buried cables installed in ducts.
- Appendix 4 — updated volt-drop data supporting the new methods.
What this changes on site
- Long sub-main runs to detached garages, workshops and EV chargers can now be sized without the previous over-conservative penalty.
- Re-run your voltage-drop calculations for buried ducted feeds — you may drop a conductor size.
Industry-wide change
Individual competence (Electrotechnical Assessment Specification)
The rule that used to define the biggest debate between installers and scheme providers — settled.
A3:2024 position
A Qualified Supervisor's sign-off could carry work performed by less-qualified operatives on Solar PV, EV charging and EICRs, provided the QS retained overall responsibility.
A4:2026 change
Every person performing high-risk work (Solar PV, EV charging, EICRs) must hold their own Level 3 qualification. Sole reliance on a QS sign-off is no longer acceptable.
Regulations affected
- Electrotechnical Assessment Specification (EAS) — individual competence requirement.
- City & Guilds 2391-52 or equivalent required for those undertaking periodic inspection and testing.
What this changes on site
- Audit your operatives now: identify who is doing PV / EV / EICR work without an individual Level 3.
- Book the appropriate qualification (2391-52 for inspection, 2921/2919 for EV, 2399 for PV) before the October deadline.
- Scheme providers will ask for evidence at re-assessment — keep certificates centralised.
Revision
Section 722 — EV supply equipment
Builds on the Section 722 framework introduced by A2.
A3:2024 position
722.411.4.1 permits PME earthing where open-PEN detection cuts the L+N+PE within 5 s at ≥ 70 V rms, or where the installation uses a TT arrangement. Practical wording around bidirectional (V2H / V2G) chargers was thin.
A4:2026 change
Section 722 is updated to align with Chapter 57 and Section 551 for bidirectional charging. Open-PEN protection remains the primary mitigation. Documentation requirements for V2H / V2G installations are formalised.
Regulations affected
- 722 — bidirectional EV chargers treated as generating sets and cross-referenced to Chapter 57.
- 722.411.4.1 — open-PEN detection thresholds retained.
What this changes on site
- Standard 7 kW home chargers largely unchanged in practice — most already use O-PEN protection or a dedicated earth rod.
- V2H / V2G installs now attract Chapter 57 obligations if a battery is present.
Key dates
Amendment 4 timeline
- 15 January 2026IET and BSI sign off A4 content.
- 15 April 2026Orange Book published — voluntary adoption begins.
- 15 April – 15 October 2026Transition period — A3 and A4 both accepted; both C&G exams available.
- 31 July 2026EAL current qualification closes for new registrations.
- 15 October 2026A3 (Brown Book + Amendment 3 PDF) withdrawn. All new installation work must comply with A4. NICEIC requires access to the Orange Book.
- 31 December 2026EAL current qualification closes for certifications.
Sources
Official references
The definitive text is the printed Orange Book from the IET / BSI. Links below point to primary sources used to compile this page.
How A4 affects your installation
New work Paul designs from 15 October 2026 onward will be certified to A4:2026. Existing installations remain compliant with the amendment in force when they were designed — an EICR reports non-compliances against the current standard as informational codes (C3) rather than failures, unless they present a real safety issue.
Summaries on this page are for guidance only. Always refer to the current printed BS 7671:2018+A4:2026 for the authoritative wording. No liability accepted for reliance on this summary — see the disclaimer on the calculators page.