SORIVO Engineering · Codes & Compliance · United Kingdom

BS 7671 Amendment 4 (2026) for Cable Buyers: Chapter 57 Batteries, Section 716 PoE & What Changes Before 15 October 2026

The 18th Edition gets its fourth amendment — and with it a dedicated chapter for stationary battery storage, a first-ever section for power over Ethernet, and a hard six-month clock on the edition you are allowed to certify against. Written for distributors, EPC specifiers and importers quoting UK projects.

Published 30 Aug 2026 · Updated 31 Aug 2026 · Reviewed by Luo Qiang

Sheet03
Basis EditionBS 7671:2018 +A4:2026
Issued / Rev.2026-08-31 · C
Checked ByL. QIANG
Direct Answer BS 7671:2018+A4:2026 — the "Orange Book" — was published by IET and BSI on 15 April 2026 and becomes the sole accepted edition on 15 October 2026, when the previous version is withdrawn. For cable buyers, three changes matter most: a new Chapter 57 that restricts where stationary battery systems can be installed — published guidance reports lofts and escape routes as ruled out — and requires thermal-runaway mitigation on battery circuits; a new Section 716 covering power over Ethernet, where data cables now carry extra-low-voltage DC with bundling and thermal considerations; and a new Section 545 for ICT functional earthing. Between those dates, both editions count as current. Anything you import, stock, or install for UK projects after 15 October should be quoted and documented against A4.

If you buy cable for the UK market — as a distributor, an EPC contractor, or a brand importing from Asia — this amendment is not background reading. It has a hard deadline attached, and deadlines are what turn "we'll update our specs eventually" into rejected submittals in October.

Scope of this guideOne honest note before we start: we're a cable manufacturer, not a UK certification body, and we did not work from the paywalled standard text. This guide is a synthesis of published summaries — NICEIC's own amendment page, IET-linked installer guides, and code-training write-ups — cross-checked against each other, translated into what the change means for cable selection and procurement documents. Where the summaries agree, we say so plainly; where only one goes into detail, we say that too. For clause-exact wording, buy the BSI/IET publication — and for anything ambiguous, ask the designer of record.

01What Is Amendment 4, and Why Does 15 October 2026 Matter?

Amendment 4 is the latest update to the 18th edition of the IET Wiring Regulations (BS 7671:2018). It was published on 15 April 2026, and from that day the new text was live for designs. The previous edition — the 2018+A2:2022+A3:2024 book, per NICEIC's summary — stays valid during a six-month transition, then is withdrawn on 15 October 2026.

The six-month coexistence window between publication of Amendment 4 and withdrawal of the previous edition Timeline from 15 April 2026, when BS 7671:2018+A4:2026 was published, to 15 October 2026, when the previous edition is withdrawn. Between the dates both editions count as current; afterwards only A4 applies to new work. FIG. 1 · ONE EDITION IN, ONE EDITION OUT — AND THE SIX MONTHS WHERE BOTH COUNT A2 + A3 sole edition COEXISTENCE — BOTH EDITIONS CURRENT certificates and EICRs may be issued against either A4:2026 ONLY quote & document to A4 15 APR 2026 15 OCT 2026 published by IET & BSI live for designs from this date previous edition withdrawn new work designed & certified to A4 time → Not retrospective: existing compliant installations are not swept out. Additions and alterations made after 15 Oct are covered by A4.
Fig. 1 — The whole risk sits in the amber band. Cable ordered in September for a project energizing in November lands under A4 even if the RFQ quoted the old book.

Two practical consequences of that window:

  • Right now, both editions count as current. Installation certificates and EICRs can be issued against either. If you're holding stock or mid-project, nothing forces a redo.
  • After 15 October, only A4 exists. New work is designed and certified against the amended text. Existing, compliant installations aren't retrospective casualties — but per Virtual College's installer guide, any addition or alteration made after that date must meet the new requirements, including Chapter 57 for anything touching a battery system.

For procurement, the transition is where the risk hides. Cable ordered in September for a project energizing in November will be installed under A4 even if the RFQ was written against the old book. Put the governing edition into the contract language now — the same discipline we recommend in our cable supply contract clauses guide.

02Chapter 57: Battery Installations Get Their Own Rulebook

The headline change for anyone in solar, storage, or backup power. Chapter 57 — stationary secondary battery installations — is described in the published reviews as covering domestic battery storage (including solar-paired systems), commercial energy storage, grid-connected arrays, and backup/UPS functions, with self-contained UPS appliances and vehicle traction batteries out of scope.

Chapter 57 scope as described in published reviews Two panels. In scope: domestic battery storage including solar-paired systems, commercial energy storage, grid-connected arrays, and backup or UPS function installations. Out of scope per the same reviews: self-contained UPS appliances and vehicle traction batteries. FIG. 2 · CHAPTER 57 — WHAT THE PUBLISHED REVIEWS PUT INSIDE AND OUTSIDE THE CHAPTER IN SCOPE — STATIONARY SECONDARY BATTERIES ✓domestic battery storage (incl. solar-paired) ✓commercial & grid-connected energy storage ✓backup / UPS function installations ✓grid-connected arrays OUT OF SCOPE — PER THE SAME REVIEWS ✗self-contained UPS appliances ✗vehicle traction batteries The second exclusion matters if you quote into EV-plus-storage projects: a stationary array is Chapter 57; a vehicle pack is not. Scope as described in NICEIC's and Virtual College's reviews of A4:2026 — not clause text reproduced here. Confirm the boundaries in the chapter itself before they reach a drawing.
Fig. 2 — Chapter 57 is a stationary-storage chapter. Two exclusions are as commercially relevant as the inclusions, because they decide which rulebook your DC cable is quoted against.

Where the guidance says batteries can't go

Post-publication guidance from installers' bodies and training providers reports that lofts are ruled out — the cited reasons include extreme summer temperatures, poor ventilation, combustible materials nearby, and fire risk directly above sleeping areas — along with escape routes, corridors and stairwells. Virtual College's installer guide goes further and gives working distances for external installations, clear of windows, doors and ventilation openings and away from stored flammables, citing 1 m and 2 m buffers respectively.

Treat all of the above as what the published guidance says rather than clause text we have verified line by line: the direction (lofts and escape routes are out; separation from openings and combustibles is required) is consistent across every source we read, while the exact wording and numbers belong in BS 7671:2018+A4:2026 itself. Locations the guidance describes as acceptable: garages, utility rooms with fire separation, dedicated plant rooms, and weatherproof external installations. For non-domestic work, a formal fire risk assessment informs location and fire protection.

Dwelling cross-section with battery location verdicts reported in published guidance A simple house section with seven numbered zones: loft, stairwell and corridors, cellar without direct external access, garage, utility room, plant room, and an external weatherproof unit. Published guidance reports lofts and escape routes as prohibited, cellars as restricted, and garages, fire-separated utility rooms, plant rooms and weatherproof external locations as acceptable. FIG. 3 · BATTERY LOCATIONS — VERDICTS AS REPORTED IN PUBLISHED GUIDANCE (NOT CLAUSE TEXT) LOFT habitable rooms GARAGE UTILITY PLANT CELLAR ESS 1 2 3 4 5 6 7 VERDICT AS REPORTED IN THE GUIDANCE WE READ 1 Loft / roof space extreme summer heat, poor ventilation, above bedrooms PROHIBITED 2 Stairwells, corridors, escape routes the route out must stay clear of the hazard PROHIBITED 3 Cellar without direct external access ventilation and rescue access both degrade RESTRICTED 4 Garage attached or detached, keeps the risk out of habitable space ACCEPTABLE 5 Utility room with fire separation the usual retrofit answer inside the envelope ACCEPTABLE 6 Dedicated plant room non-domestic: backed by a formal fire risk assessment ACCEPTABLE 7 Weatherproof external installation kept clear of windows, doors and ventilation openings ACCEPTABLE Buffers cited by one installer guide: 1 m from windows / doors / ventilation openings, 2 m from stored combustibles. Those two figures are single-source and indicative. The principle — separation from escape routes and openings — is what is consistent.
Fig. 3 — Schematic section, not a code diagram. The colour of each zone is the guidance's verdict, not a clause reference; section keys 1–7 match the legend on the right.

What it means for the cabling you buy

Battery circuit chain showing where Chapter 57 requirements land on cable specification A single-line chain from AC supply through isolation, a bidirectional inverter, DC protection and the stationary battery. The DC side is marked always-live; the DC cable and its protective device are specified as a pair; the guidance lists battery management, temperature monitoring, automatic disconnection and smoke or heat detection. FIG. 4 · WHERE CHAPTER 57 TOUCHES THE CABLE, TRACING THE POWER FLOW THE CHAIN A SUBMITTAL NOW HAS TO DESCRIBE ACSUPPLY ISOLATION& SWITCHING BIDIRECTIONALINVERTER DCPROTECTION STATIONARY BATTERYthe Chapter 57 subject two-way ALWAYS-LIVE DC SIDE — EVEN AFTER AC IS DISCONNECTED Spec pair → the DC cable and its overcurrent device are now chosen together; AC-rated devices are not always suitable for DC duty. The guidance lists BMS, temperature monitoring, automatic disconnection on fault and smoke/heat detection; labels cover voltage and capacity. Schematic only — not a wiring diagram, and not a substitute for the chapter and the manufacturer's instructions.
Fig. 4 — Read left to right, this is the documentation chain: thermal data for the interconnect, a DC-rated device specified against it, and labelling that survives the isolation procedure.
  • Battery circuits get explicit sizing, protection, and labelling requirements. LedgerCert's summary calls out "detailed guidance on cable sizing, protection, and labelling for battery storage circuits." Expect to be asked for thermal ratings and derating data on battery interconnect cables, not just ampacity at 30 °C.
  • Thermal runaway mitigation moves from best practice into the requirements. The guidance lists battery management systems, temperature monitoring, automatic disconnection on fault conditions, and smoke or heat detection in the battery space. Cables feeding battery systems become part of a safety chain — and the documentation you ship with them should read that way.
  • Two-way energy flow changes protection selection. With V2H/V2G and bidirectional solar-battery systems, protective devices must handle current flowing both ways, and standard AC-rated devices aren't always suitable for DC or bidirectional use. The DC-side cable and its overcurrent device now need to be specified as a pair.
  • Safe isolation assumes the battery is always live. A battery "will continue to present a live DC voltage even after the main AC supply is disconnected." Isolation labelling and DC-rated disconnect access become part of the install — worth reflecting in your cable marking and documentation packages.

One connection worth knowing: the guidance we read ties domestic battery installations explicitly to PAS 63100:2024, the battery installation code of practice — Virtual College's review states this directly. What that means for procurement is the useful part: the cable spec conversation now sits inside a documented chain of standards rather than a rule-of-thumb. Which regulation number does the tying is a detail to confirm in the published text, not something to put on a submittal from a blog.

If you're speccing battery interconnect or DC distribution cable, our BESS cable selection whitepaper covers voltage-class logic that maps directly onto these requirements, and our ESS energy storage cable is built for exactly this duty.

03Section 716: Power over Ethernet Enters the Wiring Regulations

For the first time, BS 7671 has a dedicated section for PoE — distributing extra-low-voltage DC over balanced data cabling in smart buildings. Cameras, access points, lighting, all the powered devices that used to live outside the electrician's world are now, in effect, part of the installation.

The engineering issue is heat. A Cat6A cable carrying 802.3bt-class power dissipates warmth in its conductors, and when cables are bundled or run in insulation, that heat has nowhere to go. Section 716 addresses this with thermal and bundling considerations for powered data cables — the details sit in the section's tables, and we won't invent numbers here. What a buyer needs to know:

Section 716 — the thermal problem in bundled data cable and the datasheet questions it creates Left: a bundle of seven data cables in cross-section with heat arrows trapped inside, illustrating conductor heating from PoE current. Right: a power sourcing switch feeding cameras, access points and lighting over balanced data cable. No numeric derating values are shown because none were available in the sources checked. FIG. 5 · SECTION 716 IN ONE PICTURE — POWER HEATS THE PAIR, THE ROUTE DECIDES WHERE IT GOES THERMAL MECHANISM I²R loss in every conductor, trapped by the bundle around it WHAT STARTS APPEARING ON A DATA-CABLE DATASHEET PoE SWITCHpower sourcing equip. cameras access points luminaires ELV DC + data 802.3bt class · conductor temp rating · bundle-size guidance · LSZH jacket option the three questions the channel will ask ⚑ No derating percentages appear in the summaries we read. Section 716's tables govern — buy the standard before quoting one. Installers under NICEIC schemes must show understanding of Section 716, per NICEIC's summary — the pressure arrives at the counter.
Fig. 5 — Deliberately number-free. The mechanism (heat, bundling, route) is what changes the specification conversation; the percentages belong to the section's tables.
  • Data cable specs will start quoting PoE duty. Conductor temperature ratings and bundle-size guidance become part of the conversation, not an afterthought.
  • Installers must "demonstrate an understanding" of Section 716 under NICEIC schemes — so your channel customers will increasingly ask whether your data cables are suited to powered runs.
  • LSZH jacketing matters in exactly the routes PoE fills. Offices, hotels, hospitals — the buildings where PoE density is highest are the ones where low smoke halogen-free requirements bite. Our Cat6A/Cat8 S/FTP LSZH data cable is specified for that overlap.

04Section 545: Functional Earthing Gets Its Own Section

The third structural addition covers functional earthing and functional equipotential bonding for ICT equipment and systems — network cabinets, servers, broadcast gear. The key conceptual change, per NICEIC and code-training summaries: a clean distinction between protective earthing (touch safety) and functional earthing (equipment performance).

Protective earthing versus functional earthing and the colour identification reported for each Two panels. Left: protective earthing, green-yellow conductor, purpose is touch safety. Right: functional earthing for ICT, pink identification per Table 51 as reported in NICEIC's summary, preferably throughout the conductor or at minimum at the termination, with green-yellow not permitted for this duty. FIG. 6 · TWO EARTHS, TWO JOBS — AND FOR THE FIRST TIME TWO IDENTIFICATIONS PROTECTIVE EARTHING · PE green-and-yellow purpose: protection against electric shock already covered by the existing rules the earth every circuit already carries FUNCTIONAL EARTHING · FE — SECTION 545 pink — per Table 51, as reported preferably throughout the conductor; at minimum identified at the termination purpose: equipment performance, not shock ✗ green-and-yellow is not permitted for this duty (per NICEIC's summary) ⚑ The pink identification and the "preferably / at minimum at termination" wording come from one source only — NICEIC's summary. Confirm against Table 51 before quoting a pink-sheathed or pink-marked FE conductor. Practical risk: FE conductor identity surfaces at termination, mid-project — the wrong moment to discover your supplier has none.
Fig. 6 — Section 545's real procurement consequence is a new line item on the schedule: a functionally earthed conductor that is deliberately not green-and-yellow.

For cable buyers, one detail stands out: NICEIC's summary notes that functional earthing conductors are identified pink in Table 51 — preferably throughout the conductor, but at minimum identified at the termination point, with green/yellow explicitly not permitted. If your UK customers are asking about pink-sheathed or pink-marked FE conductors for data-room work, that's where it comes from. We covered the broader colour-code landscape across HD 308, BS 7671, and the NEC in a separate conductor colour guide.

05Two Quieter Changes That Touch Cable Directly

Beyond the three headline sections, two items from the amendment matter to anyone quoting cable into UK projects:

Two secondary changes: conductor grouping in ferrous enclosures and separate buried-cable appendix data Left: line, neutral and protective conductors of the same circuit grouped in one ferrous enclosure, versus split across enclosures where eddy-current heating is the concern. Right: a cable in direct contact with soil versus a cable inside a buried duct, which the amended appendices reportedly treat with separate data. FIG. 7 · TWO SECONDARY ITEMS THAT CHANGE HOW YOU SIZE AND QUOTE REG. 521.5.1 — GROUP A CIRCUIT'S CONDUCTORS L N PE all together → ✓ magnetic fields cancel L N PE separate enclosure split → ✗ eddy-current heating steel trunking & gland plates APPENDIX DATA — BURIED RUNS SPLIT INTO TWO CASES direct soil contact one set of tables in duct / conduit a second set ⚑ Both items are reported by one code-training summary (ECalPro) and are attributed as such — they are not clause text we verified. Re-check buried calculations against the amended appendix before quoting; our soil thermal resistivity method covers the inputs that move.
Fig. 7 — Neither item makes headlines; both change a datasheet line. Single-core in steel trunking is the classic place a "grouping" rule bites after the fact.
  • Conductors grouped in ferromagnetic enclosures (Regulation 521.5.1). Per one code-training summary, line, neutral, and protective conductors of the same circuit must be grouped together in ferrous enclosures — the point being to prevent eddy-current heating when a circuit's conductors are split. Relevant to single-core cable arrangements in steel trunking and gland plates; we touch the physics in our guide to conductor selection.
  • New buried-cable data in the appendices. The amendment reportedly adds voltage-drop and current-carrying-capacity data for cables in buried ducts, and distinguishes direct soil contact from duct or conduit installation. If you size UK buried runs with our cable sizing guide or the soil thermal resistivity method, this appendix is worth aligning your calculations with.

06The SORIVO Buyer's Checklist Before 15 October

  1. Audit every live RFQ against the deadline. Anything installed after 15 October 2026 gets designed and certified to A4. Update the "governing standard" line in your tender documents now, not at handover.
  2. Ask battery-system suppliers for Chapter 57-aligned documentation. Cable datasheets for battery circuits should show thermal data and suitability for the installation environment the new chapter assumes — not just a generic ampacity table.
  3. Prepare PoE-specific answers for data cable. Bundle limits, temperature ratings, and LSZH options. If your data cable datasheet can't answer a Section 716 question, expect the question again from the next customer.
  4. Check functional earthing conductor availability. Pink identification per Table 51 is the kind of detail that surfaces at termination, mid-project — too late to source. If you supply data rooms, ask about FE conductor options early.
  5. Don't panic-buy replacements for compliant stock. The amendment is not retrospective. Cable already installed to the previous edition and compliant stays compliant; the change bites on new design, additions, and alterations.

07Quick Reference: What Changes at a Glance

Table 1 · BS 7671:2018+A2+A3 → BS 7671:2018+A4:2026 (Rev. C · 2026-08-31)
ItemBefore A4Under A4:2026Buyer action
Governing editionBS 7671:2018+A2:2022+A3:2024BS 7671:2018+A4:2026 from 15 Oct 2026Update contract and RFQ standard references
Battery installationsScattered provisions; PAS 63100 as best practiceDedicated Chapter 57; published guidance reports lofts & escape routes ruled out, plus thermal runaway mitigationRequest thermal/protection data on battery circuit cables
PoE / powered data cablingOutside BS 7671 scopeNew Section 716 with thermal & bundling rulesQuote data cables with PoE duty and LSZH options
ICT functional earthingHandled informallyNew Section 545; pink identification per Table 51Check FE conductor availability and marking
Buried cable sizing dataGeneral tablesNew duct vs soil data in appendices (per code-training summary)Re-check buried run calculations against new appendix data
Existing installs—Not retrospective; additions/alterations must complyNo forced replacement of compliant stock

Clause-exact requirements — especially the 1 m / 2 m location buffers, the Section 716 thermal tables and the Table 51 colour rules — should be confirmed against the BS 7671:2018+A4:2026 publication itself before they go into a contract or a design. This guide synthesizes published summaries from NICEIC, IET-linked installer resources and code-training sources, cross-checked for consistency.

08Frequently Asked Questions

Q1

When does BS 7671 Amendment 4 become mandatory?

It was published on 15 April 2026 and could be applied to designs from that date. The previous edition is withdrawn on 15 October 2026; after that, only A4:2026 is valid for new work. Between the two dates, both editions count as current.

Q2

Does Chapter 57 apply to my existing battery installation?

No — the amendment is not retrospective. An existing, compliant installation can stay as it is. But any addition or alteration made after 15 October 2026 must meet Chapter 57, and installers surveying older systems (say, a loft battery) are expected to note departures in EICR documentation.

Q3

Where can batteries be installed under Chapter 57?

The published guidance is consistent on the direction: lofts and escape routes are out, with corridors, stairwells and cellars without direct external access also flagged. Locations the guidance describes as workable include garages, utility rooms with fire separation, dedicated plant rooms, and weatherproof external installations — provided the system stays accessible for maintenance and doesn't compromise fire escape. Non-domestic installs should back location decisions with a formal fire risk assessment. Confirm the exact wording against A4 itself before it goes on a drawing.

Q4

Does Section 716 change the data cable I buy for PoE?

It formalizes what good practice already suggested: data cables carrying extra-low-voltage DC need thermal and bundling consideration, especially at higher PoE power classes. Ask your supplier for conductor temperature ratings and bundle guidance rather than assuming a standard datasheet covers powered runs — and favour LSZH jackets in occupied buildings.

Q5

What should I ask my cable supplier for before 15 October?

Three things: confirmation that battery-cable datasheets carry the thermal and protection data Chapter 57's environment assumes, PoE-suitability guidance (temperature ratings and bundle limits) for data cables, and availability of pink-identified functional earthing conductors where data-room work is in scope. Sorivo ships UK-market documentation packages with test reports and can quote against A4-aligned requirements directly.

Next step

QUOTING CABLE INTO A UK PROJECT THAT OVERSPANS 15 OCTOBER?

Send us the certification date, not the order date. SORIVO will quote battery interconnect, PoE-rated data cable and functional earthing conductors with the documentation package A4-era submittals expect — or email sale@sorivocable.com directly.

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Senior cable application engineer at Sorivo
Reviewed by Luo Qiang — Senior Cable Application Engineer, Sorivo
15+ years in industrial and renewable energy cable specification. Experienced in cable specification aligned with IEC standards.
Sources
NICEIC, "Understanding BS 7671:2018 + Amendment 4:2026"; ECalPro, "BS 7671 Amendment 4 (2026) — Complete Guide" (vendor code-training content); LedgerCert, "BS 7671 Amendment 4 (2026): What Electricians Need to Know"; Virtual College, "Battery Storage & BS 7671 Amendment 4" (installer training guide); IET / BSI publication dates corroborated via a provincial WTO/TBT alert service. The two publication and withdrawal dates are consistent across four independent summaries; detail items that appear in only one summary are attributed in the text and flagged in the figures. BS 7671:2018+A4:2026, published jointly by IET and BSI, remains the text of record — this article was written from published summaries, not from the paywalled standard. Figures are schematic drawings of summarized guidance, not code artwork.

Related reading
BS 5467 vs BS 6724 Armoured Cable · BS 6387 vs IEC 60331 Fire-Resistant Cable Standards · BS 8519 Fire-Resistant Cable Guide · High-Rise Riser Cable Sizing to BS 7671 · AWA Cable UK Guide · Building Cable Fire Compliance Guide
This article summarizes published information about BS 7671 Amendment 4 for general guidance. The governing text is the BS 7671:2018+A4:2026 publication itself; verify clause-level details before contractual or design use.