A change to the Wiring Regulations will not stop a production line on the day it is published. Its effects are usually felt more quietly: in a design decision, a procurement specification, a shutdown plan or a certificate that has to stand up to scrutiny months later. For industrial businesses, that makes the transition to BS 7671 Amendment 4 a planning issue now, rather than something to leave until the October deadline is close.

The IET and BSI published BS 7671:2018+A4:2026 on 15 April 2026. The previous version, BS 7671:2018+A2:2022+A3:2024, remains valid during a six-month transition period and will be withdrawn on 15 October 2026. Until then, electrical installers may work to either edition. The practical challenge for manufacturers is making sure that projects already being scoped, designed or scheduled for a future shutdown are based on a clear and appropriate standard from the outset.

What BS 7671 Amendment 4 changes

BS 7671 is the UK national standard for electrical installations and covers new low-voltage installations, additions and alterations, and periodic inspection and testing. Amendment 4 is a substantial update, with confirmed changes that reflect the way electrical infrastructure is evolving. The headline areas include a new chapter on stationary secondary batteries, a new section on functional earthing and functional equipotential bonding for information and communication technology equipment, a new section on Power over Ethernet, and a major revision of the requirements for medical locations.

Not every change will affect every factory in the same way. A site installing battery storage has a different risk profile from one extending a production line, upgrading its data infrastructure or replacing switchgear. The starting point should therefore be a review of the work a business is planning, the systems already in place and the information available to those responsible for design, installation and maintenance.

Stationary batteries move firmly into the electrical design conversation

For industrial sites considering battery energy storage, the new chapter on stationary secondary batteries is likely to be one of the most significant parts of BS 7671 Amendment 4. The IET says the requirements address system design, power conversion equipment, bidirectional or hybrid inverters, and the suitability of protective devices where energy can flow in two directions. Battery location, ventilation and fire-risk mitigation also receive clear attention.

That reinforces an important point for manufacturers: a battery installation cannot be treated as an isolated container or piece of equipment. It interacts with the incoming supply, site distribution, protection strategy, operational load profile, fire strategy and, in some cases, on-site generation. Those relationships need to be considered early, while the design can still be influenced, rather than after equipment has been ordered or a preferred location has been agreed.

The appropriate solution will depend on the characteristics of the site and the proposed system. Decisions about capacity, protection, siting, ventilation and fire precautions require competent, project-specific assessment; general guidance cannot replace that work.

Functional earthing matters as factories become more connected

Modern production environments depend on much more than power circuits. Control systems, industrial networks, sensors, communications equipment and data infrastructure now sit alongside the machinery they support. Amendment 4 introduces requirements for functional earthing and functional equipotential bonding for ICT equipment and systems, making this an area that electrical, controls and IT or OT teams should understand together.

The practical risk is not simply a technical detail being missed. Problems can arise when responsibility sits between different suppliers, drawings do not show the complete arrangement, or protective and functional requirements are discussed in isolation. Before commissioning new connected equipment or modifying a control system, sites should establish who owns the earthing design, how interfaces will be documented and what information must be handed over for future maintenance.

Power over Ethernet is no longer just a data-cabling question

Power over Ethernet allows compatible network cabling to carry both data and extra-low-voltage DC power. It may be used for equipment such as network devices, sensors, cameras, access points or some lighting applications, and its use can grow gradually as a site becomes more connected.

The new Section 716 introduces requirements covering the selection of power supplies and cables using SELV and PELV systems, as well as the design, installation and verification of the relevant infrastructure. For an industrial site, the sensible conclusion is that existing structured cabling should not automatically be assumed suitable simply because it can carry data. Cable selection, connections, loading, environmental conditions and the intended use all need to form part of a competent assessment.

What should industrial sites review before 15 October 2026?

The transition does not call for a rushed, site-wide replacement programme. It does call for clarity. Engineering and facilities teams can use the months before October to identify where the amendment intersects with live projects and to prevent avoidable redesign, delay or uncertainty later.

• Confirm the design basis. For each live or planned project, record which edition is being used and make sure specifications, quotations, designs, inspection plans and certification follow the same basis.
• Review battery and generating projects early. Where a site is considering BESS, solar integration, hybrid inverters or another source capable of two-way energy flow, revisit the protection strategy, siting and wider fire-risk considerations before committing to equipment or layout.
• Map connected infrastructure and responsibilities. For projects involving PoE, ICT, control networks or functional earthing, define the boundaries between the electrical contractor, controls integrator, IT or OT team and equipment supplier.
• Check the handover information. Up-to-date drawings, schedules, certificates, equipment details and maintenance information make it much easier to assess an alteration safely and to understand how a new system affects the installation around it.
• Plan competence and training. Anyone designing, installing, inspecting or maintaining work to the new amendment needs access to the current requirements and an understanding of the changes relevant to their role.

Use the changeover to improve the quality of future projects

The best outcome from a standards update is not simply a new book on the shelf. It is better project definition. When the edition, design assumptions, responsibilities and records are agreed early, an electrical project is easier to price, schedule, install and maintain. This is especially valuable in manufacturing environments, where work often has to fit around short shutdown windows and where late changes can affect several contractors at once.

It is also worth looking beyond the immediate amendment. If drawings are incomplete, alterations have accumulated without a coherent record, or the site’s electrical infrastructure has not been reviewed alongside production growth, the transition provides a useful prompt to address those gaps. That wider review is not a blanket requirement created by Amendment 4, but it can reveal where ageing assets, undocumented changes or future load demands deserve attention.

A practical, site-specific response

AES works with manufacturers and industrial operators on electrical contracting, power and distribution, machinery installations, switchgear replacement, planned maintenance and energy projects. That breadth matters when a regulatory change affects more than one part of the site. The aim is not to make every project larger; it is to make sure the work is properly defined, correctly integrated and supported by the documentation the site will need afterwards.

If you have electrical work planned for late 2026, or you are considering battery storage, changes to distribution or new connected equipment, now is a sensible time to review the design basis. AES can assess the proposed scope in the context of your existing installation and help you plan the next steps. Any final compliance decisions should be made by a competent professional using the current standard and the actual conditions on site.

FAQs

When does BS 7671 Amendment 4 become the only current edition?

BS 7671:2018+A4:2026 was published on 15 April 2026. During the transition, installers may work to either the new Orange Book or the previous Brown Book with Amendment 3. The previous version remains valid until 15 October 2026, when it is withdrawn.

Does Amendment 4 mean every existing industrial installation must be upgraded immediately?

No blanket conclusion should be drawn without assessing the installation and the work being undertaken. The amendment is directly relevant to new low-voltage installations, additions and alterations, and periodic inspection and testing. Existing arrangements should be reviewed by a competent professional where a change, inspection finding or site-specific risk indicates that action may be needed.

Which Amendment 4 changes are most relevant to manufacturers?

That depends on the site, but stationary battery installations, functional earthing for ICT equipment and systems, and Power over Ethernet are likely to be particularly relevant to industrial businesses investing in energy storage, connected production equipment or network-powered devices.