The IET's 18th Edition Wiring Regulations have underpinned electrical installation practice in the UK since their introduction in 2018. Amendment 4 is the most significant update to BS 7671 since Amendment 2, and if you work in electrical installation, inspection, or testing, it directly affects how you work, what you specify, and how you demonstrate compliance.

Here is what you need to understand before it comes into force.

Why Amendment 4 Matters

Amendments to BS 7671 are not cosmetic exercises. They reflect genuine changes in technology, risk understanding, and installation practice. Amendment 4 addresses several areas that have evolved considerably over recent years, including the widespread adoption of EV charging infrastructure, increased reliance on solar PV and battery storage systems, and updated requirements around protective devices and earthing arrangements.

The practical consequence is straightforward: installations that were compliant under the previous amendment may require re-evaluation, and test and inspection professionals need to be confident that their methods and documentation reflect the updated requirements.

Key Areas of Change

The changes introduced in Amendment 4 span several sections of BS 7671, but a few areas carry particular weight for those involved in testing and inspection work.

'Protection against electric shock' has seen further refinement, with updated requirements around automatic disconnection of supply and additiona guidance on RCD types and their application. The distinction between Type AC, Type A, and Type F RCDs has become more clearly defined in terms of where each is required, reflecting the reality that modern loads - variable speed drives, EV chargers, switch-mode power supplies - generate DC fault current components that Type AC devices cannot reliably detect.

EV charging installations receive substantially expanded treatment. The requirements around Mode 3 and Mode 4 charging, protective conductor sizing, and the use of RCDs in charging circuits have been brought into sharper focus. If you are regularly commissioning or inspecting EV charge points, the updated section is essential reading rather than background knowledge.

Solar PV and battery energy storage systems also receive more detailed coverage. The interaction between generation, storage, and the public supply network creates fault scenarios that earlier editions of the regulations did not fully anticipate. Amendment 4 tightens the requirements in these areas, particularly around isolation, labelling, and the behaviour of protective devices under fault conditions.

What Changes for Testing and Inspection

For those carrying out initial verification and periodic inspection and reporting, Amendment 4 has direct implications for how certain tests are conducted and recorded.

The updated requirements around RCD selection mean that inspectors need to be confident they are identifying the correct device type for the application, not simply confirming that an RCD is present. This requires a working understanding of the load types connected downstream and the fault current characteristics they produce. A Type AC RCD on a circuit supplying a modern EV charger is not compliant, regardless of whether it trips within the required disconnection time.

Earth fault loop impedance testing requirements remain broadly consistent with previous amendments, but the updated guidance on protective conductor sizing and earthing arrangements in certain installation types may affect how results are interpreted and recorded on Electrical Installation Certificates and Periodic Inspection Reports.

Professionals using multifunction installation testers should ensure their instruments support the full range of tests required under the updated standard. This is not typically a hardware limitation for modern instruments from manufacturers such as Fluke, Megger, or Metrel, but it is worth confirming that firmware and test sequences are current. If you are working to a documented test schedule, reviewing it against the Amendment 4 requirements before it becomes the operative standard is time well spent.

The Transition Period

As with previous amendments, there will be a defined transition period during which both the existing and updated versions of BS 7671 remain acceptable for new installations. The specific dates and transition arrangements are published by the IET and should be checked directly via the IET Standards website (https://www.theiet.org/publishing/iet-standards/) for the most current information.

What matters practically is that you understand the direction of travel and are not caught out specifying or certifying to a superseded standard once the transition period closes. Clients, building control bodies, and insurers increasingly expect documentation that reflects current requirements, and the cost of revisiting completed work is considerably higher than the cost of staying current.

Training and Qualifications

Amendment 4 will require updates to City & Guilds 2382 and associated qualifications. If you hold a current 18th Edition qualification, you should expect a requirement to complete an Amendment 4 update assessment before the transition period closes. Training providers are already scheduling courses, and demand is likely to be high as the operative date approaches.

For engineers and technicians who do not hold a formal qualification but work in areas affected by the changes - facilities management, industrial maintenance, HVAC commissioning - reviewing the updated sections relevant to your work is straightforward good practice. The IET publishes guidance documents and commentary alongside the regulations themselves.

Staying Prepared

The publication of Amendment 4 is a prompt to review your test equipment, your documentation practices, and your working knowledge of the areas most affected by the changes. None of this requires a wholesale overhaul for most professionals, but it does require deliberate attention rather than assuming continuity with what you already know.

If you have questions about whether your current test instruments meet the requirements for work under Amendment 4, or you need guidance on selecting equipment suited to EV, PV, or battery storage commissioning work, our team at Test Meter can help you work through the specifics. The right instrument for the job is not always the most expensive one, but it does need to be the right one.