BS 7671 Amendment 3: A3:2024 Update Training

BS 7671:2018+A3:2024 is the third amendment to the 18th Edition of the IET Wiring Regulations. It was issued on 31 July 2024 as a free PDF supplement — not a new book and not a replacement for the existing brown book (BS 7671:2018+A2:2022). Electricians should download the supplement and read it alongside their existing copy of BS 7671.

Amendment 3 is a focused amendment, primarily addressing the growing need for guidance on installations where power can flow in both directions through switching and control devices. This is driven by the rapid adoption of solar PV systems, battery energy storage systems, and vehicle-to-grid (V2G) EV chargers — all of which can feed energy back into the installation and, in some cases, back to the distribution network.

For electricians studying for or holding the 18th Edition qualification (C&G 2382), Amendment 3 is required knowledge. Exam questions may reference the A3:2024 Section 530 requirement and the concept of bidirectional power flow. For practising electricians, understanding A3:2024 is essential for any installation involving solar PV, battery storage, or V2G charging.

The central addition in Amendment 3 is the new bidirectional device requirement within Section 530 of BS 7671. This addition sits within Part 5 of BS 7671 (Selection and Erection of Equipment) and specifically within Chapter 53 (Switching Devices). It states that where a switching device or control device may be subjected to power flow in both directions, the device must be suitable for that duty.

This seems like common sense — of course a device should be suitable for its intended use. But the practical reality is that many electricians have been installing solar PV systems, battery storage, and other microgeneration equipment without checking whether every device in the circuit path is rated for reverse current flow. Some MCBs, RCBOs, and isolators are designed with a specific line (supply) terminal and load terminal — if current flows in the reverse direction, the device may not operate correctly during a fault, potentially failing to disconnect.

Understand the A3:2024 bidirectional device requirement

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A bidirectional device is a switching or protective device that is designed to operate correctly regardless of the direction of current flow through it. The supply can be connected to either terminal, and the device will provide its rated protection in both directions. Many modern MCBs and RCBOs from major manufacturers are bidirectional, but this cannot be assumed — always check the manufacturer data.

A unidirectional device is designed for current flow in one direction only. It has a designated line (supply) terminal and a load terminal. If the current direction is reversed — as can happen with bidirectional power flow — the device may not provide its rated protection. Unidirectional devices are not suitable for installation in circuits where bidirectional power flow can occur, unless additional measures prevent reverse flow through the device.

For existing installations being inspected under an EICR, an inspector should check whether any microgeneration or energy storage is present and, if so, verify that all devices in the affected circuits are suitable for bidirectional operation. A non-compliant device in a bidirectional circuit could be classified as a C2 (Potentially Dangerous) observation.

For many electricians, the practical impact of Amendment 3 is focused on specific installation types. If you are installing solar PV, battery storage, or V2G chargers, you need to apply the A3:2024 Section 530 bidirectional device requirement from the design stage. If you are carrying out general domestic or commercial installation work without microgeneration, the regulation has minimal direct impact on your day-to-day work — but you still need to know it.

When designing an installation with bidirectional power flow, the steps are:

For EV charger installations, Amendment 3 is particularly relevant where vehicle-to-grid (V2G) or vehicle-to-home (V2H) chargers are installed. These chargers can discharge the vehicle battery back into the property, creating bidirectional power flow through the consumer unit and potentially through the main supply fuse and meter.

If you hold the 18th Edition qualification (C&G 2382), you do not need to resit the exam for Amendment 3 — your qualification remains valid. However, you do need to update your working knowledge to ensure you are aware of the new regulation and can apply it correctly in practice.

For electricians registered with competent person schemes such as NICEIC, NAPIT, or ELECSA, awareness of amendments is part of your ongoing CPD (Continuing Professional Development) obligation. Most scheme providers expect their registered electricians to stay current with amendments to BS 7671 and to be able to demonstrate that awareness during assessments.

The Elec-Mate CPD training platform includes a dedicated Amendment 3 module that covers every aspect of A3:2024 in structured, bite-sized lessons. Complete the module, pass the quiz, and receive a CPD certificate — all from your phone.

Complete your Amendment 3 CPD in one session

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Understanding where Amendment 3 sits in the broader timeline of BS 7671 helps put its significance in context.

The 18th Edition lifecycle typically runs for approximately 7 to 10 years before a new edition is published. The 19th Edition is not expected before 2028 at the earliest. In the meantime, amendments keep the standard current with technological developments — particularly the rapid growth of renewable energy, energy storage, and electric vehicle charging installations.

Staying current with each amendment is not optional — it is a professional obligation for any electrician designing, installing, inspecting, or certifying electrical installations under BS 7671.