Amendment 3 of BS7671 comes into effect

Today (31st July 2024), Amendment 3 of ‘BS 7671 Requirements for Electrical Installations IET Wiring Regulations’, comes into immediate effect. BS 7671:2018+A3:2024, addresses a key issue regarding the selection and installation of protective devices, particularly where installed with an additional source of power, such as battery storage, or solar PV.

The amendment is limited to the addition of two new definitions within Part 2:

• Bidirectional protective device. A protective device where it is intended by the manufacturer that a source of supply is connected to either or both sets of connection terminals
• Unidirectional protective device. A protective device where it is intended by the manufacturer that a source of supply is only connected to one defined set of connection terminals.

along with the addition of a new, UK-specific regulation, and note, within Chapter 53:

530.3.201 Selection and erection of equipment for protection shall take account of appropriate use of either a unidirectional protective device or a bidirectional protective device.

NOTE: Product standards as listed in Appendix 1 for some protective devices, including RCCBs, RCBOs, circuit-breakers and AFDDs, require these devices to be marked to indicate if they are unidirectional e.g. "in" and "out" or "line" and "load" or arrows.

These additions were required after it became apparent that some protective devices may suffer from reduced effectiveness where installed in wiring systems subject to bidirectional current flow. These include but are not limited to, circuits connecting solar PV inverters or battery electric storage systems (BESS) with a consumer unit/distribution board.

Whilst the amendment may be out of step with the normal cycle of amendments to the regulations, it was deemed an important change to the technical content and was warranted. (Note: corrigenda, occasionally used in updating the regulations, are solely for the remedy of editorial issues and not for addition or alteration of technical content or intent).