Understanding the 3rd Amendment to BS7671: 18th Edition

Reason for Communication:  

On the 31st of July 2024, the Institute of Engineering and Technology published its 3rd Amendment to BS7671: 18th Edition.  

What has changed in this standard:  

Two new definitions for devices have been included: 

Bidirectional protective device. 

This is a protective device where a power supply may be connected to either set of connection terminals. The power flow may be in either direction. 

The product standard outlines that the Neutral terminals must be marked with “N” and the Live terminals marked with “L” or left blank.  

Unidirectional Protective Device. 

This is a protective device where it is intended the power supply is only connected to one defined set of connection terminals. The power flow is in one direction only. 

The product standards are outlined with in Appendix 1 of the document for Circuit protection devices to indicate if they are unidirectional. Examples include: “in” and “out” or “line” and “load” or arrows. 

New Published Regulation:   

in addition, a new regulation has been added to Chapter 53 that gives clear definition when defining and installing devices for protection, switch control, monitoring and circuit isolation. This also covers the potential and possible directions for power flow.   If power flow is not in a single direction, only appropriate bidirectional devices shall be selected and used.  

Where is this relevant:  

With the increased demand to incorporate PV, Battery storage, and EV into homes, the regulation has been updated to further ensure that these installations are safe. Feeding power back into a circuit that is unidirectional could result in damage to the device, compromising safety to the home and users.  

How are British General prepared this change:   

British General has a range 18th Edition Amendment 3 Bi-directional devices for installations that feed into and draw power through the same circuit protection device.  

These consist of Bi-directional RCD’s, Circuit Breakers, and Double Pole RCBO devices.  

View the full BG Circuit protection range here: www.bgelectrical.uk/uk/circuit-protection

• BS7671: 18th Edition Amendment 3 was published on July 31, 2024.

• Two new device definitions introduced: Bidirectional (allow power flow in both directions), and Unidirectional (allow power flow in one direction) Protective Devices.

• A new regulation in Chapter 53 clarifies installation rules for protective, control, and isolation devices based on power flow direction.

• The update is critical for integrating PV, battery storage, and EV systems into homes.

• British General offers 18th Edition Amendment 3-compliant bidirectional devices, including RCDs, circuit breakers, and RCBOs.