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On-Site Guide (BS 7671:2018+A2:2022) (Electrical Regulations)

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Provides step-by-step guidance on the design of electrical installations. The guide will be useful for apprentices and trainees carrying out the calculations necessary for a basic installation and has been fully updated to BS 7671:2018+A2:2022. Impartiality is the governing principle of how BSI provides its services. Impartiality means acting fairly and equitably in its dealings with people and in all business operations. It means decisions are made free from any engagements of influences which could affect the objectivity of decision making. The guidance is based on the requirements of BS 7671: 2018+A2:2022 Requirements for Electrical Installations, and references to Regulation numbers are to those contained in that Standard. Additional Details Author

On-Site Guide (BS 7671:2018+A2:2022), 8th Edition - ISSWWW On-Site Guide (BS 7671:2018+A2:2022), 8th Edition - ISSWWW

Whilst some testers are capable of testing different types of RCD with a variety of fault currents, BS 7671:2018+A2:2022 only requires an AC test to show compliance. This means that the test instrument needs to be set to the Type AC RCD setting regardless of RCD Type.


The Amendment continues the thread of embracing new technologies and Prosumer’s Low Voltage Electrical Installations is an exciting step into the future of renewable sources of energy and their integration into our lives. Similarly, for instruments with a setting for Type B RCDs a multiplier of two times I Δn is applied as required by the product standard, BS EN 62423:2012 Type F and type B residual current operated circuit-breakers with and without integral overcurrent protection for household and similar uses. Includes the latest guidance on third-party certification schemes and covers relevant parts of the Building Regulations, including Fire Safety, Ventilation and Conservation of Energy. This guide has been fully updated to BS 7671:2018+A2:2022.

BS 7671:2018+A2:2022 Changes to RCD testing in BS 7671:2018+A2:2022

Arcs can be caused by insulation defects in cables, damage to cables by impact and penetration of nails and screws, loose terminal connections, and so on. An AFDD is designed to operate (trip) when a dangerous arc is detected by analysing the signature of the arc. Switching arcs caused by fluorescent lighting, for example, should not cause an AFDD to operate. AFDDs can be installed in distribution boards and consumer units to protect final circuits and should be installed in accordance with the manufacturer’s instructions. When installing components from a different manufacturer to that of the existing equipment in a distribution board or consumer unit, it is important to seek advice from the manufacturer that the new equipment is suitable and compatible.

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The early style Residual Current Devices (RCDs) were highly effective protective devices but they have proven to be less reliable in modern buildings as a consequence of DC leakage and DC fault currents caused by electronic equipment. Subsequently, new types of RCD have been developed.

On-Site Guide (BS 7671:2018) (Electrical Regulations) (PDF) On-Site Guide (BS 7671:2018) (Electrical Regulations) (PDF)

Note: A new ‘foundation earthing’ requirement has been introduced into Chapter 54 to make arrangements for a suitable earth electrode provision for PEIs not connected to the LV public supply network.

What is the maximum disconnection time for TT earthing systems using an RCD for fault protection?

Dan Palmer, Associate Director of Committees at BSI said: “BS 7671 is one of the UK’s most important standards, providing authoritative requirements to promote electrical safety. The changes introduced in this new amendment will help electrical professionals keep up to date with new and innovative technologies, as well as ensuring they have current knowledge about designing safe installations.”

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