18th Edition - Changes to Appendices
05 July 2018
Significant changes made to the appendices are summarised below.
Appendix 3
This now also contains the former content of Appendix 14 relating to the correction of tabulated or calculated values of maximum earth fault loop when a comparison is being made between these and measured values.
Appendix 6
A number of changes have been made to the model forms for certification and reporting to reflect changes made throughout the requirements of BS 7671. These are discussed in greater detail elsewhere in this issue of Connections.
Appendix 14
This appendix now gives guidance on the determination of prospective fault current (PFC). It describes ‘Rules of thumb’ that may be used to estimate the prospective fault current between two or more line conductors based on results obtained when testing between a line and neutral.
Guidance is also given on safety precautions that should be taken when determining PFC by testing and the responsibilities placed on those carrying out live testing by the Electricity at Work Regulations 1989.
This appendix also states that in domestic (household) or similar premises, where a consumer unit to BS EN 61439-3 is used and the maximum prospective fault current declared by the Distribution Network Operator is 16 kA, it is not necessary to measure or calculate prospective fault current at the origin of the supply.
Appendix 17
It was originally proposed that there would be a ‘Part 8’ introduced into BS 7671 covering energy efficiency. As a result of the commenting process it was decided that the draft was not sufficiently developed and the industry relatively unprepared for its implementation, and so this was edited to produce content for this informative appendix.
HD 60364-8-1 will be published by British Standards Institution as a separate standard and, looking forward, it is likely that there will be a normative chapter covering energy efficiency in BS 7671 at a later date.
Appendix 17 covers the following with respect to energy efficiency:
- Lighting
- Metering
- Cable losses
- Harmonics
- Transformer losses
- Power-factor correction
It should be noted that any measures taken to make an electrical installation more efficient must not compromise the safety of a building’s occupants, property or livestock.
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