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Wiring Regulations 543.7 Explained
What are the changes in BS7671: 2008?
This revised standard includes the changes necessary to maintain technical alignment with European Harmonization Documents. It’s important to note that all of the regulations have been renumbered to align with the International Electrotechnical Commission’s (IEC) numbering system. This has also involved partial restructuring of the standard with Part 6 becoming Part 7 and vice-versa. But let’s start at Part 1; additional regulations relate to the requirements to protect against voltage disturbances and to implement measures against electromagnetic influences. Part 2, ‘Definitions’, includes a number of significant new and amended definitions. New requirements relating to safety services and continuity of service considered necessary during the intended life of the installation are addressed in Part 3. There are several significant changes to Part 4, ‘Protection for safety’. Whilst the fundamental principles of shock protection remain the same, the changes to definitions such a
The Tables in Chapter 41 for earth fault loop impedances are based on a nominal voltage of 230 V (not 240 V), hence the values are slightly changed. The Chapter also includes a new Table 41.5 giving maximum values of earth fault loop impedance for RCDs.
Chapter 42, Protection against thermal effects now includes the requirements for where particular risks of fire exist (previously in Section 482).Chapter 43, Protection against overcurrent now includes the requirements previously given in Section 473.
In Part 5, ‘Selection and erection of wiring systems’ will now include requirements for busbar trunking systems and powertrack systems. The requirements relating to cables concealed in a wall or partition have been altered so that protection by a 30mA RCD is an additional requirement for ‘unprotected’ cables (e.g. twin and earth cables installed in a chase less than 50mm deep); it must be emphasised that such cables must still be installed in ‘safe’ zones. Previously, the requirements for protection, isolation, switching, control and monitoring were covered in several different sections of BS 7671. In the 17th Edition, Chapter 53 now includes all the requirements relating to these issues. ‘Earthing arrangements and protective conductors’, Chapter 54, now incorporates the requirements applicable to equipment with high protective conductor currents which were previously given in Section 607.
Protection against voltage disturbances (Chapter 44) has now been expanded including a new Section 442, ‘Protection of low voltage installations against temporary overvoltages due to earth faults in the high voltage system and due to faults in the low voltage system’.
Chapter 55, ‘Other equipment’, includes additional requirements to ensure the safe connection of low voltage generating sets, including small scale embedded generators. ‘Luminaires and lighting installations’, Section 559, gives a new set of requirements for fixed outdoor lighting installations, extra-low voltage lighting installations, lighting for display stands and highway power supplies and street furniture (previously in Section 611).
In ‘Inspection and testing’, Part 6, the requirements are generally similar to those in BS 7671: 2001. The minimum values of insulation resistance have been increased. Into Part 7, ‘Special installations or locations’, there are significant changes and additions; Section 607 and Section 611 have been moved into the main body of the regulations (as Sections 543 and 559 respectively).
Zone 3 is no longer defined and supplementary bonding is no longer required, providing the installation has main bonding in accordance with Part 41. Every circuit in the special location, including lighting circuits, must have 30 mA RCD protection.
All Powerplan products are manufactured to comply with Section 607, utilising as a minimum a 4mm protective conductor within a flexible conduit. Whenever a ring circuit is installed or extended, Section 607 rules should be applied if there is any expectation that it will be used to power IT or similar equipment. If a circuit is being modified, the existing part of the installation should be checked for compliance – dual earth sockets, no spurs and separate terminations at the consumer unit – and brought into line if necessary. Finally, when testing is carried out, the earth loop continuity must always be checked.
An installation complying with BS 6396 “Electrical Systems in Office and Educational Furniture“ can not meet the requirements to comply with Section 607 of the Wiring Regulations and should not be confused with this. BS 6396 gives guidance on the maximum number and fuse rating of the socket outlets that can be plugged into the fixed wiring of a permanent installation by a BS1363 fused plug to a Ring or Radial socket outlet circuit. As stated in Section 607-02-01:
“The exception to the requirements of regulation 607-03-01, no special precaution is necessary for equipment having a protective conductor current not exceeding 3.5mA”.
Therefore a circuit utilizing a standard BS1363 plug top as its supply must not exceed a 3.5mA Protective Earth Conductor Current.
If further assistance is required, please contact Powerplan technical department:
Tel: 01995 640844
Email: enquiries@powerplan.co.uk
Section 607 - Cable Management Details