View source for BS7671 Wiring regs changes - 17th edition

This is the foreword of the 2008 edition of BS761 - the 17th edition of the wiring regs (the red book). It summarises the changes from the 16th edition (brown book). Note there are further changes to those listed here, introduced by [[BS7671 Amendment 1]] (the green book)

==Foreword==

<span class="font1">'''Foreword'''</span>

<span class="font3">This British Standard is published under the direction of the British Electrotechnical Committee (BEC) and The Institution of Engineering and Technology (IET).</span>

<span class="font3">Following a full review, this Standard replaced the 16th Edition of the IEE Wiring Regulations BS 7671i2001 as amended. Copyright is held jointly by The IET and BSI.</span>

<span class="font3">Technical authority for this Standard is vested in the Joint IET/BSI Technical Committee JPEL/64. This Joint Technical Committee, which is responsible for the work previously undertaken by the IEE Wiring Regulations Committee and the BSI Technical Committee PEL/64, meets the constitutional and operational requirements of both parent bodies. JPEL/64 has the responsibility for the content of this British Standard under the joint authority of the IET and the BSI Standards Board.</span>

<span class="font3">All references in this text to the Wiring Regulations or the Regulation(s), where not otherwise specifically identified, shall be taken to refer to BS 7671:2008 Requirements for Electrical Installations.</span>

<span class="font1">'''Introduction to BS 7671:2008'''</span>

<span class="font3">BS 7671:2008 Requirements for Electrical Installations was issued on 1<sup>st</sup> January 2008 and is intended to come into effect on 1<sup>st</sup> July 2008. Installations designed after 30<sup>th</sup> June 2008 are to comply with BS 7671:2008.</span>

<span class="font3">The Regulations apply to the design, erection and verification of electrical installations, also additions and alterations to existing installations. Existing installations that have been installed in accordance with earlier editions of the Regulations may not comply with this edition in every respect. This does not necessarily mean that they are unsafe for continued use or require upgrading.</span>

<span class="font3">BS 7671:2008 includes changes necessary to maintain technical alignment with CENELEC harmonization documents. A summary of the main changes is given below.</span>

<span class="font0">'''NOTE 1'''<span class="font2"><nowiki>: This is not an exhaustive list.</nowiki></span></span>

<span class="font0">'''NOTE 2: '''<span class="font2">Particular attention is drawn to </span>Section <span class="font2">701. This section now allows socket-outlets (other than SELV and shaver supply units to BS EN 61558-2-5) to be installed in locations containing a bath or shower 3m horizontally beyond the boundary of zone 1.</span></span>

<span class="font0">'''Regulation 131.6 '''<span class="font3">adds requirements to protect against voltage disturbances and implement measures against electromagnetic influences. In doing so, the design shall take into consideration the anticipated electromagnetic emissions, generated by the installation or the installed equipment, which shall be suitable for the current-using equipment used with, or connected to, the installation.</span></span>

<span class="font0">'''Regulation 132.13 '''<span class="font3">requires that documentation for the electrical installation, including that required by </span>Chapter <span class="font3">51, </span>Part 6 and Part 7, <span class="font3">is provided for every electrical installation.</span></span>

<span class="font0">'''Chapter 35 '''<span class="font3">Safety services, recognises the need for safety services as they are frequently regulated by statutory authorities whose requirements have to be observed, e.g. emergency escape lighting, fire alarm systems, installations for fire pumps, fire rescue service lifts, smoke and heat extraction equipment.</span></span>

<span class="font0">'''Chapter 36 '''<span class="font3">Continuity of service, requires that an assessment be made for each circuit of any need for continuity of service considered necessary during the intended life of the installation.</span></span>

<span class="font0">'''Chapter 41 '''<span class="font3">Protection against electric shock, now refers to basic protection, which is protection under normal conditions (previously referred to as protection against direct contact), and fault protection, which is protection under fault conditions (previously referred to as protection against indirect contact). </span>Chapter <span class="font3">41 now includes those requirements previously given in Section 471 of BS 7671:2001.</span></span>

<span class="font0">Chapter <span class="font3">41 now requires that for the protective measure of automatic disconnection of supply for an a.c. system, additional protection by means of an RCD with a rated residual operating current </span><span class="font2">(iAn) </span><span class="font3">not exceeding 30 mA and an operating time not exceeding 40 ms at a residual current of 5 Un be provided for socket-outlets with a rated current not exceeding 20 A that are for use by ordinary persons and are intended for general use, and for mobile equipment with a current rating not exceeding 32 A for use outdoors. This additional protection is now to be provided in the event of failure of the provision for basic protection and/or the provision for fault protection or carelessness by users of the installation. Note that certain exceptions are permitted - refer to Regulation 411.3.3.</span></span>

<span class="font0">Chapter <span class="font3">41 includes Tables 41.2, 41.3 and 41.4 for earth fault loop impedances (replacing Tables 41B1, 41B2 and 41D). These new tables are based on a nominal voltage of 230 V (not 240 V), hence the values are</span></span>
<span class="font3">slightly reduced. It has been clarified that where an RCBO is referred to in these Tables, the overcurrent characteristic of the device is being considered.</span>

<span class="font0">Chapter 41 <span class="font3">includes a new </span>Table 41.5 <span class="font3">giving maximum values of earth fault loop impedance for RCDs to BS EN 61008-1 and BS EN 61009-1.</span></span>

<span class="font3">FELV is recognised as a protective measure and the new requirements are detailed in Regulation <span class="font0">411.7.</span></span>

<span class="font0">Chapter 41 <span class="font3">includes the UK reduced low voltage system. Requirements are given in Regulation </span>411.8.</span>

<span class="font0">'''Chapter 42 '''<span class="font3">Protection against thermal effects, includes requirements in Section 422 Precautions where particular risks of fire exist (These requirements were previously stated in Section 482 of BS 7671:2001).</span></span>

<span class="font0">'''Chapter 43 '''<span class="font3">Protection against overcurrent, includes those requirements previously given in Section 473 of BS 7671:2001. Information on the overcurrent protection of conductors in parallel is given in Appendix 10.</span></span>

<span class="font0">'''Chapter 44 '''<span class="font3">Protection against voltage disturbances, includes a new </span>Section 442, <span class="font3">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. This new section provides for the safety of the low voltage system under fault conditions including faults in the high voltage system, loss of the supply neutral in the low voltage system and short-circuit between a line conductor and neutral in the low voltage installation.</span></span>

<span class="font0">'''Section 443 '''<span class="font3">Protection against overvoltages of atmospheric origin or due to switching, retains the existing text from BS 7671 and adds regulations enabling designers to use a risk assessment approach when designing installations which may be susceptible to overvoltages of atmospheric origin.</span></span>

<span class="font0">'''Chapter 52 '''<span class="font3">Selection and erection of wiring systems, now includes busbar trunking systems and powertrack systems.</span></span>

<span class="font3">It is now required to protect cables concealed in a wall or partition (at a depth of less than 50 mm) by a 30 mA RCD where the installation is not intended to be under the supervision of a skilled or instructed person, if the normal methods of protection including use of cables with an earthed metallic covering, mechanical protection (including use of cables with an earthed metallic covering, or mechanical protection) cannot be employed. This applies to a cable in a partition where the construction includes metallic parts other than fixings <u>irrespective of the depth of the cable.</u></span>

<span class="font3">Table 52.2 Cable surrounded by thermal insulation, gives slightly reduced derating factors, to take account of the availability of material with improved thermal insulation.</span>

<span class="font0">'''Chapter 53 '''<span class="font3">Protection, isolation, switching, control and monitoring. Simplification means that requirements previously in Chapter 46, Sections 476 and 537 of BS 7671:2001 are now in this single chapter. </span>Chapter 53 <span class="font3">also includes a new </span>Section 532 <span class="font3">Devices for protection against the risk of fire, and a new </span>Section 538 <span class="font3">Monitoring devices.</span></span>

<span class="font0">'''Chapter 54 '''<span class="font3">Earthing arrangements and protective conductors. The requirement that a metallic pipe of a water utility supply shall not be used as an earth electrode is retained in Regulation 542.2.4 which also states that other metallic water supply pipework shall not be used as an earth electrode unless precautions are taken against its removal and it has been considered for such a use. An example of other metallic water supply pipework could be a privately owned water supply network.</span></span>

<span class="font3">A note to Regulation <span class="font0">543</span>.4<span class="font0">.1 </span>states that in Great Britain, regulation 8(4) of the Electricity Safety, Quality and Continuity Regulations 2002 prohibits the use of PEN conductors in consumers' installations. Regulation <span class="font0">543.7 </span>has earthing requirements for the installation of equipment having high protective conductor currents, previously in Section 607 of BS 7671:2001.</span>

<span class="font0">'''Chapter 55 '''<span class="font3">Other equipment, includes new additional requirements in Regulation </span>551.7 <span class="font3">to ensure the safe connection of low voltage generating sets including small-scale embedded generators (SSEGs).</span></span>

<span class="font0">'''Section 559 '''<span class="font3">Luminaires and lighting installations, is a new series of Regulations giving requirements for fixed lighting installations, outdoor lighting installations, extra-low voltage lighting installations, lighting for display stands and highway power supplies and street furniture (previously in Section 611 of BS 7671:2001).</span></span>

<span class="font0">'''Chapter 56 '''<span class="font3">Safety services, has been expanded in line with IEC standardization.</span></span>

<span class="font0">'''Part 6'''<span class="font3">Inspection and testing, was Part 7 of BS 7671:2001. Changes have been made to the requirements</span></span>

<span class="font3">for insulation resistance; when testing SELV and PELV circuits at 250 V, the minimum insulation resistance is raised to 0.5 M Ohm; for systems up to and including 500 V, including FELV, the minimum insulation resistance is raised to 1.0 M Ohm.</span>

<span class="font4">'''''Part 7'''''<span class="font3">''Special installations or locations, was Part 6 of BS 7671:2001. The structure of Part 7 includes the''</span></span>

<span class="font3">following changes.</span>

<span class="font3">Section 607 in BS 7671:2001 relating to high protective conductor currents has been incorporated into <span class="font0">Chapter 54.</span></span>

<span class="font3">Section 608 in BS 7671:2001 relating to caravans, motor caravans and caravan parks has been incorporated into <span class="font0">Section 708: </span>Electrical installations in caravan/camping parks and similar locations and <span class="font0">Section 721: </span>Electrical installations in caravans and motor caravans.</span>

<span class="font3">Section 611 in BS 7671:2001 relating to highway power supplies is now incorporated into <span class="font0">Section 559. '''The following major changes are incorporated in Part 7: Section 701 '''</span>Locations containing a bath tub or shower basin.</span>

<span class="font3">Zone 3 is no longer defined.</span>

<span class="font3">Each circuit in the special location must have 30 mA RCD protection.</span>

<span class="font3">Supplementary bonding is no longer required providing the installation has main bonding in accordance with <span class="font0">Chapter 41.</span></span>

<span class="font3">This section now allows socket-outlets (other than SELV and shaver supply units to BS EN 61558-2-5) to be installed in locations containing a bath or shower 3m horizontally beyond the boundary of zone 1.</span>

<span class="font0">'''Section 702 '''<span class="font3">Swimming pools and other basins. This special location now includes basins of fountains. Zones A, B and C in BS 7671:2001 are replaced by zones 0, 1 and 2.</span></span>

<span class="font0">'''Section 703 '''<span class="font3">Rooms and cabins containing sauna heaters. Zones A, B, C and D in BS 7671:2001 are replaced by zones 1, 2 and 3 (with changed dimensions).</span></span>

<span class="font0">'''Section 704 '''<span class="font3">Construction and demolition site installations. The reduced disconnection times (0.2 s) and the 25 V equation no longer appear.</span></span>

<span class="font0">'''Section 705 '''<span class="font3">Agricultural and horticultural premises. The reduced disconnection times (0.2 s) and the 25 V equation no longer appear. Additional requirements applicable to life support systems are included.</span></span>

<span class="font0">'''Section 706 '''<span class="font3">Conducting locations with restricted movement, was Section 606 in BS 7671:2001.</span></span>

<span class="font0">'''Section 708 '''<span class="font3">Electrical installations in caravan/camping parks and similar locations, now includes the requirement that each socket-outlet must be provided individually with overcurrent and RCD protection.</span></span>

<span class="font0">'''The following new sections are now included in Part 7:'''</span>

<span class="font0">'''Section 709 '''<span class="font3">Marinas and similar locations</span></span>

<span class="font0">'''Section 711 '''<span class="font3">Exhibitions, shows and stands</span></span>

<span class="font0">'''Section 712 '''<span class="font3">Solar photovoltaic (pv) power supply systems</span></span>

<span class="font0">'''Section 717 '''<span class="font3">Mobile or transportable units</span></span>

<span class="font0">'''Section 721 '''<span class="font3">Electrical installations in caravans and motor caravans - previously in Section 608 of BS 7671:2001</span></span>

<span class="font0">'''Section 740 '''<span class="font3">Temporary electrical installations for structures, amusement devices and booths at fairgrounds, amusement parks and circuses</span></span>

<span class="font0">'''Section 753 '''<span class="font3">Floor and ceiling heating systems.</span></span>

<span class="font3">Appropriate changes have been made to <span class="font0">'''Appendices 1 to 7, '''</span>in particular the methods and tables used in <span class="font0">'''Appendix 4.'''</span></span>

<span class="font0">'''The following new appendices are now included:'''</span>

<span class="font0">'''Appendix 8 '''<span class="font3">Current-carrying capacity and voltage drop for busbar trunking and powertrack systems </span>'''Appendix 9 '''<span class="font3">Definitions - multiple source, d.c. and other systems </span>'''Appendix 10 '''<span class="font3">Protection of conductors in parallel against overcurrent </span>'''Appendix 11 '''<span class="font3">Effect of harmonic currents on balanced three-phase systems </span>'''Appendix 12 '''<span class="font3">Voltage drop in consumers' installations</span></span>

<span class="font0">'''Appendix 13 '''<span class="font3">Methods for measuring the insulation resistance/impedance of floors and walls to Earth or to the protective conductor system</span></span>

<span class="font0">'''Appendix 14 '''<span class="font3">Measurement of earth fault loop impedance:</span></span>

<span class="font3">consideration of the increase of the resistance of conductors with increase of temperature</span>

<span class="font0">'''Appendix 15 '''<span class="font3">Ring and radial final circuit arrangements, Regulation 433.1</span></span>


==See also==

[[Category:Electrical]]