CONTENTS Introduction to BS 7671:2008 4 Notes on the plan of the 17th edition 10 Part 1 Scope, object and fundamental principles 11 Chapter 11 Scope 12 Chapter 12 Object and effects 14 Chapter 13 Fundamental principles 14 Part 2 Definitions 20 Part 3 Assessment of general characteristics 37 Chapter 31 Purpose, supplies and structure 38 Chapter 32 Classification of external influences 39 Chapter 33 Compatibility 40 Chapter 34 Maintainability 40 Chapter 35 Safety services 41 Chapter 36 Continuity of service 41 Part 4 Protection for safety 42 Chapter 41 Protection against electric shock 43 Chapter 42 Protection against thermal effects 64 Chapter 43 Protection against overcurrent 70 Chapter 44 Protection against voltage disturbances and electromagnetic disturbances 78 Part 5 Selection and erection of equipment 86 Chapter 51 Common rules 88 Chapter 52 Selection and erection of wiring systems 96 Chapter 53 Protection, isolation, switching, control and monitoring 110 Chapter 54 Earthing arrangements and protective conductors 125 Chapter 55 Other equipment 136 Chapter 56 Safety services 151 Part 6 Inspection and testing 155 Chapter 61 Initial verification 155 Chapter 62 Periodic inspection and testing 162 Chapter 63 Certification and reporting 163 Part 7 Special installations or locations 164 Section 700 General 164 Section 701 Locations containing a bath or shower 165 Section 702 Swimming pools and other basins 170 Section 703 Rooms and cabins containing sauna heaters 179 Section 704 Construction and demolition site installations 181 Section 705 Agricultural and horticultural premises 183 Section 706 Conducting locations with restricted movement 188 Section 708 Electrical installations in caravan / camping parks and similar locations 190 Section 709 Marinas and similar locations 193 Section 711 Exhibitions, shows and stands 197 Section 712 Solar photovoltaic (PV) power supply systems 200 Section 717 Mobile or transportable units 204 Section 721 Electrical installations in caravans and motor caravans 209 Section 740 Temporary electrical installations for structures, amusement devices and booths at fairgrounds, amusement parks and circuses 219 Section 753 Floor and ceiling heating systems 224 APPENDICES 227 1 British Standards to which reference is made in the Regulations 228 2 Statutory regulations and associated memoranda 240 3 Time/current characteristics of overcurrent protective devices and rcds 243 4 Current-carrying capacity and voltage drop for cables and flexible cords 252 5 Classification of external influences 318 6 Model forms for certification and reporting 331 7 Harmonized cable core colours 342 8 Current-carrying capacity and voltage drop for busbar trunking and powertrack systems 345 9 Definitions multiple source, d.c. and other systems 346 10 Protection of conductors in parallel against overcurrent 353 11 Effect of harmonic currents on balanced three-phase systems 356 12 Voltage drop in consumers installations 358 13 Methods for measuring the insulation resistance/impedance of floors and walls to Earth or to the protective conductor system 359 14 Measurement of earth fault loop impedance: consideration of the increase of the resistance of conductors with increase of temperature 361 15 Ring and radial final circuit arrangements, Regulation 433.1 362 Index 364 3Foreword This British Standard is published under the direction of the British Electrotechnical Committee (BEC) and The Institution of Engineering and Technology (IET). Following a full review, this Standard replaced the 16th Edition of the IEE Wiring Regulations BS 7671:2001 as amended. Copyright is held jointly by The IET and BSI. 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. 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. Introduction to BS 7671:2008 st BS 7671:2008 Requirements for Electrical Installations was issued on 1 January 2008 and is intended to come st th into effect on 1 July 2008. Installations designed after 30 June 2008 are to comply with BS 7671:2008. 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. BS 7671:2008 includes changes necessary to maintain technical alignment with CENELEC harmonization documents. A summary of the main changes is given below. NOTE 1: This is not an exhaustive list. NOTE 2: Particular attention is drawn to Section 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. Regulation 131.6 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. Regulation 132.13 requires that documentation for the electrical installation, including that required by Chapter 51, Part 6 and Part 7, is provided for every electrical installation. Chapter 35 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. Chapter 36 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. Chapter 41 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). Chapter 41 now includes those requirements previously given in Section 471 of BS 7671:2001. Chapter 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 (I ) not exceeding n 30 mA and an operating time not exceeding 40 ms at a residual current of 5 I be provided for socket-outlets n 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. Chapter 41 includes Tables Table 41.2, Ta ebl41.3 and Tabl e41.4 for earth fault loop impedances (replacing Tables T ebla41B1, Tbale 41B2 and Table 41D). These new tables are based on a nominal voltage of 230 V (not 240 V), hence the values are 4