Practical Guide to The Wiring Regulations

Geoffrey Stokes, CEng FIEE FCIBSE EurIng was Principal Engineer at the National Inspection Council for Electrical Installation Contracting, and is now a consultant.John T Bradley, BSc CEng MIET FCIBSE EurIng is Principal Engineer at the Electrical Safety Council.

• About the authors xviiPreface to the Fourth Edition xixAcknowledgements xxiNotation xxiii1 Plan and terminology of BS 7671:2008 and supporting publications 11.1 Plan of BS 7671:2008 11.2 Terminology of BS 7671:2008 51.3 Supporting publications 62 Electricity, the law, standards and codes of practice 72.1 General 72.2 Electricity: the hazards 72.3 The law 122.4 Standards and codes of practice 133 Scope, object and fundamental principles 173.1 General 173.2 Scope 173.3 Object and effects 203.4 Fundamental principles 214 Assessment of general characteristics 294.1 General 294.2 Loading, maximum demand and diversity 294.3 Arrangement of live conductors and type of earthing 354.4 Nature of supply 404.5 Supplies for safety services and standby purposes 444.6 Installation circuit arrangements 444.7 External influences 454.8 Compatibility 454.9 Maintainability 465 Protection against electric shock 475.1 General 475.2 Provisions for basic protection 515.3 Protective measure: automatic disconnection of supply 535.4 Protective measure: double or reinforced insulation 755.5 Protective measure: electrical separation 775.6 Protective measure: extra-low voltage provided by SELV or PELV 785.7 Additional protection 815.8 Obstacles and placing out of reach 825.9 Protective measures for application only where the installation is controlled or under the supervision of skilled or instructed persons 836 Protection against thermal effects 896.1 General 896.2 Fire caused by electrical equipment 916.3 Precautions where particular risks of danger of fire exist 956.4 Burns 1007 Protection against overcurrent, undervoltage and overvoltage 1017.1 General 1017.2 Nature of protective devices 1027.3 Protection against overload 1047.4 Protection against fault current 1107.5 Determination of prospective fault current 1127.6 Characteristics of protective devices 1287.7 Overcurrent protection of conductors in parallel 1317.8 Coordination of overload and fault current protection 1347.9 Protection according to the nature of circuits and distribution systems 1357.10 Protection against undervoltage 1367.11 Protection against overvoltage 1378 Isolation and switching 1398.1 General 1398.2 Main switch 1438.3 Isolation 1458.4 Switching off for mechanical maintenance 1518.5 Emergency switching and other forms of switching for safety 1538.6 Emergency stopping 1578.7 Functional switching 1588.8 Identification and notices 1609 Equipment selection: common rules 1619.1 General 1619.2 Compliance with standards 1619.3 Operational conditions, external influences and accessibility 1629.4 Identification and notices 1649.5 Mutual detrimental influences 1769.6 Compatibility 1789.7 Operation and maintenance manual 17910 Wiring systems 18110.1 Wiring systems 18110.2 External influences 18510.3 Proximity to other services: general 19910.4 Methods of installation of cables 20510.5 Resistances of copper conductors 21710.6 Electrical connections 21810.7 Cable supports and cable management systems 22410.8 Minimizing the risk of fire 23010.9 Electromagnetic and electromechanical effects 23110.10 Conduit and trunking cable capacities 23310.11 Maintainability 23811 Switchgear, protective devices and other equipment 24111.1 Switchgear and protective devices: general 24111.2 Switchgear and controlgear 24111.3 Selection of devices for overload and fault current protection: general 24311.4 Overcurrent protective devices 24711.5 Residual current devices 26111.6 Identification of overcurrent protective devices 27111.7 Discrimination 27211.8 Other equipment 27912 Protective conductors, earthing and equipotential bonding 28912.1 Protective conductors 28912.2 Earthing 30712.3 Earthing requirements for the installation of equipment having high protective conductor currents 31412.4 Protective bonding 31813 Specialized installations 32513.1 General 32513.2 Emergency lighting 32513.3 Fire detection and alarm systems 32613.4 Petrol filling stations and liquid petroleum gas stations 33113.5 Installations in dusty environments 33113.6 Installations in underground and multistorey car parks, etc 33213.7 Installations in multi-occupancy blocks of flats 33213.8 Installations in ‘Section 20 buildings’ 33213.9 Installations in churches 33413.10 Installations in thatched properties 33413.11 Extra-low voltage lighting 33513.12 Outdoor lighting installations, highway power supplies and street furniture 33813.13 Security lighting 34113.14 Welding equipment 34213.15 Entertainers’ equipment 34213.16 Generator sets 34214 Safety services 34714.1 Safety services: general 34714.2 Common sources 34814.3 Parallel and nonparallel sources 35014.4 Circuit and equipment requirements 35114.5 Protection against overcurrent and electric shock under fault conditions 35115 The smaller installation 35315.1 Scope 35315.2 The IEE On-Site Guide and the NICEIC Domestic Electrical Installation Guide 35315.3 User’s requirements 35315.4 Wiring systems 35515.5 Electricity distributor’s requirements 35515.6 Assessment of supply characteristics 35515.7 ‘Meter tails’ 35615.8 System earthing arrangements 35715.9 Main protective bonding 36015.10 Minimum cross-sectional area of earthing and main protective bonding conductors 36015.11 Supplementary bonding 36215.12 Devices for protection against overcurrent and for fault protection 36215.13 Devices for isolation and switching 36315.14 Final circuit design 36315.15 Remote buildings 38415.16 Minimum number of socket-outlets in domestic premises 38515.17 Modifications to existing installations 38515.18 Inspection, testing, verification and certification of the smaller installation 38716 Special installations and locations 38916.1 General 38916.2 Locations containing a bath or shower 38916.3 Swimming pools and other basins 39816.4 Rooms and cabins containing sauna heaters 40716.5 Construction-site installations 40716.6 Agricultural and horticultural premises 41316.7 Conducting locations with restricted movement 42116.8 Electrical installations in caravan/camping parks and similar locations 42216.9 Marinas and similar locations 42916.10 Exhibition shows and stands 43016.11 Solar photovoltaic power supply systems 43516.12 Mobile or transportable units 44016.13 Electrical installations in caravans and motor caravans 44516.14 Temporary electrical installations for structures, amusement devices and booths at fairgrounds, amusement parks and circuses 45116.15 Floor and ceiling heating systems 45217 Inspection, testing, certification and reporting 45917.1 Inspection, testing, certification and reporting: general 45917.2 Test instruments 45917.3 Safety in electrical testing 46217.4 Test methods 46317.5 Initial verification 48317.6 Periodic inspection and testing 51217.7 Alterations and additions 53417.8 Inspection, testing and certification of specialized installations 535Appendix Standards to which reference has been made 537Bibliography 545Index of figures 547Index of tables 551Index of regulation numbers 557Subject index 579