Electrical Installation Designs

Mr. Bill Atkinson (deceased) Bill Atkinson was the writer's pseudonym used by Alan Smith, the original author of the book. He worked in the electrical installation industry and at the NICEIC.Mr. Roger Lovegrove, Consultant, Surrey, UK Roger Lovegrove is an electrical consultant. He is a member of the Electrical Contractors' Association techinical committees and of the joint IEE/BSI Wiring Regulations committee. With his vast knowledge in this area of electrical engineering, he has updated Bill Atkinson’s original text for this fourth edtition.Mr. Gary Gundry,   Senior Engineer, Electrical Safety Council, UK Mr Gundry worked for Seeboard and Eastern Electricity, before becoming a lecturer at Lowestoft College, teaching electrical contracting and electrical engineering up to HNC level. He joined NICEIC in 1999 after spending three years as a Director and Qualified Supervisor of a business enrolled as an Approved Contractor, where he worked in the Standards division on the NICEIC Technical Manual. He is now Senior Engineer at Electrical Safety Council.Mr. Martyn Allen, Senior Engineer, Electrical Safety Council Martyn Allen's experience in the electrical installation industry spans 30 years. He served an apprenticeship and worked as an electrician with British Coal, spent 16 years in engineering insurance risk management and then joined the Electrical Safety Council. He is a Chartered Electrical Engineer and Corporate Member of the IET. He is a member of the Joint Technical Committee JPEL/64 Panel C – Shock Protection and Isolation and Switching.

• About the Authors xviiPreface to the Fourth Edition xixAcknowledgements xxv1 Introduction 11.1 Layout of chapters 11.2 Wiring regulations 21.3 Terminology 21.4 Competence and responsibility 31.5 Procedures 31.6 Inspection and test 41.7 Completion 51.8 Working methods and materials 51.9 Operatives 51.10 Materials 51.11 Amendments to BS 7671: 2008 61.12 Voltages 61.13 Voltage drop 62 Three Bedroom House 82.1 The bare minimum 92.2 Standards 92.3 Building regulations 112.4 Load assessment 112.5 A typical domestic supply 122.6 Project specification 122.7 Wiring systems and cable sizes 122.8 Lighting 122.9 13 A socket-outlets 132.10 Cable sizes 152.11 Circuit protection 152.12 Additional protection for socket-outlets 152.13 Arrangement of circuits 162.14 Arrangement of consumer unit 162.15 Main switch 172.16 Earthing and bonding 172.17 Gas services bonding and external meters 182.18 Supplementary bonding 193 A Block of Retirement Flatlets 213.1 Two schemes 213.2 Early considerations 213.3 Other interested parties 223.4 Building details 223.5 Part 1 – Flats 243.6 Part 2 – Landlord’s areas 294 Overcurrent Protection 354.1 Overload 354.2 Overload protection 364.3 Overload protective devices 374.4 Fault current 384.5 Fault Current Protection 394.6 Omission of fault current protection 394.7 Short-circuit rating 394.8 Disconnection times 414.9 Earth loop impedance 424.10 Summary of cb specification 424.11 Conclusion 435 An Architect’s Office 445.1 Other interested parties 445.2 Building structure and finishes 455.3 Electrical requirements 465.4 Skirting system 515.5 Underfloor system 515.6 Socket-outlets 515.7 Lighting circuits 515.8 Battened out ceilings 525.9 Extra-Low Voltage lighting (elv) 525.10 Group transformers 535.11 Individual transformers 535.12 Fire prevention 535.13 Arrangement of circuits 535.14 Distribution boards 545.15 Cable sizes 555.16 Switchgear 555.17 Print machine 575.18 Wall heaters in toilets 575.19 Storage heaters 575.20 Presence of 400 Volts 585.21 Access to switchgear 585.22 Earthing and bonding 585.23 Main earthing terminal 585.24 False ceiling grid 595.25 Computer installations 605.25.1 Computer supplies 605.26 High protective conductor currents 605.27 Mains filters 605.28 Uninterruptible Power Supplies (UPS) 616 A High Street Shop 626.1 Special considerations 626.2 Other interested parties 636.3 Building structure and finishes 636.4 Electrical requirements 636.5 Loading and diversity 636.6 Lighting 656.7 Socket-outlets 666.8 Other appliances 676.9 Phase balance 686.10 Wiring systems 686.11 Start by considering cost 696.12 Shop area 696.13 Bakery area 696.14 Temperature limit of 70° C 706.15 Temperature limit of 90° C 706.16 Final selection and cable sizes 706.17 Bakery wiring 706.18 Shop wiring 716.19 Distribution board 716.20 Cable sizes 726.21 Switchgear 736.22 Isolation and switching 736.23 Earthing and bonding 736.24 Main earthing terminal (MET) 736.25 False-ceiling grid 746.26 Steel tables in the bakery 747 Earthing and Bonding 757.1 Terminology 757.2 Definitions 767.3 Green-and-yellow conductors 767.4 Protective earthing and protective equipotential bonding 777.5 Protective Multiple Earthing (PME) 777.6 Reliability of the earth-neutral path 787.7 Main bonding 797.8 Single fault condition 817.9 Supplementary bonding 827.10 Circuit Protective Conductors (CPCs) 827.11 Steel conduit and trunking 837.12 Steel wire armoured cable 847.13 Comparison of thermoplastic (PVC) and thermosetting (XLPE) armoured cable 847.14 Continuity of cable glands 847.15 Equipment having high protective conductor currents 867.16 Protective conductor currents 867.17 'High integrity' earthing 877.18 Earth monitoring and isolated supplies 877.19 Socket-outlets for desktop computers 887.20 Connections of protective conductors 897.21 Residual current devices 898 Car Service Workshop 908.1 Standards and recommendations 908.2 An adaptable design 918.3 Motor vehicle repair premises 918.4 Other interested parties 918.5 Building structure and finishes 918.6 Construction 948.7 Electrical requirements 948.8 Health and safety executive guidance and regulations 948.9 Health and safety guidance note HSG 261 958.10 Wiring regulations 968.11 Load assessment and maximum demand 968.12 Maximum demand load and diversity 968.13 Lighting 978.14 Welder 998.15 Compressor 998.16 Gas blowers 1008.17 Phase balance 1008.18 Estimate of maximum demand 1018.19 What about a distribution circuit (sub-main)? 1028.20 Wiring systems 1028.21 Workshop 1028.22 Office 1058.23 Arrangement of circuits 1058.24 Distribution boards 1058.25 Cable sizes 1058.26 Isolation and switching 1078.27 Machinery 1078.28 Cooker 1078.29 Gas boiler 1078.30 110 V transformer 1088.31 Earthing and bonding 1088.32 Main earthing terminal 1098.33 Protective conductors at distribution board B 1098.34 Armoured cable glands 1098.35 Steel conduit and trunking 1109 Circuits 1119.1 Terminology 1119.2 Colours of three phases 1119.3 Conventional circuits 1129.4 Lighting circuits 1129.5 Induction 1139.6 Socket-outlet circuits 1139.7 Changing methods 1139.8 Ring main obsolescence 1139.9 History of the ring final circuit 1149.10 Times have changed 1149.11 Alternative methods 1169.12 Radial circuits 1179.13 Introducing the tree 1179.14 20 A tree 1179.14.1 Domestic 1179.14.2 Commercial and similar 1179.15 32 A tree 1189.16 Switching and control 1199.17 Comparison of systems 1209.18 32 A ring final circuit 1209.19 20 A tree 1219.20 Composite circuits 12110 Farming and Horticulture 12310.1 Why farms are different 12410.2 Special earthing requirements on farms with TT systems 12610.3 Earth electrodes 12710.4 Alternative electrodes 12710.5 Bonding 12810.6 Supplementary bonding 12910.7 Residual current devices 12910.8 Shock protection 13010.9 General requirements for automatic disconnection of supply (ADS) 13110.10 Fire protection 13210.11 Automatic life support for high density livestock rearing 13210.12 Switchgear 13310.13 Wiring systems 13410.14 Overhead or underground wiring 13410.15 Non-metallic wiring systems 13510.16 Steel Wire Armoured (SWA) cable 13610.17 Twin and earth cable 13610.18 General rules regarding farm electrical installations 13611 Isolation and Switching 13811.1 Isolation and switching 13811.2 Isolation 13911.3 Mechanical maintenance 14011.4 Emergency switching 14111.5 Labelling and notices 14312 A Village Sports Centre 14512.1 Special conditions 14512.2 Codes of practice 14512.3 Other interested parties 14612.4 Building details 14612.5 Structure and finishes 14712.6 Electricity supply and requirements 14812.7 Off-peak tariff 14812.8 Normal tariff 14812.9 Load assessment and diversity 15012.10 Off-peak heating 15012.11 Normal tariff 15012.12 Total estimated maximum current demand 15212.13 Wiring systems 15212.14 Circuitry and cable sizing 15412.15 Cable grouping factors 15512.16 Arrangement of circuits 15612.17 Switchgear 15712.18 Shock protection 15712.19 Earthing 15712.20 Bonding 15712.21 An occasional problem 15712.22 Solutions 15812.23 Requirements for a TT installation 15913 An Indoor Swimming Pool 16013.1 Special conditions 16013.2 Other interested parties 16113.3 Building details 16113.4 Application of zoning to this project 16213.5 Dehumidifiers 16713.6 Changing room/shower area 16713.7 Loading and diversity for the swimming pool project 16813.8 Wiring systems 16913.9 Cable sizes 17013.10 Distribution board 17013.11 Isolation 17113.12 110 V system 17113.13 Earthing 17213.14 Local supplementary bonding 17213.15 Floor grid 17214 Cables and Wiring Systems 17414.1 External influences 17414.2 Cost considerations 17514.3 Choosing suitable cable routes 17514.4 Is armouring always necessary? 17514.5 Fire barriers 17514.6 Holes through fire barriers 17614.7 Sealing the wiring system 17614.8 Work in progress 17614.9 Records 17714.10 Hidden cables 17714.11 Cables within a floor 17714.12 Cables above false ceilings 17814.13 Cables in walls 17814.14 Mechanically protected cables 17914.15 Fire and smoke 17914.16 Thermoplastic (PVC) insulation 18014.17 Thermosetting (XLPE) 18114.18 Silicone rubber 18114.19 Low smoke zero halogen (LS0H) 18114.20 Mineral insulated copper sheathed (MICS) cables 18214.21 Heat transference from cables 18214.22 Wiring systems and cable management 18214.23 Emergency systems 18214.24 Care with wiring systems 18314.25 Thermoplastic (PVC) insulated and sheathed cables 18314.26 Thermosetting (PVC) insulated conduit cables 18314.27 Steel conduit systems and trunking 18414.28 Plastic conduit systems and trunking 18414.29 MICS cables 18414.30 Steel wire armoured cables 18514.31 Silicone insulated PVC sheathed cables 18515 Inspection, Testing and Certification 18615.1 Labelling and documentation 18715.2 Specification and manual 18715.3 Regulations 18715.4 Electrical installation certificate (EIC) 18715.5 Signatories 19015.6 Alterations and additions 19215.7 Limits of responsibility 19215.8 Deviations and departures 19315.9 New materials and inventions 19315.10 Particulars of the installation 19415.11 Inspections and test schedules 19415.12 Inspection procedures 19415.13 Testing 19715.14 Continuity testing 19815.15 Polarity 19815.16 Continuity of protective conductors 19815.17 Continuity of ring circuit conductors 19815.18 Insulation resistance 20015.19 Earth fault loop impedance 20215.20 Supply impedance Ze 20415.21 Earth loop impedance of circuits Zs 20515.22 Prospective fault current 20615.23 Operation of residual current devices 20616 A Caravan Park 20816.1 Measures for protection against electric shock 20816.2 Earthing arrangements 20916.3 PME must not be used for caravans 20916.4 Electrical equipment (external influences) 21016.5 Wiring systems 21016.6 Cables buried in the ground 21016.7 Overhead cables 21016.8 Caravan pitch electrical supply equipment 21116.9 Plugs and socket-outlets 21117 Residual Current Devices 21317.1 How does an RCD work? 21417.2 Fault protection 21417.3 Additional protection 21717.4 Requirements to provide additional protection by RCDs 21717.5 RCDs incorporated into a consumer unit, to meet the requirements for additional protection 21817.6 Protection against fire 22017.7 Avoiding a hazard and/or minimising an inconvenience due to the tripping of an RCD 22117.8 Reducing the possibility of unwanted tripping of RCDs 22117.9 Use of a ‘front-end’ 30 mA RCD is generally considered unacceptable practice 22217.10 Installations forming part of a T T system 22217.11 RCDs connected in series 22317.12 Labelling 22318 Flood Lighting (Outdoor Lighting) Project 22418.1 Lighting arrangement 22418.2 General requirements 22418.3 Wiring system 22518.4 Protective measures 22618.5 Load assessment 22618.6 Rating of the overcurrent protective device 22718.7 Circuit design 22718.8 Voltage drop consideration 22818.9 Switchgear 23019 Circuit Design Calculations 23119.1 Design process 23119.2 Protective conductors 23519.3 Worked example 23519.4 Solution 236Index 239