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Electrical Installation Designs. 4th Edition - Product Image

Electrical Installation Designs. 4th Edition

  • Published: January 2013
  • 270 Pages
  • John Wiley and Sons Ltd

A practical and highly popular guide for electrical contractors of small installations, now fully revised in accordance with the latest wiring regulations

The book is a clearly written practical guide on how to design and complete a range of electrical installation projects in a competitive manner, while ensuring full compliance with the new Wiring Regulations (updated late 2008). The updated regulations introduced changes in terminology, such as ‘basic’ and ‘fault protection’, and also changed the regulation numbers. This new edition reflects these changes. It discusses new sections covering domestic, commercial, industrial and agricultural projects, including material on marinas, caravan sites, and small scale floodlighting. This book provides guidance on certification and test methods, with full attention given to electrical safety requirements.   Other brand new sections cover protective measures, additional protection by means of RCDs, the new cable guidelines for thin wall partitions and Part P of the Building Regulations. 
- Provides simple, practical guidance on how to design electrical installation projects, including worked examples READ MORE >

About the Authors xvii

Preface to the Fourth Edition xix

Acknowledgements xxv

1 Introduction 1

1.1 Layout of chapters 1

1.2 Wiring regulations 2

1.3 Terminology 2

1.4 Competence and responsibility 3

1.5 Procedures 3

1.6 Inspection and test 4

1.7 Completion 5

1.8 Working methods and materials 5

1.9 Operatives 5

1.10 Materials 5

1.11 Amendments to BS 7671: 2008 6

1.12 Voltages 6

1.13 Voltage drop 6

2 Three Bedroom House 8

2.1 The bare minimum 9

2.2 Standards 9

2.3 Building regulations 11

2.4 Load assessment 11

2.5 A typical domestic supply 12

2.6 Project specification 12

2.7 Wiring systems and cable sizes 12

2.8 Lighting 12

2.9 13 A socket-outlets 13

2.10 Cable sizes 15

2.11 Circuit protection 15

2.12 Additional protection for socket-outlets 15

2.13 Arrangement of circuits 16

2.14 Arrangement of consumer unit 16

2.15 Main switch 17

2.16 Earthing and bonding 17

2.17 Gas services bonding and external meters 18

2.18 Supplementary bonding 19

3 A Block of Retirement Flatlets 21

3.1 Two schemes 21

3.2 Early considerations 21

3.3 Other interested parties 22

3.4 Building details 22

3.5 Part 1 – Flats 24

3.6 Part 2 – Landlord’s areas 29

4 Overcurrent Protection 35

4.1 Overload 35

4.2 Overload protection 36

4.3 Overload protective devices 37

4.4 Fault current 38

4.5 Fault Current Protection 39

4.6 Omission of fault current protection 39

4.7 Short-circuit rating 39

4.8 Disconnection times 41

4.9 Earth loop impedance 42

4.10 Summary of cb specification 42

4.11 Conclusion 43

5 An Architect’s Office 44

5.1 Other interested parties 44

5.2 Building structure and finishes 45

5.3 Electrical requirements 46

5.4 Skirting system 51

5.5 Underfloor system 51

5.6 Socket-outlets 51

5.7 Lighting circuits 51

5.8 Battened out ceilings 52

5.9 Extra-Low Voltage lighting (elv) 52

5.10 Group transformers 53

5.11 Individual transformers 53

5.12 Fire prevention 53

5.13 Arrangement of circuits 53

5.14 Distribution boards 54

5.15 Cable sizes 55

5.16 Switchgear 55

5.17 Print machine 57

5.18 Wall heaters in toilets 57

5.19 Storage heaters 57

5.20 Presence of 400 Volts 58

5.21 Access to switchgear 58

5.22 Earthing and bonding 58

5.23 Main earthing terminal 58

5.24 False ceiling grid 59

5.25 Computer installations 60

5.25.1 Computer supplies 60

5.26 High protective conductor currents 60

5.27 Mains filters 60

5.28 Uninterruptible Power Supplies (UPS) 61

6 A High Street Shop 62

6.1 Special considerations 62

6.2 Other interested parties 63

6.3 Building structure and finishes 63

6.4 Electrical requirements 63

6.5 Loading and diversity 63

6.6 Lighting 65

6.7 Socket-outlets 66

6.8 Other appliances 67

6.9 Phase balance 68

6.10 Wiring systems 68

6.11 Start by considering cost 69

6.12 Shop area 69

6.13 Bakery area 69

6.14 Temperature limit of 70° C 70

6.15 Temperature limit of 90° C 70

6.16 Final selection and cable sizes 70

6.17 Bakery wiring 70

6.18 Shop wiring 71

6.19 Distribution board 71

6.20 Cable sizes 72

6.21 Switchgear 73

6.22 Isolation and switching 73

6.23 Earthing and bonding 73

6.24 Main earthing terminal (MET) 73

6.25 False-ceiling grid 74

6.26 Steel tables in the bakery 74

7 Earthing and Bonding 75

7.1 Terminology 75

7.2 Definitions 76

7.3 Green-and-yellow conductors 76

7.4 Protective earthing and protective equipotential bonding 77

7.5 Protective Multiple Earthing (PME) 77

7.6 Reliability of the earth-neutral path 78

7.7 Main bonding 79

7.8 Single fault condition 81

7.9 Supplementary bonding 82

7.10 Circuit Protective Conductors (CPCs) 82

7.11 Steel conduit and trunking 83

7.12 Steel wire armoured cable 84

7.13 Comparison of thermoplastic (PVC) and thermosetting (XLPE) armoured cable 84

7.14 Continuity of cable glands 84

7.15 Equipment having high protective conductor currents 86

7.16 Protective conductor currents 86

7.17 'High integrity' earthing 87

7.18 Earth monitoring and isolated supplies 87

7.19 Socket-outlets for desktop computers 88

7.20 Connections of protective conductors 89

7.21 Residual current devices 89

8 Car Service Workshop 90

8.1 Standards and recommendations 90

8.2 An adaptable design 91

8.3 Motor vehicle repair premises 91

8.4 Other interested parties 91

8.5 Building structure and finishes 91

8.6 Construction 94

8.7 Electrical requirements 94

8.8 Health and safety executive guidance and regulations 94

8.9 Health and safety guidance note HSG 261 95

8.10 Wiring regulations 96

8.11 Load assessment and maximum demand 96

8.12 Maximum demand load and diversity 96

8.13 Lighting 97

8.14 Welder 99

8.15 Compressor 99

8.16 Gas blowers 100

8.17 Phase balance 100

8.18 Estimate of maximum demand 101

8.19 What about a distribution circuit (sub-main)? 102

8.20 Wiring systems 102

8.21 Workshop 102

8.22 Office 105

8.23 Arrangement of circuits 105

8.24 Distribution boards 105

8.25 Cable sizes 105

8.26 Isolation and switching 107

8.27 Machinery 107

8.28 Cooker 107

8.29 Gas boiler 107

8.30 110 V transformer 108

8.31 Earthing and bonding 108

8.32 Main earthing terminal 109

8.33 Protective conductors at distribution board B 109

8.34 Armoured cable glands 109

8.35 Steel conduit and trunking 110

9 Circuits 111

9.1 Terminology 111

9.2 Colours of three phases 111

9.3 Conventional circuits 112

9.4 Lighting circuits 112

9.5 Induction 113

9.6 Socket-outlet circuits 113

9.7 Changing methods 113

9.8 Ring main obsolescence 113

9.9 History of the ring final circuit 114

9.10 Times have changed 114

9.11 Alternative methods 116

9.12 Radial circuits 117

9.13 Introducing the tree 117

9.14 20 A tree 117

9.14.1 Domestic 117

9.14.2 Commercial and similar 117

9.15 32 A tree 118

9.16 Switching and control 119

9.17 Comparison of systems 120

9.18 32 A ring final circuit 120

9.19 20 A tree 121

9.20 Composite circuits 121

10 Farming and Horticulture 123

10.1 Why farms are different 124

10.2 Special earthing requirements on farms with TT systems 126

10.3 Earth electrodes 127

10.4 Alternative electrodes 127

10.5 Bonding 128

10.6 Supplementary bonding 129

10.7 Residual current devices 129

10.8 Shock protection 130

10.9 General requirements for automatic disconnection of supply (ADS) 131

10.10 Fire protection 132

10.11 Automatic life support for high density livestock rearing 132

10.12 Switchgear 133

10.13 Wiring systems 134

10.14 Overhead or underground wiring 134

10.15 Non-metallic wiring systems 135

10.16 Steel Wire Armoured (SWA) cable 136

10.17 Twin and earth cable 136

10.18 General rules regarding farm electrical installations 136

11 Isolation and Switching 138

11.1 Isolation and switching 138

11.2 Isolation 139

11.3 Mechanical maintenance 140

11.4 Emergency switching 141

11.5 Labelling and notices 143

12 A Village Sports Centre 145

12.1 Special conditions 145

12.2 Codes of practice 145

12.3 Other interested parties 146

12.4 Building details 146

12.5 Structure and finishes 147

12.6 Electricity supply and requirements 148

12.7 Off-peak tariff 148

12.8 Normal tariff 148

12.9 Load assessment and diversity 150

12.10 Off-peak heating 150

12.11 Normal tariff 150

12.12 Total estimated maximum current demand 152

12.13 Wiring systems 152

12.14 Circuitry and cable sizing 154

12.15 Cable grouping factors 155

12.16 Arrangement of circuits 156

12.17 Switchgear 157

12.18 Shock protection 157

12.19 Earthing 157

12.20 Bonding 157

12.21 An occasional problem 157

12.22 Solutions 158

12.23 Requirements for a TT installation 159

13 An Indoor Swimming Pool 160

13.1 Special conditions 160

13.2 Other interested parties 161

13.3 Building details 161

13.4 Application of zoning to this project 162

13.5 Dehumidifiers 167

13.6 Changing room/shower area 167

13.7 Loading and diversity for the swimming pool project 168

13.8 Wiring systems 169

13.9 Cable sizes 170

13.10 Distribution board 170

13.11 Isolation 171

13.12 110 V system 171

13.13 Earthing 172

13.14 Local supplementary bonding 172

13.15 Floor grid 172

14 Cables and Wiring Systems 174

14.1 External influences 174

14.2 Cost considerations 175

14.3 Choosing suitable cable routes 175

14.4 Is armouring always necessary? 175

14.5 Fire barriers 175

14.6 Holes through fire barriers 176

14.7 Sealing the wiring system 176

14.8 Work in progress 176

14.9 Records 177

14.10 Hidden cables 177

14.11 Cables within a floor 177

14.12 Cables above false ceilings 178

14.13 Cables in walls 178

14.14 Mechanically protected cables 179

14.15 Fire and smoke 179

14.16 Thermoplastic (PVC) insulation 180

14.17 Thermosetting (XLPE) 181

14.18 Silicone rubber 181

14.19 Low smoke zero halogen (LS0H) 181

14.20 Mineral insulated copper sheathed (MICS) cables 182

14.21 Heat transference from cables 182

14.22 Wiring systems and cable management 182

14.23 Emergency systems 182

14.24 Care with wiring systems 183

14.25 Thermoplastic (PVC) insulated and sheathed cables 183

14.26 Thermosetting (PVC) insulated conduit cables 183

14.27 Steel conduit systems and trunking 184

14.28 Plastic conduit systems and trunking 184

14.29 MICS cables 184

14.30 Steel wire armoured cables 185

14.31 Silicone insulated PVC sheathed cables 185

15 Inspection, Testing and Certification 186

15.1 Labelling and documentation 187

15.2 Specification and manual 187

15.3 Regulations 187

15.4 Electrical installation certificate (EIC) 187

15.5 Signatories 190

15.6 Alterations and additions 192

15.7 Limits of responsibility 192

15.8 Deviations and departures 193

15.9 New materials and inventions 193

15.10 Particulars of the installation 194

15.11 Inspections and test schedules 194

15.12 Inspection procedures 194

15.13 Testing 197

15.14 Continuity testing 198

15.15 Polarity 198

15.16 Continuity of protective conductors 198

15.17 Continuity of ring circuit conductors 198

15.18 Insulation resistance 200

15.19 Earth fault loop impedance 202

15.20 Supply impedance Ze 204

15.21 Earth loop impedance of circuits Zs 205

15.22 Prospective fault current 206

15.23 Operation of residual current devices 206

16 A Caravan Park 208

16.1 Measures for protection against electric shock 208

16.2 Earthing arrangements 209

16.3 PME must not be used for caravans 209

16.4 Electrical equipment (external influences) 210

16.5 Wiring systems 210

16.6 Cables buried in the ground 210

16.7 Overhead cables 210

16.8 Caravan pitch electrical supply equipment 211

16.9 Plugs and socket-outlets 211

17 Residual Current Devices 213

17.1 How does an RCD work? 214

17.2 Fault protection 214

17.3 Additional protection 217

17.4 Requirements to provide additional protection by RCDs 217

17.5 RCDs incorporated into a consumer unit, to meet the requirements for additional protection 218

17.6 Protection against fire 220

17.7 Avoiding a hazard and/or minimising an inconvenience due to the tripping of an RCD 221

17.8 Reducing the possibility of unwanted tripping of RCDs 221

17.9 Use of a ‘front-end’ 30 mA RCD is generally considered unacceptable practice 222

17.10 Installations forming part of a T T system 222

17.11 RCDs connected in series 223

17.12 Labelling 223

18 Flood Lighting (Outdoor Lighting) Project 224

18.1 Lighting arrangement 224

18.2 General requirements 224

18.3 Wiring system 225

18.4 Protective measures 226

18.5 Load assessment 226

18.6 Rating of the overcurrent protective device 227

18.7 Circuit design 227

18.8 Voltage drop consideration 228

18.9 Switchgear 230

19 Circuit Design Calculations 231

19.1 Design process 231

19.2 Protective conductors 235

19.3 Worked example 235

19.4 Solution 236

Index 239

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.

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