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FFIRS 10/29/2012 23:51:15 Page 1

Electrical Installation Designs

FFIRS 10/29/2012 23:51:15 Page 2

FFIRS 11/08/2012 13:45:57 Page 3

Electrical Installation DesignsFourth Edition

Bill AtkinsonDeceased

Roger LovegroveElectrical Contractors’ Association, UK

Gary GundryThe Electrical Safety Council, UK

FFIRS 10/29/2012 23:51:15 Page 4

This edition first published 2013# 2013, John Wiley & Sons, Ltd

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Library of Congress Cataloging-in-Publication Data

Electrical installation designs / Bill Atkinson ... [et al.]. – 4th ed.

p. cm.

Includes bibliographical references and index.

ISBN 978-1-119-99284-4 (pbk.)

1. Electric wiring, Interior. 2. Electrical engineering. I. Atkinson, Bill.

TK3271.A8 2013

621.319’24–dc23

2012030909

A catalogue record for this book is available from the British Library.

ISBN: 978-1-119-99284-4

Set in 10/12 pt Sabon-Roman by Thomson Digital, Noida, India.

FTOC 10/30/2012 16:42:28 Page 5

Contents

About the Authors xvii

Preface to the Fourth Edition xix

Acknowledgements xxv

1 Introduction 11.1 Layout of chapters 11.2 Wiring regulations 21.3 Terminology 21.4 Competence and responsibility 31.5 Procedures 3

1.5.1 Design 31.5.2 Installation 4

1.6 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 6

2 Three Bedroom House 82.1 The bare minimum 92.2 Standards 9

2.2.1 National House Building Council (NHBC) 92.2.2 Relevant wiring regulations 9

2.3 Building regulations 112.3.1 Smoke detectors 11

2.4 Load assessment 11

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2.5 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 15

2.11.1 Rewireable fuses 152.11.2 Cartridge fuses 152.11.3 Circuit-breakers (cb) 15

2.12 Additional protection for socket-outlets 152.13 Arrangement of circuits 16

2.13.1 Residual current protection 162.13.2 Circuit-breakers (cb) 16

2.14 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 19

3 A Block of Retirement Flatlets 213.1 Two schemes 213.2 Early considerations 21

3.2.1 Metering and distribution 213.3 Other interested parties 223.4 Building details 22

3.4.1 Construction 223.5 Part 1 – Flats 24

3.5.1 Mains distribution 243.5.2 Electrical requirements in flats 243.5.3 Load assessment and maximum demand 253.5.4 Wiring system 253.5.5 Wiring hints 253.5.6 Wiring in false ceilings 263.5.7 Wiring in roof space 273.5.8 Cable sizes 273.5.9 Arrangement of circuits 273.5.10 Consumer unit 283.5.11 Earthing and bonding 283.5.12 Earthing terminal 293.5.13 Bonding 29

3.6 Part 2 – Landlord’s areas 293.6.1 Meter cupboard 293.6.2 Supplies to flats 29

Contents

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3.6.3 Landlord’s electrical requirements 303.6.4 Diversity 303.6.5 Lighting 313.6.6 Socket-outlets 313.6.7 Other equipment 313.6.8 Total load 313.6.9 Cable sizes and circuitry 313.6.10 Lighting 323.6.11 Socket-outlets 323.6.12 Other equipment 333.6.13 Distribution board 333.6.14 Residual current protection 333.6.15 Switchgear 333.6.16 Switching 343.6.17 Wiring 343.6.18 Earthing 343.6.19 Emergency systems 34

4 Overcurrent Protection 354.1 Overload 354.2 Overload protection 364.3 Overload protective devices 37

4.3.1 Rewirable fuses 374.3.2 High Breaking Capacity (HBC) fuses 374.3.3 Circuit-breakers 374.3.4 The ‘type’ of circuit-breaker 37

4.4 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 43

5 An Architect’s Office 445.1 Other interested parties 445.2 Building structure and finishes 455.3 Electrical requirements 46

5.3.1 Loading and diversity 475.3.2 Storage heaters 495.3.3 Print machine 505.3.4 Socket-outlets 50

Contents

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5.3.5 Total load 505.3.6 Wiring system 50

5.4 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 60

5.25.1 Computer supplies 605.26 High protective conductor currents 605.27 Mains filters 605.28 Uninterruptible Power Supplies (UPS) 61

6 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 70

Contents

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6.15 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 73

6.22.1 Main switch 736.22.2 Appliances 73

6.23 Earthing and bonding 736.24 Main earthing terminal (MET) 736.25 False-ceiling grid 746.26 Steel tables in the bakery 74

7 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) 77

7.5.1 Why earth at all? 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 86

7.16.1 Items of stationary equipment 877.17 ‘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 89

8 Car Service Workshop 908.1 Standards and recommendations 908.2 An adaptable design 91

Contents

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8.3 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 97

8.13.1 Office lighting load 998.13.2 Workshop lighting load 99

8.14 Welder 998.15 Compressor 998.16 Gas blowers 100

8.16.1 Provision for spray area 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 102

8.21.1 Steel conduit and trunking 1028.21.2 Steel Wire Armoured (SWA) cable 103

8.22 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 110

9 Circuits 1119.1 Terminology 1119.2 Colours of three phases 111

Contents

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9.3 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 116

9.11.1 Multiple plug sizes 1169.12 Radial circuits 1179.13 Introducing the tree 1179.14 20 A tree 117

9.14.1 Domestic 1179.14.2 Commercial and similar 117

9.15 32 A tree 1189.15.1 Domestic 1199.15.2 Commercial and similar 119

9.16 Switching and control 1199.17 Comparison of systems 1209.18 32 A ring final circuit 120

9.18.1 Disadvantages 1209.18.2 Advantage 120

9.19 20 A tree 1219.19.1 Disadvantage 1219.19.2 Advantages 121

9.20 Composite circuits 121

10 Farming and Horticulture 12310.1 Why farms are different 124

10.1.1 Environment 12410.1.2 Livestock 12410.1.3 Equipotential zones 12410.1.4 Electrical systems 125

10.2 Special earthing requirements on farms with TT systems 12610.2.1 Warning 126

10.3 Earth electrodes 12710.4 Alternative electrodes 127

10.4.1 Earth tapes and wires 12710.4.2 Structural steelwork 12810.4.3 Concrete reinforcement 12810.4.4 Earthing grids or plates 12810.4.5 Pipework of other services 128

Contents

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10.5 Bonding 12810.5.1 Main bonding 128

10.6 Supplementary bonding 12910.7 Residual current devices 129

10.7.1 Discrimination 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 134

10.14.1 Metallic conduit 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 136

11 Isolation and Switching 13811.1 Isolation and switching 13811.2 Isolation 139

11.2.1 Main switch 13911.3 Mechanical maintenance 14011.4 Emergency switching 141

11.4.1 Domestic 14211.4.2 Industrial 14211.4.3 Emergency stopping decisions 142

11.5 Labelling and notices 143

12 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 150

12.11.1 Showers 15012.11.2 Changing room 150

Contents

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12.11.3 Sink water heaters 15112.11.4 Cooker 15112.11.5 Socket-outlets 15112.11.6 Beer chiller 15112.11.7 Lighting 151

12.12 Total estimated maximum current demand 15212.13 Wiring systems 152

12.13.1 Insulated and sheathed cables 15212.13.2 Steel conduit and trunking 15312.13.3 Emergency systems 15412.13.4 Plastic conduit and trunking 154

12.14 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 159

13 An Indoor Swimming Pool 16013.1 Special conditions 16013.2 Other interested parties 16113.3 Building details 161

13.3.1 Construction 16113.3.2 Electrical requirements 162

13.4 Application of zoning to this project 16213.4.1 Zone 0 16313.4.2 Zone 1 16413.4.3 Zone 2 16613.4.4 Other current-using equipment of swimming pools 166

13.5 Dehumidifiers 16713.6 Changing room/shower area 167

13.6.1 Switchgear, controlgear and accessories 16813.6.2 Current-using equipment 168

13.7 Loading and diversity for the swimming pool project 16813.7.1 Lighting 16813.7.2 Dehumidifiers 16913.7.3 Socket-outlets and hair dryer 169

13.8 Wiring systems 16913.9 Cable sizes 170

Contents

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13.10 Distribution board 17013.11 Isolation 17113.12 110 V system 17113.13 Earthing 17213.14 Local supplementary bonding 17213.15 Floor grid 172

14 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 185

15 Inspection, Testing and Certification 18615.1 Labelling and documentation 18715.2 Specification and manual 187

Contents

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15.3 Regulations 18715.4 Electrical installation certificate (EIC) 18715.5 Signatories 190

15.5.1 Designer 19015.5.2 Installer 19215.5.3 Inspection and testing 192

15.6 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 198

15.17.1 Test no. 1 19815.17.2 Test no. 2 198

15.18 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 206

16 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 211

17 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 217

Contents

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

17.6 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 TT system 22217.11 RCDs connected in series 22317.12 Labelling 223

18 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 230

19 Circuit Design Calculations 23119.1 Design process 231

19.1.1 Step 1: Determine the characteristics of supply and the load 23219.1.2 Step 2: Select the cable and protective device 23219.1.3 Step 3: Check that the voltage drop is acceptable 23319.1.4 Step 4: Check that electrical shock protection is acceptable 23319.1.5 Step 5: Check that the conductors are protected against prospective

fault current 23419.2 Protective conductors 23519.3 Worked example 23519.4 Solution 236

Index 239

Contents

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About the Authors

Roger Lovegrove’s extensive experience in the electrical contracting industry spans over 50 years.He served an apprenticeship, worked as an electrician and contracts engineer and then managedhis own business for 18 years. Having left electrical contracting, he became a consultantspecialising in inspecting, testing and surveying electrical installations. For a number of yearshe delivered lectures for ECA and IIE on various topics associated with BS 7671, the IEEWiring Regulations. He is a Fellow of the IET and serves on the joint IET/BSI WiringRegulations Committee. For many years an ECA member, he has served on the association’stechnical committee. Also, he has represented UK electrical contracting interests on Internationaland European electrical installation standards working groups.

Gary Gundry is one of the UK’s leading electrical safety trainers and presenters. Working at theElectrical Safety Council (ESC), he primarily produces technical guidance material for theelectrical industry and safety literature for consumers. He also serves on one of the fourcommittees responsible for the technical content of the Wiring Regulations (BS 7671);accordingly, he is able to speak authoritatively (to audiences of any number) on the requirementsof the Seventeenth Edition of the Wiring Regulations.

Prior to working at the ESC, Gary was a Senior Engineer at NICEIC Training delivering bespoketraining courses all over the United Kingdom, and before that he worked in the Standardsdivision on, among other things, the NICEIC’s Technical Manual.

Before joining the NICEIC in 1999, he was a Director and Qualified Supervisor of an electricalcontracting business enrolled as an NICEIC Approved Contractor.

Gary began his career as an apprentice with SEEBoard, and later joined Eastern Electricity.

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Preface to the Fourth Edition

There are many books on electrical installation practice where the focus is on calculations andregulations. Electrical Installation Designs has been written from a different viewpoint. Typicalprojects are examined to produce designs that will fit current standards.

Most electrical contractors have an understanding of requirements related to their own regulareveryday activities, where work is carried out using rule-of-thumb methods. Repetitive designsare used. Many installers claim that they are not designers and show concern that they are nowrequired to certify the adequacy of an installation design.

In practice, problems only arise when an unusual project is undertaken or there is a change inregulations.

There is no harm in using a standardised design, rather in the way that an experienced cook uses apublished recipe for a cake. Electrical Installation Designs is a book of recipes. The installer mayselect a design that corresponds as near as possible to the contract in hand and take up suchtechnical and regulatory advice as is required. This will reduce the need for lengthy calculationsand detailed study of BS 7671, Requirements for Electrical Installations (IET WiringRegulations).

Most basic electrical installations may be completed by a competent person, with appropriateguidance to avoid serious problems and hazards.

Project chapters illustrate methods that could be used for particular types of installation rangingfrom a house to an industrial workshop. The ideas are by no means exclusive. Alternativesolutions are always possible. In many instances carrying out detailed calculations and utilisingdifferent circuitry will be more profitable. By their very nature, simplified examples of fictionalprojects can only produce generalised results.

The book contains special chapters on earthing, isolation and switching and overcurrentprotection, which give a down to earth interpretation of the regulations.

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Electrical installation students and non-electrical associates in the construction industry willappreciate the user-friendly approach. Nevertheless, this is not a do-it-yourself book for theuntrained person. Warnings are therefore given where more specialised study is necessary. Forexample, readers are advised not to embark on installations in hazardous areas (such as petrolfilling stations) without further training. Apart from moral implications and contractual risks,statutory requirements are such that incompetent work may carry criminal penalties.

Although the emphasis is on tried and tested methods, some new techniques are introduced.The most significant is the option for tree circuitry as an alternative to the ring final circuit. Thisis the first book to give designers the opportunity to compare the advantages of the tree systemfor both domestic and commercial installations. In recent years, consumer requirements havechanged. It is essential that the industry keeps an open mind on changes in traditional wiringpractice. Introduced in this fourth edition are new chapters on Residual Current Devices and,for those readers who require a basic understanding of circuit design, a chapter explaining theprocess for carrying out simple cable design calculations.

Amendments

The Institution of Electrical Engineers (IEE) joint wiring regulations committee amendedBS 7671: 1992 (16th edition) in 1994, 1997 and 1999. In 2001, the standard was renamedBS 7671: 2001 with further amendments, and minor amendments were made again in 2002.

In 2008, a complete review of the 16th edition saw the publication of the 17th edition:BS 7671: 2008. The first amendment to the 17th edition was published in 2011 and came fullyinto force on 1 January 2012. This latest amendment also introduced the rebranded name of theIEE, namely the IET (Institution of Engineering and Technology). The most recent edition ofBS 7671 incorporates all alterations and additions to the European HD 384 series of standards.

As is often the case, many of the changes are of a minor nature in order to harmonise with otherstandards. However, significant changes were introduced in BS 7671: 2008 (17th edition)with several other significant changes being introduced in its first amendment, in 2011. Theseare summarised in the following tables – Table A.1 summarises the changes introduced byBS 7671: 2008 (17th edition) and Table A.2 summarises the significant changes introducedby Amendment 1 to BS 7671: 2008:

This book takes account of all amendments published since the 17th edition of the WiringRegulations was first issued in 2008, including those introduced by Amendment 1, which wasfirst issued in 2011 and which came into effect on 1 January 2012.

Roger Lovegrove and Gary Gundry

Preface to the Fourth Edition

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Table A.1 Summary of changes introduced by BS 7671: 2008 (17th edition).

BS 7671reference

Subject Summary of notable change/new content

General Regulation numberingsystem

The 17th edition introduced the adoption of the IEC numbering system, inwhich the Regulation numbers are separated by a decimal point, rather thana hyphen as was previously the case.

Chapter 41 Protection againstelectric shock

Chapter was rewritten.

Protection against direct contact – was replaced by basic protection.

Protection against indirect contact – was replaced by fault protection.

Introduction of term ‘Additional protection’. Socket-outlets with a ratedcurrent not exceeding 20A and intended for general use by ordinary personsmust be protected by 30mA RCDs.

Mobile equipment having a current rating of 32 A or less for use outdoorsmust also have 30 mA RCD protection.

Chapter 52 Selection and erectionof wiring systems

For installations not under the supervision of a skilled or instructed person,such as domestic or similar installations, cables that are buried in a wall orpartition at a depth of 50mm or less and are not enclosed in earthed metalliccovering (metallic armouring), earthed conduit, earthed trunking or havemechanical protection capable of resisting nails, screws or the like, arerequired to be protected by a 30mA RCD as well as being installed inthe so-called ‘safe zones’.

Similarly cables that are installed in metal framed walls require 30mA RCDprotection if not otherwise protected by earthed metallic covering, earthedconduit, earthed trunking or have mechanical protection capable of resistingnails, screws or the like, to be protected by a 30mA RCD, unless theinstallation is under the control of skilled or instructed persons, suchas office buildings and industrial premises.

Section 559 Luminaires and lighting A new section applicable to all general lighting installations as appropriate toparticular locations and structures. Requirements for fixed outdoor lighting,highway power supplies and street furniture are also included, which werepreviously in Part 6.

Part 6 Inspection and testing Was previously Part 7.

Part 7 Special installations orlocations

Was previously Part 6.

701 – Locations containing a bath or a shower.

Zones 0, 1 and 2 as defined in the 16th edition were retained. Zone 3 wasremoved. All circuits supplying equipment in bathrooms and shower roomsare required to be protected by 30mA RCDs.

Supplementary bonding is no longer required, provided all of the followingthree conditions are met:

� all final circuits of the location are protected by a 30mA RCD;

� all final circuits of the location meet the required disconnection times;

� main bonding of services within the property is correctly installed.

(Continued)

Preface to the Fourth Edition

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Table A.1 Continued.

BS 7671reference

Subject Summary of notable change/new content

SELV (separated extra-low voltage) socket-outlets and shaver socket-outletsare permitted outside Zone 1

230 V socket-outlets are permitted, provided they are more than 3 metreshorizontally from the boundary of zone 1.

708 – Electrical installations in caravan/camping parks and similarlocations. Formerly caravans, motor caravans and caravan parks in the16th edition.

New Sections were added as follows:

709 – Marinas and similar locations;

711 – Exhibitions, shows and stands;

712 – Solar photovoltaic (PV) power supply systems;

717 – Mobile or transportable units;

721 – Electrical installations in caravans and motor caravans;

740 – Temporary electrical installations for structures, amusement devicesand booths at fairgrounds, amusement parks and circuses.

Table A.2 Summary of changes introduced by Amendment 1 to BS 7671: 2008.

BS 7671reference

Subject Summary of notable change/new content

General Regulation numberingsystem

In order to further implement changes to the requirements given in theInternational (IEC) and European (CENELEC) base documents, anumber of the requirements contained in BS 7671 are particular to theUnited Kingdom. Those Regulations are identified via a ‘10X’ suffix.For example, Regulation 522.6.100.

General References to ESQCR 2002 Amendments have been made throughout BS 7671 to clarify therequirements of the Electricity Safety, Quality and ContinuityRegulations 2002 with regard to the suitability for use of ProtectiveMultiple Earthing (PME).

Tables 41.2;41.4; and41.6

BS 88 fuses Amended to reflect changes in product standards for cartridge fuses.

Table 41.5 Simplification of table Scope of the table revised to cover only circuits at a nominal a.c. rmsline-to-earth voltage (U0) of 230 V.

Section 444 Measures againstelectromagneticdisturbances

New section added,Measures against electromagnetic disturbances.

(Continued)

Preface to the Fourth Edition

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Table A.2 Continued.

BS 7671reference

Subject Summary of notable change/new content

514.10.1 Nominal voltages Simplification of wording regarding enclosures within which nominalvoltages exceeding 230V to earth are present but may not beexpected.

Requirement relating to nominal voltage exceeding 230 V betweensimultaneously accessible enclosures has been deleted.

522.6.100 Cables in floor or ceilingvoids

Clarification provided by adding indent relating to SELV and PELVcircuits.

522.6.101 Cables in walls or partitions Clarification provided by adding indent relating to SELV and PELVcircuits.

522.6.103 Cables in partitions havingmetallic parts

Clarification provided by adding indent relating to SELV and PELVcircuits.

526.3 Connections Maintenance-free accessories complying with BS 5733 recognised asan option for not needing to be accessible for inspection andmaintenance.

Section 534 Surge protection devices New section added, Devices for protection against overvoltage.

Section 710 Medical locations New section added,Medical locations.

Section 729 Operating and maintenancegangways

New section added, Operating and maintenance gangways.

Appendix 4 Current-carrying capacityand voltage drop for cables

New clauses added: 5.5, Rating factors for triple harmonic currents infour-core and five-core cables with four cores carrying current and 5.6Harmonic currents in line conductors. (New clauses based on textthat was previously in Appendix 11).

New clause added: 6.4, Voltage drop in consumers’ installations.(Text was previously in Appendix 12).

Appendix 6 Model forms for certificationand reporting

Introduction of Electrical Installation Condition Report to replacePeriodic Inspection Report.

New Schedule added: Condition report inspection schedule fordomestic and similar premises with up to 100 A supply.

New item added for other types of installation: Examples of itemsrequiring inspection for an electrical installation condition report.

Appendix 16 Protection againstovervoltage

New Appendix added: Devices for protection against overvoltage.

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Acknowledgements

Gary Gundry would like to thank Roger Lovegrove for the opportunity to update this publica-tion and for his encouragement and support during the reviewing and commenting stage of theproject.

Gary would also like to thank his employer, The Electrical Safety Council (ESC), for grantingpermission to update this publication, and for allowing him to reproduce any copyright material,where applicable. In recognition of this, and as a gesture of good faith, he has requested his shareof the royalties be sent directly to the Electrical and Electronics Industries Benevolent Association(EEIBA), for as long as he remains employed at the ESC. The EEIBA is a charity dedicated tohelping those in hardship and distress who work or have worked in the Electrical and ElectronicsIndustry.

Special thanks goes to Peter, Liz, Laura and their colleagues at Wiley for the book design conceptand typesetting, and to the Institution of Engineering and Technology for its permission to repro-duce some of the model certificates and associated forms shown in Appendix 6 of the SeventeenthEdition of the IET Wiring Regulations.

Gary would also like to express thanks to his mentors and family for their endless patience, sup-port and encouragement along the way.

Finally, any views expressed within this publication are those of the authors’ so they should notbe associated with their employers, where applicable.

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