(cid:1)(cid:2)(cid:3)(cid:4)(cid:5)(cid:6)(cid:4)(cid:7)(cid:3)(cid:8) (cid:9)(cid:10)(cid:11)(cid:7)(cid:8)(cid:12)(cid:4) (cid:13)(cid:14)(cid:5)(cid:6)(cid:4)(cid:2)(cid:7)(cid:6)(cid:15)(cid:16)(cid:17)(cid:3)(cid:6)(cid:18) (cid:1)(cid:2)(cid:3)(cid:4)(cid:5)(cid:6)(cid:7)(cid:8)(cid:9)(cid:6)(cid:10)(cid:11)(cid:8) (cid:1)(cid:2)(cid:2)(cid:3)(cid:4)(cid:5)(cid:6)(cid:5)(cid:7)(cid:8)(cid:3)(cid:9)(cid:10)(cid:8)(cid:11)(cid:12)(cid:13)(cid:14)(cid:5)(cid:15)(cid:7)(cid:16) (cid:17)(cid:18)(cid:3)(cid:19)(cid:20)(cid:19)(cid:21)(cid:3)(cid:22)(cid:3)(cid:23)(cid:24)(cid:24)(cid:21)(cid:3)(cid:9)(cid:10)(cid:25)(cid:11)(cid:5)(cid:6)(cid:10)(cid:26)(cid:10)(cid:7)(cid:14)(cid:16)(cid:3)(cid:27)(cid:15)(cid:6)(cid:3)(cid:2)(cid:12)(cid:10)(cid:28)(cid:14)(cid:6)(cid:5)(cid:28)(cid:13)(cid:12)(cid:3)(cid:1)(cid:7)(cid:16)(cid:14)(cid:13)(cid:12)(cid:12)(cid:13)(cid:14)(cid:5)(cid:15)(cid:7)(cid:16) (cid:19) (cid:1)(cid:7)(cid:28)(cid:12)(cid:11)(cid:29)(cid:5)(cid:7)(cid:8)(cid:3)(cid:30)(cid:26)(cid:29)(cid:3)(cid:31)(cid:15)(cid:3)(cid:21)(cid:3)(cid:22)(cid:3)(cid:23)(cid:24)(cid:24)(cid:23) Published by: The Institution of Electrical Engineers, Savoy Place, LONDON, United Kingdom. WC2R 0BL ©2002: The Institution of Electrical Engineers Issued December 1992 Reprinted July 1993, with minor amendments 2nd edition November 1995 3rd edition 1999 4th edition 2003 Copies may be obtained from: The Institution of Electrical Engineers PO Box 96, STEVENAGE, United Kingdom. SG1 2SD Tel: +44 (0)1438 767 328 Fax: +44 (0)1438 742 792 Email: [email protected] http://www.iee.org.uk/publish/ All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means — electronic, mechanical, photocopying, recording or otherwise — without the prior written permission of the publisher. While the author, the publisher and contributors believe that the information and guidance given in this work is correct, all parties must rely upon their own skill and judgement when making use of it. Neither the author, the publisher nor any contributor assume any liability to anyone for any loss or damage caused by any error or omission in the work, whether such error or omission is the result of negligence or any other cause. Where reference is made to legislation it is not to be considered as legal advice. Any and all such liability is disclaimed. ISBN 0 85296 993 7, 2003 (cid:0)CD GN5 Protection Against Electric Shock, inc 16th Edition 2001 Amd No 1 2 Contents ACKNOWLEDGEMENTS 6 PREFACE 7 INTRODUCTION 8 SECTION 1 THE WIRING REGULATIONS 10 1.1 Object 10 1.2 Electric shock 10 1.3 Statutory Regulations 11 1.4 Philosophy of shock protection 12 1.5 Protection against both direct and indirect contact 13 SECTION 2 PROTECTION AGAINST DIRECT CONTACT 14 2.1 Introduction 14 2.2 Summary of prescribed measures 15 2.3 Insulation of live parts 16 2.4 Barriers or enclosures 18 2.5 Obstacles 20 2.6 Placing out of reach 21 2.7 Supplementary protection by residual current devices 22 2.8 Other measures and precautions 23 SECTION 3 PROTECTION AGAINST INDIRECT CONTACT 25 3.1 Introduction 25 3.2 Summary of prescribed measures 27 3.3 Earthed equipotential bonding and automatic disconnection of supply 29 3.4 Earthing 29 3.5 Equipotential bonding 30 3.6 Main equipotential bonding 31 3.7 Automatic disconnection of supply 33 3.8 Use of Class II equipment or equivalent insulation 44 3.9 Non-conducting location 48 3.10 Earth-free local equipotential bonding 50 3.11 Electrical separation 51 (cid:0)CD GN5 Protection Against Electric Shock, inc 16th Edition 2001 Amd No 1 3 SECTION 4 PROTECTION BY MEANS OF EXTRA-LOW VOLTAGE 54 4.1 Introduction 54 4.2 General 55 4.3 SELV 56 4.4 PELV 58 4.5 FELV 59 4.6 Calculation of loop impedance PELV and FELV circuits 60 SECTION 5 EARTHING 61 5.1 Connections to earth 61 5.2 Earth electrodes 65 5.3 Earthing conductors 66 5.4 Main earthing terminals or bars 66 5.5 Functional earthing 67 5.6 Combined protective and functional arrangements 68 SECTION 6 CIRCUIT PROTECTIVE CONDUCTORS 69 6.1 General 69 6.2 Sizing of circuit protective conductors 70 SECTION 7 EQUIPOTENTIAL BONDING 73 7.1 Main equipotential bonding 73 7.2 Supplementary equipotential bonding 75 SECTION 8 SPECIAL INSTALLATIONS OR LOCATIONS 80 8.1 The increased risks 80 8.2 Supplementary and modified requirements 81 8.3 Equipment having high protective conductor currents 82 8.4 Equipotential bonded floor grids 82 SECTION 9 PROTECTIVE MULTIPLE EARTHING 88 9.1 Introduction 88 9.2 Supply system 89 9.3 Additional earth electrode for PME supplies 90 9.4 Special locations 91 APPENDIX A: MAXIMUM PERMISSIBLE MEASURED EARTH FAULT LOOP IMPEDANCE 97 APPENDIX B: RESISTANCE OF COPPER AND ALUMINIUM CONDUCTORS 103 APPENDIX C: MINIMUM SEPARATION DISTANCE BETWEEN ELECTRICITY SUPPLY CABLES AND TELECOMMUNICATIONS CABLES 108 INDEX 110 (cid:0)CD GN5 Protection Against Electric Shock, inc 16th Edition 2001 Amd No 1 4 Co-operating Organisations The Institution of Electrical Engineers acknowledges the contribution made by the following organisations in the preparation of this Guidance Note. Association of Manufacturers of Domestic Appliances (AMDEA) S A MacConnacher BSc CEng MIEE British Cables Association C K Reed I Eng MIIE British Electrotechnical & Allied Manufacturers Association Ltd R Lewington Associate IEE British Electrotechnical Approvals Board P D Stokes MA CEng MRAeS British Standards Institution W E Fancourt Chartered Institution of Building Services Engineers Eur Ing G Stokes BSc(Hons) CEng FIEE FCIBSE City & Guilds of London Institute H R Lovegrove IEng FIIE Electrical Contractors’ Association D Locke IEng MIIE ACIBSE Electrical Contractors’ Association of Scotland t/a SELECT D Millar Electrical Installation Equipment Manufacturers’ Association Ltd Eur Ing M H Mullins BA CEng FIEE FIIE Electricity Association D J Start BSc CEng MIEE ERA Technology Ltd M W Coates B Eng Federation of the Electronics Industry F W Pearson CEng MIIE The GAMBICA Association Ltd K A Morriss BSc CEng MIEE MInstMC Health & Safety Executive Eur Ing J A McLean FIEE FIOSH Institution of Electrical Engineers P R L Cook CEng FIEE MCIBSE (Editor) P E Donnachie BSc CEng FIEE Institution of Incorporated Engineers P Tootill IEng MIIE Lighting Association K R Kearney IEng MIIE National Inspection Council for Electrical Installation Contracting Safety Assessment Federation Limited J Gorman BSc (Hons) CEng MIEE Society of Electrical and Mechanical Engineers serving Local Government C Tanswell CEng MIEE MCIBSE (cid:0)CD GN5 Protection Against Electric Shock, inc 16th Edition 2001 Amd No 1 5 Acknowledgements References to British Standards are made with the kind permission of BSI. Complete copies can be obtained by post from: BSI Customer Services 389 Chiswick High Road London W4 4AL Tel: General Switchboard: 020 8996 9000 For ordering: 020 8996 7000 For information or advice: 020 8996 7111 For membership: 020 8996 7002 Fax: For orders: 020 8996 7001 For information or advice: 020 8996 7048 Advice is included from Engineering Recommendation G12/3 ‘Requirements for the application of protective multiple earthing to low voltage networks’ with the kind permission of the Electricity Association. Complete copies of this and other Engineering Recommendations can be obtained by post from: The Electricity Association Engineering Publications 30 Millbank London SW1P 4RD Tel: 020 7963 5700 Fax: 020 7931 0356 (cid:0)CD GN5 Protection Against Electric Shock, inc 16th Edition 2001 Amd No 1 6 Preface This Guidance Note is part of a series issued by the Wiring Regulations Policy Committee of the Institution of Electrical Engineers to enlarge upon and simplify some of the requirements in BS 7671 : 2001 inc Amd No 1 (formerly the Sixteenth Edition of the IEE Wiring Regulations). Significant changes made in this 4th edition are sidelined. Note that this Guidance Note does not ensure compliance with BS 7671. It is intended to explain some of the requirements of BS 7671 but electricians should always consult BS 7671 to satisfy themselves of compliance. The scope generally follows that of BS 7671 and the principal section numbers are shown on the left. The relevant Regulations and Appendices are noted in the right-hand margin. Some Guidance Notes also contain material not included in BS 7671 but which was included in earlier editions. All of the Guidance Notes contain references to other relevant sources of information. Electrical installations in the United Kingdom which comply with BS 7671 are likely to satisfy Statutory Regulations such as the Electricity at Work Regulations 1989, but this cannot be guaranteed. It is stressed that it is essential to establish which Statutory and other Regulations apply and to install accordingly. For example, an installation in premises subject to licensing may have requirements different from, or additional to, BS 7671 and these will take precedence. (cid:0)CD GN5 Protection Against Electric Shock, inc 16th Edition 2001 Amd No 1 7 Introduction This Guidance Note is principally concerned with Chapter 41 of BS 7671 — Protection against electric shock. Neither BS 7671 nor the Guidance Notes are design 131-01-01 guides. It is essential to prepare a full specification prior to commencement or alteration of an electrical installation. The specification should set out the detailed design and provide sufficient information to enable competent persons to carry out the installation and to commission it. The specification must include a description of how the system is to operate and all the design and operational parameters. It must provide for all the commissioning procedures that will be required and for the provision of adequate information to the user. This will be by means of a diagram, chart or table providing the information required in Regulation 514-09, an operational manual 514-09-01 or schedule. It must be noted that it is a matter of contract as to which person or organisation is responsible for the production of the parts of the design, specification and any operational manual. The persons or organisations who may be concerned in the preparation of the specification include: The Designer The Installer The Distributor of Electricity The Installation Owner and/or User The Architect The Fire Prevention Officer All Regulatory Authorities Any Licensing Authority The Health and Safety Executive (cid:0)CD GN5 Protection Against Electric Shock, inc 16th Edition 2001 Amd No 1 8 The Insurers The Planning Supervisor In producing the design, advice should be sought from the installation owner and/or user as to the intended use. Often, as in a speculative building, the intended use is unknown. The specification and/or the operational manual must set out the basis of use for which the installation is suitable. Precise details of each item of equipment should be 132-01 obtained from the manufacturer and/or supplier and 120-02 compliance with appropriate standards confirmed. 511 The operational manual must include a description of how the system as installed is to operate and all commissioning records. The manual should also include manufacturers’ technical data for all items of switchgear, luminaires, accessories, etc and any special instructions that may be needed. The Health and Safety at Work etc Act 1974 Section 6 is concerned with the provision of information. Guidance on the preparation of technical manuals is given in BS 4884: Technical manuals and BS 4940: Technical information on construction products and services. The size and complexity of the installation will dictate the nature and extent of the manual. This Guidance Note does not attempt to follow the 400-01-01 pattern of BS 7671 too closely. Instead, a particular protective measure is considered in all its aspects, as far as possible, before the next measure is addressed. The order in which the protective measures are considered is not significant. (cid:0)CD GN5 Protection Against Electric Shock, inc 16th Edition 2001 Amd No 1 9 Section 1 — The Wiring Regulations 1.1 Object One of the principal objects of BS 7671 is the 130-01-01 130 provision of protection against electric shock. 1.2 Electric shock Electric shock is defined as a dangerous Part 2 130 physiological effect resulting from the passage of electric current through a human body or livestock. A useful reference document is British Standards Institution (BSI) publication PD 6519 ‘Guide to effects of current on human beings and livestock’. This relates the magnitude and duration of electric currents to the probable severity of their effects, based on information gathered internationally. Two conditions of electric shock are recognised: (i) under normal conditions, i.e. Direct contact which Part 2 is contact of persons or livestock with live parts, 130-02-01 sometimes called electric shock in normal service, and (ii) under single fault conditions, i.e. Indirect contact Part 2 which is contact of persons or livestock with 130-02-02 exposed-conductive-parts (such as the metallic enclosure of an item of Class I equipment) made live by a fault, sometimes called electric shock in case of a fault. With regard to indirect contact, the information referred to above entered the 15th Edition of the Wiring Regulations, as the adoption in normal dry situations of 0.4 s as the maximum disconnection time for a socket-outlet circuit (except for one specifically provided for fixed equipment) and 5 s as that for a circuit feeding fixed equipment. This approach has been adopted in the International and European Standards, as it offers the most practical means of fulfilling the basic requirements for protection against electric shock. (cid:0)CD GN5 Protection Against Electric Shock, inc 16th Edition 2001 Amd No 1 10