ELECTRICAL INSTALLATIONS AND REGULATIONS BY J. F. WHITFIELD Lecturer in Electrical Engineerings Norwich City College PERGAMON PRESS OXFORD · LONDON · EDINBURGH · NEW YORK TORONTO · PARIS · FRANKFURT Pergamon Press Ltd., Headington Hill Hall, Oxford 4 & 5 Fitzroy Square, London W.l Pergamon Press (Scotland) Ltd., 2 & 3 Teviot Place, Edinburgh 1 Pergamon Press Inc., 44-01 21st Street, Long Island City, New York 11101 Pergamon of Canada Ltd., 6 Adelaide Street, East Toronto, Ontario Pergamon Press S.A.R.L., 24 rue des Écoles, Paris 5e Pergamon Press GmbH, Kaiserstrasse 75, Frankfurt-am-Main Copyright © 1966 Pergamon Press Ltd. First edition 1966 Library of Congress Catalog Card No. 65-28103 Printed in Great Britain by Bell and Bain Ltd., Glasgow This book is sold subject to the condition that it shall not, by way of trade, be lent, resold, hired out, or otherwise disposed of without the publisher's consent, in any form of binding or cover other than that in which it is published (2368/66) LIST OF TABLES Table 1. Symbols 14 Table 2. Heavy Gauge Welded Conduit 91 Table 3. Light Gauge Welded Conduit 97 Table 4. Earth-fault Loop Impedances 146 Table 5. Average Luminous Efficiency of Lamps 204 Table 6. High-pressure Mercury-vapour Lamps 210 IX Λ* PREFACE THE purpose of this book is to provide the electrician with a clear picture of the rules which apply to his work and to explain the reasons for them. It does not seek to replace the Regulations for the Electrical Equipment of Buildings published by the Institution of Electrical Engineers. Indeed, the reader is strongly advised to obtain " The Regulations " for use in conjunction with this book, which is based on the 13th edition with amendments including those issued in 1962 and 1963. Notice has also been taken of the " Recent Interpretations " issued from time to time by the I.E.E. Installation work covers an immense field. The impossibility of adequately describing all its facets in a work of this length is fully appreciated by the writer. However, it is hoped that the text may be of use to all electricians who seek a full understanding of their work, as well as to students taking City and Guilds course number 51—Electrical Installation Work. " B " course students have been particularly borne in mind whilst writing the book, but it should also prove interesting to those in the " A " and " C " courses. The choice of illustrations has been guided by two basic principles. First, that photographs of the commonplace should be avoided. Second, that circuit diagrams should be simplified so that the reader can see immediately the principle involved, without having to disentangle it from a maze of detail. A very short account of the electrical theory needed to assist understanding of this book is given in Chapter 2. A companion volume giving more detailed electrical theory is to be published. Norwich J. F. WHITFIELD EDITOR'S NOTE THIS comprehensive book has been written to provide a guide to modern electrical installations practice and regulations. It is based on the 13th edition (plus amendments) of the Régule tions for the Electrical Equipment of Buildings which is published by the Institu­ tion of Electrical Engineers. A 14th edition of the Regulations is being prepared which will include the amendments and allow for some rearrangement of material. It was considered not desirable to hold up publication of this book until the new edition of the Regulations appeared, and any changes in them will be incorporated in subsequent editions of this book. N. HILLER ACKNOWLEDGEMENTS THE writer acknowledges with grateful thanks the assistance of numerous organizations and individuals who have helped in the preparation of the book, including: The Institution of Electrical Engineers, for permission to refer to Regulations for the Electrical Equipment of Buildings. The City and Guilds of London Institute for permission to reproduce past examination questions. The year, paper and question numbers appear after each question. Where answers are given, these have been worked by the writer, who takes full responsibility for their accuracy. Many firms who have assisted with illustrations, each of which is acknowledged individually. Dr. J. P. English, who read the section on artificial respiration and made valuable suggestions. Organizations who have assisted with information, including the British Safety Council, Nife Batteries Ltd. Mrs. C. Addison-Carter who typed the manuscript, and my wife who assisted in checking it. xii CHAPTER 1 INTRODUCTION 1.1. THE INSTALLATION AND THE ELECTRICIAN The installation An electrical installation is the complete system of wiring and apparatus which is used to feed electrical energy from the position at which it is made available in the building concerned to the point or points at which it is to be used. It will consist of the " mains gear ", made up of switching systems and protection against excessive currents, including dangerous earth-leakage currents; the cabling system, which may take one or more of numerous forms ; and the final outlets or apparatus, which can vary from a decorative candle lamp to an industrial furnace. It can be seen, therefore, that the range covered by electrical installations is considerable. In size they can vary from a single outlet point to the complete installation for a large building. In technical difficulty they can range from a light controlled by a one-way switch, to the extremely complicated control system for an oil-burning heating plant. It is seldom that two installations are identical and the electrician is rarely concerned with repetition work. Materials Not only is the list of types of installation an almost endless one, but very often one particular installation could be carried out using one or more of a number of different systems. For instance, a warehouse could be wired with tough rubber cables, plastic cables, mineral-insulated cables, cables drawn into conduit or placed in trunking, a grid suspension system, etc. The choice of a particular 1 2 ELECTRICAL INSTALLATIONS AND REGULATIONS system will depend on the exact use of the premises, on their construction, on cost, and on the risk involved. To be efScient, an electrician must know all the systems thoroughly and should be able to advise a customer on which type of installation he needs. The task of remaining knowledgeable on all available systems is a difficult one and can be only fully carried out by taking an interest in the trade press and particularly in manufacturers' and wholesalers' catalogues. The electrician A competent electrician is a man with wide experience. He must be a craftsman, capable of carrying out a job neatly and quickly. He must be technically sound and have a clear understanding of the theory behind his work. And he must be a man of character, capable of advising a client, guiding him to a correct choice, and above all, resisting the pressure which may be brought to bear on him to lower his standards and do a poor job for a lower price. Many electricians argue that the second and third points, i.e. technical knowledge and ability to handle the customer, are the work of the supervisors and managers. To some extent this is true, but a man cannot be a competent and fully trained electrician without them. And some day he may be the manager. 1.2. THE REGULATIONS Need for Regulations It has been stressed how very full the list of types of installation can be. In Section 1.4 the dangers of fire and shock, which are always present when electricity is used, will be stressed. In order that all of the many installations carried out by electricians of varying ability may be safe to use, a set of rules which must be followed clearly is necessary. Most countries have their own rules and there is considerable variation in the standard which they set. The Institution of Electrical Engineers issue the regulations which apply in Great Britain. There is no law which says that these regulations must be followed, but all those concerned with installation work INTRODUCTION 3 should make certain that they are complied with, and Electricity Boards will not connect their supply to an installation which is of a lower standard than that laid down. The Regulations Rules and Regulations for the Prevention of Fire Risks arising from Electric Lighting were issued in 1882, but as the use of electricity increased and new systems were developed, revisions became necessary. These revisions have to be made from time to time, and the current rules, entitled Regulations for the Electrical Equipment of Buildings y are the 13th edition and were issued by the Institution of Electrical Engineers in 1955, amendments appearing in 1958, 1961, 1962, and 1963. It can be seen, therefore, that continual revision of the Regulations is carried out to keep them up to date. The Regulations are generally accepted as setting a standard as good as any in the world and are used in many countries. It should be noticed that the Regulations are for " Buildings ". They do not cover overhead and underground line systems, or ships, aircraft, cars, etc., for which there are separate rules. However, a memorandum Recommended Practice for Electrical Installations in Caravans was issued separately in 1954 and should be referred to when necessary. A copy of the Regulations, which can be obtained from the Secretary, The Institution of Electrical Engineers, Savoy Place, London W.C.2, should be read in conjunction with this book, which makes no attempt to replace them. Students may find the wording of the Regulations difficult. The wording used ensures that the rules set out are made as precise as possible, and it is not easy to see how it could be improved without making the Regulations much longer. Layout of the Reguhtions Since the Regulations take up about 180 pages, no electrician can be expected to learn them by heart. A good working knowledge is essential, however, and this can be obtained more easily if we understand how the rules are laid out. The Regulations consist of the following main sections : 4 ELECTRICAL INSTALLATIONS AND REGULATIONS (1) Part I—Requirements for safety. This part consists of eleven short regulations which should be studied carefully. These are the actual Regulations. A very important note is worth quoting in full— GOOD WORKMANSHIP IS ESSENTIAL FOR COMPLIANCE WITH THESE REGULATIONS. (2) Part II—Means of securing compliance with the requirements of Part I. These rules require the most careful study, as they detail the requirements for different types of circumstance and instal­ lation. They are divided into eight sections, each of which deals with a specific topic. Numbering is arranged to indicate the section concerned ; e.g. Regulation 207 is the seventh regulation in the second section. Some of the regulations of Part II include tables where the information is given more readily in this form. Both Parts I and II have wide margins with brief titles for each Regulation to provide easy identification. (3) A total of thirty-nine tables are given after Part II, dealing with such matters as cable sizes, cable ratings, cable bends, cable supports, capacity of conduits, etc. These tables will be mentioned as the need for them arises, but it would be wise of a student to read through the titles of the tables, so that he is conversant with their contents. (4) Supplemental appendices. These extra sections deal with special items not covered in Part II, such as private generating plant, earthing to water mains, etc. Tables are included where necessary. (5) Index. This index is prepared most carefully and is invaluable for finding the regulations applying to a particular case. A little practice will enable the student to find quickly the information he needs, but the use of an index should not be considered as a substi­ tute for a full knowledge of the Regulations. There are some cases where more than one regulation will apply and application of incomplete rules can lead sometimes to dangerous situations. 1.3. OTHER RULES AND REGULATIONS Although the Regulations for the Electrical Equipment of Buildings is by far the most important work of reference to be studied in