Paul Rosenberg - Audel Guide to the 2011 National Electrical Code: All New Edition

This book is printed on acid-free paper.

Copyright 2011 by John Wiley & Sons, Inc. All rights reserved

Published by John Wiley & Sons, Inc., Hoboken, New Jersey

Published simultaneously in Canada

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, scanning, or otherwise, except as permitted under Section 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 646-8600, or on the web at www.copyright.com . Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, (201) 748-6011, fax (201) 748-6008, or online at www.wiley.com/go/permissions .

Limit of Liability/Disclaimer of Warranty: While the publisher and the author have used their best efforts in preparing this book, they make no representations or warranties with respect to the accuracy or completeness of the contents of this book and specifically disclaim any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives or written sales materials. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional where appropriate. Neither the publisher nor the author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.

For general information about our other products and services, please contact our Customer Care Department within the United States at (800) 762-2974, outside the United States at (317) 572-3993 or fax (317) 572-4002.

Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. For more information about Wiley products, visit our web site at www.wiley.com .

Library of Congress Cataloging-in-Publication Data:

ISBN: 978-1-118-00389-3 (pbk.); ISBN 978-1-118-02610-6 (ebk); ISBN 978-1-118-02611-3 (ebk);
ISBN 978-1-118-02612-0 (ebk); ISBN 978-1-118-02613-7 (ebk); ISBN 978-1-118-02614-4 (ebk)

Foreword

I think that almost everyone who has been required to use the National Electrical Code (NEC) on a regular basis has often wished that it were easier to understand. Often, it seems that it lacks sufficient clarity and detail; other times, it seems to be overflowing with useless information. The purpose of this book is to help the reader sort through the voluminous code regulations and find the information he or she needs, with a minimum of effort. Perhaps it would help to understand where this code book comes from.

The National Electrical Code is one of many codes and standards published by the National Fire Protection Association (NFPA), a not-for-profit corporation. The code is revised every three years in order to keep up with new materials, tools, and methods that are constantly being developed. This work is performed by 21 separate committees, each consisting of approximately 10 to 15 persons, the majority of them engineers, and each of them sponsored by some organization, including manufacturers, industry organizations, and unions. Members of each committee meet several times, discuss all proposed changes, accepting some and rejecting others, and rewrite (as required) the sections of the Code that were assigned to their committee. Then, they circulate the changes among the various committees, coordinate the changes, and rewrite again. So, obviously, the updating of the NEC is no small chore. But the real difficulty is that it must remain applicable to all types of electrical installations, leaving no gaps. Because of this, it becomes rather difficult to interpret in many instances.

The purpose of this book is to arrange all of the pertinent requirements of the NEC in a manner that is user-friendly, allowing the reader to find the needed information painlessly and quickly. The challenge with the NEC is that many communities use it as law, and as such, it must be written accordingly. Every possible facet of every type of electrical installation must be covered. Because of this, the NEC is full of engineering requirements, installation requirements, and manufacturing requirementsall in engineering lingo and legalese. It's not hard to see why it is such a difficult document to comprehend. In order to make the NEC more easily understood and applicable, a number of guides have been written, most of which have a legitimate place. These guides serve to make all parts of the NEC understandable. They are written for engineers, designers, installers, and inspectors.

The book you now hold in your hands is substantially different from standard NEC guidebooks. Rather than covering everything in the NEC , we concentrated only on the requirements for electrical installations. By omitting the engineering and manufacturing requirements, much of the confusion of the NEC is eliminated in one stroke. This leaves only the rules that actually apply to installing electrical wiringwhich is the reason the Code is referred to 99 percent of the time.

This book is designed exclusively for the installer of electrical wiring, and is the result of many years of supervising and instructing electricians in the requirements of the NEC . Every effort has been made to make this book as easy to use as possible, both for the professional electrician and for the homeowner who wishes to do his or her own electrical work safely and efficiently, avoiding hassles with the local electrical inspector.

For actually installing electrical wiring, this book should be more useful than the standard NEC handbooks. For engineering questions, however, the National Electrical Code should be consulted.

Throughout this book, you will see substantive changes for the 2011 NEC highlighted. Bear in mind that these changes will have the force of law once the 2011 Code is adopted in your jurisdiction.

As you go through both this book and the Code , you will find numerous references to other codes and standards. These various codes and standards are useful but must always be used in conjunction with the NEC , not separate from it. It is critical to remember that codes are generally adopted as law by local municipalities, while standards are not. So codes contain mandatory requirements and standards contain suggested methods.

Finally, please remember that good workmanship and safety consciousness are essential ingredients for any good electrical installation. Like fire, electricity can be the best of friends or the worst of foes. Without careful workmanship and an overriding concern for the safety of the installation and the installer, no electrical installation is worthwhile.

My sincere thanks go to all of the fine people I've worked with down through the yearsI have had the good fortune of working with some of the finest people in the industry.

Paul Rosenberg

National Electrical Code and ( NEC ) are registered trademarks of the National Fire Protection Association, Inc., Quincy, MA.

Introduction

The National Electrical Code is written as a minimum standard for electrical installation for the protection of life and property. It does not necessarily define the best installation methods, merely the minimum safety standards. Many purchasers of electrical installations will want to surpass the code.