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Copyright © 2003, 1997 by The McGraw-Hill Companies, Inc. All rights reserved. Manufactured in the United States of America. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a da...

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Copyright © 2003, 1997 by The McGraw-Hill Companies, Inc. All rights reserved. Manufactured in the United States of America. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of the publisher. 0-07-142579-9 The material in this eBook also appears in the print version of this title: 0-07-137751-4.

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CONTENTS Preface

Chapter 1 Planning for Electrical Design

vii

1

Chapter 2 Power Generation and Transmission

37

Chapter 3 Power System Equipment

57

Chapter 4 Substations and Electrical Distribution

109

Chapter 5 Service Entrance, Loadcenters, and Grounding

133

Chapter 6 Wire, Cable, and Circuit Components

173

Chapter 7 Branch Circuit Design and Device Wiring

243

Chapter 8 Lighting, Lamps, and Luminaires

269

Chapter 9 Telephone, Multimedia, and Alarm Systems

321

Chapter 10 Electric Motors and Starters

345

Chapter 11 Emergency and Standby Systems

379

Chapter 12 Electrical Surges and Surge Protection

399

PREFACE This is the second edition of the Handbook of Electrical Design Details (HEDD), originally published in 1997. It is a well-illustrated reference book on electrical power and lighting—how it is generated, transmitted, distributed, and used. Considerable new information has been added in this edition but it is a smaller volume, making it more user-friendly and easier to keep on a desk or shelf. Among the topics new to this edition are computer-aided electrical drawing (CAD), basic switch and receptacle circuit wiring, outdoor low-voltage wiring, telephone and structured wiring, and electrical surge protection. This book begins with a discussion of electrical drawing and symbols and the importance of specifications in electrical projects. The chapters that follow cover power generation, transmission, and distribution. Design details of generators and transformers and their role in delivering electric power to consumers’ homes or buildings are included. Aerial and buried service entrances are explained and illustrated, as are main panels or loadcenters and the principles of earth grounding. Properties of wire and cable are presented, and the dimensions and the details of basic electrical wiring devices are described and illustrated. The rules for installing branch circuit wiring are given along with an example of a load calculation and the reasons for load balancing. Extensive coverage is given to lighting, lamps, and indoor and outdoor lighting design. Other chapters explain telephone and structured wiring, electric motors, emergency and standby electrical systems, and the essentials of surge protection. This edition of HEDD makes many references to the National Electrical Code® (NEC®)* on all topics governed by the code, such as wiring protection, wiring methods and materials, and standard equipment, where appropriate for reader guidance. In the chapters on wire, cable, and wiring devices, individual drawings represent whole classes of standard products such as switches, receptacles, and lamps, replacing the many repetitive catalog pages that appeared in the first edition. Each chapter begins with a content summary called “Contents at a Glance” and an Overview of the chapter. In addition, there are separate glossaries of technical terms at the ends of the chapters on transformers, electrical service entrance, wiring, lighting, motors, telecommunications, emergency and standby systems, and surge protection, for handy reference and quick memory refreshing. This second edition of HEDD has been written in an informal descriptive style, with minimal use of mathematics. The readers most likely to benefit from this book are electrical contractors, electricians, and instructors. Others who will find this volume helpful are those employed in the electrical industry in manufacturing, service, *National Electrical Code and NEC are registered trademarks of the National Fire Protection Association, Quincy, Massachusetts.

Copyright 2003, 1997 by The McGraw-Hill Companies, Inc. Click Here for Terms of Use.

1 PLANNING FOR ELECTRICAL DESIGN

CONTENTS AT A GLANCE Overview

Drawing Line Widths and Styles

Electrical Drawing Objectives

Electrical Graphic Symbols

Electrical Drawing Preparation

Electronic Graphic Symbols

Computer-Aided Drawing

Drawing Schedules

Electrical CAD Software

Electrical Project Drawings

CAD Drawing Plotters

Electrical Product and Work Standards

Drawing Sizes and Conventions

What Are Electrical Specifications?

Drawing Reproduction

Overview A successful electrical power and lighting project depends on effective planning in the form of drawings, schedules, and contract specifications. This contract documentation provides a concise picture of the objectives for the electrical project work to be done. It also serves as a record of intent for owners and as instructions and guidance for Copyright 2003, 1997 by The McGraw-Hill Companies, Inc. Click Here for Terms of Use.

2

PLANNING FOR ELECTRICAL DESIGN

contractors, electricians, installers, and others performing the work. Contract documents, which might also include surveys and test data, are legal documents, and they can be used as evidence in court cases involving contractor malfeasance, or failure to comply with the intent of the drawings and specifications. The present conformity to accepted formats for drawings and specifications is the result of years of practical experience reinforced by accepted national and international standards issued by government agencies and private standards organizations. The standards organizations are advised by experienced personnel from the ranks of manufacturers, contractors, and other interested parties. The intent of standards is to produce unambiguous documentation that is understandable by all project participants, from engineers and architects to contractors, project supervisors, electricians, and installers. This chapter discusses the preparation of drawings and schedules and their reproduction. It also explains and illustrates typical standard electrical symbols used on planview, one-line, and schematic drawings for electrical construction, and identifies the principal government and industry agencies whose standards affect all phases of electrical work. Appendix A is a compilation of American National Standards Institute (ANSI) electrical symbols and National Electrical Manufacturers Association (NEMA) plug and receptacle and circuit wiring configuration diagrams. Appendix B contains the front matter and selected commonly used sections of a typical electrical specification, to show how a written specification is organized, its legal language, and its style.

Electrical Drawing Objectives Drawing for an electrical project serves three distinct functions. 1 Describes the electrical project in sufficient detail to allow electrical contractors to

use the drawings in estimating the cost of materials, labor, and services when preparing a contract bid. 2 Instructs and guides electricians in performing the required wiring and equipment installation while also warning them of potential hazards such as existing wiring, gas pipes, or plumbing systems. 3 Provides the owner with an “as-built” record of the installed electrical wiring and equipment for the purposes of maintenance or planning future expansion. The owner then becomes responsible for recording all wiring and equipment changes. A typical electrical drawing consists of solid or dashed lines representing wiring or cables and symbols for luminaires, receptacles, switches, auxiliary systems, and other electrical devices and their locations on a scaled architectural floor plan of a home or building. The drawings also include title blocks to identify the project, the designers or engineers, and the owner, and change blocks to record any changes that have been made since the drawing was first issued. In any given set of electrical drawing there are also specialized drawings such as one-line, elevation or riser, and electrical equipment installation drawings. There

ELECTRICAL DRAWING PREPARATION

3

might be no drawing requirements for relatively simple electrical projects such as updating the amperage capacity of a home or extending branch wiring into a basement, attic, or extension. In these situations, all information needed can be included in a written proposal or other contractual agreement. For commercial projects or new home construction, formal drawings are required to gain approvals from building inspectors and the local electric utility. A typical set will include several 24
36 in. architectural floor plans marked with the appropriate electrical graphic symbols. The set might also include drawings for telephone and multimedia structured wiring, outdoor wiring, or a security system. By contrast, major large-scale construction projects such as shopping centers, highrise office buildings, factories, hospitals, and scientific laboratories might require dozens of 24
36 in. (or larger) sheets, depending on the size and complexity of the project. These might include one-line drawings and manufacturer-furnished wiring diagrams for installing equipment. For complex projects, special instructions and installation schedules will also be included.

Electrical Drawing Preparation The preparation of electrical drawings for updating an existing electrical system or constructing a new one is the responsibility of a consulting architect, engineer, or designated experienced employee in an architectural or consulting engineering firm. The actual drawing could be performed by on-staff electrical engineers or designers, or it could be subcontracted out to consultants specializing in electrical power and lighting design. However, consulting engineering firms are usually retained to design and supervise the construction and electrical work in major commercial, industrial, and government projects. These firms employ registered professional electrical, mechanical, structural, and civil engineers as well as specialists in writing specifications and drafting for large-scale projects. Some engineering firms also employ registered professional architects who are experienced in building design. All of these specialists might participate in the preparation and approval of electrical drawings and specifications, because close coordination between these disciplines will help to avoid mistakes or oversights that are costly and time-consuming to correct in the field. If a project is to include custom-made electrical-powered equipment such as machine tools, generators, conveyors, escalators, or elevators, the project manager will request generic drawings of that equipment from qualified vendors for estimating and planning purposes. These drawings will show floor space and ceiling height requirements for the installation of the equipment, the relative positions of any necessary auxiliary equipment, and the recommended positions of all piping and wiring required. The drawings will also show the correct orientation of the equipment to assure sufficient space for operators and maintenance personnel to move around the equipment to gain access to all removable panels or hatches and to provide for the swing radius of any hinged doors. If the equipment is large, measurements for minimum space requirements to move the equipment into the building will be included.

4

PLANNING FOR ELECTRICAL DESIGN

These measurements will be useful in sizing entryways or scheduling the installation before the walls are covered. In some cases large units such as machine tools, furnaces, or elevators will require the preparation of special concrete foundations, and construction drawings will be provided by the manufacturer. This work must be completed prior to the delivery of the equipment. Generic drawings will be replaced by drawings of the actual custom-built equipment after it has been ordered. These drawing might be accompanied by installation, operation, and maintenance manuals prepared specifically for the project. These will later become part of the owner’s engineering documentation. The electrical contractor might have his or her own staff designers prepare supplementary electrical drawings if they are needed to clarify certain aspects of the installation, help to avoid mistakes, speed up the work, or provide extra guidance for the field supervisors.

Computer-Aided Drawing Most large engineering consulting and architectural firms in the United States have made the transition from manual to computer-aided drawing (CAD). These companies have had to purchase computer workstations, applications software, and plotters, as well as pay for personnel training in CAD. The dedicated workstations and off-theshelf high-performance desktop computers now available are capable of supporting the most sophisticated commercial CAD software available. The pricing for both is far lower today than it was only a few years ago, making CAD affordable even for small design firms and individual professional consultants. The acronym CAD also stands for computer-aided design, but this is a misnomer. CAD programs do not do design work; that must still be done by skilled draftspersons, designers, or engineers with sufficient technical knowledge and training to perform professional-level work. CAD drawing can be learned on the job, in trade and technical schools, or at training facilities set up by software vendors. However, the training in a software vendor’s classes focuses on teaching the company’s proprietary software and might not include instruction in the use of competitive or alternative software. An experienced electrical designer or drafter might require months of on-the-job practice with specific CAD software to become proficient enough in its use to do professional work on the workstation more cost-effectively than it could be done by traditional manual drawing. The software needed for electrical power and lighting design work typically consists of two components: a general purpose two-dimensional (2-D) CAD software package and supplementary applications-specific electrical design software. While it is possible to do professional electrical drafting with basic off-the-shelf 2-D CAD drawing software, the addition of the supplementary electrical design software will relieve the

COMPUTER-AIDED DRAWING

5

user of the onerous task of creating custom files of symbols and other design elements specific to electrical construction. The supplementary applications-specific software is expected to pay for itself within a short period of time and increase drawing productivity. This software typically contains a complete library of electrical symbols, which can be selected from a menu and dragged into position on the workstation screen for proper placement on the architectural or oneline drawings. Most electrical drawing software permits the user to modify the industry standard symbols or create new ones for specific devices or equipment. Many corporate clients of architectural or engineering consulting firms as well as U.S. government agencies have their own drafting style guides, which must be followed in the performance of contract work. They might, for example, have their own specialized symbols or make specific selections in cases where two or more alternative symbols are approved and accepted by the industry. All drawings produced for the bidding process and later construction phases must be drawn in accordance with these guidelines. Some CAD programs are capable of producing the proper forms and making the necessary calculations to produce material lists and cost estimates based on the number and type of symbols placed on the drawing. The benefits of CAD electrical drawing are the following. ■ Saving time in the preparation of all types of electrical drawings. ■ Eliminating the tedious tasks of lettering and drawing uniform lines and symbols. ■ Permitting the transfer of large sections of drawings prepared originally for one

project to be reused on a different project. ■ Providing databases of “families” of master digitized drawings that can be modi-

fied for reuse on other projects or become de facto templates for new drawings. ■ Making rapid changes on completed and approved drawings to reflect field changes...