Electrical Grounding and Bonding, 6th Edition PDF by Phil Simmons


Electrical Grounding and Bonding, Sixth Edition

By Phil Simmons

Electrical Grounding and Bonding 6th Edition


Foreword . xi

Preface . xiii

Acknowledgments . xvii

Changes to the NEC xix

Introduction to Grounding and Bonding . 1

Objectives 1

The Mystery 2

Definitions . 3

Review of Ohm’s Law and Basic Electrical Theory . 28

Electric Shock Hazards . 32

Review Questions 34


General 38

Objectives 38

Introduction . 39

250.3 Application of Other Articles 39

250.4 General Requirements for Grounding and Bonding . 40

250.6 Objectionable Current . 52

250.8 Connection of Grounding and Bonding Equipment . 56

250.12 Clean Surfaces 59

Review Questions 60


System Grounding 63

Objectives 63

250.20 Alternating-Current Systems to Be Grounded 64

250.21 Alternating-Current Systems of 50 Volts to 1000 Volts

Not Required

to Be Grounded 69

250.22 Circuits Not to Be Grounded 72

250.24 Grounding of Service-Supplied Alternating-Current Systems . 75

250.25 Grounding Systems Permitted to Be Connected on the Supply Side of the Disconnect. 90

250.26 Conductor to Be Grounded—Alternating-Current Systems . 90

250.28 Main Bonding Jumper and System Bonding Jumper . 92

250.30 Grounding Separately Derived Alternating-Current Systems 97

250.32 Buildings or Structures Supplied by a Feeder(s)

or Branch Circuit(s) 117

250.34 Portable, Vehicle-Mounted and Trailer-Mounted

Generators . 127

250.35 Permanently Installed Generators . 131

250.36 High-Impedance Grounded Neutral Systems . 134

Review Questions 138


Grounding Electrode System and Grounding

Electrode Conductor . 142

Objectives 142

250.50 Grounding Electrode System 143

250.52 Grounding Electrodes . 144

250.53 Grounding Electrode System Installation . 150

250.54 Auxiliary Grounding Electrodes . 160

250.58 Common Grounding Electrode . 161

250.60 Use of Strike Termination Devices . 162

250.62 Grounding Electrode Conductor Material 163

250.64 Grounding Electrode Conductor Installation 163

250.66 Size of Alternating-Current Grounding Electrode Conductor 180

250.68 Grounding Electrode Conductor and Bonding

Jumper Connection to Grounding Electrodes . 183

250.70 Methods of Grounding and Bonding Conductor

Connection to Electrodes 187

Review Questions 189


Enclosure, Raceway, and Service Cable Connections 194

Objectives 194

250.80 Service Raceways and Enclosures 195

250.86 Other Conductor Enclosures and Raceways . 196

Review Questions 197


Bonding . 198

Objectives 198

250.90 General 199

250.92 Services . 200

250.94 Bonding for Communication Systems 206

250.96 Bonding Other Enclosures 207

250.97 Bonding for Over 250 Volts 211

250.98 Bonding Loosely Jointed Metal Raceways . 212

250.100 Bonding in Hazardous (Classified) Locations 213

250.102 Grounded Conductors, Bonding Conductors, and Jumpers 213

250.104 Bonding of Piping Systems and Exposed Structural Metal 219

250.106 Lightning Protection Systems . 225

Review Questions 226


Equipment Grounding and Equipment Grounding Conductors 231

Objectives 231

250.109 Metal Enclosures . 232

250.110 Equipment Fastened in Place (Fixed) or Connected

by Permanent Wiring Methods . 232

250.112 Specific Equipment Fastened in Place (Fixed)

or Connected by Permanent Wiring Methods . 233

250.114 Equipment Connected by Cord and Plug 235

250.118 Types of Equipment Grounding Conductors 237

250.119 Identification of Equipment Grounding Conductors 249

250.120 Equipment Grounding Conductor Installation 252

250.121 Restricted Use of Equipment Grounding Conductors 253

250.122 Size of Equipment Grounding Conductors . 255

250.124 Equipment Grounding Conductor Continuity . 267

250.126 Identification of Wiring Device Terminals 268

Review Questions 268


Methods of Equipment Grounding . 273

Objectives 273

250.130 Equipment Grounding Conductor Connections 274

250.134 Equipment Fastened in Place or Connected by

Permanent Wiring Methods (Fixed)—Grounding 278

250.138 Cord and Plug Connected Equipment . 279

250.140 Frames of Ranges and Clothes Dryers 280

250.142 Use of Grounded Circuit Conductor for

Grounding Equipment 282

250.146 Connecting Receptacle Grounding Terminal

to an Equipment Grounding Conductor 283

250.148 Continuity of Equipment Grounding Conductors

and Attachment in Boxes 288

Review Questions 291


Grounding of Specific Equipment Covered in

Chapter 5 of the NEC . 295

Objectives 295

Introduction . 296

Class I, Class II, and Class III Hazardous (Classified) Locations 296

250.100 Bonding in Hazardous (Classified) Locations 296

Article 517, Health Care Facilities 299

517.11 General Installation—Construction Criteria . 299

517.13 Equipment Grounding Conductor for Receptacles

and Fixed Electric Equipment in Patient Care Spaces 300

517.14 Panelboard Bonding 307

517.16 Use of Isolated Ground Receptacles . 308

517.17 Ground-Fault Protection of Equipment 310

Article 547, Agricultural Buildings . 318

547.9 Electrical Supply to Building(s) or Structure(s) from

a Distribution Point . 318

547.10 Equipotential Planes and Bonding of Equipotential Planes 321

Article 550, Mobile Homes, Manufactured Homes,

and Mobile Home Parks . 323

550.32 Service Equipment 323

550.33 Feeder 326

Article 551, Recreational Vehicles and Recreational Vehicle Parks . 327

551.76 Grounding – Recreational Vehicle Site Supply Equipment 328

Article 555 Marinas, Boatyards, Floating Buildings,

and Commercial and Noncommercial Docking Facilities 330

555.1 Scope . 330

555.4 Location of Service Equipment 330

555.10 Signage 331

555.13 Bonding of Non-Current-Carrying Metal Parts. . 331

555.35 Ground-Fault Protection of Equipment (GFPE)

and Ground-Fault Circuit-Interrupter (GFCI) Protection . 332

555.37 Equipment Grounding Conductor . 333

555.53 Ground-Fault Protection . 334

555.54 Grounding . 335

555.55 Insulated Neutral. . 335

555.56 Equipment Grounding. 336

Review Questions 336

Appendix A: Some Fundamentals of Equipment-Grounding

Circuit Design . 342

Appendix B: Investigation and Testing of Footing-Type

Grounding Electrodes for Electrical Installations 351

Appendix C: Understanding Ground Resistance Testing . 361

Appendix D: Report of Research on Conduit Fitting

Ground-Fault Current Withstand Capability 392

Index . 400

Electricity follows the basic laws of physics, regardless of whether it is current flow over ungrounded (“hot”) conductors, over grounded conductors (sometimes neutral conductors), or in the grounding system. So, if we can understand basic circuit flow, we can understand the requirements and performance rules for grounding and bonding of electrical systems and equipment. You will find several of the illustrations in this book to be fairly basic and uncomplicated. This complements the overall effort to make the rules for grounding and bonding as easy to understand as possible and to take the concepts of grounding and bonding back to the basics.

I want to mention here and applaud the efforts of Ronald P. O’Riley, who wrote a book titled Electrical Grounding: Bringing Grounding Back to Earth, through the sixth edition. Mr. O’Riley is now deceased. Although this book is not based on or intended to be a continuation of Mr. O’Riley’s efforts, our goals in presenting a book on grounding and bonding of electrical systems are very similar. Quoting from the preface to Mr. O’Riley’s

sixth edition:
“The author’s wish is for this book to be a learning experience for members, and those in training for a career in the electrical industry. It is the author’s hope that simplifying, illustrating, reasoning through, and coordinating the grounding requirements, as contained in Article 250 of the National Electrical Code®, will promote better understanding and use of the Code. This can result in safer, cleaner electrical installations and maintenance. The first rule is to make it safe: the second is to make it work. Both can be done. With this thought in mind, this book is directed at vocational instructors of electricity, electrical engineers, design engineers, construction electricians making installations in the field, maintenance electricians at factories or buildings, electrical inspectors, and many other members of the electrical industry. It is also the author’s hope that the apprentice or person preparing for a career in the electrical industry and studying the

National Electrical Code® will find the detailed explanations and accompanying diagrams in this book to be an interesting learning experience.” Electrical Grounding and Bonding is based on my many years of experience in teaching subjects related to the NEC, field experience in the electrical construction industry, and association with the International Association of Electrical Inspectors (IAEI).

Other than the Introduction, which includes an explanation of many definitions applicable to electrical grounding and bonding along with a brief review of electrical theory, this book is organized by section number of the NEC. For example, if you’re interested in learning about requirements for a grounding electrode system, you can follow the rule from the NEC Section 250.50 to an identical code reference in this book. Other features of the organization of this book are as follows:

  1. The requirement from the NEC is included. Note that in most cases, the requirement is paraphrased rather than being a direct quote.
  2. The requirement is discussed and explained.
  3. An illustration of the requirement is provided.
  4. Where appropriate, there is an explanation of how to comply with the rules, such as determining the appropriate size system bonding conductor.
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