Mike Holt's lllustrated Guide to

Understanding the
NATIONAL
ELECTRICAL CODE
Volume 1 • Articles 90 - 480

Based on the 2011 NEC

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Mike Holt's lllustrated Guide to

Understanding the
NATIONAL
ELECTRICALCODE
Volume 1 • Articles 90 - 480

Based on the 2011 NEC ,1.

Since 1974
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Mike Holt's lllustrated Guide to Understanding the 2011 National Electrical Code, Volume 1
 Tab e of Conténts
Introduction xv 110.14 Conductor Termination and Spiicing 46
Atwut This Textbook xvii 110.15 High-Leg Conductor Identification 51
How to Use the National Electrical Code xix 110.16 Are-Flash Hazard Warning 52
About the Author xxii 110.21 Manufacturer's Markings 52
About the Graphic Illustrator xxiii 110.22 Identification of Disconnecting Means 52
Mike Holt Enterprises Team xxiv 110.24 Available Fault Current 52
Part II. 600V, Nominal, or Less 53
110.26 Spaces About Electrical Equipment 53
ARTICLE 90—INTRODUCTION TO THE 110.27 Guarding 59
NATIONAL ELECTRICAL CODE i 110.28 EnclosureTypes 59
90.1 Purpose ofthe A/5C 1 Chapter 1. General—Practice Questions 60
90.2 Scope ofthe/VEC 2
90.3 Code Arrangement 4
90.4 Enforcement 5 CHAPTER 2—WIRING AND PROTECTION 65
90.5 Mandatory Requirements and Explanatory Material 6
90.6 Formal Interpretations 7
ARTICLE 200—USE AND IDENTIFICATION OF
90.7 Examination of Equipment for Product Safety 7 GROUNDED CONDUCTORS 67
90.9 Units of Measurement 7 Part I. General 68
Article 90. Introduction—Practice Questions 8 200.1 Scope 68
200.2 General 68
200.4 Grounded Conductors 68
CHAPTER1—GENERAL 11 200.6 Grounded Conductor Identification 68
200.7 Use of White or Gray Color 70
ARTICLE 10Q-DEFINITIONS 13 200.9 Terminal Identification 71
Definitions 13 200.10 Identification of Termináis 71
200.11 Polarity 71
ARTICLE 110—REQUIREMENTS FOR ELECTRICAL
INSTALLATIONS 41 ARTICLE 210—BRANCH CIRCUITS 73
Partí. General Requirements 41 Part L General Provisions 74
110.1 Scope 41 210.1 Scope 74
110.2 Approval of Conductors and Equipment 41 210.2 Other Articles 74
110.3 Examination, Identification, Installation, and Use of 210.3 Branch-Circuit Rating 74
Equipment 41 210.4 Multiwire Branch Circuits 74
110.4 Voltages 42 210.5 Identification for Branch Circuits 78
110.5 Copper Conductors 42 210.6 Branch-Circuit Voltage Limitations 78
110.6 Conductor Sizes 42 210.7 Múltiple Branch Circuits 79
110.7Wiring Integrity 43 210.8 GFCI Protection 79
110.8 Suitable Wiring Methods 43 210.11 Branch Circuits Required 85
110.9 Interrupting Protection Rating 43 210.12 Arc-Fault Circuit-lnterrupter Protection for Dweiling Units 87
110.10 Circuit Impedance, Short-Circuit Current Rating, and 210.18 Guest Rooms and Guest Suites 88
Other Characteristics 45 Part II. Branch-Circuit Ratings 88
110.11 Deteriorating Agents 45 210.19 Conductor Sizing 88
110.12 Mechanical Execution of Work 46 210.20 Overcurrent Protection .-. 90
110.13 Mounting and Cooling of Equipment 46

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 Table of Contents

210.21 Outlet Device Rating 91 220.83 Existing Dweiling Unit Calculations 128
210.23 Permissible Loads 92 220.84 Multifamily—Optional Load Calculation 129
210.25 Brancti Circuits in Buildings with Múltiple Occupancies 93 220.85 Optional Calculation—Two Dweiling Units 130
Part III. Required Outlets 93 220.87 Determining Existing Loads 130
210.50 General 93
ARTICLE 225—OUTSIDE BRANCH CIRCUITS AND
210.52 Dweiling Unit Receptacle Outlet Requirements 93
FEEDERS 131
210.60 Receptacles in Guest Rooms, Guest Suites, Dormitories,
Part \ General 131
and Similar Occupancies 101
225.1 Scope 131
210.62 Show Windows 101
225.2 Other Articles 132
210.63 Heating, Air-Conditioning, and Refrigeration (HACR)
225.6 Mínimum Size of Conductors 132
Equipment 102
225.7 Luminaires Installed Outdoors 133
210.70 Lighting Outlet Requirements 103
225.15 Supports Over Buildings 133
ARTICLE 215—FEEDERS 107 225.16 Attachment 133
215.1 Scope 107 225.17 Masts as Support 133
215.2 Mínimum Rating 107 225.18 Clearance for Overhead Conductors 133
215.3 Overcurrent Protection Sizing 109 225.19 Clearances from Buildings 134
215.4 Feeders with Common Neutral Conductor 109 225.22 Raceways on Exterior Surfaces of Buildings or Other
215.6 Equipment Grounding Conductor ....109 Structures 135
215.10 Ground-Fault Protection of Equipment 110 225.26 Trees for Conductor Support 136
215.12 Conductor Identification 110 225.27 Raceway Seal 136
Part II. Buildings or Other Structures Supplied by a
ARTICLE 220—BRANCH-CIRCUIT, FEEDER, AND
Feeder(s) or Branch Circuit(s) 136
SERVICE CALCULATIONS 111 225.30 Number of Supplies 136
Part 1. General 111 225.31 Disconnecting Means 136
220.1 Scope 111 225.32 Disconnect Location 136
220.3 Application of Other Articles 111 225.33 Máximum Number of Disconnects 138
220.5 Calculations 111 225.34 Grouping of Disconnects 138
Part II. Branch-Circuit Load Calculations 112 225.35 Access to Occupants 138
220.12 General Lighting 112 225.36 Identified as Suitable for Service Equipment 138
220.14 Other Loads—All Occupancies 113 225.37 Identification of Múltiple Feeders 138
220.18 Máximum Load on a Branch Circuit 116 225.38 Disconnect Construction 138
Part 111. Feeder and Service Calculations 118 225.39 Rating of Disconnecting Means 138
220.40 General 118
ARTICLE 230—SERVICES 140
220.42 General Lighting Demand Factors 118
220.43 Commercial—Show Window and Track Lighting Load 118 Part I. General 141
220.44 Other than Dweiling Unit—Receptacle Load 119 230.1 Scope 141
220.50 Motor Load 120 230.2 Number of Services 141
220.51 Fixed Electric Space-Heating Load 120 230.3 Not to Pass Through a Building/Structure 142
220.52 Dweiling Unit—Small-Appliance and Laundry Load 120 230.6 Conductors Considered Outside a Building 142
220.53 Dweiling Unit—Appliance Load 120 230.7 Service Conductors Sepárate from Other Conductors 142
220.54 Dweiling Unit—Electric Clothes Dryer Load 121 230.8 Raceway Seats 143
220.55 Dweiling Unit—Electric Ranges and Cooking Appliances...122 230.9 Clearance from Building Openings 143
220.56 Commercial—Kitchen Equipment Load 124 230.10 Vegetation as Support 144
220.60 Noncoincident Loads 124 Part II. Overhead Service Conductors 144
220.61 Feeder/Service Neutral Unbalanced Load 124 230.23 Overhead Service Conductor Size and Rating 144
Part IV. Optional Calculations for Computing Feeder and 230.24 Vertical Clearance for Overhead Service Conductors 145
Service Loads 127 230.26 Point of Attachment 146
220.82 Dweiling Unit—Optional Load Calculation 127 230.27 Means of Attachment 146
230.28 Service Masts Used as Supports 146

Mike HoiVs Iliustrated Guide to Understanding the 2011 National Electrical Code, Volume 1
 Table of Contents

Part III. Underground Service Conductors 147 240.54 Type S Fuses, Adapters, and Fuseholders 173
230.31 Underground Service Conductor Size and Rating 147 Part Vi. Cartridge Fuses and Fuseholders 174
230.32 Protection Against Damage 147 240.60 General 174
Part IV. Service-Entrance Conductors 148 240.61 Classification 174
230.40 Number of Service-Entrance Conductor Sets 148 Part VII. Circuit Breakers 175
230.42 Size and Rating 148 240.80 Method of Operation 175
230.43 Wiring Methods 149 240.81 Indicating 175
230.46 Spiiced Conductors 149 240.82 Nontamperable 175
230.50 Protection Against Physical Damage 149 240.83 Markings 175
230.51 Cable Supports 150 240.85 Applications 176
230.54 Overhead Service Locations 150
230.56 High-Leg Identification 150 ARTICLE 250—GROUNDING AND BONDING 177
Part V Service Equipment—General 151 Partí. General 177
230.66 Usted as Suitable for Service Equipment 151 250.1 Scope 177
250.2 Definitions 177
Part VI. Service Equipment—Disconnecting Means 151
250.4 General Requirements for Grounding and Bonding 179
230.70 Disconnect Requirements 151
250.6 Objectionable Current 185
230.71 Number of Disconnects 153
250.8 Termination of Grounding and Bonding Conductors 189
230.72 Grouping of Disconnects 153
250.10 Protection of Fittings 189
230.76 Manual or Power Operated 154
250.12 Clean Surfaces 189
230.77 Indicating 154
230.79 Rating of Disconnect 154 Part II. System Grounding and Bonding 189
230.81 Connection to Termináis 155 250.20 Systems Required to be Grounded 189
230.82 Connected on Supply Side of the Service Disconnect 155 250.21 Üngrounded Systems—50V to Less Than 10OV 190
250.24 Service Equipment—Grounding and
Part VII. Service Equipment Overcurrent Protection 156
Bonding 190
230.90 Overtoad Protection Required 156
250.28 Main Bonding Jumper and System Bonding Jumper 195
230.95 Ground-Fault Protection of Equipment 156
250.30 Separateiy Oerived Systems—Grounding and Bonding 197
ARTICLE 240—OVERCURRENT PROTECTION 158 250.32 Buildings or Structures Supplied by a Feeder or Branch
Part I. General 158 Circuit 203
240.1 Scope 158 250.34 Generators—Portable and Vehicle-Mounted 205
240.2 Definitions 159 250.35 Permanently Installed Generators 206
240.3 Protection of Equipment 160 250.36 High-Impedance Grounded Systems 206
240.4 Protection of Conductors 160 Part lli. Grounding Electrode System and Grounding Electrode
240.5 Protection of Flexible Cords and Fixture Wires 163 Conductor 207
240.6 Standard Ampere Ratings 164 250.50 Grounding Electrode System 207
240.10 Supplementary Overcurrent Protection 164 250.52 Grounding Electrode Types 208
240.13 Ground-Fault Protection of Equipment 164 250.53 Grounding Electrode Installation Requirements 210
240.15 üngrounded Conductors 165 250.54 Auxiliary Grounding Electrodos 215
Part II. Location 166 250.58 Common Grounding Electrode 216
240.21 Overcurrent Protection Location in Circuit 166 250.60 Lightning Protection Electrode 217
240.24 Location of Overcurrent Devices 170 250.62 Grounding Electrode Conductor 217
250.64 Grounding Electrode Conductor Installation 218
Part IIL Enclosures 172
250.66 Sizing Grounding Electrode Conductor 220
240.32 Damp or Wet Locations 172
250.68 Termination to the Grounding Electrode 222
240.33 Vertical Position 172
250.70 Grounding Electrode Conductor Termination Fittings 223
Part V Plug Fuses, Fuseholders, and Adapters 173
Part IV. Grounding Enclosure, Raceway, and Service
240.50 General 173
Cable Connections 223
240.51 Edison-Base Fuses 173
250.80 Service Raceways and Enclosures 223
240.52 Edison-Base Fuseholders 173
250.86 Other Enclosures 223
240.53 TypeS Fuses 173

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 Table of Contents

Part V. Bonding 224 Part III. Connecting Surge protective devices 256
250.90 General 224 285.23 Type 1 SPD—Une Side of Service Equipment 256
250.92 Bonding Equipment for Services 224 285.24 Type 2 SPD—Feeder Circuits 256
250.94 Intersystem Bonding Termination 227 285.25 Type 3 SPDs—Branch Circuits 257
250.96 Bonding Other Enclosures 229 Chapter 2. Wiring and Protection—Practice Questions 258
250.97 Bonding Metal Parts Containing 277V and 480V Circuits... 229
250.102 Bonding Conductors and Jumpers 230
250.104 Bonding of Piping Systems and Exposed Structural CHAPTER 3—WIRING METHODS AND
Metal 232 MATERIALS 273
250.106 Lightning Protection System 235
ARTICLE 300—WIRING METHODS 277
Part VI. Equipment Grounding and Equipment Grounding
Part l General 277
Conductors 236
300.1 Scope 277
250.110 Fixed Equipment Connected by Permanent Wiring
300.3 Conductors 278
Methods—General 236
300.4 Protection Against Physical Damage 280
250.112 Specific Equipment Fastened in Place or Connected
300.5 Underground Installations 283
by Permanent Wiring Methods 236
300.6 Protection Against Corrosión and Deterioration 287
250.114 Cord-and-Plug-Connected Equipment 237
300.7 Raceways Exposed to Different Temperatures 288
250.118 Types of Equipment Grounding Conductors 237
300.8 Not Permitted in Raceways 289
250.119 Identification of Equipment Grounding Conductors 240
300.9 Raceways in Wet Locations Above Grade 289
250.120 Equipment Grounding Conductor Installation 242
300.10 Electrical Continuity 289
250.121 Use of Equipment Grounding Conductors 242
300.11 Securing and Supporting 290
250.122 Sizing Equipment Grounding Conductor 242
300.12 Mechanical Continuity 292
250.126 Identification of Wiring Device Termináis 245
300.13 Spiices and Pigtails 293
Part VII. Methods of Equipment Grounding 245
300.14 Length of Free Conductors 294
250.130 Replacing Nongrounding Receptacles 245
300.15 Boxes or Conduit Bodies 295
250.134 Equipment Fastened in Place or Connected by Wiring
300.16 Raceway or Cable to Open or Concealed Wiring 297
Methods 246
300.17 Raceway Sizing 297
250.136 Equipment Considered Grounded 247
300.18 Inserting Conductors in Raceways 299
250.138 Cord-and-Plug-Connected Equipment 247
300.19 Supporting Conductors in Vertical Raceways 299
250.140 Ranges, Ovens, and Clothes Dryers 247
300.20 Induced Currents in Ferrous Metal Enclosures and
250.142 Use of Neutral Conductor for Equipment Grounding 247
Raceways 300
250.146 Connecting Receptacle Grounding Terminal to Metal
300.21 Spread of Fire or Products of Combustión 301
Enclosure 248
300.22 Wiring in Ducts Not for Air Handiing, Fabricated Ducts
250.148 Continuity and Attachment of Equipment Grounding
for Environmental Air, and Other Spaces For Environmental
Conductors in Boxes 251
Air (Plenums) 302
Part VIII. Direct-Current Systems 252 300.23 Paneis Designed to Allow Access 304
250.166 Sizing Grounding Electrode Conductor 252
ARTICLE 310—CONDUCTORS FOR GENERAL WIRING 306
ARTICLE 285—SURGE PROTECTIVE DEVICES (SPDS) 254
Part I. General 306
Partí. General 255 310.1 Scope 306
285.1 Scope 255
Part II. Installation 306
285.3 Uses Not Permitted 255
310.10 Uses Permitted 306
285.4 Number Required 255
310.15 Conductor Ampacity 309
285.5 Listing 255
Part Itl. Construction Specification 316
285.6 Short-Circuit Current Rating 255
310.104 Conductor Construction and Application 316
Part II. Installation 256
310.106 Conductors 318
285.11 Location 256
310.110 Conductor Identification 319
285.12 Routing of Conductors 256

VIII Mike HolVs lllustrated Guide to Understanding the 2011 National Electrical Code, Volume 1
 Table of Contents

ARTICLE 312—CABINETS, CUTOUT BOXES, AND METER 320.108 Equipment Grounding Conductor 345
SOCKET ENCLOSURES 320
ARTICLE 330—METAL-CUD CABLE (TYPE MC) 346
312.1 Scope 320
Part I. General 346
PARTI.INSTALLATION 321
330.1 Scope 346
312.2 Damp or Wet Locations 321
330.2 Definition 346
312.3 Installed inWaIls 321
312.4 Repairing Gaps 321 Part II. Installation 346
312.5 Enclosures 321 330.10 Uses Permitted 346
312.6 Deflection of Conductors 322 330.12 Uses Not Permitted 347
312.8 Enclosures Witti Spiices, Taps, and Feed-Through 330.17 Through or Parallel to Framing Members 347
Conductors 322 330.23 In Accessible Attics or Roof Spaces 348
330.24 Bends 348
ARTICLE 314—OUTLET, DEVICE, PULL AND JUNCTION 330.30 Securing and Supporting 348
BOXES; CONDUIT BODIES; AND HANDHOLE 330.40 Fittings 349
ENCLOSURES 324 330.80 Conductor Ampacities 350
Part I. Scope and General 324 Part III. Construction Specifications 350
314.1 Scope 324 330.108 Equipment Grounding Conductor 350
314.3 Nonmetallic Boxes 324
ARTICLE 334—NONMETALLIC-SHEATHED CABLE
314.4 Metal Boxes 324
(TYPES NM AND NMC) 351
PartlL Installation 324
314.15 Damp orWet Locations 324 Part L General 351
314.16 Number of 6 AWG and Smaller Conductors in Boxes and 334.1 Scope 351
Conduit Bodies 325 334.2 Definition 351
314.17 Conductors That Enter Boxes or Conduit Bodies 329 334.6 Listed 351
314.20 Boxes Recessed in Watis or Ceitings 330 Part II. installation 352
314.21 Repairing Noncombustible Surfaces 330 334.10 Uses Permitted 352
314.22 Surface Extensions 330 334.12 Uses Not Permitted 353
314.23 Support of Boxes and Conduit Bodies 331 334.15 Exposed 353
314.27 Outlet Box 334 334.17 Through or Parallel to Framing Members 354
314.28 Boxes and Conduit Bodies for Conductors 4 AWG and 334.23 Attics and Roof Spaces 354
Larger 335 334.24 Bends 355
314.29 Wiring to beAccessible 339 334.30 Securing and Supporting 355
314.30 Handhole Enclosures 339 334.80 Conductor Ampacity 356
Part ill. Construction Specifications 358
ARTICLE 320—ARMORED CABLE (TYPE AC) 341 334.100 Construction 358
Partí. General 341 334.104 Conductors 358
320.1 Scope 341 334.108 Equipment Grounding Conductor 358
320.2 Definition 341 334.112 Insulation 358
Part IL Installation 341
320.10 Uses Permitted 341 ARTICLE 338—SERVICE-ENTRANCE CABLE
320.12 Uses Not Permitted 342 (TYPES SE AND USE) 359
320.15 Exposed Work 342 Partí. General 359
320.17 Through or Parallel to Framing Members 342 338.1 Scope 359
320.23 In Accessible Attics or Roof Spaces 343 338.2 Definitions 359
320.24 Bends 343 Part II. Installation 359
320.30 Securing and Supporting 343 338.10 Uses Permitted 359
320.40 Boxes and Fittings 344 338.12 Uses Not Permitted 360
320.80 Conductor Ampacity 345 338.24 Bends 360
Part III. Construction Specifications 345
320.100 Construction 345

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 Table of Contents

ARTICLE 340—UNDERGROUND FEEDER AND BRANCH- ARTICLE 348—FLEXIBLE METAL CONDUIT (TYPE FMC).... 373
CIRCUIT CABLE (TYPE UF) 361 Part I. General 373
Partí. General 361 348.1 Scope 373
340.1 Scope 361 348.2 Definition 373
340.2 Definition 361 348.6 Listing Requirements 373
340.6 Listing Requirements 361 Part il. Installation 373
Part II. Installation 361 348.10 Uses Permitted 373
340.10 Uses Permitted 361 348.12 Uses Not Permitted 373
340.12 Uses Not Permitted 362 348.20 Trade Size 373
340.24 Bends 362 348.22 Number of Conductors 374
340.80 Ampacity 362 348.24 Bends 374
340.112 Insulation 362 348.26 Number of Bends (360°) 374
348.28 Trimming 374
ARTICLE 342—INTERMEDIATE METAL CONDUIT 348.30 Securing and Supporting 374
(TYPE IMC) 363 348.42 Fittings 375
Partí. General 363 348.60 Grounding and Bonding 375
342.1 Scope 363
342.2 Definition 363 ARTICLE 350—LIQUIDTIGHT FLEXIBLE METAL CONDUIT
342.6 Listing Requirements 363 (TYPE LFMC) 377

Part II. Installation 363 PartL General 377

342.10 Uses Permitted 363 350.1 Scope 377
342.14 Dissimilar Metals 364 350.2 Definition 377
342,20 Trade Size 364 350.6 Listing Requirements 377
342.22 Number of Conductors 364 Part li. Installation 377
342.24 Bends 364 350.10 Uses Permitted 377
342.26 Number of Bends (360°) 364 350.12 Uses Not Permitted 377
342.28 Reaming 364 350.20 Trade Size 377
342.30 Securing and Supporting 365 350.22 Number of Conductors 378
342.42 Couplings and Connectors 366 350.24 Bends 378
342.46 Bushings 367 350.26 Number of Bends (360°) 378
350.30 Securing and Supporting 378
ARTICLE 344—RIGID METAL CONDUIT (TYPE RMC) 368 350.42 Fittings 379
Partí. General 368 350.60 Grounding and Bonding 379
344.1 Scope 368
344.2 Definition 368 ARTICLE 352—RIGID POLYVINYL CHLORIDE CONDUIT
344.6 Listing Requirements 368 (TYPE PVC) 380

Part II. Installation 368 Partí. General 380

344.10 Uses Permitted 368 352.1 Scope 380
344.14 Dissimilar Metáis 369 352.2 Definition 380
344.20 Trade Size 369 Part II. Installation 380
344.22 Number of Conductors 369 352.10 Uses Permitted 380
344.24 Bends 369 352.12 Uses Not Permitted 381
344.26 Number of Bends (360°) 369 352.20 Trade Size 382
344.28 Reaming 370 352.22 Number of Conductors 382
344.30 Securing and Supporting 370 352.24 Bends 382
344.42 Couplings and Connectors 371 352.26 Number of Bends (360°) 382
344.46 Bushings 372 352.28 Trimming 382
Part IIL Construction Specifications 372 352.30 Securing and Supporting 382
344.130 Standard Lengths 372 352.44 Expansión Fittings 383

D Mike HoiVs iilustrated Guide to Understanding the 2011 National Electrical Code, Volume 1
 Table of Contents

352.46 Bushings 384 362.28 Trimming 396

352.48 Joints 384 362.30 Securing and Supporting 396
352.60 Equipment Grounding Conductor 384 362.46 Bushings 397
362.48 Joints 397
ARTICLE 356—LIQUIDTIGHT FLEXIBLE NONMETALLIC 362.60 Equipment Grounding Conductor 397
CONDUIT (TYPE LFNC) 386
Partí. General 386 ARTICLE 376—METAL WIREWAYS 398
356.1 Scope 386 Partí. General 398
356.2 Definition 386 376.1 Scope 398
356.6 Listing Requirement 386 376.2 Definition 398
Part II. installation 386 Part II. Installation 398
356.10 Uses Permitted 386 376.10 Uses Permitted 398
356.12 Uses Not Permitted 387 376.12 Uses Not Permitted 398
356.20 Trade Size 387 376.21 Conductors—Maximum Size 398
356.22 Number of Conductors 387 376.22 Number of Conductors and Ampacity 398
356.24 Bends 387 376.23 Wireway Sizing 399
356.26 Number of Bends (360°) 387 376.30 Supports 399
356.30 Securing and Supporting 387 376.56 Spiices, Taps, and Power Distribution Blocks 399
356.42 Fittings 388
ARTICLE 380—MULTIOUTLET ASSEMBLIES 401
356.60 Equipment Grounding Conductor 388
Part i. General 401
ARTICLE 358—ELECTRICAL METALLIC TUBING 380.1 Scope 401
(TYPE EMT) 389 Part II. Installation 401
PartL General 389 380.10 Uses Permitted 401
358.1 Scope 389 380.12 Uses Not Permitted 401
358.2 Definition 389 380.76 Through Partitions 401
358.6 Listing Requirement 389
ARTICLE 386—SURFACE METAL RACEWAYS 402
Part II. Installation 389
358.10 Uses Permitted 389 PartL General 402
358.12 Uses Not Permitted 390 386.1 Scope 402
358.20 Trade Size 390 386.2 Definition 402
358.22 Number of Conductors 390 386.6 Listing Requirements 402
358.24 Bends 390 Part IL Installation 402
358.26 Number of Bends (360°) 391 386.10 Uses Permitted 402
358.28 Reaming and Threading 391 386.12 Uses Not Permitted 403
358.30 Securing and Supporting 391 386.21 Size of Conductors 403
358.42 Couplings and Connectors 392 386.22 Number of Conductors 403
386.30 Securing and Supporting 403
ARTICLE 362—ELECTRICAL NONMETALLIC TUBING 386.56 Spiices and Taps 403
(TYPEENT) 393 386.60 Equipment Grounding Conductor 403
Partí. General 393 386.70 Sepárate Compartments 404
362.1 Scope 393
362.2 Definition 393 ARTICLE 392—CABLE TRAYS 405

Part II. Installation 393 Partí. General 405

362.10 Uses Permitted 393 392.1 Scope 405
362.12 Uses Not Permitted 395 392.2 Definition 405
362.20 Trade Sizes 396 Part II. Installation 405
362.22 Number of Conductors 396 392.10 Uses Permitted 405
362.24 Bends 396 392.12 Uses Not Permitted 406
362.26 Number of Bends (360°) 396 392.18 Cable Tray Installations 406

Mike Holt Enterprises, Inc. • www.MikeHolt.com • 888.NEC.C0DE (632.2633)

 Table of Contents

392.20 Cable and Conductor Installation 407 ARTICLE 406—RECEPTACLES, CORD CONNECTORS,
392.22 Number of Conductors or Cables 407 AND AHACHMENT PLUGS (CAPS) 440
392.30 Securing and Supporting 407 406.1 Scope 440
392.46 Bushed Raceway 407 406.2 Definitions 440
392.56 Cable Spiices 407 406.3 Receptacle Rating and Type 440
392.60 Equipment Grounding Conductor 408 406.4 Genera! Installation Requirements 441
392.80 Ampacity of Conductors 409 406.5 Receptacle Mounting 443
Chapter 3. Wiring Methods And Materials— 406.6 Receptado Faceplates 444
Practice Questions 410 406.7 Attachment Plugs, Cord Connectors, and Flanged Surface
Devices 445
406.9 Receptacles in Damp or Wet Locations 445
CHAPTER 4—EQUIPMENT FOR 406.11 Connecting Receptacle Grounding Terminal to
GENERAL USE 423 Equipment Grounding Conductor 447
406.12Tamper-Resistant Receptacles in Dweiling Units 447
ARTICLE 400—FLEXIBLE CORDS AND FLEXIBLE 406.13 Tamper-Resistant Receptacles in Guest Rooms and
CABLES 425 Guest Suites 447
400.1 Scope 425 406.14 Tamper-Resistant Receptacles in Child Care Facilities 447
400.3 Suitability 425
400.4 Types of Flexible Cords and Flexible Cables 425 ARTICLE 408—SWITCHBOARDS AND PANELBOARDS 448
400.5 Ampacity of Flexible Cords and Flexible Cables 425 Part I. General 448
400.7 Uses Permitted 426 408.1 Scope 448
400.8 Uses Not Permitted 427 408.3 Arrangement of Busbars and Conductors 448
400.10 Pulí at Joints and Termináis 428 408.4 Fieid Identification 450
400.14 Protection from Damage 429 408.5 Clearance for Conductors Entering Bus Enclosures 450
400.23 Equipment Grounding Conductor Identification 429 408.7 Unused Openings 450
Part IIL Panelboards 451
ARTICLE 402—FIXTURE WIRES 430
408.36 Overcurrent Protection of Panelboards 451
402.1 Scope 430
408.37 Panelboards in Damp or Wet Locations 452
402.3 Types 430
408.40 Equipment Grounding Conductor 452
402.5 Allowabie Ampacity of Fixture Wires 430
408.41 Neutral Conductor Terminations 453
402.6 Mínimum Size 430
402.7 Raceway Size 430 Part IV. Construction Specifications 454
402.8 Neutral Conductor 431 408.54 Máximum Number of Overcurrent Devices 454
402.10 Uses Permitted 431
ARTICLE 410—LUMINAIRES, LAMPHOLDERS, AND
402.11 Uses Not Permitted 431
LAMPS 455
402.12 Overcurrent Protection 431
Part L General 455
ARTICLE 404—SWITCHES 432 410.1 Scope 455
404.1 Scope 432 410.2 Definitions 455
404.2 Switch Connections 432 410.6 Listing Required 456
404.3 Switch Enclosures 434 Part IL Luminaire Locations 456
404.4 Damp or Wet Locations 434 410.10 Luminaires in Specific Locations 456
404.6 Position of Knife Switches 435 410.11 Luminaires Near Combustible Material 458
404.7 Indicating 435 410.16 Luminaires in Clothes Closets 458
404.8 Accessibility and Grouping 436 410.18 Space for Cove Lighting 459
404.9 Switch Faceplates 436 Part III. Luminaire Outlet Boxes and Covers 459
404.10 Mounting Snap Switches 438 410.22 Outlet Boxes to be Covered 459
404.11 Circuit Breakers Used as Switches 438 410.24 Connection of Electric-Discharge and LED Luminaires 459
404.12 Grounding of Enclosures 438 Part IV. Luminaire Supports 460
404.14 Rating and Use of Snap Switches 438 410.30 Supports 460
404.15 Switch Marking 439

XII Mike HolVs lllustrated Guide to Understanding the 2011 National Electrical Code, Volume 1
 Table of Contents

410.36 Means of Support 461 422.51 Cord-and-Plug-Connected Vending Machines 476

PartV. Grounding (Bonding) 462 422.52 Electric Drinking Fountains 476
410.44 Methods of Grounding 462
ARTICLE 424^FIXED ELECTRIC SPACE-HEATING
Part VI. Wiring of Luminaires 463 EQUIPMENT 477
410.50 Polarization of Luminaires 463
Part I. General 477
410.62 Cord-Connected Luminaires 463
424.1 Scope 477
410.64 Luminaires as Raceways 464
424.3 Branch Circuits 477
410.68 Conductors and Ballasts 464
424.9 Permanently Installed Electric Baseboard Heaters with
Part VIII. Installation of Lampholders 464 Receptacles 478
410,90 Screw-Shell Lampholders 464
Part III. Electric Space-Heating Equipment 478
410.96 Lampholders in Wet or Damp Locations 464
424.19 Disconnecting Means 478
410.97 Lampholders Near Combustible Material 464
PartV. Electric Space-Heating Cables 479
PartX. Recessed Luminaires 465
424.36 Clearances of Wiring in Ceilings 479
410.110 General 465
424.38 Area Restrictions 479
410.115Thermally Protected 465
424.39 Clearance from Other Objects and Openings 479
410.116 Recessed Luminaire Clearances 465
424.44 Installation of Cables in Concrete or Poured
410.117 Wiring 465
Masonry Floors 479
Part XIL Electric-Discharge Lighting 465
PartVI.Duct Heaters 479
410.130 General 465
424.65 Disconnect for Electric Duct Heater Controllers 479
Part XIV Track Lighting 467
410.151 Installation 467 ARTICLE 43(V-M0T0RS, MOTOR CIRCUITS, AND
410.154 Fastening 467 CONTROLLERS 480
Partí. General 480
ARTICLE 411—LIGHTING SYSTEMS OPERATING AT
430.1 Scope 480
30V OR LESS 468
430.2 Definitions 480
411.1 Scope 468
430.6 Table FLC versus Motor Nameplate Current Rating 481
411.2 Definition 468
430.8 Marking on Controllers 482
411.3 Listing Required 468
430.9 Motor Controller Terminal Requirements 482
411.4 Specific Location Requirements 468
430.14 Location of Motors 483
411.5 Secondary Circuits 469
430.17 The Highest Rated Motor 483
ARTICLE 422—APPLIANCES 470 Part II. Conductor Size 483
PartL General 470 430.22 Single Motor Conductor Size 483
422.1 Scope 470 430.24 Severa! Motors—Conductor Size 483
422.2 Definitions 470 430.28 Motor Feeder Taps 484
422.3 Other Articles 471 Part III. Overload Protection 484
Part II. Branch-Circuit Requirements 471 430.31 Overload 485
422.10 Branch-Circuit Rating 471 430.32 Overioad Sizing for Continuous-Duty Motors 485
422.11 Overcurrent Protection 471 430.36 Use of Fuses for Overload Protection 486
422.12 Central Heating Equipment (Furnaces) 472 430.37 Number of Overload Devices 486
422.13 Storage Water Heaters 472 Part IV. Branch-Circuit Short-Circuit and Ground-Fault
422.15 Central Vacuums 472 Protection 486
422.16 Flexible Cords 473 430.51 General 486
422.18 Support of Ceiling Paddle Fans 474 430.52 Branch-Circuit Short-Circuit and Ground-Fault
Part IIL Disconnect 474 Protection 487
422.30 General 474 430.55 Single Overcurrent Device 488
422.31 Permanently Connected Appliance Disconnects 474 PartV. Feeder Short-Circuit and Ground-Fault
422.33 Cord-and-Plug-Connected Appliance Disconnects 475 Protection 489
422.34 Unit Switches as Disconnects 475 430.62 Feeder Protection 489

Mike Holt Enterprises, Inc. • www.MlkeHolt.com • 888.NEC.C0DE (632.2633) XIII

 Table of Contents

Part VI. Motor Control Circuits 490 ARTICLE 445—GENERATORS 500

430.72 Overcurrent Protection for Control Circuits 490 445.1 Scope 500
430.73 Protection of Conductors from Physical Damage 490 445.11 Marking 500
430.75 Disconnect for Control Circuits 490 445.12 Overcurrent Protection 500
Part VII. Motor Controllers 491 445.13 Ampacity of Conductors 500
430.83 Controller Rating 491 445.18 Disconnecting Means 502
430.84 Need Not Open All Conductors of the Circuit 491 445.19 Generators Suppiying Múltiple Loads 502
430.87 Controller for Each Motor 491
ARTICLE 450—TRANSFORMERS 503
Part IX. Disconnecting Means 491
PartL General 503
430.102 Disconnect Requirement 491
450.1 Scope 503
430.103 Operation of Disconnect 493
450.3 Overcurrent Protection 503
430.104 Marking and Mounting 493
450.9 Ventilation 504
430.107 Readily Accessible 493
450.11 Marking 505
430.109 Disconnecting Means Rating 493
450.13 Transformer Accessibility 505
430.111 Combination Controller and Disconnect 493
450.14 Disconnecting Means 505
Part XIV. Tables 494
Table 430.248 Full-Load Current, Single-Phase Motors 494 ARTICLE 480—STORAGE BAHERIES 506
Table 430.250 Full-Load Current, Three-Phase Motors 494 480.1 Scope 506
480.2 Definitions 506
ARTICLE 440—AIR-CONDITIONING AND 480.3 Wiring and Equipment Supplied from Batteries 506
REFRIGERATION EQUIPMENT 495 480.4 Overcurrent Protection for Prime Movers 507
Partí. General 495 480.5 Disconnecting Means 507
440.1 Scope 495 480.8 Racks andTrays 507
440.2 Definitions 495 480.9 Battery Locations 507
440.3 Other Articles 495 Chapter 4. Equipment For General Use—
440.4 Marking on Hermetic Refrigerant Motor-Compressors and Practice Questions 509
Equipment 495
440.6 Ampacity and Rating 496
Part II. Disconnecting Means 496 FINAL EXAM A 523
440.12 Rating and Interrupting Capaclty 496
FINAL EXAMB 532
440.13 Cord-Connected Equipment 496
440.14 Location 496
Part Itl. Overcurrent Protection 497
440.21 General 497
440.22 Short-Circuit and Ground-Fault Overcurrent Device Size ...497
Part IV. Conductor Sizing 498
440.32 Conductor Size for Single Motor-Compressors 498
Part VII. Room Air Conditioners 498
440.62 Branch-Circuit Requirements 498
440.63 Disconnecting Means 498
440.64 Supply Cords 499
440.65 Leakage Current Detector-Interrupter and Arc-Fault
Circuit Interruptor 499

XIV Mike HolVs lllustrated Guide to Understanding the 2011 National Electrical Code, Volume 1
 ntroduction
Mike HolVs lllustrated Guide to Under- Keeping up with requirements of the NEC should be the goal of every-
one involved in the safety of electrical installations. This includes elec-
standing the National Electrical Code,
trical installers, contractors, owners, inspectors, engineers, instructors,
Volume 1 and others concerned with eléctrica! installations.

This edition of Mike Holt's Iflustrated Guide to Understanding the

National Electrical Code, Volume 1 textbook is intended to provide you
with the tools necessary to understand the technicai requirements of About the 2011 NEC
the National Electrical Code (NEC)®. The writing style of this textbook,
and in all of Mike Holt's products, is meant to be informativo, practi- The actual process of changing the Code takes about two years, and
cal, useful, informal, easy to read, and applicabie for today's electri- it involves thousands of individuáis making an effort to have the NEC
cal professional. Just like all of Mike Hott's textbooks, this textbook as current and accurate as possible. Let's review how this process
contains hundreds of full-color illustrations to help you see the safety works:
requirements of the NEC in practical use, helping you visuaüze the Step 1. Proposals—November, 2008. Anybody can submit a pro-
Code in today's electrical installations. posal to change the Code before the proposal closing date. Over
This iilustrated textbook contains cautions regarding possible con- 5,000 proposals were submitted to modify the 2011 NEC. Of these
flicts or confusing Code requirements, tips on proper electrical proposals, over 300 rules were revised that significantly effect the
installations, and warnings of dangers related to improper electri- electrical industry. Some changes were editorial revisions, while
cal installations. In spite of this effort, some rutes may seem to be others were more significant, such as new articles, sections, excep-
unclear or need additional editorial improvement. tions, and Informational Notes.

This textbook can't elimínate confusing, conflicting, or controver- Step 2. Cotfe-Making Panel(s) Review Proposals—January, 2009.
sia! Code requirements, but we do try to put these requirements All Code proposals were reviewed by Code-Making Panels. There
into sharper focus to help you understand their intended purpose. were 19 panels in the 2011 Code process who voted to accept, reject,
Sometimes a requirement is so confusing nobody really understands or modify them.
its actual application. When this occurs, we'll point the situation out in Step 3. Report on Proposals (ROP)—July, 2009. The voting of the
an up-front and straightforward manner. We apologize in advance if Code-Making Panels on the proposals was published for public review
that ever seems disrespectful, but our intention is to help the industry in a document called the "Report on Proposals," frequently referred to
understand the current NEC as best as possible, point out áreas that as the "ROP."
need refinement, and empower Code users to be a part of the pro-
Step 4. Public Comments—October, 2009. Once the ROP was avail-
cess of chango to créate a better NEC tor the future.
able, public comments were submitted asking the Cocfe-Making Panel
The NECis updated every three years to accommodate new electrical members to revise their eariier actions on change proposals, based on
products and materials, changing technologies, improved installation new information. The closing date for "Comments" was October, 2009.
techniques, and make editorial improvements to improve readability.
Step 5. Comments Reviewed by Code Panels—December, 2009.
While the uniform adoption of each new edition of the Code is the
The Cocíe-Making Panels met again to review, discuss, and vote on
best approach for all involved in the electrical industry, many inspec-
public comments.
tion jurisdictions modify the NEC when it's adopted. To further com-
plícate this situation, the Code allows the authority having jurisdiction Step 6. Report on Comments (ROC)—April, 2010. The voting on the
(AHJ) the authority to waive NEC requirements or permit aiternative "Comments" was published for public review in a document called the
wiring methods contrary to Code requirements. This is only allowed "Report on Comments," frequently referred to as the "ROC."
when the compieted electrical installation is assured to provide an
Step 7. Electrical Section—June, 2010. The NFPA Electrical Section
equivalent level of safety [90.4].
discussed and reviewed the work of the Cocfe-Making Panels. The

Mike Holt Enterprises, Inc. • www.MlkeHolt.com • 888.NEC.C0DE (632.2633) XV

Electrical Section developed recommendations on tast-minute • Conductor Material. All conductors are considered copper,
motions to revise the proposed /VECdraft that would be presented at unless aluminum is identihed or specified.
the NFPA annual meeting.
• Conductor Sizing. All conductors are sized based on a THHN
Step 8. NFPA Annual Meeting—June, 2010. The 2011 NEC was copper conductor terminating on a 75°C terminal in accor-
voted by the NFPA members to approve the action of the Code- dance with 110.14(0(1). unless the question or example
Making Panels at the annual meeting, after a number of motions identifies otherwise. t.
(often called "floor actions") were voted on.
• Overcurrent Device. The term "overcurrent device" in this
Step 9. Standards CounctI Review Appeals and Approves the textbook refers to a molded case circuit breaker, unless iden-
2011 NEC—Mi, 2010. The NFPA Standards Council reviewed the tified otherwise. If a fuse is identified in the text, it's to be
record of the Code-making process and approved publication of the of the single-element type, aiso known as a "one-time tuse,"
2011 NEC unless identified otherwise.
Step 10. 2011 NEC Published—September, 2010. The 2011
National Electrical Code was published, following the NFPA Board of
Directors review of appeals.
Mike Holt's Detailed
Author's Comment: Proposals and comments can be sub- iVfCLibrary
mitted oniine at the NFPA Website {www.nfpa.org). From
the homepage, click on "Codes and Standards" at the top of If you want to really understand the
the page, then from the Codes and Standards page click on 2011 National Electrical Code, then }
"Proposals and Comments" in the box on the right-hand side of Mike Holt's Detailed Code Library
the page. The deadline for proposals to créate the 2014 National is ideal for you. This program covers
Eléctrica! Code is November 5, 2011. If you would like to see general installation requirements, branch circuits, teeders, services
something changed in the Code, you're encouraged to particí- and overcurrent protection, grounding and bonding, conductors,
pate ín the process. cables and raceways, boxes, panels, motors, transformers, and much
more. Summary questions are included in all books to help you test
your knowledge.

This program includes 3 textbooks and 10 DVDs:

The Scope of this Textbook
• Understanding the National Electrical Code Volume 1 textbook
This textbook, Understanding the National Electrical Code, Volume 1, • Understanding the National Electrical Code Volume 2 textbook
covers the general installation requirements that Mike considers to • NEC Exam Practice Questions book
be of critical importance in Articles 90 through 480 [NEC Chapters 1 • General Requirements Part 1 DVD and Part 2 DVD
through 4). This textbook is written with these stipulations: • Grounding vs. Bonding Part 1 DVD and Part 2 DVD
• Power Systems and Voltage. All power-supply systems • Wiring Methods Part 1 DVD and Part 2 DVD
are assumed to be solidly grounded ac such as: 120V sin- • Equipment for General Use DVD
gle-phase, 120/240V single-phase, 120/208V three-phase, • Special Occupancies DVD
120/240V three-phase, or 277/480V three-phase, unless • Special Equipment DVD
identified otherwise. • Limited Energy and Communication Systems DVD

• Eléctrica! Calculations. Unless the question or example

specifies three-phase, the questions and examples are based Order Mike Holt's Detailed Code Library by
on a single-phase power supply. calling 888.NEC.C0DE (632.2633) or visiting
www.MikeHolt.com
• Rounding. All calculations are rounded to the nearest ampere
in accordance with 220.5(B). What is the QR code above? See page xviii.

XVJ Mike HolVs lllustrated Guide to Understanding the 2011 National Electrical Code, Volume 1
 About This Textbook
This textbook is to be used along with the NEC, not as a replace- We hope that as you read through this textbook, you'll allow suffi-
ment for it, so be sure to have a copy of the 2011 National Electrical cient time to review the text along with the outstanding graphics and
Code handy Compare what Mike is explaining in this book to what examples, which are invaluable to your understanding.
the Code book says, and discuss any topics that you find difficult to
understand with others.

You'll notice that in this book, a great dea! of the NEC wording has Textbook Format
been paraphrased, and some of the article and section titles appear
different from the wording in the actual Code. Mike believes doing so This textbook follows the A/ECformat, but it doesn't cover every Code
makes it easier to understand the content of the rule, so keep this in requirement. For example, it doesn't include every article, section,
mind when comparing this textbook against the actual NEC. subsection, exception, or Informational Note. So don't be concerned
if you see the textbook contains Exception 1 and Exception 3, but not
Exception 2.

Important Features for the 2011 Edition of This Textbook

In order to better meet the needs of our customers, we have improved the layout of this textbook with some new feaures, in addition to the
features from the 2008 edition which were so successful. These features include:

Special Sections which contain additional information

to better help you understand a concept are identified
with a light gray background and colored frame.

Graphics that contain a 2011 Code change will have a

green border with a green 2011 CC icón
next to the heading.

Any /VfC changes will be in green underlined text in all

graphics. tf you see a green bordered graphic with no
green underlined text, it most likely indicates that the
Code change is the removal of some text. Graphics
without a color border support the concept being dis-
cussed, but nothing in the graphic was affected by a
change for 2011.

Any 2011 Code is denoted by underlined text and in the

corresponding chapter color. For example, in Chapter 1
the change text will be red and underlined; Chapter 2
the change text will be cyan and underlined, and so on.
Examples or practical application questions with their
answer and solution have a light yellow background.

Mike Holt Enterprises, Inc. • www.MikeHolt.com • 888.NEC.C0DE (632.2633) xvi I

 About This Textbook

Cross-References and Author's Comments QR Codes

Cross References. This textbool< contains several NEC cross- B Ú ^ B ^^3^ 's this? It is a QR Code and gives you the abil-
references to other related Code requirements to hefp you develop ity to use your smartphone to take a photo (using a
a better understanding of how the NEC rules relate to one another. barcode reader app) and be directed to a website. For
These cross-references are indicated by Code section numbers in example, the QR Code to the left when captured will
brackets, an example of which is "[90.4]." direct your smartphone to the Mike Holt Enterprises
website. We have included these in various places in our book to
Author's Comments. "Author's Comments," written by Mike, are
make it easier for you to go directly to the website page referenced.
intended to help you understand the NEC material, and to bring to
!n order to use a QR code, you will need an app for your phone that
your attention things of which you should be aware.
allows your phone to read this barcode. Your phone may already
have the ability to sean this barcode, but if not visit the website
www.mobile-barcodes.com/qr-code-sofhware for more information.
Difficult Concepts

As you progress through this textbook, you might find that you don't
understand every explanation, example, calculation, or comment. Textbook Errors and Corrections
Don't become frustrated, and don't get down on yourself. Remember,
Humans develop the text, graphics, and layout of this textbook, and
this is the National Electrical Code and sometimes the best attempt
since currently none of us are pertect, there may be a few errors. This
to exptain a concept isn't enough to make it perfectly clear. If you're
can occur because the NEC\s dramaticaliy changed each Code cyc\e;
still confused, visit www.MikeHolt.com, and post your question on the
new articles are added, some are deleted, some are relocated, and
Code Forum for help.
many are renumbered. We take great care in researching the NEC
requirements to ensure this textbook is correct. If you believe there's
an error of any kind in this textbook (typographical, grammatical,
Different interpretations
technicai, or anything else), no matter how insignificant, please let us

Some electricians, contractors, instructors, inspectors, engineers, and know.

others enjoy the challenge of discussing the A/fC requirements, hope- Any errors found after printing are listed on our
fully in a positivo and productivo manner This give-and-take is impor- Website, so if you find an error, first check to see if
tant to the process of better understanding the Code requirements it's already been corrected. Go to www.MikeHolt.com,
and application. However, if you're going to get into an NEC discus- click on the "Books" link, and then the "Corrections"
sion, please don't spout out what you think without having the actual link {www.MikeHolt.com/bookcorrections.htm).
Code book in your hand. The professional way of discussing an NEC
requirement is by referring to a specific section, rather than taiking in If you don't find the error listed on the Website, contact us by sending
vague generalities. an E-mail to Corrections@MikeHolt.com. Be sure to include the book
title, page number, and any other pertinent information.

You TUbe

Visit the Mike Holt channel on YouTube to see video

clips that accompany this and our other 2011 books
{wv\/w.youtube.com/user/MikeHoltNEC).

XVIII Mike HolVs lllustrated Guide to Understanding the 2011 National Electrical Code, Volume 1
 How to Use the
National Electrical Code
The National Electrical Code is written for persons who understand article. For example, Section 250.2 contains the definitions of terms
electrical terms, theory, safety procedures, and electrical trade prac- that only apply to Article 250—Grounding and Bonding.
tices. These individuáis include electricians, electrical contractors,
electrical inspectors, electrical engineers, designers, and other qual-
ified persons. The Code isn't written to serve as an instructivo or
Small Words, Grammar, and Punctuation
teaching manual for untrained individuáis [90.1 (C)].

Learning to use the NEC is like learning to play the game of chess; It's not only the technicai words that require cióse attention, because
it's a great game if you enjoy mental warfare. When learning to play even the simplest of words can make a big difference to the applica-
chess, you must first learn the ñames of the game pieces, how the tion of a rule. The word "or" can imply altérnate cholees for equipment
pieces are placed on the board, and how each piece moves. wiring methods, while "and" can mean an additional requirement.
Let's not forget about grammar and punctuation. The location of a
Once you understand the fundamentáis, you're ready to start play-
comma can dramaticaliy change the requirement of a rule.
ing the game. Ünforíunately, at this point all you can do is make crude
moves, because you really don't understand how all the information
works together. To play chess well, you'll need to learn how to use
your knowledge by working on sub-tle strategies before you can work Slang Terms or Technicai Jargon
your way up to the more intriguing and complicated moves.
Electricians, engineers, and other trade-related professionals use
slang terms or technicai jargon that isn't shared by all. This makes it
very difficult to communicate because not everybody understands the
Not a Game
intent or application of those slang terms. So where possible, be sure
you use the proper word, and don't use a word if you don't under-
Electrical work isn't a game, and it must be taken very seriously.
stand its definition and application. For example, lots of electricians
Learning the basics of electricity, important terms and concepts, as
use the term "pigtail" when describing the short conductor for the
well as the basic layout of the NEC gives you just enough knowledge
connection of a receptacle, switch, luminaire, or equipment. Although
to be dangerous. There are thousands of specific and unique applica-
they may understand it, not everyone does.
tions of electrical installations, and the Code doesn't cover every one
of them. To safely apply the NEC, you must understand the purpose of
a rule and how it affects the safety aspects of the installation.
NEC Styie and Layout

fffC Terms and Concepts Before we get into the details of the NEC, we need to take a few
moments to understand its style and layout. Understanding the struc-
The NEC contains many technicai terms, so it's crucial for Code users ture and writing style of the Code is very important before it can be
to understand their meanings and their applications. If you don't used and applied effectively. The National Electrical Code is organized
understand a term used in a Code rule, it will be impossibie to properly into ten major components.
apply the NEC requirement. Be sure you understand that Article 100
1. Table of Contents
defines the terms that apply to two or more Code articles. For example,
2. Article 90 (Introduction to the Code)
the term "Dweiling Unit" is found in many articles; if you don't know
3. Chapters 1 through 9 (major categories)
what a dweiling unit is, how can you apply the requirements for it?
4. Articles 90 through 840 (individual subjects)
In addition, many articles have terms unique for that specific arti- 5. Parts (divisions of an article)
cle and definitions of those terms are only applicabie for that given 6. Sections and Tables [Code requirements)

Mike Holt Enterprises, Inc. • www.MikeHott.com • 888.NEC.C0DE (632.2633) XIX

 How to Use the NEC

7. Exceptions {Code permissions) 5. Parts. Larger articles are subdivided into parts.
8. Informational Notes (explanatory material)
Because the parts of a Code article aren't included in the sec-
9. Annexes (information)
tion numbers, we have a tendency to forget what "part" the NEC
10. Index
rule is relating to. For example, Table 110.34(A) contains working
1. Table of Contents. The Table of Contents displays the layout of space clearances for electrical equipment. If we aren't careful, we
the chapters, articles, and parts as well as the page numbers. It's an might think this table applies to all electrical installations, but Table
excellent resource and should be referred to periodicaliy to observe 110.34(A) is located in Part lil, which only contains requirements for
the interrelationship of the various NEC components. When attempt- "Over 600 Volts, Nominal installations." The rules for working clear-
ing to lócate the rules for a particular situation, knowledgeable Code ances for electrical equipment for systems 600V, nominal, or less are
users often go first to the Table of Contents to quickly find the specific contained in Table 110.26(A)(1), which is located in Part 11—600 Volts,
NEC Pan that applies. Nominal, or Less.

6. Sections and Tables.

2. Introduction. The NEC begins with Article 90, the introduction to
the Code. It contains the purpose of the NEC, what's covered and Sections. Each NEC rule is called a "Code Section." A Code section
what isn't covered along with how the Code is arranged. It aiso gives may be broken down into subsections by letters in parentheses (A), (B),
information on enforcement and how mandatory and permissive rules and so on. Numbers in parentheses (1), (2), and so forth, may further
are written as well as how explanatory material is included. Article break down a subsection, and lowercase letters (a), (b), and so on, fur-
90 aiso includes information on formal interpretations, examination of ther break the rule down to the third level. For example, the rule requir-
equipment for safety, wiring planning, and information about format- ing all receptacles in a dweiling unit bathroom to be GFCI protected
ting units of measurement. is contained in Section 210.8(A)(1). Section 210.8(A)(1) is located in
Chapter 2, Article 210, Section 8, Subsection (A), Sub-subsection (1).
3. Chapters. There are nine chapters, each of which is divided into arti-
cles. The articles fall into one of four groupings: General Requirements Many in the industry incorrectly use the term "Article" when referring
to a Code section. For example, they say "Article 210.8," when they
(Chapters 1 through 4), Specific Requirements (Chapters 5 through 7),
should say "Section 210.8." Section numbers in this book are shown
Communications Systems (Chapter 8), and Tables (Chapter 9).
without the word "Section," unless they begin a sentence. For exam-
Chapter 1 General ple, Section 210.8(A) is shown as simply 210.8(A).
Chapter 2 Wiring and Protection
Tables. Many Code requirements are contained within tables, which
Chapter 3 Wiring Methods and Materials
are lists of NEC requirements placed in a systematic arrangement.
Chapter 4 Equipment for General Use
The titles of the tables are extremely important; you must read them
Chapter 5 Special Occupancies
carefully in order to understand the contents, applicahons, limitations,
Chapter 6 Special Equipment
and so forth, of each table in the Code. Many times notes are provided
Chapter 7 Special Conditions
in or below a table; be sure to read them as well since they're aiso
Chapter 8 Communications Systems (Telephone, Data, Satellite, part of the requirement. For example, Note 1 for Table 300.5 explains
Cable TV and Broadband) how to measure the cover when burying cables and raceways, and
Chapter 9 Tables-Conductor and Raceway Specifications Note 5 explains what to do if solid rock is encountered.
4. Articles. The NEC contains approximately 140 articles, each of 7. Exceptions. Exceptions are Code requirements or permissions
which covers a specific subject. For example: that provide an aiternative method to a specific requirement. There
are two types of exceptions—mandatory and permissive. When a rule
Article 110 General Requirements
has several exceptions, those exceptions with mandatory require-
Article 250 Grounding and Bonding
ments are listed before the permissive exceptions.
Article 300 Wiring Methods
Article 430 Motors and Motor Controllers Mandatory Exceptions. A mandatory exception uses the words
Article 500 Hazardous (Classified) Locations "shall" or "shall not." The word "shall" in an exception means that if
Article 680 Swimming Pools, Fountains, and Similar Installations you're using the exception, you're required to do it in a particular way.
Article 725 Remote-Control, Signaling, and Power-Limited Circuits The phrase "shall not" means it isn't permitted.

Article 800 Communications Circuits

XX Mike HoiVs Iliustrated Guide to Understanding the 2011 Nationai Electrical Code, Volume 1
 How to Use the NEC

I can quickly go to the Table of Contents and see it lists the Service
Permissive Exceptions. A permissive exception uses words such as
Equipment Disconnecting Means requirements in Part VI.
"sha!! be permitted," which means it's acceptable (but not mandatory)
to do it in this way.
Author's Comment: The number 70 precedes all page num-
8. informational Notes. An informational Note contains explana-
bers because the NECls NFPA Standard Number 70.
tory material intended to clarify a rule or give assistance, but it isn't a
Code requirement. Index. If you use the Index, which lists subjects in alphabetical order,
to look up the term "service disconnect," you'll see there's no listing.
9. Annexes. Annexes aren't a part of the NEC requirements, and are
If you try "disconnecting means," then "services," you'll find that the
included in the Code ior informational purposes only.
Index specifies that the rule is located in Article 230, Part VI. Because
Annex A. Product Safety Standards the NEC doesn't give a page number in the Index, you'll need to use
AnnexB. Application Information for Ampacity Calculation the Table of Contents to find the page number, or flip through the
Annex C. Raceway Pili Tables for Conductors and Fixture Wires of Code to Article 230, then continué to flip through pages until you find
the Same Size Part VI.
Annex D. Examples
Many people complain that the NEC only confusos them by taking
Annex E. Types of Construction
them in circles. As you gain experience in using the Code and deepen
Annex F. Critical Operations Power Systems (COPS)
your understanding of words, terms, principies, and prácticos, you'll
Annex G. Supervisory Control and Data Acquisition (SCADA)
hnd the NEC much easier to understand and use than you originatly
Annex H. Administration and Enforcement
thoughL
Annex I. Recommended Tightening Torques

10. Index. The Index at the back of the NEC is helpful in locating a
specific rule.
Gustomizing Your Code Book
Changes to the NEC since the previous edition(s), are identified by
shading, but rules that have been relocated aren't identified as a One way to increase your comfort level with the Code is to custom-
change. A bullet symbol "•" is located on the margin to indícate the ize it to meet your needs. You can do this by highiighting and under-
location of a rule that was deleted from a previous edition. New arti- lining important A/fC requirements, and by attaching tabs to important
cles contain a vertical line in the margin of the page. pages. Be aware that if you're using your Code book to take an exam,
some exam centers don't allow markings of any type.

Highiighting. As you read through this textbook, be sure you highlight

How to Lócate a Specific Requirement those requirements in the Code that are the most important or rele-
vant to you. Use yellow for general interest and orange for important
How to go about finding what you're looking for in the Code depends, requirements you want to find quickly. Be sure to highlight terms in
to some degree, on your experience with the NEC Code experts typ- the Index and the Table of Contents as you use them.
ically know the requirements so well they just go to the correct rule
Underlining. Underline or circle key words and phrases in the NEC
without any outside assistance. The Table of Contents might be the
with a red pen (not a lead pencil) and use a 6-inch ruler to keep
only thing very experienced NEC users need to lócate the requirement
lines straight and neat. This is a very handy way to make important
they're looking for. On the other hand, average Code users should use
requirements stand ouL A small 6-inch ruler aiso comes in handy for
all of the tools at their disposal, inciuding the Table of Contents and
locating specific information in the many Corfe tables.
the Index.
Tabbing the NEC. By placing tabs on Code articles, sections, and
Table of Contents. Let's work out a simple example: What NEC rule
tables, it will make it easier for you to use the NEC. However, too
specifies the máximum number of disconnects permitted for a ser-
many tabs will defeat the purpose. You can order (¡jj^jj^g
vice? If you're an experienced Code user, you'll know Article 230
a set of Code tabs designed by Mike Holt oniine at
applies to "Services," and because this article is so large, it's divided
www.MikeHolt.com, or by calling 1.888.NEC.C0DE ^ ^ ^ S
up into múltiple parts (actuaily eight parts). With this knowledge, you
(632.2633). H ^ © 2

Mike Holt Enterprises, Inc. • www.MIkeHolt.com • 888.NEC.C0DE (632.2633) XXI

 About the Author
Mike Hon IMike HoH—Special Acknowledgments

Mike Holt worl^ed bis way up through the elec- First, 1 want to thank God for my godly wife who's always by my side
trical trade from an apprentice electrician to and my children, Belynda, Melissa, Autumn, Steven, Michael, Meghan,
become one of the most recognized experts and Brittney.
in the world as it relates to eléctrica! power
A special thank you must be sent to the staff at the National Fire
installations. He has wori^ed as a journey-
Protection Association (NFPA), publishers of the NEC—\n particu-
man electrician, master electrician, and
lar Jeff Sargent for his assistance in answering my many Code ques-
electrical contractor. Mike's experience in
tions over the years. Jeff, you're a "first class" guy, and l admire your
the real world gives him a unique understand-
dedication and commitment to helping others understand the NEC.
ing of how the NEC relates to electrical instal-
Other former NFPA staff members l would like to thank include John
lations from a practical standpoint. You'll find his writing style to be
Caloggero, Joe Ross, and Dick Murray for their help in the past.
direct, nontechnical, and practical.
A personal thank you goes to Sarina, my long-time friend and office
Did you know that he didn't finish high school? So if you struggled in
manager. It's been wonderful working side-by-side with you for over
high school or if you didn't finish it at all, don't let this get you down,
25 years nurturing this company's growth from its small beginnings.
you're in good company. As a matter of fact, Mike Culbreath, Master
Electrician, who produces the finest electrical graphics in the his-
tory of the electrical industry didn't finish high school either. So two
high school dropouts produced the text and graphics in this textbook!
However, realizing success depends on one's continuing pursuit of
education. Mike immediately attained his GED (as did Mike Culbreath)
and ultimately attended the University of Miami's Gradúate School for
a Master's degree in Business Administration (MBA).

Mike Holt resides in Central Florida, is the father of seven children,

and has many outside interests and activities. He's a six-time National
Barefoot Water-Ski Champion (1988, 1999, 2005, 2006. 2007, and
2008), has set many nationai records, has competed in three World
Championships (2006, 2008, and 2010) and continúes to train and
work out year-round so that he can qualify to ski in the 2012 World
Barefoot Championships at the age of 61!

What sets him apart from some, is his commitment to living a bai-
anced lifestyle; placing God first, family, career, then self.

xxii Mike HoiVs lllustrated Guide to Understanding the 2011 National Electrical Code, Volume 1
 About the Graohic Illustrator
Mike Culbreath Special Acknowledgments

Mike Culbreath devoted his career to the I want to thank my wonderful children, Dawn and Mac, who have had
electrical industry and worked his way up to put up with me during the Code revisión seasons.
from an apprentice electrician to master
I would like to thank Steve Ame, our amazing technicai editorial direc-
electrician. While working as a journeyman
tor, Eric Stromberg, an etectricat engineer and super geek (and I mean
electrician, he suffered a serious on-the-job knee injury. With a keen
that in the most complimentary manner, this guy is brilliant), and Ryan
interest in continuing education for electricians, he compieted courses
Jackson, an outstanding and very knowledgeable code guy, for help-
at Mike Holt Enterprises, Inc. and then passed the exam to receive
ing me keep our graphics as technically correct as possible.
his Master Electrician's license. In 1986, after attending classes at
Mike Holt Enterprises, Inc., he joined the staff to update material and 1 aiso want to give a special thank you to Cathleen Kwas for making
later studied computer graphics and began iilustrating Mike Holt's me look good with her outstanding layout design and typesetting
textbooks and magazine articles. He's worked with the company for skills. I would aiso like to acknowledge Belynda Holt Pinto, our Chief
almost 25 years and, as Mike Holt has proudty acknowledged, has Operations Officer and the rest of the outstanding staff at Mike Holt
heiped to transform his words and visions into lifelike graphics. Enterprises, for all the hard work they do to help produce and distrib-
ute these outstanding products.

And last but not least, I need to give a special thank you to Mike Holt
for not firing me about 25 years ago when I "borrowed" one of his
computers and took it home to begin the process of learning how
to do computer illustrations. He gave me the opportunity and time
needed to develop my computer graphic skiils. He's been an amaz-
ing friend and mentor since I met him as a student many years ago.
Thanks for believing in me and allowing me to be part of the Mike
Holt Enterprises family.

Mike Holt Enterprises, Inc. • www.MikeHolt.com • 888.NEC.C0DE (632.2633) XXII!

 ke Holt
Enterprises Team
Editorial Team Steve has worked for Mike Holt as a technicai editor and video team
participant since 2002, and used Mike Holt's books in his classes for
I want to ttiank Toni Culbreath and Barbara Parks wtio worked tire- a number of years before that. Steve is very thankful to have been
lessly to proofread and edit the final stages of this publication. Their associated with an industry leader like Mike who provides excellent
attention to detall and dedication to this project is greatly appreciated. training products to help students progress in the electrical industry.
Steve has been active in the South Dakota Electrical Council, serving
on the Board of the Black Hills Chapter in various capacities and is the
Production Team current Chapter President.

Steve and his wife Deb live in Rapid City, S.Dak. where they're both
I want to thank Cathleen Kwas who did the layout and production of
active in their church and community, and love to spend time with
this book. Her desire to créate the best possible product for our cus-
their children and grandchildren. Most of all, Steve and Deb both
tomers is greatly appreciated.
endeavor to put God first in their lives and in their home.

Video Team Members Víctor M. Ammons

Electrical Department Manager
The following special persons provided assistance in the development
TMG Engineers, Inc.
of this textbook; particularly in ensuring that the technicai content is
Edison, New Jersey
accurate. In addition, they all provided outstanding technicai advice
tmg-engrcom
as they served on the video team along with author Mike Holt and a
guest appearance by graphic illustrator Mike Culbreath. Víctor Ammons was born in North Carolina,
but has lived primarily in New Jersey since
the age of five. He spent his high school and college vacation times
Steve Ame working in a small, family-owned electrical contracting firm. Vio mar-
Technicai Training Consultant ried Anne, his high school sweetheart, after his sophomore year at
Arne Electro Tech North Carolina State University, from which both graduated with
Rapid City. S.Dak. honors two years later. After four years in the Army, during which time
ElectricalMaster.com their first child was born in Germany, Vic and Anne alternated get-
ting MBA degrees. They now have three married children and three
Steve Ame has worked in various posi- grandchildren.
tions in the electrical industry since
1974 inciuding electrician, electrical contractor, full-time instructor, Vic is a licensed electrical contractor and has spent several years
and department chair in technicai postsecondary education. running the family contracting business while his father's health
Steve has developed and taught curriculum for many elec- declined. He later trained and turned the business over to his brother-
trical training courses as well as university business and in-law and then returned to the engineering field. Vic is a registered
leadership courses. He's compieted a Bachelor's degree in Tech- Professional Engineer in New Jersey, is LEED accredited, and has
nicai Education and a Master's degree in Administrativo Studies. served in several officer positions for the local branch of the National
Currently, he provides electrician exam prep and continuing education Professional Engineers Society. He is now the Electrical Department
Corfe classes in South Dakota, Wyoming, and surrounding states using Manager for TMG Engineers in Edison, New Jersey.
Mike Holt's textbooks and material. He enjoys seeing a student's "lights
Vic now resides in west central New Jersey in an área with a few
come on" as they come to a point of understanding and have the "ah-
dozen families among nearly a thousand acres of woodlands. Yes,
ha" experience of learning something new.
there are still woodlands in New Jersey; they haven't gotten around

xxiv Mike HolVs Iliustrated Guide to Understanding the 2011 National Electrical Code, Volume 1
 Mike Holt Enterprises Team

to paving them all yet. Vic and Anne celebrated their anniversary work for Dow Chemical where he designed power distribution sys-
in 2010, are avid square and round dancers, and are active in sev- tems for major industrial complexos in the U.S., Spain, Brazil, and
eral clubs. He's aiso an amateur beekeeper. Both are active in several Germany. Eric was very involved in both creating Electrical standards
capacities in their church. and procedures as well as checking existing standards and proce-
dures for alignment with nationai standards.

Ryan Jackson He aiso worked as a Construction Manager where he ensured Code

Electrical Inspector compliancy of installations as well as provided field engineering sup-
Draper City, Ut port. Eric currently has his own business and spends a good deal of
WestValley City, UT time teaching classes in both the National Electrical Code and electri-
cal circuits. He is aiso a member of the Electrical Safety and Licensing
Ryan Jackson is a combination inspector Advisory Board for the State of Texas.
in the Sait Lake City, Utah, área. He began Eric lives in Lake Jackson, Texas, with his wife Jane. They have three
doing electrical work at the age of 18. At the age of 23 Ryan landed children: Ainsley, Austin, and Brieanna. Ainsley is a teacher in Boston
his first job as an electrical inspector, and subsequently became cer- who will be getting married in the summer of 2011. Austin will be
tified in building, plumbing, and mechanical inspection (commercial enlisting in the Air Forcé, and Brieanna started college in the Fall of
and residential), as well as building and eléctrica! plan review. Two 2010.
years after becoming an inspector, he was approached by a friend in
the área asking him to fill in at an electrical seminar for him. After his
first class he was hooked, and is now a highiy sought-after seminar J. Kevin Vogel
instructor. Ryan has taught in several states, and loves helping people Professional Engineer/Instructor
increase their understanding of the Code. Crescent Electric Supply
Coeurd'Alene,ID
In 2005, Ryan met Mike Holt in SaIt Lake City, and they became
www.cesco.com and www.trindera.com.
friends immediately. He helped Mike with his Understanding ttie NEC,
l/o/ume 2 videos and began editing his books as well. Ryan believes
Kevin Vogel graduated from Santa Clara
that there are only a small handful of opportunities that change a per-
University in 1964 with a Bachelor of Science degree in Mechanical
son's life and career, and meeting Mike was one of them.
Engineering. A licensed Professional Engineer since 1969, he worked
Ryan can often be found in his garage turning wood on his lathe, and as Chief Engineer for a división of Square D Company that manufac-
in the autumn you'll find him at as many University of Utah football tured electric heaters and thermoplastic outlet boxes. He aiso was
games as he can attend, which is typically all of them. Ryan married employed as an electrician and holds a Master Electrician's license.
his high school sweetheart, Sharie, and they have two beauíiful chil-
In 1978, Kevin co-founded an electrical Wholesale distribution busi-
dren together: Kaitiynn and Aaron.
ness that was acquired in 1991 by Crescent Electric Supply Company.
Kevin continúes to work in that part of the industry, and is a certi-
fied instructor for National Electrical Code classes in the states of
Eric Stromberg
Idaho and Washington. He aiso serves as a consultant to Trindera
Electrical Engineer/Instructor
Engineering, an electrical engineering firm located in Coeur d'Alene.
Stromberg Engineering, Inc.
Lake Jackson, TX Kevin and his beloved wife Linda have been married since 1966, and
www.strombergengineering.com have been blessed with 13 wonderful children and 20 (so far) grand-
children. Kevin is extremely grateful to God for all of the gifts He has
Eric Stromberg started in the Electrical field bestowed on him and his loved ones.
by working as a journeyman electrician for a
small contractor in the Houston área while going to college pursu-
ing a degree in Electrical Engineering. After graduation, in 1982, Eric
worked as an electronic technician where he installed and maintained
life safety control systems in high rise buildings. In 1989, Eric went to

Mike Holt Enterprises, Inc. • Www.MikeHolt.com • 888.NEC.C0DE (632.2633) XXV

Notes

xxvi Mike HoiVs iliustrated Guide to Understanding the 2011 National Electrical Code, Volume 1
 90.2 Introduction to ttie National Electrical Code

Note: Hazards in electrical systems often occur because circuits are Author's Comments:
overloaded or not properly installed in accordance witli tiie NEC.
Tiiese often occur if the initial wiring didn't provide reasonable provi- • See the definition of "Overcurrent" in Article 100.
sions for system changes or for the increase in the use of electricity. • The NEC is used in Chile, Ecuador, Perú, and the Philippines.
It's aiso the electrical code for Colombia, Costa Rica, México,
Author's Comments: Panamá, Puerto Rico, and Venezuela. Because of these adop-
• See the definition of "Overload" in Article 100. tions, the NEC is available in Spanish from the National Fire
Protection Association, 617.770.3000, or www.NFPA.Org.
• The /VECdoesn't require electrical systems to be designed or
installed to accommodate future loads. However, the electri-
cal designer, typically an electrical engineer, is concerned with 90.2 Scope oíXheMEC
not only ensuring electrical safety (Code compliance), but aiso
with ensuring the system meets the customers' needs, both (A) What Is Covered. The NEC contains requirements necessary for
of today and in the near future. To satisfy customers' needs, the proper installation of electrical conductors, equipment, and race-
electrical systems are often designed and installed above the ways; signaling and communicahons conductors, equipment, and
mínimum requirements contained in the NEC. But just remem- raceways; as well as optical fiber cables and raceways for the follow-
ber, if you're taking an exam, licensing exams are based on ing locations; Figure 90-3
your understanding of the mínimum Code requirements.

(C) Intention. The Code is intended to be used by those skilled and Scope of the NEC
knowledgeable in electrical theory, electrical systems, construction, 90.2(A)
Warehouse
and the installation and operation of electrical equipment. It isn't a
design specification standard or instruction manual for the untrained
and unqualified. Bu\^jness Office

(D) Relatíon to International Standards. The requirements of the

NEC address the fundamental safety principies contained in the
International Electrotechnical Commission (lEC) standards, inciuding
protection against electric shock, adverse thermal effects, overcur-
The NEC covers the installation of power, lighting,
rent, fault currents, and overvoltage. Figure 90-2
signaling, and Communications conductors, cables,
equipment. and raceways; and optical fiber cables
and raceways for both indoor and outdoor applications.

NEC Relation to International Standards

90.1(D) and Note
Figure 90-3
The NEC addresses the safety principies
contained in the lEC such as:
• Protection against electric shock (1) Public and private premises, inciuding buildings or structures,
• Adverse thermal effects mobile homes, recreational vehicles, and floahng buildings.
• Overcurrent
• Fault currents (2) Yards, lots, parking lots, carnivals, and industrial substations.
• Overvoltage
(3) Conductors and equipment connected to the utility supply

(4) Installations used by an electric utility, such as office buildings,

warehouses, garages, machine shops, recreational buildings, and
other electric utility buildings that aren't an integral part of a utili-
ty's generating plant, substation, or control centén Figure 90-4

Figure 90-2

Mil(e HolVs lllustrated Guide to Understanding the 2011 National Electrical Code, Volume 1
 Introduction to the National Electrical Code 90.2

Scope of the NEC - Utility Buildings Scope of the NEC

90.2(A)(4) Communications Utilities Exemption
90.2(B)(4)

Tff
I Generating Plant

Warehouse Communications utility equipment located in building

spaces used exclusively for such use isn't required
to comply with NEC installation requirements.

Buildings used by the electric utility, such /

3-
as ofTices, warehouses, garages, and
Communications Room
machine shops are covered by the Code.

Figure 90-4 The NEC still applies to electrical equipment such as

receptacles, switches, and luminaires located in spaces
used exclusively for utility Communications equipment.
IB) VJhat isn't Covered. The NEC doesn't apply to:
Figure 90-5
(1) Transportation Vehicles. Installations in cars, trueles, boats. ships
and watercratt, planes, electric trains, or underground mines.

(2) Mining Equipment. Installations underground ín mines and self- Scope of the NEC
propelled mobile surface mining machinery and its attendant electri- Communications Utilities Exemption
90.2(B)(4)
cal trailing cables.

(3) Raiiways. Railway power, signaling, and Communications wiring.

(4) Communications Utilities. The installation requirements of the

/ Telephone or
NEC úon'i apply to Communications (telephone), Community Antenna /Cable TV Equipment
Televisión (CATV), or network-powered broadband utility equipment
Communications equipment in
located in building spaces used exclusively for these purposes, or out- Electrical \
general building spaces must be
Equipment Roomi
doors if the installation is under the exclusive control of the Communi- installed per the NEC [90.2(A)].
í f f r f r f r fí ^
cations utility. Figures 90-5 and 90-6
r nk-^
Author's Comment: Interior wiring for Communications sys-
tems, not in building spaces used exclusively for these purposes,
must be installed in accordance with the following Chapter 8
Articles: Figure 90-6

• Telephone and Data, Article 800

• CATV, Article 820 (5) Electric Utilities. The /VfC doesn't apply to installations under the
• Network-Powered Broadband, Article 830 exclusive control of an electric utility where such installations:

a. Consist of service drops or service laterals and associated

metering. Figure 90-7

b. Are on property owned or leased by the electric utility for the

purpose of generation, transformation, transmission, distribu-
tion, or metering of electric energy. Figure 90-8

Mike Holt Enterprises, Inc. • www.MikeHolt.com • 888.NEC.C0DE (632.2633) 3

Introduction to the National Electrical Code

Code Arrangement • Annex C. Raceway Fill Tables for Conductors and Fixture
90.3
Wires of the Same Size
General Requirements
• Annex D. Examples
" Ciiapter 1 - General
• Chapter 2 - Wiring and Protection • Annex E. Types of Construction
• Chapter 3 - Wihng Methods and Materials • Annex F. Critical Operations Power Systems (COPS)
• Chapter 4 - Equipment for General Use
• Annex G. Supervisory Control and Data Acquisition (SCADA)
Chapters 1 through 4 generally apply to all applications.
Special Requirements • Annex H. Administration and Enforcement ^
• Chapter 5 - Special Occupancies
• Chapter 6 - Special Equipment
• Chapter 7 - Special Conditions 90.4 Enforcement. The Code Is intended to be suitable for
Chapters 5 through 7 can supplement or modify the enforcement by governmental bodies that exercise legal jurisdiction
general requirements of Chapters 1 through 4.
over eléctrica! installations for power, lighting, signaling circuits, and
• Chapter 8 - Communications Systems
Chapter 8 requirements aren't subject to requirements in Communications systems, such as: Figure 90-11
Chapters 1 through 7, unless there's a specific reference in
Chapter 8 to a rule in Chapters 1 through 7.
• Chapter 9 - Tables
Chapter 9 tables are applicabie as referenced in the NEC Enforcement (Inspection)
and are used for calculating raceway sizes, conductor ftll, 90.4
and voltage drop.
•Annexes A through I

m
Annexes are for information only and aren't enforceable.
Copyrii^ 2011. wwwMkaHoM.com Signaling
ilingjl Power.
Lighting
Figure 90-10 Communications
T I . 1 ^
Special Requirements. The requirements contained in Chapters 5,6,
and 7 apply to speciai occupancies, special equipment, or other spe-
cial conditions. These chapters can supplement or modify the require-
ments in Chapters 1 through 4. Power, lighting, signaling, and Communications systems5
must be installed in accordance with the NEC Í90.2{A)]

JL
Communications Systems. Chapter 8 contains the requirements and they must be inspected by the AHJ to ensure
Code compliance.
for Communications systems, such as telephone systems, antenna - . i , , W . i . ,ékmmmmA^mt^kmm
wihng, CATV, and network-powered broadband systems. Communi-
Figure 90-11
cations systems aren't subject to the general requirements of
Chapters 1 through 4, or the special requirements of Chapters 5
through 7, unless there's a specific reference in Chapter 8 to a rule in Signaling circuits which include:
Chapters 1 through 7. • Article 725 Class 1, Class 2, and Class 3 Remote-Control,
Signaling, and Power-Limited Circuits
Author's Comment: An example of how Chapter 8 works is in
• Article 760 Fire Alarm Systems
the rules for working space about equipment. The typical 3 ft
• Article 770 Optical Fiber Cables and Raceways
working space isn't required in front of Communications equip-
ment, because Table 110.26(A)(1) isn't referenced in Chapter 8. Communications systems which include:

• Article 800 Communications Circuits (twisted-pair

Tables. Chapter 9 consists of tables applicabie as referenced in the
conductors)
A/fC.The tables are used to calcúlate raceway sizing, conductor fill,
the radius of raceway bends, and conductor voltage drop. • Article 810 Radio and Televisión Equipment (satellite dish
and antenna)
Annexes. Annexes aren't part of the Code, but are included for infor- • Article 820 Community Antenna Televisión and Radio
mational purposes. There are eight Annexes: Distribution Systems (coaxial cable)
• Annex A. Product Safety Standards • Article 830 Network-Powered Broadband Communi-
• Annex B, Application Information for Ampacity Calculation cations Systems

Mike Holt Enterprises, Inc. • www.l\/likeHolt.com • 888.NEC.C0DE (632.2633) a

 Introduction to the National Electrical Code

Author's Comment: The installation requirements for signaling Approval of Equipment

circuits and Communications circuits are covered in Mike Holt's 90.4
Understanding the National Eléctrica! Code. Volume 2 textbook.

The enforcement of the NEC is the responsibility of the authority

having jurisdiction (AHJ), who is responsible for interpreting require-
ments, approving equipment and materials, waiving Code require-
ments, and ensuring equipment is installed in accordance with listing
I i
instructions.
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Author's Comment: See the definition of "Authority Having
Jurisdiction" in Article 100.
Only the AHJ has the authority to approve equipment and
Interpretation ofthe Requirements. The authority having jurisdiction materials. Approval is typically based on product listing.
is responsible for interpreting the NEC, but his or her decisions must
Figure 90-12
be based on a specific Code requirement. If an installation is rejected,
the authority having jurisdiction is legally responsible for informing
the installer of which specific NEC Me was violated. Waiver of New Product Requirements. If the 2011 NEC requires
products that aren't yet available at the time the Code is adopted, the
Author's Comment: The art of getting along with the author- authority having jurisdiction can allow products that were acceptable
ity having jurisdiction consists of doing good work and knowing in the previous CodeXo continué to be used.
what the Code actuaily says (as opposed to what you only think
it says). It's aiso useful to know how to choose your batíies when Author's Comment: Sometimes it takes years before testing
the inevitable disagreement does occur. laboratories establish product standards for new NEC require-
ments, and then it takes time before manufacturers can design,
Approval of Equipment and Materials. Only the authority having juris- manufacture, and distribute these products to the marketplace.
diction has authority to approve the installation of equipment and
materials. Typically the authority having jurisdiction will approve equip-
ment listed by a product testing organization, such as Underwriters
90.5 Mandatory Requirements and Explanatory
Laboratories Inc. (UL). The NEC doesn't require all equipment to be
Material.
listed, but many state and local AHJs do. See 90.7,110.2,110.3, and (A) Mandatory Requirements. In the NECXhe words "shall" or "shall
the definitions for "Approved," "Identified," "Labeled," and "Listed" in not," indícate a mandatory requirement.
Article 100. Figure 90-12
Author's Comment: For the ease of reading this textbook,
Author's Comment: According to the NEC, the authority having the word "shall" has been replaced with the word "must," and
jurisdiction determines the approval of equipment. This means the words "shali not" have been replaced with "must not."
he or she can reject an installation oí listed equipment and can Remember that in many places, we will paraphrase the Code
approve the use of unlisted equipment, Given our highiy litigious instead of providing exact quotes, to make it easier to read and
society, approval of unlisted equipment is becoming increasingly understand.
difficult to obtain.
(B) Permissive Requirements. When the Code uses "shall be per-
Waiver of Requirements. By special permission, the authority having mitted" it means the identified actions are permitted but not required,
jurisdiction can waive specihc requirements in the Code or permit and the authority having jurisdiction isn't permitted to restrict an
aiternative methods where it's assured equivalent safety can be installation from being done in that manner. A permissive rule is often
achieved and maintained. an exception to the general requirement.

Author's Comment: Special permission is defined in Article

100 as the written consent of the authority having jurisdiction.

6 Mike Holt's lllustrated Guide to Understanding the 2011 National Electrical Code, Volume 1
 Introduction to the National Electrical Code 90.9

Author's Comment: For ease of reading, the phrase "shall be

permitted," as used in the Code, has been replaced in this text-
book with the phrase "is permitted" or "are permitted."

(C) Explanatory Material. References to other standards or sections

of the NEC, or information related to a Code rule, are included in the
form of Informational Notes. Such notes are for information only and
aren't enforceable as a requirement of the NEC.

For example, Informational Note 4 in 210.19tA)(1) recommends

that the voltage drop of a circuit not exceed 3 percent. This isn't a
requirement; it's just a recommendation.

Author's Comment: For convenience and ease of reading in

this textbook,! will identify Informational Notes simply as "Note."
Figure 90-13
(D) Informativa Annexes. Nonmandatory information annexes con-
tained in the back of the Code book are for information only and aren't
enforceable as a requirement of the NEC. 90.9 Units of Measurement.
(B) Dual Systems of Units. Both the metric and inch-pound mea-
90.6 Formal Interpretations. To promote unlformlty of inter- surement systems are shown in the NEC, with the metric units
pretation and application of the provisions of the NEC, formal interpre- appearing first and the inch-pound system immediately íollowing in
tation procedures have been established and are found in the NFPA parentheses.
Regulations Governing Committee Projects.
Author's Comment: This is the standard practice in all NFPA
Author's Comment: This is rarely done because it's a very standards, even though the U.S. construction industry uses inch-
time-consuming process, and formal interpretations from the pound units of measurement, You will need to be cautious when
NFPA aren't binding on the authority having jurisdiction. using the tables in the Code because the additional units can
make the tables more complex and more difficult to read.
90.7 Examination of Equipment for Product Safety.
(D) Compliance. Installing electrical systems in accordance with the
Product evaluation for safety is typically performed by a testing lab-
metric system or the inch-pound system is considered to comply with
oratory, which publishes a list of equipment that meets a nation-
the Code.
ally recognized test standard. Products and materials that are listed,
labeled, or identified by a testing laboratory are generally approved by
Author's Comment: Since compliance with either the metric or
the authority having jurisdiction.
the inch-pound system of measurement constitutes compliance
with the NEC, this textbook uses only inch-pound units.
Author's Comment: See Article 100 for the definition of
"Approved."

Listed, factory-installed, infernal wiring and construction of equip-

ment need not be inspected at the time of installation, except to
detectalterations or damage [300.1(B)]. Figure 90-13

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 ARTICLE
Practice
Questions
These questions are based on the 2011 National Utilities may be subject to compliance with codes and stan-
Electrical Code. Please use the 2011 NEC Code book to dards covering their regulated activities as adopted under
answer the following questions. governmental law or regulation.

(a) True
Article 90. Introduction—Practice Questions (b) False

1. The NEC \s .
Communications wiring such as telephone, antenna, and CATV
(a) intended to be a design manual wiring within a building shall not be required to comply with
(b) meant to be used as an instruction guide for untrained the installation requirements of Chapters 1 through 7, except
persons where specifically referenced in Chapter 8.
(c) for ttie practical safeguarding of persons and property
(d) published by the Bureau oí Standards (a) True
(b) False

2. Hazards often occur because of .

The has the responsibility for deciding on the approval
(a) overloading of wiring systems by methods or usage not in of equipment and materials.
conformity with the NEC
(b) initial wiring not providing for increases in the use of elec- (a) manufacturer
tricity (b) authority having jurisdiction

(c) a and b (c) testing agency

(d) none of these (d) none of these

3. This Code covers the installation of for public and 8. The authority having jurisdiction has the responsibility for

private premises, inciuding buildings, structures, mobile

homes, recreational vehicles, and floating buildings. (a) making interpretations of rules
(a) optical fiber cables (b) deciding upon the approval of equipment and materials

(b) electrical equipment (c) waiving specific requirements in the Code and permitting
(c) raceways altérnate methods and material if safety is maintained

(d) all of these (d) all of these

4. Installations of Communications equipment that are under 9. When the Code uses " ," it means the identified actions
the exclusive control of Communications utiüties, and located are allowed but not required, and they may be options or alter-
outdoors or in building spaces used exclusively for such instal- nativo methods.
lations covered by the NEC. (a) shall
(a) are (b) shall not
(b) are sometimes (c) shall be permitted

(c) are not (d) a or b

(d) may be

Mil(e HolVs lllustrated Guide to Understanding the 2011 National Electrical Code, Volume 1
 Practice Questions Article 90

10. Explanatory material, such as references to other standards,

references to related sections of the NEC, or information related
to a Code rule, are included in the form of Informational Notes.

(a) True
(b) False

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