Practical Electrical Wiring
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Practical Electrical Wiring
Residential, Farm, Commercial and Industrial

22nd edition, Based on the 2014 National Electrical Code®
Frederic P. Hartwell and Herbert P. Richter

Table of contents

Tables xviii Foreword xx
Preface to the ninth edition xxii
Preface to the twentieth edition xxiii
Introduction and guide xxiv

1 NEC, Product Standards, and Inspection 1
National Electrical Code (NEC) 2
Product standards and certification 5
Inspection 12

2 Numbers, Measurements, and Electricity 14
Numbering 14
Abbreviations 14
Metric system 15
Temperature conversion 17
Arithmetic refresher 18
Units of electrical measurement 20
Reading meters and paying for electricity 26
How we use wires to carry electricity 31
Ohm’s law: how current, voltage, and resistance interrelate 32
Voltage drop: a price to be paid for using electric power 34
Three-wire systems: two voltages for the price of one 37

3 AC and DC; Power Factor; Transformers 38
Direct current, alternating current, and nonlinear loads 38
How transformers work and what they do for us 48

4 Basic Electrical Power Utilization Systems 55
The service is the usual energy source 55
Overload protection protects against sustained overheating 56
Short-circuit and ground-fault protection prevents damage from
Electrical arcs 56
Service conductors involve unique overcurrent protection problems 57
Service disconnects—“readily accessible” and other NEC requirements 58
Service and building disconnects 58
Circuits 61
Panelboards (and switchboards) 63

5 Basic Devices and Equipment 67
Receptacle outlets for connecting loads 68
Switches for controlling outlets 70

6 Overcurrent Devices 85
Fuses 86
Circuit breakers 90
Arc-fault circuit interrupters 90
Breakers vs fuses 92
Determining proper rating of overcurrent device 92

7 Selecting Conductors 98
Choosing a type of wire insulation 99
Understanding wire sizes 101
Understanding ampacity and the nec ampacity tables 103
Reducing voltage drop 107

8 Making Wire Connections and Splices 113
Remove insulation before connecting or splicing wires 113
Terminals for connecting wires to devices 115
Making splices 119
Solutions to reliability problems of connections and splices 122

9 Grounding for Safety 129
Three types of grounding 129
Grounding terminology 130
System grounding 132
Equipment grounding helps prevent electric shock 136
Grounding-type receptacles increase safety 142
Ground-fault circuit interrupters (gfci) 145

10 Outlet and Switch Boxes 150
Boxes serve dual purpose 150
Knockouts allow conduit or cable entry 150
Types of boxes 152
Installing boxes 155
Calculating allowable number of wires in box 160

11 Wiring Methods 163
Wiring methods using tubular raceways (conduit and tubing) 163
Cabled wiring methods 185
Thermal insulation degrades wiring method ampacities 201
Flexible cords are not wiring methods 200

12 Planning Residential Installations 204
Factors in adequate wiring 204
NEC emphasizes receptacle placement rules in dwellings 205
NEC requires lighting, usually with switch control 209
Special rules apply to receptacles 210
Room-by-room wiring needs 211
Putting your wiring plan on paper 216

13 Residential Electrical Distribution 220
Install enough branch circuits for convenience and safety 220
Size the service for present and future needs 229
Service equipment must be suitable for its function 236
Surge protective devices 241

14 Residential Lighting 242
Measuring light—how much do you need? 242
What quality of light do you need? 247
Layered lighting and special effects 248
How to select incandescent lamps 251
Fluorescent lighting saves energy 255

15 Residential and Farm Motors 263
How electric motors are rated 263
Types of motors commonly used 267
Five requirements for every motor installation 272
Maintaining residential and farm motors 278


16 Installing Service Entrances and Grounds 279
From the street (or utility right-of-way) to the building 279
Service-entrance wiring on a building 288
Service conductors entering buildings 296
Location and wiring of service equipment 297
Provide a safe grounding system for the service 299
Bonding for water and other systems is required for safety 306

17 Installing of Specific Outlets 308
Wiring simple device and fixture openings 308
Wiring garages and outbuildings 333

18 Finishing: Installation of Switches, Receptacles, and Luminaires 340
Installing conventional devices in interior locations 340
Installing conventional luminaires 346
Luminaires that don’t mount directly to outlet boxes 351
Paddle fans have special requirements 355
Outdoor and other wet locations require special procedures 357
Test your installation before energizing it 358

19 Limited-Energy Wiring 362
Fire resistance of limited-energy cabling 362
Workmanship 363
Signaling and control wiring 363
Communications circuits 368

20 Wiring for Multiple Circuits and Specialized Loads 372
Three-wire circuits 372
Three-phase, four-wire circuits 376
Nec notations for voltage systems 376
How the nec classifies appliances 377
Receptacles for appliances 377
Appliance circuits 381
Wiring methods for ranges and other special appliances 383
Special applications 388
Solar photovoltaic systems 390

21 Modernizing Old Work 396
Wiring methods in old work 396
Concealed wiring techniques 398
Surface wiring techniques 411
When to replace old wiring 413
Methods for retaining existing panel(s) 414

22 Farm Wiring 419
How to set up the electrical distribution system at a farm 419
How to wire branch circuits and outlets in farm buildings 432

23 On-Site Engine Power Generation and Supply of Premises Wiring 440
Engine generators and optional standby systems 440
Emergency and legally required standby systems 450
Interconnected power production 453

24 Manufactured Homes, Recreational Vehicles, and Parks 454
Defining the terms used in this chapter 454
Manufactured (mobile) homes and parks 456
Recreational vehicles and parks 459
Requirements for nonresidential uses of mobile homes and rvs 465

25 Wiring Apartment Buildings 466
From simple to complex—start with a single apartment 466
Requirements for service entrance for the building 468
Wiring the service to a larger apartment building 473


26 Sizing Conductors for All Load Conditions 476
Middles and ends of wires require separate calculations 476
Termination restrictions protect devices 478
The middle of the wire—preventing conductors from
Overheating 482
Choosing a conductor 487
Wires in parallel 489

27 Nonresidential Wiring Methods and Materials 493
How to connect wiring to enclosures 493
Nonresidential applications may involve different grounding
Rules 505
What other wiring methods are you likely to use? 508

28 Planning Nonresidential Installations 523
What are common nonresidential distribution systems? 523
Grounding nonresidential systems 540
What is a separately derived system and how is it grounded? 546
How to install and protect transformers and their conductors 549
What branch circuits can be used? 553
What luminaires can be used on various circuits? 554
What allowances does the nec provide for temporary wiring? 556

29 Nonresidential Lighting 559
Group relamping 559
Tungsten-halogen lamps 559
Fluorescent lighting becomes more of a science 560
Quality of illumination 564
Modern control systems address energy concerns 565
High-intensity discharge (hid) lighting 568
Incorporate luminaire characteristics in the lighting design 573
Remote source lighting (fiber optics) 576
Light-emitting diodes (leds) 577

30 Industrial and Commercial Motor Applications 578
Motor ratings and motor circuit terminology 578
Article 608
Fire pump motor “protection” isn’t like anything else in the nec 611
Industrial control panels 612

31 Wiring Specific Locations and Occupancies 613
Office spaces must provide floor-plan flexibility 613
Retail stores—lighting as a merchandising tool 618
Places of assembly are allowed comparatively few wiring methods 619
Good schools showcase good lighting design 620
Church lighting presents unique challenges 621
Wiring in wet, corrosive, and outdoor locations 622
Wiring for signs and outline lighting—unique grounding provisions 625
Hazardous (classified) locations require very high workmanship standards 626
Appendix 638
About the authors 645
Further reading 646
Index 647

List of Tables

    Table 2-1. Orders of Magnitude: Notation for Large and Small Numbers
    Table 2-2. Commonly Used English-Metric Equivalents
    Table 2-3. Typical Electric Rates
    Table 2-4. Ohm's Law and Other Formulas (for Two-Wire Circuits)
    Table 6-1. Comparison of Time-Delay and Ordinary Fuses
    Table 6-2. Characteristics of Control-Circuit, Power, and Lighting Cartridge Fuses by UL Classification
    Table 10-1. Volumes of Selected Standard Metal Boxes
    Table 10-2. Volume Required Per Conductor
    Table 14-1. Characteristics of Lamps
    Table 14-2. Effect of Voltage on Lamps
    Table 14-3. Characteristics of Common Fluorescent Lamps
    Table 15-1. Maximum Advisable Distances (in feet) from Service Equipment to Single-Phase Motor for Different Wire Sizes
    Table 24-1. [NEC Table 551.73] Demand Factors for Feeders and Service-Entrance Conductors for Park Sites
    Table 26-1. NEC Table 310.16 (extracts)
    Table 27-1 [NEC Table 300.19(A)] Spacings for Conductor Supports
    Table 29-1. Characteristics of Fluorescent Lamps (Non-Compact)
    Table 29-2. Comparison of Three HID Lamp Types
    Table 30-1. Motor Locked-Rotor Code Letters [from NEC 430.7(b)]
    Table 30-2. Maximum Size of Short-Circuit and Ground-Fault Protection for Motor Branch Circuits [from NEC Table 430.52]

Appendix Tables

    Table A-1. Abbreviations
    Table A-2. [NEC Table 310.16] Allowable Ampacities Of Insulated Conductors Rated 0 through 2000 Volts, 60°C through 90°C (140°F through 194° F) Not More than Three Current-Carrying Conductors In Raceway, Cable, or Earth (Directly Buried), Based on Ambient Temperature of 30°C (86°F)
    Table A-3. [NEC Table 310.15(B)(2)(a)] Adjustment Factors for More than Three Current-Carrying Conductors In a Raceway or Cable
    Table A-4. [NEC Table 430.148] Full-Load Currents in Amperes, Single-Phase Alternating-Current Motors
    Table A-5. [NEC Table 430.150] Full-Load Current Three-Phase Alternating-Current Motors
    Table A-6. [NEC Chapter 9, Table 8] Conductor Properties

Park Publishing, Inc.
2nd edition, March 2014
Softcover, 700 pages, 475 illustrations
ISBN 978-0971977983
Price $79.95