Preface...x Chapter 1 Electrical Fundamentals

Transcription

1 Preface...x Chapter 1 Electrical Fundamentals Unit 1 Matter...3 Introduction Matter Atomic Theory Law of Electrical Charges Law of Atomic Charges...5 Negative Atomic Charge...5 Positive Atomic Charge Charged Material (Static Charge)...5 Static Voltage...6 Reducing Static Charge Neutralizing a Charge Lightning Lightning Protection...7 Unit 1 Summary...9 Unit 1 Conclusion...10 Unit 1 Practice Questions...11 Unit 2 Electron Theory...15 Introduction Electron Orbits Valence Electrons Freeing Electrons from an Atom Conductors Insulators Semiconductors Atomic Bonding Compounds...17 Unit 2 Summary...19 Unit 2 Conclusion...20 Unit 2 Practice Questions...21 Unit 3 Magnetism...23 Introduction The Natural Magnet Magnetic Polarities Magnetic Compass Magnetic Molecule Magnetic Properties How to Magnetize Iron Permanent and Temporary Magnets Demagnetizing Magnets Magnetic Lines of Force Magnetic Materials Law of Attraction and Repulsion Retentivity Permeability...26 Unit 3 Summary...27 Unit 3 Conclusion...28 Unit 3 Practice Questions...29 Unit 4 Electricity...33 Introduction Electrical Current Flow (Electricity) Electricity...34 Chemical Activity (Electrochemistry)...34 Magnetism (Magnetoelectricity)...34 Light (Photoelectricity)...35 Thermo Energy (Thermoelectricity)...36 Pressure (Piezoelectricity) Useful Purposes of Electricity...37 Electrochemistry...37 Electromagnetism...37 Heat (Resistance)...38 Illumination (Lighting) Danger of Electricity...39 Understanding Electrical Shock Hazard...39 What Determines the Severity of Electrical Shock?...39 Clearing a Ground Fault...40 Fire...41 Electrical Arc Blast National Electrical Code...42 Unit 4 Summary...43 Unit 4 Conclusion...45 Unit 4 Practice Questions...46 Unit 5 Electromagnetism...49 Introduction Electromagnetism in a Wire Field Intensity Field Interaction Field Interaction of Loops...50 iv iv

2 5.5 Electromagnetism in a Coil Magnetic Core Ampere and Turns...51 Unit 5 Summary...52 Unit 5 Conclusion...53 Unit 5 Practice Questions...54 Unit 6 Uses of Electromagnetism...57 Introduction Basic Electric Meters...57 Voltmeter...58 DC Voltmeter...58 DC Ammeter...58 Clamp-on AC Ammeter...59 Ohmmeters...60 Wheatstone Bridge...60 Megohmmeter Electric Motor...60 Motor Components...60 Understanding Motor Motion Electrical Generator...62 DC Generator...62 AC Generator Electromagnetic Relay...63 Contacts...63 Holding Relay...64 Unit 6 Summary...65 Unit 6 Conclusion...67 Unit 6 Practice Questions...68 Chapter 1 Final Exam...70 Chapter 2 Basic Electricity Unit 7 The Electrical Circuit...77 Introduction The Electrical Circuit Electron Current Flow Theory Conventional Current Flow Theory Voltage (Pressure) Resistance...79 Conductor Resistance Electric Current Power Electrical Formulas...80 Unit 7 Summary...81 Unit 7 Conclusion...82 Unit 7 Practice Questions...83 Unit 8 Math...85 Introduction Whole Numbers Decimal Fractions Percentages Multiplier Percent Increase Reciprocals Squaring a Number Square Root Volume Kilo Rounding Off Parentheses Testing Your Answer for Reasonableness...91 Unit 8 Summary...92 Unit 8 Conclusion...93 Unit 8 Practice Questions...94 Unit 9 Electrical Formulas...99 Introduction Electrical Circuit Power Source Direct Current Alternating Current Conductance Circuit Resistance Ohm s Law Ohm s Law and Alternating Current Direct Current Alternating Current Ohm s Law Formula Circle PIE Formula Circle Formula Wheel Using the Formula Wheel Power Losses of Conductors Cost of Power Power Changes with the Square of the Voltage Power Example at 230V Power Example at 208V Power Example at 240V Unit 9 Summary Unit 9 Conclusion Unit 9 Practice Questions Chapter 2 Final Exam v v

3 Chapter 3 Basic Electrical Circuits Unit 10 Series Circuits Introduction Practical Uses of the Series Circuit Lighting Control Circuit Signaling Circuit Internal Equipment Wiring Understanding Series Calculations Resistance Voltage Kirchoff s Voltage Law Kirchoff s Current Law Power Series Circuit Calculations Power Calculations Variations Series Circuit Notes Series-Connected Power Supplies Unit 10 Summary Unit 10 Conclusion Unit 10 Practice Questions Unit 11 Parallel Circuits Introduction Practical Uses of the Parallel Circuit Receptacle Lighting Other Uses Understanding Parallel Calculations Voltage Kirchoff s Current Law Power Circuit Resistance Equal Resistance Method Product-Over-Sum Method Reciprocal Method Parallel Circuit Notes Parallel-Connected Power Supplies Unit 11 Summary Unit 11 Conclusion Unit 11 Practice Questions Unit 12 Series-Parallel Circuits Introduction Review of Series and Parallel Circuits Series Circuit Review Parallel Circuit Review Working Series-Parallel Circuits Voltage Unit 12 Summary Unit 12 Conclusion Unit 12 Practice Questions Unit 13 Multiwire Circuits Introduction Neutral Conductor Grounded Conductor Current Flow on the Grounded (Neutral) Conductor Wire Circuit Wire, 120/240V, Single-Phase Circuit Balanced Systems Unbalanced Current Wire, 120/240V, Single-Phase Circuit Wire Circuit from a 4-wire, Three-Phase System Wire, Three-Phase Circuit Multiwire Branch Circuit Wire Circuit Voltage Drop Multiwire Circuit Voltage Drop Dangers of Multiwire Circuits Fire Hazard Destruction of Equipment as Well as Fire Hazard NEC Requirements Unit 13 Summary Unit 13 Conclusion Unit 13 Practice Questions Chapter 3 Final Exam Chapter 4 Electrical Systems and Protection Unit 14 The Electrical System Introduction Current Flow Utility Neutral Current Path Multipoint Neutral Ground Utility Ground-Fault Current Path Premises Neutral Current Path Single Point Neutral Bond Premises Ground-Fault Current Path Earth as Ground Fault Path for Systems 600V or Less vi vi

4 14.6 Utility High-Voltage Transmission Lines Conductor Voltage Drop Conductor Power Loss Current Reducing Voltage Drop and Power Loss kv Transmission Line Generating Plants Step-Up Substation at Generating Plant Transmission Line Step-Down Substation Primary Distribution Feeders Distribution Transformer Secondary Distribution Line Unit 14 Summary Unit 14 Conclusion Unit 14 Practice Questions Unit 15 Protection Devices Introduction Part A Overcurrent Protection Devices Overcurrent Protection Overload Ground Fault Short Circuit Clearing Faults Time Current Curves Remove Dangerous Touch Voltage Overcurrent Protection Device Types Fuse Construction Overload Protection Short-Circuit and Ground-Fault Protection Circuit Breaker Trip Elements Thermal Trip Element Magnetic Trip Element Circuit Breaker Types Inverse-Time Adjustable-Trip Instantaneous-Trip Available Short-Circuit Current Interrupting Rating Short-Circuit Current Rating Current-Limiting Protection Part B Ground-Fault Circuit Interrupters How a GFCI Works Neutral-to-Case Detection Line-to-Neutral Shock Hazard GFCI Fails Circuit Remains Energized GFCI Test Button Part C Arc-Fault Circuit Interrupter Arcing Definition Series Versus Parallel Arc Series Arc Parallel Arc AFCI and the NEC AFCI How They Operate Part D Ground-Fault Protection of Equipment Ground-Fault Protection of Equipment Definition Unit 15 Summary Unit 15 Conclusion Unit 15 Practice Questions Chapter 4 Final Exam Chapter 5 Alternating Current Unit 16 Alternating Current Introduction Current Flow Why Alternating Current is Used How Alternating Current is Produced AC Generator Waveform Direct-Current Waveform Alternating-Current Waveform Sine Wave Sinusoidal Waveform Nonsinusoidal Waveform Nonsymmetrical Waveform Frequency Phase Degrees Lead or Lag Leading Lagging Values of Alternating Current Instantaneous Value Peak Value Effective Value RMS Value Unit 16 Summary Unit 16 Conclusion Unit 16 Practice Questions vii vii

5 Unit 17 Capacitance Introduction Capacitor Current Flow Charged Capacitor Electrical Field Discharging a Capacitor Determining Capacitance Plate Distance Surface Area Dielectric Strength Uses of Capacitors Electronic Power Supplies Phase Relationship Unit 17 Summary Unit 17 Conclusion Unit 17 Practice Questions Unit 18 Induction Introduction Self-Induction Induced Voltage and Applied Current Opposes Current Flow Aids the Current Flow Conductor AC Resistance Eddy Currents Skin Effect Impedance Conductor Shape Current Winding Frequency Magnetic Cores Core Material Core Length Core Area Self-Induced and Applied Voltage Current Flow Inductive Reactance Phase Relationship Uses of Induction Unit 18 Summary Unit 18 Conclusion Unit 18 Practice Questions Unit 19 Power Factor and Efficiency Introduction Inductors and Capacitors Part A Power Factor Apparent Power (Volt-Ampere) True Power (Watts) Direct Current Alternating Current Power Factor Unity Power Factor Power Factor Formulas Cost of True Power Effects of Power Factor Part B Efficiency Efficiency Efficiency Formulas Unit 19 Summary Unit 19 Conclusion Unit 19 Practice Questions Chapter 5 Final Exam Chapter 6 Motors, Generators, and Transformers Unit 20 Motors Introduction Part A Motor Basics Motor Principles Stator Rotor Dual-Voltage AC Motors Motor Horsepower Rating Motor Current Ratings Motor Full-Load Ampere (FLA) Rating Actual Motor Current Motor Full-Load Current (FLC) Rating Calculating Motor FLA Single-Phase Three-Phase Motor-Starting Current Motor-Running Current Motor Locked-Rotor Current (LRC) Motor Overload Protection NEC Requirement Part B Direct-Current Motors Direct-Current Motor Principles Direct-Current Motor Types Shunt-Wound DC Motor Series-Wound DC Motor viii viii

6 20.12 Reversing the Rotation of a DC Motor Part C Alternating-Current Motors AC Induction Motor Alternating-Current Motor Types Squirrel-Cage Induction Motor Synchronous Motor Wound-Rotor Motor Universal Motor Reversing the Rotation of an AC Motor Unit 20 Summary Unit 20 Conclusion Unit 20 Practice Questions Unit 21 Generators Introduction Direct-Current Generator Excitation Current Alternating-Current Generator Three-Phase Generators Unit 21 Summary Unit 21 Conclusion Unit 21 Practice Questions Unit 22 Transformers Introduction Transformer Basics Primary Versus Secondary Mutual Induction Secondary Induced Voltage Autotransformers Step-Down Transformers Step-Up Transformers Power Losses Conductor Resistance Loss Flux Leakage Loss Eddy Currents Hysteresis Losses Harmonic Current Efficiency Transformer Turns Ratio Transformer kva Rating Current Flow Current Rating Unit 22 Summary Unit 22 Conclusion Unit 22 - Practice Questions Chapter 6 Final Exam Basic Electrical Theory Final Exam Basic Electrical Theory Final Conclusion Annex A Grounding and Bonding Introduction Understanding the Basics of Electrical Systems Understanding Electrical Shock Hazard What Determines the Severity of Electrical Shock Clearing a Ground Fault Why Grounding is Often Difficult to Understand Scope Definitions Other Code Sections General Requirements for Grounding and Bonding (A) Summary Objectionable (Neutral) Current Index ix ix

7 Article 90 Introduction Purpose of the NEC Scope of the NEC Code Arrangement Enforcement Mandatory Requirements and Explanatory Material Formal Interpretations Examination of Equipment for Product Safety Units of Measurement...7 Article 90 Questions...8 Chapter 1 General...9 Article 100 Definitions...11 Article 110 Requirements for Electrical Installations...31 Part I. General Requirements Scope Approval of Equipment Examination, Identification, Installation, and Use of Equipment Voltages Copper Conductors Conductor Sizes Conductor Insulation Suitable Wiring Methods Interrupting Protection Rating Short-Circuit Current Rating Deteriorating Agents Mechanical Execution of Work Mounting and Cooling of Equipment Conductor Termination High-Leg Conductor Identification Flash Protection Warning Manufacturer s Markings Identification of Disconnecting Means...43 Part II. 600V, Nominal or Less Spaces About Electrical Equipment Guarding...48 Article 110 Questions...49 Chapter 2 Wiring and Protection...51 Article 200 Use and Identification of Grounded Neutral Conductor Scope Identification of the Grounded Neutral Conductor Use of White or Gray Color Terminal Identification Identification of Terminals Polarity...57 Article 200 Questions...58 Article 210 Branch Circuits...59 Part I. General Provisions Scope Other Articles Branch-Circuit Rating Multiwire Branch Circuits Identification for Branch Circuits Branch-Circuit Voltage Limitation Branch-Circuit Receptacle Requirements GFCI-Protected Receptacles Branch-Circuits Required Arc-Fault Circuit-Interrupter (AFCI) Protection Guest Rooms and Guest Suites...71 Part II. Branch-Circuit Ratings Conductor Sizing Overcurrent Protection Outlet Device Rating Permissible Loads Common Area Branch Circuits...75 vi

8 Understanding the National Electrical Code, Volume 1 Part III. Required Outlets General Dwelling Unit Receptacle Outlet Requirements Receptacles in Guest Rooms or Guest Suites for Hotels and Motels Heating, Air-Conditioning, and Refrigeration Equipment (HACR) Lighting Outlet Requirements...82 Article 210 Questions...85 Article 215 Feeders Scope Minimum Rating Overcurrent Protection High-Leg Conductor Identification Ground-Fault Protection of Equipment Identification for Feeders...89 Article 215 Questions...91 Article 220 Branch-Circuit, Feeder, and Service Calculations...93 Part I. General Scope Application of Other Articles Calculations...94 Part II. Branch-Circuit Load Calculations General Lighting Other Loads All Occupancies Maximum Load on a Branch Circuit...99 Part III. Feeder and Service Calculations General General Lighting Demand Factors Commercial Show Window and Track Lighting Load Commercial Receptacle Load Motor Load Fixed Electric Space-Heating Load Dwelling Unit Small-Appliance and Laundry Load Dwelling Unit Appliance Load Dwelling Unit Electric Clothes Dryer Load Dwelling Unit Electric Ranges and Cooking Appliances Commercial Kitchen Equipment Load Noncoincident Loads Feeder/Service Neutral Unbalanced Load Part IV. Optional Calculations for Computing Feeder and Service Loads Dwelling Unit Optional Load Calculation Table of Contents Multifamily Optional Load Calculation Optional Calculation Two Dwelling Units Article 220 Questions Article 225 Outside Wiring Part I General Requirements Scope Other Articles Minimum Size Conductors Luminaires Installed Outdoors Supports Over Buildings Attachment Masts as Support Clearances Clearances from Buildings Raceways on Exterior Surfaces of Buildings or Other Structures Trees for Conductor Support Part II. More Than One Building or Structure Number of Supplies Disconnecting Means Disconnect Location Maximum Number of Disconnects Grouping of Disconnects Access to Occupants Identified as Suitable for Service Equipment Identification of Multiple Supplies Disconnect Construction Rating of Disconnecting Means Article 225 Questions Article 230 Services Part I. General Scope Number of Services Pass Through a Building or Structure Conductors Considered Outside a Building Service Conductors Separate from Other Conductors Raceway Seals Clearance from Building Openings Vegetation as Support Part II. Overhead Service-Drop Conductors Size and Rating Clearances Point of Attachment Means of Attachment Service Masts Used as Supports vii

9 Table of Contents Understanding the National Electrical Code, Volume 1 Part III. Underground Service-Lateral Conductors Size and Rating Protection Against Damage Part IV. Service Entrance Conductors Number of Service-Entrance Conductor Sets Size and Rating Wiring Methods Cable Trays Spliced Conductors Protection Against Physical Damage Aboveground Service Cable Supports Connections at Weatherheads High-Leg Identification Part V. Service Equipment General Identified as Suitable for Service Equipment Part VI. Service Equipment Disconnecting Means General Number of Disconnects Grouping of Disconnects Manual or Power Operated Rating of Disconnect Equipment Connected to the Supply Side of the Service Disconnect Part VII. Service Equipment Overcurrent Protection Overload Protection Required Ground-Fault Protection of Equipment Article 230 Questions Article 240 Overcurrent Protection Part I. General Scope Definitions Protection of Equipment Protection of Conductors Protection of Flexible Cords and Fixture Wires Standard Ampere Ratings Supplementary Overcurrent Protection Ground-Fault Protection of Equipment Part II. Location Ungrounded Conductors Overcurrent Protection Location in Circuit Location of Overcurrent Protection Devices Part III. Enclosures Damp or Wet Locations Vertical Position Part V. Plug Fuses, Fuseholders, and Adapters Edison-Base Fuse Type S Fuses Type S Fuses, Adapters, and Fuseholders Part VI. Cartridge Fuses and Fuseholders General Classification Part VII. Circuit Breakers Method of Operation Indicating Markings Applications Article 240 Questions Article 250 Grounding and Bonding Part I. General Scope Definitions General Requirements for Grounding and Bonding Objectionable Current Termination of Grounding and Bonding Conductors Protection of Fittings Clean Surface Part II. System Grounding and Bonding Systems Required to be Grounded and Bonded Grounding and Bonding at Service Equipment Main Bonding Jumper and System Bonding Jumper Grounding and Bonding of Separately Derived AC Systems Buildings or Structures Supplied by a Feeder or Branch Circuit Generators Portable and Vehicle-Mounted High-Impedance Grounded Neutral Systems Part III. Grounding Electrode System and Grounding Electrode Conductor Grounding Electrode System Grounding (Earthing) Electrodes Installation of Grounding Electrode System Supplementary Electrodes Resistance of Ground Rod Electrode Common Grounding (Earthing) Electrode Lightning Protection System Grounding (Earthing) Electrode Grounding Electrode Conductor Material Grounding Electrode Conductor Installation viii

10 Understanding the National Electrical Code, Volume 1 Table of Contents Grounding Electrode Conductor Size Grounding Electrode Conductor Termination Grounding Electrode Conductor Termination Fitting Part IV. Grounding (Bonding) of Enclosure, Raceway, and Service Cable Service Enclosures Other Enclosures Part V. Bonding Service Bonding Grounding (Bonding) of Communications Systems Bonding Other Enclosures Bonding 277V/480V Bonding Hazardous (Classified) Locations Bonding Jumper Bonding of Piping Systems and Exposed Structural Metal Lightning Protection System Part VI. Equipment Grounding (Bonding) and Equipment Grounding (Bonding) Conductors Fixed Equipment Connected by Permanent Wiring Methods General Fixed Equipment Connected by Permanent Wiring Methods Specific Equipment Connected by Cord and Plug Types of Equipment Grounding (Bonding) Conductors Identification of Equipment Grounding (Bonding) Conductor Sizing Equipment Grounding (Bonding) Conductor Identification of Wiring Device Terminals Part VII. Methods of Equipment Grounding (Bonding) Equipment Grounding (Bonding) Conductor Connections Grounding (Bonding) Fixed Equipment Grounding (Bonding) Cord-and-Plug Connected Equipment Grounding (Bonding) Ranges, Ovens, and Clothes Dryers Use of Grounded Neutral Conductor for Equipment Grounding (Bonding) Connecting Receptacle Grounding Terminal to Box Continuity and Attachment of Equipment Grounding (Bonding) Conductors to Boxes Article 250 Questions Article 280 Surge Arresters Part I. General Scope Definition Number Required Surge Arrester Selection Part II. Installation Location Routing of Conductors Part III. Connecting Surge Arresters Installed at Services of Less Than 1,000V Installed on the Load Side of Services of Less Than 1,000V Article 280 Questions Article 285 Transient Voltage Surge Suppressors (TVSSs) Part I. General Scope Definition Uses Not Permitted Number Required Listing Short-Circuit Current Rating Part II. Installation Location Routing of Conductors Part III. Connecting Transient Voltage Surge Suppressors Connection Article 285 Questions Chapter 3 Wiring Methods and Materials Article 300 Wiring Methods Part I. General Requirements Scope Conductors Protection Against Physical Damage Underground Installations Protection Against Corrosion and Deterioration Raceways Exposed to Different Temperatures Not Permitted in Raceways Electrical Continuity Securing and Supporting ix

11 Table of Contents Understanding the National Electrical Code, Volume Mechanical Continuity Splices and Pigtails Length of Free Conductors Boxes or Conduit Bodies Raceway Sizing Inserting Conductors in Raceways Supporting Conductors in Vertical Raceways Induced Currents in Metal Parts Spread of Fire or Products of Combustion Ducts, Plenums, and Air-Handling Spaces Panels Designed to Allow Access Article 300 Questions Article 310 Conductors For General Wiring Scope Conductors Stranded Conductors Conductors in Parallel Minimum Size Conductors Location Corrosive Conditions Insulation Temperature Limitation Conductor Identification Conductor Construction Conductor Ampacity Article 310 Questions Article 312 Cabinets, Cutout Boxes, and Meter Socket Enclosures Scope Part I. Installation Damp, Wet, or Hazardous (Classified) Locations Installed in Walls Repairing Gaps Around Plaster, Drywall, or Plasterboard Edges Enclosures Used for Raceway and Splices Article 312 Questions Article 314 Outlet, Device, Pull and Junction Boxes, Conduit Bodies, and Handhole Enclosures Part I. Scope and General Scope Nonmetallic Boxes Metal Boxes Short-Radius Conduit Bodies Part II. Installation Damp, Wet, or Hazardous (Classified) Locations Number of 6 AWG and Smaller Conductors in Boxes and Conduit Bodies Conductors That Enter Boxes or Conduit Bodies Boxes Recessed in Walls or Ceilings Repairing Gaps Around Boxes Surface Extensions Support of Boxes and Conduit Bodies Covers and Canopies Outlet Box Boxes and Conduit Bodies for Conductors 4 AWG and Larger Wiring to be Accessible Handhole Enclosures Article 314 Questions Article 320 Armored Cable (Type AC) Part I. General Scope Definition Part II. Installation Uses Permitted Uses Not Permitted Exposed Work Through or Parallel to Framing Members In Accessible Attics or Roof Spaces Bends Secured and Supported Boxes and Fittings Conductor Ampacities Part III. Construction Specifications Construction Equipment Grounding (Bonding) Article 320 Questions Article 330 Metal-Clad Cable (Type MC) Part I. General Scope Definition Part II. Installation Uses Permitted Uses Not Permitted Through or Parallel to Framing Members In Accessible Attics or Roof Spaces Bends Part II. Installation Secured and Supported x

12 Understanding the National Electrical Code, Volume 1 Table of Contents Fittings Conductor Ampacities Part III. Construction Specifications Equipment Grounding (Bonding) Article 330 Questions Article 334 Nonmetallic-Sheathed Cable (Types NM and NMC) Part I. General Scope Definition Listed Part II. Installation Uses Permitted Uses Not Permitted Exposed Through or Parallel to Framing Members Attics and Roof Spaces Bends Secured or Supported Conductor Ampacity Part III. Construction Specifications Construction Conductors Equipment Grounding Insulation Article 334 Questions Article 336 Power and Control Tray Cable (Type TC) Part I. General Scope Definition Part II. Installation Uses Permitted Uses Not Permitted Article 336 Questions Article 338 Service-Entrance Cables (Types SE and USE) Part I. General Scope Definition Part II. Installation Uses Permitted Bends Article 338 Questions Article 340 Underground Feeder and Branch-Circuit Cable (Type UF) Part I. General Scope Definition Listing Requirements Part II. Installation Uses Permitted Uses Not Permitted Bends Ampacity Insulation Article 340 Questions Article 342 Intermediate Metal Conduit (Type IMC) Part I. General Scope Definition Listing Requirements Part II. Installation Uses Permitted Dissimilar Metals Trade Size Number of Conductors Bends Number of Bends (360 ) Reaming Secured and Supported Couplings and Connectors Bushings Article 342 Questions Article 344 Rigid Metal Conduit (Type RMC) Part I. General Scope Definition Listing Requirements Part II. Installation Uses Permitted Dissimilar Metals Trade Size Number of Conductors Bends Number of Bends (360 ) Reaming Secured and Supported Couplings and Connectors xi

13 Table of Contents Understanding the National Electrical Code, Volume Bushings Article 344 Questions Article 348 Flexible Metal Conduit (Type FMC) Part I. General Scope Definition Listing Requirements Part II. Installation Uses Permitted Uses Not Permitted Trade Size Number of Conductors Bends Number of Bends (360 ) Trimming Secured and Supported Fittings Bonding Article 348 Questions Article 350 Liquidtight Flexible Metal Conduit (Type LFMC) Part I. General Scope Definition Listing Requirement Part II. Installation Uses Permitted Uses Not Permitted Trade Size Number of Conductors Bends Number of Bends (360 ) Secured and Supported Fittings Bonding Article 350 Questions Article 352 Rigid Nonmetallic Conduit (Type RNC) Part I. General Scope Definition Part II. Installation Uses Permitted Uses Not Permitted Trade Size Number of Conductors Bends Number of Bends (360 ) Trimming Secured and Supported Expansion Fittings Bushings Joints Grounding (Bonding) Article 352 Questions Article 353 High-Density Polyethylene Conduit (Type HDPE) Part I. General Scope Definition Listing Requirements Part II. Installation Uses Permitted Uses Not Permitted Trade Size Number of Conductors Bends How Made Bends Number in One Run Trimming Bushings Joints Splices and Taps Grounding (Bonding) Article 353 Questions Article 354 Nonmetallic Underground Conduit with Conductors (Type NUCC) Part I. General Scope Definition Listing Requirement Part II. Installation Uses Permitted Uses Not Permitted Trade Size Bends Number of Bends (360º) Trimming Bushings Joints Conductor Terminations Article 354 Questions xii

14 Understanding the National Electrical Code, Volume 1 Article 356 Liquidtight Flexible Nonmetallic Conduit (Type LFNC) Part I. General Scope Definition Listing Requirement Part II. Installation Uses Permitted Uses Not Permitted Trade Size Number of Conductors Bends Number of Bends (360 ) Secured and Supported Fittings Grounding (Bonding) Article 356 Questions Article 358 Electrical Metallic Tubing (Type EMT) Part I. General Scope Definition Listing Requirement Part II. Installation Uses Permitted Uses Not Permitted Trade Size Number of Conductors Bends Number of Bends (360 ) Reaming and Threading Secured and Supported Coupling and Connectors Article 358 Questions Article 362 Electrical Nonmetallic Tubing (Type ENT) Part I. General Scope Definition Part II. Installation Uses Permitted Uses Not Permitted Trade Sizes Number of Conductors Bends Number of Bends (360 ) Table of Contents Trimming Secured and Supported Bushings Joints Grounding (Bonding) Article 362 Questions Article 376 Metal Wireways Part I. General Scope Definition Part II. Installation Uses Permitted Uses Not Permitted Conductor Maximum Size Number of Conductors Wireway Sizing Supports Splices and Taps Article 376 Questions Article 378 Nonmetallic Wireways Part I. General Scope Definition Part II. Installation Uses Permitted Uses Not Permitted Conductor Maximum Size Number of Conductors Wireway Sizing Supports Expansion Fittings Splices and Taps Grounding (Bonding) Article 378 Questions Article 380 Multioutlet Assembly Scope Uses Through Partitions Article 380 Questions Article 384 Strut-Type Channel Raceways Part I. General Scope Definition xiii

15 Table of Contents Understanding the National Electrical Code, Volume 1 Part II. Installation Uses Permitted Uses Not Permitted Conductor Maximum Size Number of Conductors Securing and Supporting Splices and Taps Grounding (Bonding) Article 384 Questions Article 386 Surface Metal Raceways Part I. General Scope Definition Listing Requirements Part II. Installation Uses Permitted Uses Not Permitted Size of Conductors Number of Conductors Securing and Supporting Splices and Taps Grounding (Bonding) Separate Compartments Article 386 Questions Article 388 Surface Nonmetallic Raceways Part I. General Scope Definition Listing Requirements Part II. Installation Uses Permitted Uses Not Permitted Size of Conductors Number of Conductors Splices and Taps Grounding (Bonding) Separate Compartments Article 388 Questions Article 392 Cable Trays Scope Definition Uses Permitted Uses Not Permitted Installation Grounding (Bonding) Cable Installation Article 392 Questions Chapter 4 Equipment for General Use Article 400 Flexible Cords and Flexible Cables Scope Suitability Types of Flexible Cords and Flexible Cables Ampacity of Flexible Cords and Flexible Cables Uses Permitted Uses Not Permitted Pull at Joints and Terminals Overcurrent Protection Protection from Damage Article 400 Questions Article 402 Fixture Wires Scope Types Allowable Ampacity of Fixture Wires Minimum Size Raceway Size Grounded Neutral Conductor Uses Permitted Uses Not Permitted Overcurrent Protection Article 402 Questions Article 404 Switches Scope Switch Connections Switch Enclosures Wet Locations Position of Knife Switches Indicating Accessibility and Grouping Switch Cover Plates (Faceplate) Mounting Snap Switches Circuit Breakers Used as Switches Grounding (Bonding) Metal Enclosures Rating and Use of Snap Switches Switch Marking Article 404 Questions Article 406 Receptacles, Cord Connectors, and Attachment Plugs Caps Scope xiv

16 Understanding the National Electrical Code, Volume Receptacle Rating and Type General Installation Requirements Receptacle Mounting Receptacle Faceplates Attachment Plugs, Cord Connectors, and Flanged Surface Devices Receptacles in Damp or Wet Locations Connecting Receptacle Grounding Terminal to Box Article 406 Questions Article 408 Switchboards and Panelboards Part I. General Scope Arrangement of Busbars and Conductors Circuit Directory or Circuit Identification Clearance for Conductor Entering Bus Enclosures Unused Openings Part III. Panelboards Classification of Panelboards Number of Overcurrent Protection Devices Overcurrent Protection of Panelboard Panelboards in Damp or Wet Locations Grounding (Bonding) of Panelboards Grounded Neutral Conductor Terminations Article 408 Questions Article 410 Luminaires, Lampholders, and Lamps Part I. General Scope Part II. Luminaire Locations Luminaires in Specific Locations Clothes Closets Part III. Luminaire Outlet Boxes and Covers Outlet Boxes to be Covered Connection of Electric-Discharge Luminaires Part IV. Luminaire Supports Supports Means of Support Part V. Grounding (Bonding) Exposed Luminaire Parts Part VI. Wiring of Luminaires Polarization of Luminaires Cord-Connected Luminaires Luminaires Used as a Raceway Table of Contents Wiring Luminaires Connected Together Branch-Circuit Conductors and Ballast Part VIII. Lampholders Screw-Shell Lampholder Part XI. Recessed Luminaires Thermally Protected Recessed Luminaire Clearances Wiring Part XIII. Electric-Discharge Lighting General Luminaire Mounting Part XV. Track Lighting Definition Installation Fastening Part XVI. Decorative Lighting and Similar Accessories Listing of Decorative Lighting Article 410 Questions Article 411 Lighting Systems Operating at 30V or Less Scope Definition Listing Required Locations Not Permitted Secondary Circuits Article 411 Questions Article 422 Appliances Part I. General Scope Other Articles Part II. Branch-Circuit Requirements Branch-Circuit Rating Overcurrent Protection Fossil Fuel Heating Equipment (Furnaces) Storage Water Heaters Central Vacuum Flexible Cords Support of Ceiling-Suspended (Paddle) Fans Part III. Disconnect Permanently Connected Appliance Disconnect Cord-and-Plug Connected Appliance Disconnect Unit Switch as Disconnect Cord-and-Plug Connected Vending Machines Article 422 Questions xv

17 Table of Contents Understanding the National Electrical Code, Volume 1 Article 424 Fixed Electric Space-Heating Equipment Part I. General Scope Branch Circuits Permanently Installed Electric Baseboard Heaters with Receptacles Part III. Electric Space-Heating Equipment Disconnecting Means Part V. Electric Space-Heating Cables Installation of Cables in Concrete or Poured Masonry Floors Part VI. Duct Heaters Disconnect for Electric Duct Heater Controller Article 424 Questions Article 430 Motors, Motor Circuits, and Controllers Part I. General Scope Definitions Table FLC Versus Motor Nameplate Current Rating Marking on Controllers Motor Controller Terminal Requirements Location of Motors The Highest-Rated Motors Part II. Conductor Size Single Motor Conductor Size Several Motors Conductor Size Motor Feeder Taps Part III. Overload Protection Overload Overload Sizing Continuous-Duty Motors Use of Fuses for Overload Protection Number of Overload Devices Part IV. Branch-Circuit Short-Circuit and Ground-Fault Protection General Branch-Circuit Short-Circuit and Ground-Fault Protection Single Overcurrent Protective Device Part V. Feeder Short-Circuit and Ground-Fault Protection Feeder Protection Part VI. Motor Control Circuits Overcurrent Protection for Control Circuits Disconnect for Control Circuit Part VII. Motor Controllers Controller Rating Need Not Open All Conductors of the Circuit Controller for Each Motor Motor Controller Enclosure Types Part IX. Disconnecting Means Disconnect Requirement Disconnect Opens All Conductors Marking and Mounting Readily Accessible Disconnecting Means Rating Combination Controller-Disconnect Part X. Adjustable-Speed Drive Systems General Conductors Minimum Size and Ampacity Overload Protection Disconnecting Means Part XIV. Tables Table Full-Load Current, Single-Phase Motors Table Full-Load Current, Three-Phase Motors Table Locked-Rotor Currents Article 430 Questions Article 440 Air-Conditioning and Refrigeration Equipment Part I. General Scope Definitions Other Articles Marking on Hermetic Refrigerant Motor-Compressors and Equipment Ampacity and Rating Part II. Disconnecting Means Location Part III. Circuit Protection General Short-Circuit and Ground-Fault Protection Device Size Part IV. Conductor Sizing Conductor Size One Motor-Compressor Conductor Size Several Motor-Compressors Part VII. Room Air Conditioners Branch-Circuit Requirements xvi

18 Understanding the National Electrical Code, Volume 1 Table of Contents Disconnecting Means Supply Cord Leakage Current Detection and Interruption, and Arc-Fault Circuit Interrupter Article 440 Questions Article 445 Generators Scope Marking Overcurrent Protection Ampacity of Conductors Disconnecting Means Article 445 Questions Article 450 Transformers and Transformer Vaults Part I. General Scope Overcurrent Protection Ventilation Marking Transformer Accessibility Part III. Transformer Vaults Location Walls, Roofs, and Floors Doorways Ventilation Openings Water Pipes and Accessories Storage in Vaults Article 450 Questions Article 460 Capacitors Scope Enclosing and Guarding Part I. 600V, Nominal, and Under Conductors Rating or Setting of Motor Overload Device Article 460 Questions xvii

19 Article 90 Introduction Purpose of the NEC Scope of the NEC Code Arrangement Enforcement Mandatory Requirements and Explanatory Material Formal Interpretations Examination of Equipment for Product Safety Units of Measurement...7 Article 90 Questions...8 Chapter 1 General...9 Article 100 Definitions...11 Article 100 Questions...29 Article 110 Requirements for Electrical Installations...31 Part I. General Requirements Scope Approval of Equipment Examination, Identification, Installation, and Use of Equipment Voltages Copper Conductors Conductor Sizes Conductor Insulation Suitable Wiring Methods Interrupting Protection Rating Short-Circuit Current Rating Deteriorating Agents Mechanical Execution of Work Mounting and Cooling of Equipment Conductor Termination High-Leg Conductor Identification Flash Protection Warning Manufacturer s Markings Identification of Disconnecting Means...43 Part II. 600V, Nominal or Less Spaces About Electrical Equipment Guarding...48 Article 110 Questions...49 Chapter 5 Special Occupancies Article 500 Hazardous (Classified) Locations Scope Articles 500 Through Definitions Other Articles General Classifications of Locations Material Groups Protection Techniques Equipment Specific Occupancies Article 500 Questions Article 501 Class I Hazardous (Classified) Locations Part I. General Scope General Part II. Wiring Wiring Methods Conduit and Cable Seals Conductor Insulation Bonding Surge Protection Multiwire Branch Circuits Part III. Equipment Transformers and Capacitors Meters, Instruments, and Relays Enclosures Control Transformers and Relays Motors and Generators Luminaires vi

20 Understanding the National Electrical Code, Volume 2 Table of Contents Flexible Cords Receptacles and Attachment Plugs Low-Voltage, Limited-Energy, and Communications Systems Article 501 Questions Article 502 Class II Hazardous (Classified) Locations Part I. General Scope General Part II. Wiring Wiring Methods Seals Bonding Surge Protection Multiwire Branch Circuits Part III. Equipment Switches, Circuit Breakers, Motor Controllers, and Fuses Control Transformers Motors and Generators Luminaires Flexible Cords Receptacles and Attachment Plugs Low-Voltage, Limited-Energy, and Communications Systems Article 502 Questions Article 503 Class III Hazardous (Classified) Locations Part I. General Scope General Part II. Wiring Wiring Methods Bonding Part III. Equipment Switches, Circuit Breakers, Motor Controllers, and Fuses Control Transformers Motors and Generators Luminaires Flexible Cords Receptacles and Attachment Plugs Signaling, Alarm, Remote-Control, and Loudspeaker Systems Article 503 Questions Article 504 Intrinsically Safe Systems Scope Definitions Application of Other Articles Equipment Approval Equipment Installation Wiring Methods Separation of Intrinsically Safe Circuits Grounding (Earthing) Bonding Sealing Identification Article 504 Questions Article 511 Commercial Garages, Repair, and Storage Scope Classification of Hazardous Areas Wiring and Equipment in Hazardous (Classified) Locations Wiring and Equipment Above Hazardous (Classified) Locations Seals Special Equipment GFCI-Protected Receptacles Article 511 Questions Article 513 Aircraft Hangars Scope Classification of Locations Wiring and Equipment in Class I Locations Wiring Not Within Class I Locations Wiring in or Under Hangar Floor Sealing GFCI-Protected Receptacles Bonding Article 513 Questions Article 514 Motor Fuel Dispensing Facilities Scope Definition Classification of Locations Wiring and Equipment Within Class I Locations Wiring and Equipment Above Class I Locations Underground Wiring Raceway Seal Emergency Dispenser Disconnects Maintenance and Service of Dispensing Equipment vii

21 Table of Contents Understanding the National Electrical Code, Volume Grounding (Bonding) Article 514 Questions Article 517 Health Care Facilities Part I. General Scope Definitions Part II. Wiring and Protection Applicability Wiring Methods Grounding (Bonding) Equipment in Patient Care Areas Isolated Ground Receptacles General Care Areas Essential Electrical Systems for Hospitals Article 517 Questions Article 518 Assembly Occupancies Scope General Classifications Other Articles Wiring Methods Article 518 Questions Article 525 Carnivals, Circuses, Fairs, and Similar Events Part I. General Requirements Scope Other Articles Overhead Conductor Clearances Protection of Electrical Equipment Part II. Power Sources Services Multiple Sources of Supply Wiring Methods Rides, Tents, and Concessions Outdoor Portable Distribution or Termination Boxes GFCI-Protected Receptacles and Equipment Part IV. Grounding and Bonding Equipment Bonding Equipment Grounding (Bonding) Grounding (Bonding) Conductor Continuity Assurance Article 525 Questions Article 547 Agricultural Buildings Scope Definitions Wiring Methods Equipotential Planes and Bonding of Equipotential Planes Article 547 Questions Article 550 Mobile Homes, Manufactured Homes, and Mobile Home Parks Part I. General Scope Definitions General Requirements Receptacle Outlets Arc-Fault Circuit-Interrupter (AFCI) Protection Part III. Services and Feeders Distribution Systems Allowable Demand Factors Disconnect Feeder Article 550 Questions Article 551 Recreational Vehicles and Recreational Vehicle Parks Part I. General Scope Definitions Other Articles Part VI. Recreational Vehicle Parks Type of Receptacles Required Calculated Load Clearance for Overhead Conductors Article 551 Questions Article 555 Marinas and Boatyards Scope Definitions Transformers Electrical Connections Load Calculations for Service and Feeder Conductors Boat Receptacle Disconnecting Means Receptacles Motor Fuel Dispensing Stations Repair Facilities Article 555 Questions viii

22 Understanding the National Electrical Code, Volume 2 Table of Contents Article 590 Temporary Installations Scope All Installations Time Constraints General Ground-Fault Protection for Personnel Article 590 Questions Chapter 6 Special Equipment Article 600 Electric Signs and Outline Lighting Part I. General Scope Definitions Listing Markings Branch Circuits Disconnects Location Portable or Mobile Signs Ballasts, Transformers, and Electronic Power Supplies Article 600 Questions Article 604 Manufactured Wiring Systems Scope Definition Other Articles Uses Permitted Uses Not Permitted Construction Article 604 Questions Article 605 Office Furnishings (Wired Partitions) Scope General Partition Interconnections Fixed-Type Partitions Freestanding-Type Partitions Article 605 Questions Article 620 Elevators, Escalators, and Moving Walks Part I. General Scope Part III. Wiring Branch Circuit for Machine Room/Machinery Space Branch Circuit for Hoistway Pit Part IV. Installation of Conductors Wiring in Elevator Hoistways and Machine Rooms Part VI. Disconnecting Means and Control Disconnecting Means Part VIII. Machine Rooms, Control Rooms, Machinery Spaces, and Control Spaces GFCI-Protected Receptacles Article 620 Questions Article 625 Electric Vehicle Charging Systems Part I. General Scope Definitions Part IV. Control and Protection Personnel Protection System Loss of Primary Source Interactive Systems Article 625 Questions Article 630 Electric Welders Part I. General Scope Part II. Arc Welders Ampacity of Supply Conductors Overcurrent Protection Disconnecting Means Part III. Resistance Welders Ampacity of Supply Conductors Overcurrent Protection Disconnecting Means Article 630 Questions Article 640 Audio Signal Processing, Amplification, and Reproduction Equipment Part I. General Scope Definitions Locations and Other Articles Protection of Electrical Equipment Access to Electrical Equipment Mechanical Execution of Work Grounding (Earthing) and Bonding Wiring Methods ix

23 Table of Contents Understanding the National Electrical Code, Volume Audio Systems Near Bodies of Water Part II. Permanent Audio System Installations Use of Flexible Cords and Flexible Cables Wiring of Equipment Racks Raceway Fill Loudspeakers in Fire-Resistance Rated Partitions, Walls, and Ceilings Article 640 Questions Article 645 Information Technology Equipment Scope Information Technology Equipment Room Supply Circuits and Interconnecting Cables Cables Not in Information Technology Equipment Room Penetrations Disconnecting Means Uninterruptible Power Supplies (UPS) Grounding (Bonding) Article 645 Questions Article 647 Sensitive Electronic Equipment Scope General Wiring Methods Grounding (Bonding) Receptacles Article 647 Questions Article 680 Swimming Pools, Spas, Hot Tubs, Fountains, and Similar Installations Part I. General Requirements for Permanently Installed Pools, Storable Pools, Outdoor Spas, Outdoor Hot Tubs, or Fountains Scope Definitions Other Articles Cord-and-Plug Connected Equipment Overhead Conductor Clearance Electric Water Heater Underground Wiring Location Equipment Rooms and Pits Maintenance Disconnecting Means Part II. Permanently Installed Pools, Outdoor Spas, and Outdoor Hot Tubs Motors Area Lighting, Receptacles, and Equipment Underwater Luminaires Junction Boxes Feeders Equipotential Bonding Specialized Equipment Part III. Storable Swimming Pool General GFCI-Protected Receptacles Receptacle Locations Part IV. Spas and Hot Tubs General Emergency Switch for Spas and Hot Tubs Outdoor Installations Indoor Installations GFCI Protection Part V. Fountains General Luminaires, Submersible Pumps, and Other Submersible Equipment Bonding Methods of Grounding (Bonding) Cord-and-Plug Connected Equipment Signs in or Adjacent to Fountains GFCI-Protected Receptacles Part VII. Hydromassage Bathtubs Protection Other Electric Equipment Other Electrical Equipment Accessibility Bonding Article 680 Questions Article 690 Solar Photovoltaic Systems Part I. General Scope Article 692 Fuel Cell Systems Scope Definitions Listing Requirement Article 692 Questions Article 695 Fire Pumps Scope Power Sources Continuity of Power Transformers Power Wiring x

24 Understanding the National Electrical Code, Volume Voltage Drop Control Wiring Article 695 Questions Table of Contents Accessibility Ground-Fault Protection of Equipment Coordination Article 701 Questions Chapter 7 Special Conditions Article 700 Emergency Power Systems Part I. General Scope Application of Other Articles Equipment Approval Tests and Maintenance Capacity Transfer Equipment Signs Part II. Circuit Wiring Wiring Part III. Sources of Power General Requirements Part IV. Emergency System Circuits for Lighting and Power Loads on Emergency Branch Circuits Emergency Illumination Part VI. Overcurrent Protection Accessibility Ground-Fault Protection of Equipment Coordination Article 700 Questions Article 701 Legally Required Standby Power Systems Part I. General Scope Definitions Application of Other Articles Equipment Approval Tests and Maintenance Capacity and Rating Transfer Equipment Signs Part II. Circuit Wiring Wiring Part III. Sources of Power Legally Required Standby Systems Part IV. Overcurrent Protection Article 702 Optional Standby Power Systems Part I. General Scope Definition Application of Other Articles Equipment Approval Capacity and Rating Transfer Equipment Signs Part II. Circuit Wiring Wiring Part III. Grounding and Bonding Portable Generator Grounding and Bonding Part IV. Sources of Power Outdoor Generator Sets Article 702 Questions Article 720 Circuits and Equipment Operating at Less than 50 Volts Article 720 Question Article 725 Class 1, Class 2, and Class 3 Remote- Control, Signaling, and Power-Limited Circuits Part I. General Scope Definitions Other Articles Access to Electrical Equipment Behind Panels Designed to Allow Access Mechanical Execution of Work Safety-Control Equipment Circuit Requirements Part II. Class 1 Circuit Requirements Class 1 Circuit Classifications and Power Source Requirements Class 1 Circuit Overcurrent Protection Class 1 Circuit Wiring Methods Conductors of Different Circuits in Same Cable, Enclosure, or Raceway Class 1 Circuit Conductors Number of Conductors in a Raceway xi

25 Table of Contents Understanding the National Electrical Code, Volume 2 Part III. Class 2 and Class 3 Circuit Requirements Power Sources for Class 2 and Class 3 Circuits Equipment Marking Wiring Methods on Supply Side of the Class 2 or Class 3 Power Source Wiring Methods on Load Side of the Class 2 or Class 3 Power Source Separation from Other Systems Conductors of Different Circuits in Same Cable, Enclosure, or Raceway Class 2 or Class 3 Cables Exposed to Lightning Support Applications of Class 2 and Class 3 Cables Part VI. Listing Requirements Listing and Marking of Class 2 and Class 3 Cables Article 725 Questions Article 760 Fire Alarm Systems Part I. General Scope Definitions Other Articles Access to Electrical Equipment Behind Panels Designed to Allow Access Mechanical Execution of Work Fire Alarm Circuit and Equipment Grounding (Bonding) Fire Alarm Circuit Identification Fire Alarm Circuit Cables Exposed to Lightning Fire Alarm Circuit Requirements Part II. Nonpower-Limited Fire Alarm (NPLFA) Circuits GFCI and AFCI Protection NPLFA Circuit Overcurrent Protection NPLFA Circuit Wiring Methods Conductors of Different Circuits in Same Cable, Enclosure, or Raceway NPLFA Circuit Conductors Number of Conductors in a Raceway Part III. Power-Limited Fire Alarm (PLFA) Circuits Power Sources for PLFA Circuits Equipment Marking Wiring Methods and Materials on Load Side of the PLFA Power Source Separation from Other Circuit Conductors PLFA Circuits, Class 2, Class 3, and Communications Circuits Support Applications of Listed PLFA Cables Part IV. Listing Requirements Listing and Marking of NPLFA Cables Listing and Marking of PLFA Cables Article 760 Questions Article 770 Optical Fiber Cables and Raceways Part I. General Scope Definitions Locations and Other Articles Optical Fiber Cables Types Raceways for Optical Fiber Cables Access to Electrical Equipment Behind Panels Designed to Allow Access Mechanical Execution of Work Part III. Cables Within Buildings Listing of Optical Fiber Cables Installation of Optical Fibers and Electrical Conductors Applications of Listed Optical Fiber Cables and Raceways Part IV. Listing Requirements Listing Requirements for Optical Fiber Cables Listing Requirements for Optical Fiber Raceways Article 770 Questions Chapter 8 Communications Systems Article 800 Communications Circuits Part I. General Scope Definitions Other Articles Installation of Equipment Access to Electrical Equipment Behind Panels Designed to Allow Access Mechanical Execution of Work Overhead Communications Wires and Cables Part II. Conductors Outside and Entering Buildings Underground Circuits Entering Buildings Lightning Conductors Part III. Protection xii

26 Understanding the National Electrical Code, Volume 2 Table of Contents Primary Protection Cable Grounding Part IV. Grounding Methods Cable and Primary Protector Grounding Part V. Communications Wires and Cables Within Buildings Raceways for Communications Circuits Listing of Communications Wires and Cables Installation of Communications Circuits and Equipment Applications of Listed Communications Wires, Cables, and Raceways Part VI. Listing Requirements Communications Wires and Cables Communications Raceways Article 800 Questions Article 810 Radio and Television Equipment Part I. General Scope Other Articles Community Television Antenna Part II. Receiving Equipment Antenna Systems Support of Lead-In Cables Avoid Contact with Conductors of Other Systems Grounding Clearances Antenna Discharge Unit Grounding Conductors Article 810 Questions Article 820 Community Antenna Television (CATV) and Radio Distribution Systems Part I. General Scope Definitions Locations and Other Articles Energy Limitations Access to Electrical Equipment Behind Panels Designed to Allow Access Mechanical Execution of Work Part II. Cables Outside and Entering Buildings Overhead Cables Underground Circuits Entering Buildings Part III. Protection Grounding Cable Part IV. Grounding Methods Cable Grounding Part V. Cables Within Buildings Raceways for Coaxial Cables Listing and Markings Installation of Cables and Equipment Applications of Listed CATV Cables and Raceways Part VI. Listing Requirements Additional Listing Requirements CATV Raceways Article 820 Questions Article 830 Network-Powered Broadband Communications Systems Part I. General Scope Definitions Article 830 Questions Chapter 9 Tables Table 1 Conductor Fill Table 4 Raceway Dimensions Table 5 Conductor Cross-Sectional Area Table 8 Conductor Properties Table 9 AC Impedance for Conductors in Conduit Tubing Annex C Raceway Fill Tables Table C.1 Maximum Number of THNN/THWN Conductors in EMT Table C.10 Maximum Number of THNN/THWN Conductors in RNC xiii

27 UNIT 1 ELECTRICIAN S MATH AND BASIC ELECTRICAL FORMULAS...1 Introduction...1 PART A ELECTRICIAN S MATH...1 Introduction Whole Numbers Decimal Fractions Percentages Multiplier Percent Increase Reciprocals Squaring a Number Square Root Volume Kilo Rounding Off Parentheses Testing Your Answer for Reasonableness...6 PART B BASIC ELECTRICAL FORMULAS...7 Introduction Electrical Circuit Power Source Conductance Circuit Resistance Ohm s Law Ohm s Law and Alternating Current Ohm s Law Formula Circle PIE Formula Circle Formula Wheel Using the Formula Wheel Power Losses of Conductors Cost of Power Power Changes with the Square of the Voltage...14 PART C BASIC ELECTRIC METERS...16 Introduction Voltmeter DC Voltmeter DC Ammeter Clamp-on AC Ammeter Ohmmeters Wheatstone Bridge Megohmmeter...18 Conclusion...19 UNIT 2 ELECTRICAL CIRCUITS...49 Introduction...49 PART A SERIES CIRCUITS...49 Introduction Practical Uses of the Series Circuit Understanding Series Calculations Series Circuit Calculations Power Calculations Variations Series Circuit Notes Series-Connected Power Supplies...54 PART B PARALLEL CIRCUITS...54 Introduction Practical Uses of the Parallel Circuit Understanding Parallel Calculations Circuit Resistance Parallel Circuit Notes Parallel-Connected Power Supplies...59 PART C SERIES-PARALLEL CIRCUITS...59 Introduction Review of Series and Parallel Circuits Working Series-Parallel Circuits Voltage...61 PART D MULTIWIRE BRANCH CIRCUITS...62 Introduction Neutral Conductor Grounded Conductor...62 vi

28 Electrical NEC Exam Preparation Table of Contents 2.18 Current Flow on the Grounded Neutral Conductor Balanced Systems Unbalanced Current Multiwire Branch Circuit Dangers of Multiwire Circuits NEC Requirements...67 Conclusion...68 UNIT 3 UNDERSTANDING ALTERNATING CURRENT...97 Introduction...97 PART A UNDERSTANDING ALTERNATING CURRENT...97 Introduction Current Flow Why Alternating Current is Used How Alternating Current is Produced AC Generator Waveform Sine Wave Nonsymmetrical Waveform Frequency Phase Degrees Lead or Lag Values of Alternating Current PART B CAPACITANCE Introduction Charged Capacitor Electrical Field Discharging a Capacitor Determining Capacitance Uses of Capacitors Phase Relationship PART C INDUCTION Introduction Self-Induction Induced Voltage and Applied Current Conductor AC Resistance Impedance Conductor Shape Magnetic Cores Self-Induced and Applied Voltage Current Flow Phase Relationship Uses of Induction PART D POWER FACTOR Introduction Apparent Power (Volt-Amperes) True Power (Watts) Power Factor Unity Power Factor Power Factor Formulas Cost of True Power Effects of Power Factor PART E EFFICIENCY Introduction Efficiency Formulas Conclusion UNIT 4 MOTORS AND TRANSFORMERS Introduction PART A MOTORS Introduction Motor Principles Dual-Voltage AC Motors Motor Horsepower Rating Motor Current Ratings Calculating Motor FLA Motor-Starting Current Motor-Running Current Motor Locked-Rotor Current (LRC) Motor Overload Protection Direct-Current Motor Principles Direct-Current Motor Types Reversing the Rotation of a DC Motor AC Induction Motor Alternating-Current Motor Types Reversing the Rotation of an AC Motor PART B TRANSFORMERS Introduction Transformer Basics Secondary Induced Voltage Autotransformers Power Losses Harmonic Current Efficiency Transformer Turns Ratio Transformer kva Rating Current Flow Current Rating Conclusion vii

29 Table of Contents UNIT 5 RACEWAY AND BOX CALCULATIONS Introduction PART A RACEWAY FILL Understanding the NEC, Chapter 9 Tables Raceway and Nipple Calculations Existing Raceway Calculations Tips for Raceway Calculations PART B OUTLET BOX FILL CALCULATIONS [314.16] Sizing Box Conductors All the Same Size [Table (A)] Conductor Equivalents [314.16(B)] Sizing Box Different Size Conductors [314.16(B)] PART C PULL BOXES, JUNCTION BOXES, AND CONDUIT BODIES Pull and Junction Box Size Calculations Depth of Box and Conduit Body Sizing [314.28(A)(2) Ex] Junction and Pull Box Sizing Tips Pull Box Examples Conclusion Electrical NEC Exam Preparation 6.13 Conductor Bundling Ampacity Adjustment Factor [Table (B)(2)(a)] Ambient Temperature Correction and Conductor Bundling Adjustment Factors Current-Carrying Conductors Conductor Sizing Summary Conclusion UNIT 7 MOTOR CALCULATIONS Introduction Single Motor Conductors [430.22(A)] Motor Overcurrent Protection Overload Protection [430.6(2) and (A)] Branch-Circuit Short-Circuit Ground-Fault Protection [430.51] Feeder Conductor Size [430.24] Feeder Protection [430.61] Highest-Rated Motor [430.17] Motor Calculations Steps Motor Calculation Review Motor VA Calculations Conclusion UNIT 6 CONDUCTOR SIZING AND PROTECTION CALCULATIONS Introduction PART A GENERAL CONDUCTOR REQUIREMENTS Conductor Insulation Property [Table ] Allowable Conductor Ampacity [310.15] Conductor Sizing [110.6] Terminal Ratings [110.14(C)] Conductors in Parallel [310.4] Conductor Size Voltage Drop [210.19(A)(1) FPN No. 4 and 215.2(A) FPN No. 2] Overcurrent Protection [Article 240] Overcurrent Protection of Conductors General Requirements [240.4] Overcurrent Protection of Conductors Specific Requirements Equipment Conductor Size and Protection Examples PART B CONDUCTOR AMPACITY CALCULATIONS Conductor Ampacity [310.10] Ambient Temperature Ampacity Correction Factor [Table ] UNIT 8 VOLTAGE-DROP CALCULATIONS Introduction PART A CONDUCTOR RESISTANCE CALCULATIONS Conductor Resistance Conductor Resistance Direct-Current Circuits [Chapter 9, Table 8] Conductor Impedance Alternating-Current Circuits Alternating-Current Impedance as Compared to Direct-Current Resistance Impedance [Chapter 9, Table 9] PART B VOLTAGE-DROP CALCULATIONS Voltage-Drop Considerations NEC Voltage-Drop Recommendations Determining Circuit Conductors Voltage Drop Sizing Conductors to Prevent Excessive Voltage Drop Limiting Conductor Length to Minimize Voltage Drop Limiting Current to Limit Voltage Drop Extending Circuits Conclusion viii

30 Electrical NEC Exam Preparation Table of Contents UNIT 9 DWELLING UNIT CALCULATIONS Introduction PART A GENERAL REQUIREMENTS General Requirements Voltages [220.5(A)] Fraction of an Ampere [220.5(B)] Small-Appliance Circuits [210.11(C)(1)] Cooking Equipment Branch Circuit [Table , Note 4] Laundry Receptacle(s) Circuit [210.11(C)(2)] Lighting and Receptacles PART B STANDARD METHOD FEEDER/SERVICE LOAD CALCULATIONS Dwelling Unit Feeder/Service Load Calculations (Article 220, Part III) Dwelling Unit Feeder/Service Calculations Examples PART C OPTIONAL METHOD FEEDER/SERVICE LOAD CALCULATIONS Dwelling Unit Optional Feeder/Service Calculations [220.82] Dwelling Unit Optional Calculation Examples Neutral Calculations General [220.61] Conclusion UNIT 10 MULTIFAMILY DWELLING CALCULATIONS Introduction Multifamily Dwelling Unit Calculations General PART A STANDARD METHOD FEEDER/SERVICE LOAD CALCULATIONS Multifamily Dwelling Unit Calculation Examples Standard Method Multifamily Dwelling Unit Calculations Standard Method PART B OPTIONAL METHOD FEEDER/SERVICE LOAD CALCULATIONS Multifamily Dwelling Unit Calculations [220.84] Optional Method Multifamily Optional Method Example 1 [220.84] Multifamily Optional Method Example 2 [220.84] Conclusion UNIT 11 COMMERCIAL CALCULATIONS Introduction PART A GENERAL General Requirements Conductor Ampacity [Article 100] Conductor Overcurrent Protection [240.4] Voltages [220.5(A)] Rounding an Ampere [220.5(B)] Air-Conditioning Branch Circuit Dryers Electric Heat Kitchen Equipment Laundry Equipment Lighting Demand Factors [Tables and ] Lighting Without Demand Factors [215.2(A)(1), (A)(1), and Table ] Lighting-Miscellaneous Multioutlet Receptacle Assembly [220.14(H)] Receptacle VA Load Banks and Offices General Lighting and Receptacles [220.14(K)] Signs [220.14(F) and 600.5] PART B STANDARD METHOD FEEDER/SERVICE LOAD CALCULATIONS Feeder/Service Load Calculation Neutral Calculations [220.61] PART C EXAMPLES Bank (120/240V, single-phase) Marina [555.12] Mobile/Manufactured Home Park [550.31] Office Building (277/480V, Three-phase) Recreational Vehicle Park [551.73] Restaurant Standard Load Calculation (120/208V, Three-phase) PART D OPTIONAL METHOD FEEDER/SERVICE LOAD CALCULATIONS New Restaurant Optional Method [220.88] School Optional Method [220.86] PART E ELECTRIC WELDERS Arc Welders Resistance Welders Light Industrial Calculation Conclusion ix

31 Table of Contents UNIT 12 DELTA/DELTA AND DELTA/WYE TRANSFORMERS Introduction Definitions Current Flow PART A DELTA/DELTA TRANSFORMERS Delta Transformer Voltage Delta High-Leg Delta Line Currents Delta Phase Currents Delta Phase versus Line Current Delta Current Triangle Delta Transformer Balancing Delta Transformer Sizing Delta Panel Balancing Delta Panelboard and Conductor Sizing Delta Neutral Current Delta Maximum Unbalanced Load Delta/Delta Example Electrical NEC Exam Preparation PART B DELTA/WYE TRANSFORMERS Wye Transformer Voltage Wye Voltage Triangle Wye Transformers Current Wye Line Current Wye Phase Current Wye Phase versus Line Current Wye Transformer Balancing Wye Transformer Sizing Wye Panel Balancing Wye Panelboard and Conductor Sizing Wye Neutral Current Wye Maximum Unbalanced Load Delta/Wye Example Delta versus Wye Conclusion INDEX x

32 Introduction...vii Passing the Exam...viii The National Electrical Code...xi About the Author...xvi Unit 1 Review Quiz Articles 90 through Practice Quiz Articles 80 through Challenge Quiz Articles 90 through Annex C...21 Unit 2 Review Quiz Articles 200 through Practice Quiz Articles 200 through Challenge Quiz Articles 90 through Annex C...48 Unit 3 Review Quiz Articles 230 through Practice Quiz Articles 230 through Challenge Quiz Articles 90 through Annex C...75 Unit 4 Review Quiz Articles 250 through Practice Quiz Articles 250 through Challenge Quiz Articles 90 through Annex C Unit 5 Review Quiz Articles 310 through Practice Quiz Articles 310 through Challenge Quiz Articles 90 through Annex C Unit 6 Review Quiz Articles 342 through Practice Quiz Articles 344 through Challenge Quiz Articles 90 through Annex C Unit 7 Review Quiz Articles 386 through Practice Quiz Articles 386 through Challenge Quiz Articles 90 through Annex C Unit 8 Review Quiz Articles 410 through Practice Quiz Articles 410 through Challenge Quiz Articles 90 through Annex C Unit 9 Review Quiz Articles 500 through Practice Quiz Articles 500 through Challenge Quiz Articles 90 through Annex C Unit 10 Review Quiz Articles 517 through Practice Quiz Articles 517 through Challenge Quiz Articles 90 through Annex C Unit 11 Review Quiz Articles 645 through Practice Quiz Articles 645 through Challenge Quiz Articles 90 through Annex C Unit 12 Review Quiz Articles 702 through Annex C Practice Quiz Articles 702 through Chapter Challenge Quiz Articles 90 through Annex C vi