SECTION 1 LOW-VOLTAGE AND POWER- LIMITED SYSTEMS...1 Overview of Low-Voltage and Power-Limited Systems...3 Chapter 4 Equipment for General Use...3 Chapter 5 Special Occupancies...3 Chapter 6 Special Equipment...4 Chapter 7 Special Conditions...4 Chapter 8 Communications Systems...8 Summary of NEC Requirements for Low-Voltage Systems...13 Abandoned Cable...13 Access to Electrical Equipment...13 Burial Depth...14 Cable Marking...14 Cable Tray [392.3(A)]...15 Enclosures Not Required...15 Environmental Air Space...16 Fire-Rated Walls, Floors, and Ceilings...16 Grounding...16 Handholes...18 Listing Requirements for Cables...18 Listing Requirements for Raceways...18 Mixing Other Low-Voltage or Power-Limited Cables...18 Mixing Low-Voltage and Power-Limited Cables with Power Conductors...19 Plenum-Rated Cables...19 Plenum-Rated Raceways...19 Protection from Physical Damage...20 Raceway Not Required...20 Raceway Required...20 Raceway Used as Support...21 Raised Floor (Environmental Air Space)...21 Separation (6 ft) from Lightning Conductors...22 Separation from Power Conductors...22 Separation from Wiring Methods...22 Service Mast...22 Support of Cable...23 Suspended Ceiling (Environmental Air Space)...23 Underground Installation...24 SECTION 2 NEC REFERENCES Article 90 Introduction...27 Introduction...27 90.1 Purpose of the NEC...27 90.2 Scope of the NEC...28 90.3 Code Arrangement...29 90.4 Enforcement...29 90.5 Mandatory Requirements and Explanatory Material...30 90.7 Examination of Equipment for Product Safety...31 Article 90 Questions...32 CHAPTER 1 GENERAL Introduction...35 ARTICLE 100 DEFINITIONS...37 Introduction...37 Article 100 Questions...42 ARTICLE 110 REQUIREMENTS FOR ELECTRICAL INSTALLATIONS...45 Introduction...45 PART I. GENERAL REQUIREMENTS...45 110.1 Scope...45 110.2 Approval of Equipment...45 110.3 Examination, Identification, Installation, and Use of Equipment...45 110.5 Copper Conductors...46 110.6 Conductor Sizes...46 110.7 Conductor Insulation...46 110.8 Suitable Wiring Methods...46 110.11 Deteriorating Agents...47 110.12 Mechanical Execution of Work...47 110.13 Mounting and Cooling of Equipment...48 110.14 Conductor Termination...49 110.21 Manufacturer s Markings...51 PART II. 600V, NOMINAL OR LESS...51 110.26 Spaces About Electrical Equipment...51 110.27 Guarding...56 Article 110 Questions...57 vi
Understanding Low-Voltage and Power-Limited Systems CHAPTER 2 WIRING AND PROTECTION Introduction...61 ARTICLE 250 GROUNDING AND BONDING...63 Introduction...63 PART I. GENERAL...63 250.1 Scope...63 250.2 Definitions...64 250.4 General Requirements for Grounding and Bonding...68 250.8 Termination of Grounding and Bonding Conductors...72 250.12 Clean Surface...73 PART II. SYSTEM GROUNDING AND BONDING...73 250.20 Systems Required to be Grounded and Bonded...73 PART III. GROUNDING ELECTRODE SYSTEM AND GROUNDING ELECTRODE CONDUCTOR...75 250.50 Grounding Electrode System...75 250.52 Grounding (Earthing) Electrodes...75 250.53 Installation of Grounding Electrode System...78 250.54 Supplementary Electrodes...80 250.56 Resistance of Ground Rod Electrode...80 250.68 Grounding Electrode Conductor Termination...82 250.70 Grounding Electrode Conductor Termination Fitting...82 PART V. BONDING...82 250.94 Grounding (Bonding) of Communications Systems...82 PART VI. EQUIPMENT GROUNDING (BONDING) AND EQUIPMENT GROUNDING (BONDING) CONDUCTORS...83 250.112 Fixed Equipment Connected by Permanent Wiring Methods Specific...83 Article 250 Questions...84 CHAPTER 3 WIRING METHODS AND MATERIALS Introduction...89 ARTICLE 300 WIRING METHODS...91 Introduction...91 PART I. GENERAL REQUIREMENTS...91 300.1 Scope...91 300.3 Conductors...92 300.4 Protection Against Physical Damage...93 300.5 Underground Installations...93 300.6 Protection Against Corrosion and Deterioration...94 300.7 Raceways Exposed to Different Temperatures...96 Table of Contents 300.8 Not Permitted in Raceways...96 300.10 Electrical Continuity...97 300.11 Securing and Supporting...97 300.12 Mechanical Continuity...98 300.15 Boxes or Conduit Bodies...99 300.22 Ducts, Plenums, and Air-Handling Spaces...100 300.21 Spread of Fire or Products of Combustion...100 300.23 Panels Designed to Allow Access...102 Article 300 Questions...104 ARTICLE 314 OUTLET, DEVICE, PULL AND JUNCTION BOXES, CONDUIT BODIES, AND HANDHOLE ENCLOSURES...109 Introduction...109 PART I. SCOPE AND GENERAL...109 314.1 Scope...109 314.3 Nonmetallic Boxes...109 314.4 Metal Boxes...109 PART II. INSTALLATION...110 314.15 Damp, Wet, or Hazardous (Classified) Locations...110 314.21 Repairing Gaps Around Boxes...110 314.23 Support of Boxes and Conduit Bodies...110 314.25 Covers and Canopies...112 314.29 Wiring to be Accessible...112 314.30 Handhole Enclosures...112 Article 314 Questions...114 ARTICLE 336 POWER AND CONTROL TRAY CABLE (TYPE TC)...117 Introduction...117 PART I. GENERAL...117 336.1 Scope...117 336.2. Definition...117 PART II. INSTALLATION...117 336.10 Uses Permitted...117 336.12 Uses Not Permitted...117 Article 336 Questions...118 ARTICLE 342 INTERMEDIATE METAL CONDUIT (TYPE IMC)...119 Introduction...119 PART I. GENERAL...119 342.1 Scope...119 342.2 Definition...119 342.6 Listing Requirements...119 vii
Table of Contents PART II. INSTALLATION...119 342.10 Uses Permitted...119 342.14 Dissimilar Metals...120 342.20 Trade Size...120 342.22 Number of Conductors...120 342.24 Bends...120 342.26 Number of Bends (360 )...120 342.28 Reaming...120 342.30 Secured and Supported...120 342.42 Couplings and Connectors...122 342.46 Bushings...122 Article 342 Questions...123 ARTICLE 344 RIGID METAL CONDUIT (TYPE RMC)...125 Introduction...125 PART I. GENERAL...125 344.1 Scope...125 344.2 Definition...125 344.6 Listing Requirements...125 PART II. INSTALLATION...125 344.10 Uses Permitted...125 344.14 Dissimilar Metals...125 344.20 Trade Size...126 344.22 Number of Conductors...126 344.24 Bends...126 344.26 Number of Bends (360 )...126 344.28 Reaming...126 344.30 Secured and Supported...126 344.42 Couplings and Connectors...127 344.46 Bushings...128 Article 344 Questions...129 ARTICLE 348 FLEXIBLE METAL CONDUIT (TYPE FMC)...131 Introduction...131 PART I. GENERAL...131 348.1 Scope...131 348.2 Definition...131 348.6 Listing Requirements...131 PART II. INSTALLATION...131 348.10 Uses Permitted...131 348.12 Uses Not Permitted...131 348.20 Trade Size...131 348.22 Number of Conductors...132 348.24 Bends...132 348.26 Number of Bends (360 )...132 348.28 Trimming...132 348.30 Secured and Supported...132 Understanding Low-Voltage and Power-Limited Systems 348.42 Fittings...133 348.60 Bonding...133 Article 348 Questions...134 ARTICLE 350 LIQUIDTIGHT FLEXIBLE METAL CONDUIT (TYPE LFMC)...137 Introduction...137 PART I. GENERAL...137 350.1 Scope...137 350.2 Definition...137 350.6 Listing Requirement...137 PART II. INSTALLATION...137 350.10 Uses Permitted...137 350.12 Uses Not Permitted...137 350.20 Trade Size...137 350.22 Number of Conductors...138 350.24 Bends...138 350.26 Number of Bends (360 )...138 350.30 Secured and Supported...138 350.42 Fittings...139 350.60 Bonding...139 Article 350 Questions...140 ARTICLE 352 RIGID NONMETALLIC CONDUIT (TYPE RNC)...141 Introduction...141 PART I. GENERAL...141 352.1 Scope...141 352.2 Definition...141 PART II. INSTALLATION...141 352.10 Uses Permitted...141 352.12 Uses Not Permitted...142 352.20 Trade Size...142 352.22 Number of Conductors...142 352.24 Bends...143 352.26 Number of Bends (360 )...143 352.28 Trimming...143 352.30 Secured and Supported...143 352.44 Expansion Fittings...144 352.46 Bushings...144 352.48 Joints...144 352.60 Grounding (Bonding)...145 Article 352 Questions...146 ARTICLE 353 HIGH-DENSITY POLYETHYLENE CONDUIT (TYPE HDPE)...149 Introduction...149 viii
Understanding Low-Voltage and Power-Limited Systems PART I. GENERAL...149 353.1 Scope...149 353.2 Definition...149 353.6 Listing Requirements...149 PART II. INSTALLATION...149 353.10 Uses Permitted...149 353.12 Uses Not Permitted...150 353.20 Trade Size...150 353.22 Number of Conductors...150 353.24 Bends How Made...150 353.26 Bends Number in One Run...150 353.28 Trimming...150 353.46 Bushings...150 353.48 Joints...150 353.56 Splices and Taps...150 353.60 Grounding (Bonding)...150 Article 353 Questions...151 ARTICLE 358 ELECTRICAL METALLIC TUBING (TYPE EMT)...153 Introduction...153 PART I. GENERAL...153 358.1 Scope...153 358.2 Definition...153 358.6 Listing Requirement...153 PART II. INSTALLATION...153 358.10 Uses Permitted...153 358.12 Uses Not Permitted...154 358.20 Trade Size...154 358.22 Number of Conductors...154 358.24 Bends...154 358.26 Number of Bends (360 )...154 358.28 Reaming and Threading...155 358.30 Secured and Supported...155 358.42 Coupling and Connectors...155 Article 358 Questions...156 ARTICLE 362 ELECTRICAL NONMETALLIC TUBING (TYPE ENT)...157 Introduction...157 PART I. GENERAL...157 362.1 Scope...157 362.2 Definition...157 PART II. INSTALLATION...157 362.10 Uses Permitted...157 362.12 Uses Not Permitted...159 362.20 Trade Sizes...159 Table of Contents 362.22 Number of Conductors...159 362.24 Bends...160 362.26 Number of Bends (360 )...160 362.28 Trimming...160 362.30 Secured and Supported...160 362.46 Bushings...160 362.48 Joints...160 362.60 Grounding (Bonding)...160 Article 362 Questions...162 ARTICLE 384 STRUT-TYPE CHANNEL RACEWAYS...165 Introduction...165 PART I. GENERAL...165 384.1 Scope...165 384.2 Definition...165 PART II. INSTALLATION...165 384.10 Uses Permitted...165 384.12 Uses Not Permitted...165 384.21 Conductor Maximum Size...166 384.22 Number of Conductors...166 384.30 Securing and Supporting...166 384.56 Splices and Taps...166 384.60 Grounding (Bonding)...166 Article 384 Questions...167 ARTICLE 386 SURFACE METAL RACEWAYS...169 Introduction...169 PART I. GENERAL...169 386.1 Scope...169 386.2 Definition...169 386.6 Listing Requirements...169 PART II. INSTALLATION...169 386.10 Uses Permitted...169 386.12 Uses Not Permitted...170 386.21 Size of Conductors...170 386.22 Number of Conductors...170 386.30 Securing and Supporting...170 386.56 Splices and Taps...170 386.60 Grounding (Bonding)...170 386.70 Separate Compartments...170 Article 386 Questions...171 ARTICLE 388 SURFACE NONMETALLIC RACEWAYS...173 Introduction...173 PART I. GENERAL...173 388.1 Scope...173 388.2 Definition...173 ix
Table of Contents 388.6 Listing Requirements...173 PART II. INSTALLATION...173 388.10 Uses Permitted...173 388.12 Uses Not Permitted...173 388.21 Size of Conductors...173 388.22 Number of Conductors...173 388.56 Splices and Taps...174 388.60 Grounding (Bonding)...174 388.70 Separate Compartments...174 Article 388 Questions...175 ARTICLE 392 CABLE TRAYS...177 Introduction...177 392.1 Scope...177 392.2 Definition...177 392.3 Uses Permitted...177 392.4 Uses Not Permitted...178 392.6 Installation...178 392.7 Grounding (Bonding)...179 392.8 Cable Installation...179 Article 392 Questions...180 CHAPTER 4 EQUIPMENT FOR GENERAL USE Introduction...183 ARTICLE 400 FLEXIBLE CORDS AND FLEXIBLE CABLES...185 Introduction...185 400.1 Scope...185 400.3 Suitability...185 400.4 Types of Flexible Cords and Flexible Cables...185 400.7 Uses Permitted...185 400.8 Uses Not Permitted...186 400.10 Pull at Joints and Terminals...187 Article 400 Questions...188 ARTICLE 402 FIXTURE WIRES...189 Introduction...189 402.1 Scope...189 402.3 Types...189 402.5 Allowable Ampacity of Fixture Wires...189 402.6 Minimum Size...189 402.7 Raceway Size...189 402.10 Uses Permitted...190 402.11 Uses Not Permitted...190 Article 402 Questions...191 Understanding Low-Voltage and Power-Limited Systems ARTICLE 411 LIGHTING SYSTEMS OPERATING AT 30V OR LESS...193 Introduction...193 411.1 Scope...193 411.2 Definition...193 411.3 Listing Required...193 411.4 Locations Not Permitted...193 411.5 Secondary Circuits...194 Article 411 Questions...195 CHAPTER 5 SPECIAL OCCUPANCIES Introduction...197 ARTICLE 500 HAZARDOUS (CLASSIFIED) LOCATIONS...199 Introduction...199 500.1 Scope...199 500.2 Definitions...200 500.3 Other Articles...201 500.4 General...201 500.5 Classifications of Locations...201 500.6 Material Groups...203 500.7 Protection Techniques...204 500.8 Equipment...205 500.9 Specific Occupancies...207 Article 500 Questions...208 ARTICLE 501 CLASS I HAZARDOUS (CLASSIFIED) LOCATIONS...211 Introduction...211 PART I. GENERAL...211 501.1 Scope...211 501.5 General...211 PART II. WIRING...211 501.10 Wiring Methods...211 501.15 Conduit and Cable Seals...213 PART III. EQUIPMENT...217 501.150 Low-Voltage, Limited-Energy, and Communications Systems...217 Article 501 Questions...219 ARTICLE 502 CLASS II HAZARDOUS (CLASSIFIED) LOCATIONS...223 Introduction...223 PART I. GENERAL...223 502.1 Scope...223 502.5 General...223 x
Understanding Low-Voltage and Power-Limited Systems PART II. WIRING...224 502.10 Wiring Methods...224 502.15 Seals...225 PART III. EQUIPMENT...225 502.150 Low-Voltage, Limited-Energy, and Communications Systems...225 Article 502 Questions...227 ARTICLE 503 CLASS III HAZARDOUS (CLASSIFIED) LOCATIONS...229 Introduction...229 PART I. GENERAL...229 503.1 Scope...229 503.5 General...229 PART II. WIRING...229 503.10 Wiring Methods...229 PART III. EQUIPMENT...229 503.150 Signaling, Alarm, Remote-Control, and Loudspeaker Systems...229 Article 503 Questions...230 ARTICLE 504 INTRINSICALLY SAFE SYSTEMS...231 Introduction...231 504.1 Scope...231 504.2 Definitions...231 504.3 Application of Other Articles...231 504.4 Equipment Approval...231 504.10 Equipment Installation...231 504.20 Wiring Methods...232 504.30 Separation of Intrinsically Safe Circuits...232 504.50 Grounding (Earthing)...232 504.60 Bonding...232 504.70 Sealing...232 504.80 Identification...232 Article 504 Questions...234 CHAPTER 6 SPECIAL EQUIPMENT Introduction...237 ARTICLE 640 AUDIO SIGNAL PROCESSING, AMPLIFICATION, AND REPRODUCTION EQUIPMENT...239 Introduction...239 PART I. GENERAL...239 640.1 Scope...239 640.2 Definitions...239 640.3 Locations and Other Articles...239 640.4 Protection of Electrical Equipment...240 Table of Contents 640.5 Access to Electrical Equipment...240 640.6 Mechanical Execution of Work...240 640.7 Grounding (Earthing) and Bonding...241 640.9 Wiring Methods...242 640.10 Audio Systems Near Bodies of Water...242 PART II. PERMANENT AUDIO SYSTEM INSTALLATIONS...242 640.21 Use of Flexible Cords and Flexible Cables...242 640.22 Wiring of Equipment Racks...242 640.23 Raceway Fill...243 640.25 Loudspeakers in Fire-Resistance-Rated Partitions, Walls, and Ceilings...243 Article 640 Questions...244 ARTICLE 645 INFORMATION TECHNOLOGY EQUIPMENT...245 Introduction...245 645.1 Scope...245 645.4 Information Technology Equipment Room...245 645.5 Supply Circuits and Interconnecting Cables...245 645.6 Cables Not in Information Technology Equipment Room...247 645.7 Penetrations...247 645.10 Disconnecting Means...247 645.11 Uninterruptible Power Supplies (UPS)...247 645.15 Grounding (Bonding)...247 Article 645 Questions...248 ARTICLE 647 SENSITIVE ELECTRONIC EQUIPMENT...251 Introduction...251 647.1 Scope...251 647.3 General...251 647.4 Wiring Methods...251 647.6 Grounding (Bonding)...252 647.7 Receptacles...252 Article 647 Questions...253 CHAPTER 7 SPECIAL CONDITIONS Introduction...255 ARTICLE 720 CIRCUITS AND EQUIPMENT OPERATING AT LESS THAN 50 VOLTS...257 Introduction...257 Article 720 Questions...258 ARTICLE 725 CLASS 1, CLASS 2, AND CLASS 3 REMOTE-CONTROL, SIGNALING, AND POWER- LIMITED CIRCUITS...259 Introduction...259 xi
Table of Contents PART I. GENERAL...259 725.1 Scope...259 725.2 Definitions...260 725.3 Other Articles...261 725.7 Access to Electrical Equipment Behind Panels Designed to Allow Access...265 725.8 Mechanical Execution of Work...265 725.11 Safety-Control Equipment...266 725.15 Circuit Requirements...266 PART II. CLASS 1 CIRCUIT REQUIREMENTS...266 725.21 Class 1 Circuit Classifications and Power Source Requirements...266 725.23 Class 1 Circuit Overcurrent Protection...267 725.25 Class 1 Circuit Wiring Methods...267 725.26 Conductors of Different Circuits in Same Cable, Enclosure, or Raceway...267 725.27 Class 1 Circuit Conductors...268 725.28 Number of Conductors in a Raceway...268 PART III. CLASS 2 AND CLASS 3 CIRCUIT REQUIREMENTS...268 725.41 Power Sources for Class 2 and Class 3 Circuits...268 725.42 Equipment Marking...268 725.51 Wiring Methods on Supply Side of the Class 2 or Class 3 Power Source...268 725.52 Wiring Methods on Load Side of the Class 2 or Class 3 Power Source...269 725.55 Separation from Other Systems...269 725.56 Conductors of Different Circuits in Same Cable, Enclosure, or Raceway...271 725.57 Class 2 or Class 3 Cables Exposed to Lightning...272 725.58 Support...272 725.61 Applications of Class 2 and Class 3 Cables...273 PART VI. LISTING REQUIREMENTS...274 725.82 Listing and Marking of Class 2 and Class 3 Cables...274 Article 725 Questions...276 ARTICLE 760 FIRE ALARM SYSTEMS...279 Introduction...279 PART I. GENERAL...279 760.1 Scope...279 760.2 Definitions...279 760.3 Other Articles...280 760.7 Access to Electrical Equipment Behind Panels Designed to Allow Access...282 760.8 Mechanical Execution of Work...282 760.9 Fire Alarm Circuit and Equipment Grounding (Bonding)...283 Understanding Low-Voltage and Power-Limited Systems 760.10 Fire Alarm Circuit Identification...283 760.11 Fire Alarm Circuit Cables Exposed to Lightning...283 760.15 Fire Alarm Circuit Requirements...283 PART II. NONPOWER-LIMITED FIRE ALARM (NPLFA) CIRCUITS...283 760.21 GFCI and AFCI Protection...283 760.23 NPLFA Circuit Overcurrent Protection...283 760.25 NPLFA Circuit Wiring Methods...283 760.26 Conductors of Different Circuits in Same Cable, Enclosure, or Raceway...284 760.27 NPLFA Circuit Conductors...284 760.28 Number of Conductors in a Raceway...284 PART III. POWER-LIMITED FIRE ALARM (PLFA) CIRCUITS...284 760.41 Power Sources for PLFA Circuits...284 760.42 Equipment Marking...284 760.52 Wiring Methods and Materials on Load Side of the PLFA Power Source...285 760.55 Separation from Other Circuit Conductors...285 760.56 PLFA Circuits, Class 2, Class 3, and Communications Circuits...286 760.58 Support...286 760.61 Applications of Listed PLFA Cables...286 PART IV. LISTING REQUIREMENTS...287 760.81 Listing and Marking of NPLFA Cables...287 760.82 Listing and Marking of PLFA Cables...287 Article 760 Questions...289 ARTICLE 770 OPTICAL FIBER CABLES AND RACEWAYS...293 Introduction...293 PART I. GENERAL...293 770.1 Scope...293 770.2 Definitions...293 770.3 Locations and Other Articles...294 770.6 Optical Fiber Cables...295 770.9 Types...295 770.12 Raceways for Optical Fiber Cables...296 770.21 Access to Electrical Equipment Behind Panels Designed to Allow Access...296 770.24 Mechanical Execution of Work...297 PART III. CABLES WITHIN BUILDINGS...297 770.113 Listing of Optical Fiber Cables...297 770.133 Installation of Optical Fibers and Electrical Conductors...297 770.154 Applications of Listed Optical Fiber Cables and Raceways...298 xii
Understanding Low-Voltage and Power-Limited Systems PART IV. LISTING REQUIREMENTS...299 770.179 Listing Requirements for Optical Fiber Cables...299 770.182 Listing Requirements for Optical Fiber Raceways...300 Article 770 Questions...301 CHAPTER 8 COMMUNICATIONS SYSTEMS Introduction...303 ARTICLE 800 COMMUNICATIONS CIRCUITS...305 Introduction...305 PART I. GENERAL...305 800.1 Scope...305 800.2 Definitions...305 800.3 Other Articles...306 800.18 Installation of Equipment...307 800.21 Access to Electrical Equipment Behind Panels Designed to Allow Access...307 800.24 Mechanical Execution of Work...308 800.44 Overhead Communications Wires and Cables...308 PART II. CONDUCTORS OUTSIDE AND ENTERING BUILDINGS...309 800.47 Underground Circuits Entering Buildings...309 800.53 Lightning Conductors...309 PART III. PROTECTION...309 800.90 Primary Protection...309 800.93 Cable Grounding...309 PART IV. GROUNDING METHODS...309 800.100 Cable and Primary Protector Grounding...309 PART V. COMMUNICATIONS WIRES AND CABLES WITHIN BUILDINGS...312 800.110 Raceways for Communications Circuits...312 800.113 Listing of Communications Wires and Cables...312 800.133 Installation of Communications Circuits and Equipment...312 800.154 Applications of Listed Communications Wires, Cables, and Raceways...314 PART VI. LISTING REQUIREMENTS...315 800.179 Communications Wires and Cables...315 800.182 Communications Raceways...316 Article 800 Questions...317 ARTICLE 810 RADIO AND TELEVISION EQUIPMENT...319 Introduction...319 PART I. GENERAL...319 810.1 Scope...319 810.3 Other Articles...320 810.4 Community Television Antenna...320 Table of Contents PART II. RECEIVING EQUIPMENT ANTENNA SYSTEMS...320 810.12 Support of Lead-In Cables...320 810.13 Avoid Contact with Conductors of Other Systems...320 810.15 Grounding...321 810.18 Clearances...321 810.20 Antenna Discharge Unit...322 810.21 Grounding Conductors...322 Article 810 Questions...325 ARTICLE 820 COMMUNITY ANTENNA TELEVISION (CATV) AND RADIO DISTRIBUTION SYSTEMS...327 Introduction...327 PART I. GENERAL...327 820.1 Scope...327 820.2 Definitions...327 820.3 Locations and Other Articles...328 820.15 Energy Limitations...329 820.21 Access to Electrical Equipment Behind Panels Designed to Allow Access...329 820.24 Mechanical Execution of Work...329 PART II. CABLES OUTSIDE AND ENTERING BUILDINGS...330 820.44 Overhead Cables...330 820.47 Underground Circuits Entering Buildings...330 PART III. PROTECTION...331 820.93 Grounding Cable...331 PART IV. GROUNDING METHODS...331 820.100 Cable Grounding...331 PART V. CABLES WITHIN BUILDINGS...333 820.110 Raceways for Coaxial Cables...333 820.113 Listing and Markings...334 820.133 Installation of Cables and Equipment...334 820.154 Applications of Listed CATV Cables and Raceways...336 PART VI. LISTING REQUIREMENTS...337 820.179 Coaxial Cables...337 820.182 CATV Raceways...337 Article 820 Questions...338 ARTICLE 830 NETWORK-POWERED BROADBAND COMMUNICATIONS SYSTEMS...341 Introduction...341 PART I. GENERAL...341 830.1 Scope...341 830.2 Definitions...342 Article 830 Questions...343 xiii
Table of Contents CHAPTER 9 TABLES CONDUCTOR AND RACEWAY SPECIFICATIONS...345 Introduction...345 Table 1 Conductor Fill Percentage...346 Table 4 Raceway Dimensions...347 Table 5 Conductor Cross-Sectional Area...348 Table 8 Conductor Properties...349 Table 9 AC Impedance for Conductors in Conduit or Tubing...349 Understanding Low-Voltage and Power-Limited Systems ANNEX C CONDUIT AND TUBING FILL TABLES FOR CONDUCTORS AND FIXTURE WIRES OF THE SAME SIZE...350 Introduction...350 FINAL EXAM...353 INDEX...363 xiv