Chapter 1 Electrical Theory and Code Questions 1 Unit 1 Electrician s Math and Basic Electrical Formulas 3 Part A Electrician s Math 3 1 1 Fractions 3 1 2 Kilo 4 1 3 Knowing Your Answer 4 1 4 Multiplier 5 1 5 Parentheses 5 1 6 Percentages 5 1 7 Percent Increase 5 1 8 Percentage Reciprocals 6 1 9 Rounding 6 1 10 Squaring 7 1 11 Square Root 7 Part B Basic Electrical Formulas 8 1 12 Electrical Circuit 8 1 13 Electron Flow 8 1 14 Power Source 8 1 15 Conductance and Resistance 9 1 16 Electrical Circuit Values 10 1 17 Ohm s Law I = E/R 10 1 18 Pie Circle Formula 12 1 19 Formula Wheel 13 1 20 Power Changes With the Square of the Voltage 15 1 21 Electric Meters 15 Unit 1 Calculations Questions 18 Unit 1 Code Questions 25 Unit 1 - NEC Exam 90.1 110.12 35 Unit 2 Electrical Circuits 39 Part A Series Circuits 39 2 1 Understanding Series Calculations 40 2 2 Series Circuit Summary 42 Part B Parallel Circuit 44 2 3 Parallel Circuits Practical Uses 44 2 4 Parallel Circuits Understanding 44 2 5 Parallel Circuit Resistance Calculations 46 2 6 Parallel Circuit Summary 47 Part C Series Parallel and Multiwire Branch Circuits 48 2 7 Series and Parallel Circuits Review 48 2 8 Series-Parallel Circuit Resistance Calculations 48 Part D Multiwire Branch Circuits 49 2 9 Neutral Current Calculations 50 2 10 Multiwire Branch Circuit - Danger 52 Unit 2 Calculations Questions 54 Unit 2 Code Questions 59 Unit 2 NEC Exam Code Order 110.14 220.22 71 Unit 2 NEC Exam Random Order 90.3 220.3 73 Unit 3 Understanding Alternating Current 77 Part A Alternating Current Fundamentals 78 3 1 Current Flow 78 3 2 Alternating Current 78 3 3 Alternating Current Generator 78 3 4 Waveform 79 3 5 Armature Turning Frequency 79 3 6 Phase In and Out 80 3 7 Phase Differences in Degrees 80 3 8 Values of Alternating Current 81 Part B Induction 82 3 9 Induced Voltage and Applied Current 82 3 10 Conductor Impedance 83 3 11 Induction and Conductor Shape 83 3 12 Induction and Magnetic Cores 83 Part C Capacitance 84 3 13 Capacitor Charge, Testing and Discharging85 3 14 Use of Capacitors 86 Part D Power Factor and Efficiency 87 3 15 Apparent Power (Volt-Ampere) 87 3 16 Power Factor 88 3 17 True Power (Watts) 89 3 18 Efficiency 90 Unit 3 Calculations Questions 92 iv
Unit 3 Code Questions 100 Code Order 220.36 240.6 109 Random Order 90.2 240.5 111 Unit 4 Motors and Transformers 115 Part A Motors 115 4 1 Motor Speed Control 116 4 2 Reversing a Direct-Current Motor 116 4 3 Alternating-Current Motors 116 4 4 Reversing Alternating-Current Motors 117 4 5 Motor Volt-Ampere Calculations 117 4 6 Motor Horsepower/Watts 118 4 7 Motor Nameplate Ampere 119 Part B Transformer Basics 120 4 8 Transformer Primary and Secondary 121 4 9 Transformer Secondary and Primary Voltage 121 4 10 Autotransformers 121 4 11 Transformer Power Losses 121 4 12 Transformer Turns Ratio 122 4 13 Transformer kva Rating 123 4 14 Transformer Current 123 Unit 4 Calculations Questions 125 Unit 4 Code Questions 132 Unit 4 NEC Exam Code Order 240.8 250.122 143 Random Order 90.2 250.112 145 Chapter 2 NEC Calculations and Code Questions 149 Unit 5 Raceway, Outlet Box, and Junction Boxes Calculations 151 Part A Raceway Fill 151 5 1 Understanding The National Electrical Code, Chapter 9 151 5 2 Raceway and Nipple Calculation 156 5 3 Existing Raceway Calculation 158 5 4 Raceway Calculations Tips 159 Part B Outlet Box Fill Calculations 160 5 5 Box Sizing Conductors All the Same Size [Table 314.16(A)] 160 5 6 Box Sizing Conductor Equivalents [314.16(B)] 160 5 7 Box Sizing Different Size Conductors [314.16(B)] 162 Part C Pull, Junction Boxes, And Conduit Bodies 164 5 8 Pull and Junction Box Size Calculations 164 5 9 Pull and Junction Box Depth [314.28(A)(2), Exception] 165 5 10 Pull and Junction Box Sizing Tips 166 5 11 Pull and Junction Box Examples 166 Unit 5 Calculations Questions 168 Unit 5 Code Questions 172 Unit 5 NEC Exam Code Order 250.148 314.24 184 Unit 5 NEC Exam Random Order 250.126 314.27 186 Unit 6 Conductor Sizing and Protection Calculations 191 Part A General Conductor Requirements 191 6 1 Conductor Insulation Property [Table 310.13] 191 6 2 Conductor Allowable Ampacity [310.15] 193 6 3 Conductor Sizing [110.6] 194 6 4 Terminal Ratings [110.14(C)] 195 6 5 Conductors in Parallel [310.4] 197 6 6 Conductor Size Voltage Drop [210.19(A) FPN No. 4, and 215.2(B) FPN No. 2] 198 6 7 Overcurrent Protection [Article 240] 198 6 8 Overcurrent Protection of Conductors General Requirements [240.4] 199 6 9 Overcurrent Protection of Conductors Specific Requirements 201 6 10 Equipment Conductors Size and Protection Examples 202 Part B Conductor Ampacity Calculations 203 6 11 Conductor Ampacity [310.10] 203 6 12 Ambient Temperature Adjustment Factor [Table 310.16] 203 v
6 13 Conductor Bundling Adjustment Factor [Table 310.15(B)(2)] 205 6 14 Ambient Temperature and Conductor Bundling Adjustment Factors 206 6 15 Current-Carrying Conductors 206 6 16 Conductor Sizing Summary 209 Unit 6 Calculations Questions 210 Unit 6 Code Questions 215 Unit 6 NEC Exam Code Order 314.71 352.28 226 Unit 6 NEC Exam Random Order 90.2 354.6 228 Unit 7 Motor Calculations 233 7 1 Motor Branch Circuit Conductors [430.22(A)] 233 7 2 Motor Overcurrent Protection 234 7 3 Motor Overload Protection [430.32(A)] 235 7 4 Motor Branch Circuit Short-Circuit Ground- Fault Protection [430.52(C)(1)] 236 7 5 Motor Feeder Conductor Size [430.24] 238 7 6 Motor Feeder Protection [430.62(A)] 239 7 7 Motor Highest Rated Motor [430.17] 240 7-8 Motor Calculations Steps 240 7-9 Motor Calculation Review 242 7-10 Motor VA Calculations 243 Unit 7 Calculations Questions 245 Unit 7 Code Questions 249 Unit 7 NEC Exam Code Order 358.28 406.3 262 Unit 7 NEC Exam Random Order 90.3 406.2 264 Unit 8 Voltage Drop Calculations 269 Part A Conductor Resistance Calculations 269 8 1 Conductor Resistance 269 8 2 Conductor Resistance Direct Current Circuits, [Chapter 9, Table 8] 270 8 3 Conductor Impedance Alternating Current Circuits 271 8 4 Alternating Current Impedance As Compared To Direct Current 271 8 5 Alternating Current Impedance [Chapter 9, Table 9 of the NEC] 272 Part B Voltage Drop Calculations 274 8-6 Voltage Drop Considerations 274 8 7 Voltage Drop NEC Recommendations 274 8 8 Determining Circuit Conductors Voltage Drop 275 8 9 Sizing Conductors to Prevent Excessive Voltage Drop 278 8 10 Limiting Conductor Length to Limit Voltage Drop 279 8 11 Limiting Current to Limit Voltage Drop 280 8 12 Extending Circuits 281 Unit 8 Calculations Questions 283 Unit 8 Code Questions 288 Unit 8 NEC Exam Code Order 406.4 427.47 298 Unit 8 NEC Exam Random Order 100 427.22 300 Unit 9 Single-Family Dwelling Unit Load Calculations 305 Part A - General Requirements 305 9 1 General Requirements 305 9 2 Voltages [220.2(A)] 305 9 3 Fraction of an Ampere [220.2(B)] 305 9 4 Appliance (Small) Circuits [220.11(C)(1)] 306 9 5 Cooking Equipment Branch Circuit [Table 220.19, Note 4] 306 9 6 Laundry Receptacle(S) Circuit [220.11(C)(2)] 309 9 7 Lighting and Receptacles 309 Part B - Standard Method Feeder/Service Load Calculations 311 9 8 Dwelling Unit Feeder/Service Load Calculations (Part II of Article 220) 311 9 9 Dwelling Unit Feeder/Service Calculations Examples 312 Part C - Optional Method Feeder/Service Load Calculations 316 9-10 Dwelling Unit Optional Feeder/Service Calculations [220.30] 316 vi
9 11 Dwelling Unit Optional Calculation Examples 317 9 12 Neutral Calculations General [220.22] 319 Unit 9 Calculations Questions 320 Unit 9 Code Questions 327 Unit 9 NEC Exam Code Order 430.6 501.3 338 Unit 9 NEC Exam Random Order 110.26 501.4 340 Chapter 3 Advanced NEC Calculations And Code Questions 345 Unit 10 Multifamily Dwelling Unit Load Calculations 347 10 1 Multifamily Dwelling Unit Calculations Standard Method 347 10 2 Multifamily Dwelling Units Calculation Examples Standard Method 348 10 3 Multifamily Dwelling Units Calculation Sample Standard Method 352 10 4 Multifamily Dwelling Unit Calculations [220.32] Optional Method 353 10 5 Multifamily Dwelling Unit Example Questions [220.32] Optional Method 353 Unit 10 Calculations Questions 355 Unit 10 Code Questions 359 Unit 10 NEC Exam Code Order 503.9 555.19 372 Unit 10 NEC Exam Random Order 110.27 547.9 374 Unit 11 Commercial Load Calculations 379 Part A General 379 11 1 General Requirements 379 11 2 Conductor Ampacity [Article 100] 379 11 3 Conductor Overcurrent Protection [240.3] 380 11 4 Voltages [220.2(A)] 380 11 5 Rounding an Ampere [220.2(B)] 380 Part B Loads 380 11 6 Air-Conditioning 380 11 7 Dryers 381 11 8 Electric Heat 382 11 9 Kitchen Equipment 383 11 10 Laundry Equipment 384 11 11 Lighting Demand Factors [Table 220.3(A) and 220.11] 385 11 12 Lighting Without Demand Factors [Table 220.3(A), 215.2 and 230.42]. 385 11 13 Lighting Miscellaneous 386 11 14 Multioutlet Receptacle Assembly [220.3(B)(8)] 386 11 15 Receptacles VA Load [220.13] 387 11 16 Banks and Offices General Lighting and Receptacles 388 11 17 Signs [220.3(B)(6) and 600.5] 389 11 18 Neutral Calculations [220.22] 389 Part C Load Calculation Examples 390 Part D Load Calculation Examples 395 Unit 11 Calculations Questions 400 Unit 11 Code Questions 405 Unit 11 NEC Exam Code Order 600.6 720.4 418 Unit 11 NEC Exam Random Order 100 700.12 420 Unit 12 Delta/Delta and Delta/Wye Transformer Calculations 425 12 1 Current Flow 429 Part A Delta/Delta Transformers 431 12 2 Delta Transformer Voltage 431 12 3 Delta High -Leg 431 12 4 Delta Primary and Secondary Line Currents 431 12 5 Delta Primary or Secondary Phase Currents 432 12 6 Delta Phase versus Line 433 12 7 Delta Current Triangle 434 12 8 Delta Transformer Balancing 434 12 9 Delta Transformer Sizing 435 12 10 Delta Panel Schedule In kva 435 12 11 Delta Panelboard and Conductor Sizing 435 12 12 Delta Neutral Current 436 12 13 Delta Maximum Unbalanced Load 436 12 14 Delta/Delta Example 436 vii
Part B Delta/Wye Transformers 439 12 15 Wye Transformer Voltage 439 12 16 Wye Line and Phase Voltage Triangle 439 12 17 Wye Transformers Current 440 12 18 Wye Line Current 440 12 19 Wye Phase Current 440 12 20 Wye Phase Versus Line Current 441 12 21 Wye Transformer Loading and Balancing 442 12 22 Wye Transformer Sizing 443 12 23 Wye Panel Schedule In kva 443 12 24 Wye Panelboard and Conductor Sizing 444 12 25 Wye Neutral Current 444 12 26 Wye Maximum Unbalanced Load 444 12 27 Delta/Wye Example 445 12 28 Delta Versus Wye 447 Unit 12 Calculations Questions 448 Unit 12 Code Questions 456 Unit 12 NEC Exam Code Order 725.41 Chap. 9 464 Unit 12 NEC Exam Random Order 110.14 Chap. 9 466 NEC Final Exam 470 viii