TABLE OF CONTENTS. About the Mike Holt Enterprises Team... xviii CHAPTER 1 ELECTRICAL THEORY... 1

Transcription

1 TABLE OF CONTENTS Introduction...xv About the Mike Holt Enterprises Team... xviii CHAPTER 1 ELECTRICAL THEORY... 1 Unit 1 Electrician s Math and Basic Electrical Formulas... 1 Part A Electrician s Math Whole Numbers Decimals Fractions Percentages Multiplier Percent Increase Reciprocals Squaring a Number Parentheses Square Root Volume Kilo Rounding Off Testing Your Answer for Reasonableness... 7 Part B Basic Electrical Formulas Electrical Circuit Power Source Conductance Circuit Resistance NEC.CODE ( ) v

2 1.19 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 Unit 2 Electrical Circuits Part A Series Circuits Introduction Practical Uses of the Series Circuit Understanding Series Calculations Series Circuit Calculations Power Calculations Variations Series Circuit Notes Series-Connected Power Supplies Part B Parallel Circuits Introduction Practical Uses of the Parallel Circuit Understanding Parallel Calculations Circuit Resistance Parallel Circuit Notes Parallel-Connected Power Supplies Part C Series-Parallel Circuits Introduction Review of Series and Parallel Circuits Working With Series-Parallel Circuits Voltage vi Electrical Formulas with Calculations

3 Part D Multiwire Branch Circuits Introduction Neutral Conductor Grounded Conductor Current Flow on the Neutral Conductor Balanced Systems Unbalanced Current Multiwire Branch Circuits Dangers of Multiwire Branch Circuits NEC Requirements Unit 3 Understanding Alternating Current Part A Understanding Alternating Current Introduction Current Flow Why Alternating Current Is Used How Alternating Current Is Produced Alternating-Current Generator Waveform Sine Wave 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 NEC.CODE ( ) vii

4 Part C Induction Introduction Self-Induction Induced Voltage and Applied Current Conductor Alternating-Current Resistance Conductor Shape Magnetic Cores Self-Induced and Applied Voltage Inductive Reactance 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 Unit 4 Motors and Transformers Part A Motor Basics Introduction Motor Principles Dual-Voltage Alternating-Current Motors Motor Horsepower Ratings Motor Current Ratings Calculating Motor FLA viii Electrical Formulas with Calculations

5 4.6 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 Direct-Current Motor Alternating-Current Induction Motor Alternating-Current Motor Types Reversing the Rotation of an Alternating-Current Motor Part B Transformers Introduction Transformer Basics Secondary Induced Voltage Efficiency Transformer Turns Ratio Power Losses Transformer kva Rating Current Flow Current Rating Autotransformers CHAPTER 2 NEC CALCULATIONS Unit 5 Raceway and Box Calculations Part A Raceway Sizing Introduction Insulated Conductors and Fixture Wires Dimensions Chapter 9, Tables 5 and Raceway Properties Raceway Sizing Sizing Raceways Using Annex C Sizing Wireways Tips for Raceway Calculations NEC.CODE ( ) ix

6 Part B Outlet Box Fill Introduction Box Volume Calculations [314.16] Sizing Box Conductors All the Same Size Box Fill Calculations [314.16(B)] Outlet Box Sizing Part C Pull Boxes, Junction Boxes, and Conduit Bodies Introduction Pull/Junction Box Sizing Requirements Pull/Junction Box Sizing Tips Pull Box Examples Unit 6 Conductor Sizing and Protection Calculations Part A Conductor Requirements Conductor Insulation [ (A)] Conductor Sizes Smallest Conductor Size [ ] Conductor Size Equipment Terminal Rating [110.14(C)] Overcurrent Protection [Article 240] Part B Conductor Ampacity Introduction Conductor Heating I 2 R Limiting Excessive Temperature Conductor Ampacity Ambient Temperature Correction [310.15(B)(2)(a)] Rooftop Temperature Adder [310.15(B)(3)(c)] Ampacity Adjustment [310.15(B)(3)(a)] Combining Ambient Temperature and Conductor Bundling Adjustments Current-Carrying Conductors Wireway Conductor Ampacity Adjustment Conductor Ampacity Summary x Electrical Formulas with Calculations

7 6.16 Conductor Sizing Feeder Tap Rules Unit 7 Voltage-Drop Calculations Part A Conductor Resistance Calculations Conductor Size Conductor Resistance Alternating-Current Conductor Resistance Alternating-Current Resistance [Chapter 9, Table 9] AC versus DC Resistance Part B Voltage-Drop Considerations Introduction NEC Voltage-Drop Recommendations Determining Circuit Conductors Voltage Drop Ohm s Law Method Determining Circuit Conductors Voltage Drop Formula Method Sizing Conductors to Account for Voltage Drop Limiting Conductor Length to Minimize Voltage Drop Limiting Current to Limit Voltage Drop Unit 8 Motor and Air-Conditioning Calculations Part A Motor Calculations Scope of Article Motor Full Load Current (FLC) [430.6(A)(1)] Motor Nameplate Full Load Amperes (FLA) [430.6(A)(2)] Branch-Circuit Conductor Sizing [430.22] Feeder Conductor Sizing [430.24] Overcurrent Protection Overload Protection Sizing Branch-Circuit Short-Circuit and Ground-Fault Protection NEC.CODE ( ) xi

8 8.9 Branch Circuit Summary Combined Branch Circuit Overcurrent Protection [430.55] Feeder Short-Circuit and Ground-Fault Protection [430.62] Motor VA Calculations Adjustable Speed Drives Fire Pump Motor Circuits Part B Air-Conditioning Calculations Scope of Article Multimotor Equipment [440.4(B)] Motor-Compressor and Other Motors Short-Circuit and Ground-Fault Protection [440.22(B)(1)] Motor-Compressor and Other Motors Conductor Size [440.33] Unit 9 Dwelling Unit Calculations Part A Standard Method Load Calculations [Article 220, Part III] Introduction General Lighting and General-Use Receptacle Demand Load [220.42] Appliance Demand Load [220.53] Dryer Demand Load [220.54] Cooking Equipment Demand Load [220.55] Air-Conditioning versus Heat Demand Load [220.60] Service Conductor Sizing [310.15(B)(7)] Standard Method Load Calculations Example Part B Optional Method Load Calculations [Article 220, Part IV] Introduction Dwelling Unit Optional Load Calculation [220.82] Dwelling Unit Optional Load Calculation [220.82] Example Existing Dwelling Unit Optional Load Calculation [220.83] xii Electrical Formulas with Calculations

9 CHAPTER 3 ADVANCED NEC CALCULATIONS Unit 10 Multifamily Dwelling Calculations Introduction Part A Standard Method Load Calculations [Article 220, Part III] General Lighting and General-Use Receptacle Demand Load [220.42] Appliance Demand Load [220.53] Dryer Demand Load [220.54] Cooking Equipment Demand Load [220.55] Air-Conditioning versus Heat Demand Load [220.60] Service Conductor Sizing [310.15(B)(16)] Multifamily Dwelling Calculations Standard Method Example Part B Optional Method Load Calculations [Article 220, Part IV] Introduction Multifamily Dwelling Optional Load Calculations [220.84] Multifamily Dwelling Optional Method Example [220.84] Two-Family Dwelling Units [220.85] Unit 11 Commercial Calculations Part A General Lighting Demand Factors [Tables and ] Lighting Load 100% Demand Sign Circuit [220.14(F) and 600.5] Show-Window Lighting [220.14(G)] Multioutlet Receptacle Assembly [220.14(H)] Receptacle Load [220.14(I) and ] Banks and Offices Receptacle Demand Load [220.14(K)] NEC.CODE ( ) xiii

10 Unit 12 Transformer Calculations Introduction Part A General Transformer Basics Delta-Connected Transformers Wye-Connected Transformers Transformer kva Rating Line Currents Part B NEC Requirements Transformer Overcurrent Protection Primary Conductor Sizing Secondary Conductor Sizing ANNEX A COMMERCIAL/INDUSTRIAL WIRING, RACEWAY CHART, AND FORMULAS INDEX xiv Electrical Formulas with Calculations