Electricity and electronics for HVAC

Contents Preface xvii Acknowledgments xix Chapter 1. Introduction to Electricity 1 Performance Objectives 1 Introduction to Electricity 1 Static Electricity and Magnetism 2 Electricity 2 Electricity’s Future 3 Matter and Electricity 4 Solids, gases, and liquids 4 Atom 5 Electrons, protons, and neutrons 6 Properties of Electrons 8 Orbiting Electrons 8 Electrical Charge 9 Outer Shell 10 Valence electrons and ions 10 A Practical Unit of Charge 12 The Volt 12 Controlling Electrons 13 Difference of Potential (Voltage) 13 Electron Flow (Current) 14 Conductors 14 Resistance 14 The Electric Circuit 15 Connecting a Circuit 16 Switches Control Electron Flow 16 Schematic 17 Review Questions 17 For more information about this title, click here Chapter 2. Current,Voltage, Resistance, Power, and Ohm’s Law 19 Performance Objectives 19 Sources of Electricity 19 Chemical action 19 Heat 19 Light 20 Pressure 20 Magnetism 20 Units of Measurement 21 Unit of charge: coulomb 21 Unit of current: ampere 22 Unit of potential difference: volt 22 Unit of resistance: ohm 22 Siemens 23 Prefixes 23 Ohm’s Law 24 Ohm’s law examples 25 Ohm’s law and the closed circuit 27 Ohm’s law in other forms 29 Uses for ohm’s law 30 Power 31 Joule 31 Watt 32 Putting Electricity to Work 32 Resistors and heat 32 Mechanical energy 32 A Practical Unit of Electrical Power: Kilowatt-Hour 34 Review Questions 35 Chapter 3. Resistors, Other Electric Components, and Their Symbols 37 Performance Objectives 37 Color Code 38 Tolerance 39 Examples 39 Gold and silver third bands 40 Variable Resistors 41 Schematic 43 Types of Resistors 43 Fixed resistors 43 Tapped resistors 44 Variable resistors 44 Fusible resistors 44 Temperature-compensating resistors 47 Types of Capacitors 47 Fixed capacitors 47 Electrolytic capacitors 48 Variable capacitors 49 Types of Inductors 50 Fixed inductors 50 Variable inductors 51 Transformers 51 viii Contents Semiconductors 52 Diodes 52 Transistors 52 Switches 53 Relays 53 Fuses and Circuit Breakers 53 Lamps 55 Batteries 56 Meters 57 Reading Schematics 57 Review Questions 57 Chapter 4. Series and Parallel Circuits 59 Performance Objectives 59 Series Circuit 59 Resistances in series 61 Voltages in series 61 Current in series 61 Series circuit rules 62 Fuses 62 Parallel Circuit 63 Cells in parallel 63 Parallel circuit characteristics 63 Currents in a parallel circuit 64 Resistances in a parallel circuit 64 Parallel circuit rules 65 Series-Parallel Circuits 65 Series-parallel resistance circuits 66 Determining resistance 66 Determining current in series-parallel circuits 68 Determining voltage in series-parallel circuits 68 Review Questions 72 Chapter 5. Magnetism, Solenoids, and Relays 73 Performance Objectives 73 Permanent Magnets 74 Temporary Magnets 75 Electromagnets 75 Magnetic Theory 76 Magnetic Permeability 76 Shapes of Magnets 76 Poles of magnets 78 Electromagnetism 79 Magnetism in a coil of wire 80 Electromagnets 80 Using electromagnetism 82 The Solenoids and Relays 82 Power relays 86 Solenoid valves 86 Principles of operation 86 Applications 87 Liquid line service 87 Suction line service 89 Contents ix High-Temperature Applications 89 Hot-gas defrost service 90 Transformers for Low-Voltage Controls 91 Review Questions 92 Chapter 6. Electrical Measuring Instruments 93 Performance Objectives 93 Electricity 93 Types of Meter Movements 94 D’Arsonval meter movement 94 Analog meters 97 Parallax Error 97 Ammeters 98 Extending the range of an ammeter 99 Connecting an ammeter in the circuit 99 Clamp-on ammeters 99 AC ammeters 101 Voltmeters 101 Connecting a voltmeter 102 AC Voltmeters 102 Ohmmeters 103 Multimeters 103 Meggers 104 Digital Meters 104 Other Instruments 106 Automatic halogen leak detector 106 Electronic sight glass 107 Electronic charging meters 107 Using an Ohmmeter 108 Warning 108 Adjusting the meter 108 Review Questions 110 Chapter 7. Electrical Power: Direct Current and Alternating Current 111 Performance Objectives 111 Power Sources 111 Types of Batteries 112 Primary cell 112 Secondary cell 112 Dry Cells 112 Battery Specifications 115 Connecting Cells 115 Battery Maintenance 118 Nickel-Cadmium Cells 119 Alkaline Cells 119 Alternating Current 119 Sine Wave 120 Sine-Wave Characteristics 121 Phase 122 Average, RMS, and Peak Values of AC 122 x Contents Polyphase Alternating Current 123 Three phase 124 Three-phase connections 124 Electrical Properties of Delta and Wye 126 Delta connection (
) 126 Wye connection (Y) 126 Delta and wye summarized 126 Review Questions 127 Chapter 8. Inductors and Transformers 129 Performance Objectives 129 Changing Inductance 130 Self-Inductance 130 Mutual Inductance 133 Inductive Reactance 134 Measuring XL 134 Power in an Inductive Circuit 134 Uses for Inductive Reactance 135 Transformers 135 Mutual inductance in a transformer 135 Iron-core transformer 136 Construction 137 Types of iron-core transformers 137 Voltage Transfer 138 Step up, step down 139 Turns ratio 139 Power Transformers 140 Audio Frequency and Radio Frequency Transformers 140 Autotransformers 141 Transformer Losses 142 Inductive Circuits 144 Special handling 145 Utilizing the Inductive Delay 146 Review Questions 146 Chapter 9. Capacitors and Capacitive Reactance 147 Performance Objectives 147 The Capacitor 149 How the Capacitor Works 149 Capacity of a Capacitor 150 Breakdown Voltage 151 Basic Units of Capacitance 151 Types of Capacitors 151 Electrolytic Capacitors 153 Making an electrolytic capacitor 154 Connecting electrolytics 154 Working Voltage, Direct Current (WVDC) 155 Capacitive Reactance 155 Capacitor Causes a Lagging Voltage 156 Checking Capacitors 157 Review Questions 158 Contents xi xii Contents Chapter 10. Single-Phase and Three-Phase Alternating Current 161 Performance Objectives 161 Single-Phase and Three-Phase AC 161 Resistance, Capacitance, and Inductance 162 Power Factor 164 Distributing Electric Power 165 Polyphase 166 Circuit Breakers 169 Review Questions 171 Chapter 11. Solid-State Controls 173 Performance Objectives 173 Semiconductors 173 Semiconductor Principles 174 Diode 175 Silicon-Controlled Rectifiers 177 Transistors 178 Transistor impedances 179 Integrated Circuits 180 Solid-state demand defrost control 182 Thermistor Sensing 182 Humidity Sensing 184 Bridge Circuit 186 Unbalanced bridge 187 Sensors 189 Controllers 189 Electronic Controllers 189 Differential Amplifiers 190 Actuators 191 Other Devices 192 Solid-State Compressor Motor Protection 192 Operation of the module 192 Troubleshooting the control 194 Restoring service 196 Review Questions 197 Chapter 12. Alternating Current Motors 199 Performance Objectives 199 Motors 199 Split-Phase Motor 204 Getting the motor started 204 Repulsion Start, Induction Run Motor 206 Capacitor-Start Motor 208 Permanent Split-Capacitor Motor 210 Theory of operation 212 Capacitor-Start, Capacitor-Run Motor 215 Theory of operation 215 Three-Phase Motor 216 Theory of operation 216 Capacitor Ratings 219 Start Capacitors and Bleeder Resistors 219 Run capacitors 221 Motor Protectors 221 Compressor Motor Relays 221 Current-type relay 222 Potential-type relay 222 Review Questions 224 Chapter 13. Electrical Safety 225 Performance Objectives 225 Safety Devices 225 Safety Precautions 225 Main Switches 226 Portable Electrical Tools 227 Ground-Fault Circuit Interrupters (GFCI) 229 Types of Circuit Protectors 230 Review Questions 231 Chapter 14. Control Devices 233 Performance Objectives 233 Power Relays 233 Motor start relays 234 Relays with more than one contact 235 Thermal overload protectors 236 Time-delay relays 237 Solenoids 238 Thermostats 239 Bellows-type thermostats 239 Bimetallic-type thermostats 241 Heating and cooling thermostats 242 Microprocessor thermostats 245 Thermostat Adjustments 245 Heat anticipators 246 Cold anticipators 246 Switches of Many Types 246 Pressure Control Switches 247 Water Tower Controls 248 Review Questions 250 Chapter 15. Heating Circuits 251 Performance Objectives 251 Basic Gas Furnace Operation 252 Basic Electric Heating System 253 Basic operation 253 Ladder Diagrams 254 Manufacturer’s Diagrams 257 Field Wiring 258 Low-Voltage Wiring 258 Contents xiii Heat Pumps 260 Operation 261 Special requirements of heat-pump systems 266 Heat-pump combinations 267 High-Efficiency Furnaces 267 Operation 268 Electrical controls 269 Sequence of operation 270 Combustion process 271 Troubleshooting the Pulse Furnace 271 Review Questions 278 Chapter 16. Air-Conditioning Circuits 279 Performance Objectives 279 Basic Air-Conditioning Unit 279 Push-button switches 282 Fans 283 Schematics 283 Ladder Diagrams 287 Thermostats 287 Fan switches 291 Troubleshooting 291 Review Questions 291 Chapter 17. Refrigeration Circuits 293 Performance Objectives 293 Basic Refrigerator 293 Thermostats 293 Start relays 295 Refrigerator-Freezer Combination 295 Manual defrost 295 Automatic defrost 296 Defrosting 296 Defrost thermostats 297 Defrost cycle 299 Other Devices 302 Troubleshooting 304 Rapid Electrical Diagnosis 306 Energy-Saver Switches 309 Review Questions 310 Chapter 18. Troubleshooting 311 Performance Objectives 311 Safety 311 Handling refrigerants 312 Testing precaution 312 Electrical safety 312 Compressor Problems 312 PSC compressors 312 Air-conditioner compressors 312 xiv Contents Low-Voltage Operation 315 Using a System to Troubleshoot (Electrical) 316 Motor testing 316 Capacitor testing 317 Motor-protector relay testing 317 Using Meters to Check for Problems 318 Using a Volt-Ammeter for Troubleshooting Electric Motors 320 Clamp-on volt-ammeters 320 Looking for grounds 321 Looking for opens 322 Looking for shorts 322 Motors with Squirrel-Cage Rotors 323 Testing the Centrifugal Switch in a Single-Phase Motor 323 Testing for a Short Circuit Between Run and Start Windings 324 Capacitor testing 324 Measuring the capacity of a capacitor 325 Troubleshooting Procedure 326 Review Questions 327 Chapter 19. Controlling Electrical Power for Air-Conditioning Units 329 Performance Objectives 329 Choosing Wire Size 329 Limiting voltage loss 330 Minimum wire size 330 Wire selection 330 Wire Size and Low Voltage 330 Voltage drop calculations 332 The Effects of Voltage Variations on AC Motors 333 Selecting Proper Wire Size 335 Unacceptable Motor Voltages 336 Calculating Starting Current Values and Inrush Voltage Drops 336 Single-phase current 336 Three-phase circuits 338 Inrush voltage drop 339 Code Limitations on Amperes Per Conductor 339 Heat Generated Within Conductors 339 Circuit Protection 340 Standard rule 341 Fuses 341 One-time single-element fuses 341 Time-delay two-element fuses 342 Types of fuses 343 Thermostats 343 Thermostat as a control switch 344 Service 345 Starter Kits 346 Single-Phase Line Monitors 347 Time Delays 350 Pressure Controls 350 Head pressure controls 350 Line voltage head pressure controls 352 Contents xv Three-Phase Line Voltage Monitor 355 Current Sensing 355 Review Questions 359 Chapter 20. Careers in Air Conditioning and Refrigeration 361 Performance Objectives 361 Industries that Employ Air-Conditioning and Refrigeration Mechanics 361 Job Qualifications 364 The Future 365 Pay and Benefits 365 Teaching as a Career 367 Sources of Additional Information 367 Review Questions 369 Index 371 xvi Contents