Chapter 24 Power Transmission and Circuits ........................................ 465 24.1 Power Transmission ..................... 465 24.2 Transformers .............................. 467 24.3 Overcurrent ................................ 470 24.4 Circuit Protection ......................... 472 24.5 Electrical Connections ................. 477 Chapter 25 Induction Motors .......................... 481 25.1 Induction-Type Motors .................. 481 25.2 Single-Phase Motors ................... 485 25.3 Types of Induction Motors ............. 490 25.4 Capacitors .................................. 498 25.5 Dual-Voltage Motors .................... 503 25.6 Multi-Speed Motors ..................... 505 25.7 Three-Phase Motors .................... 505 25.8 Identifying Single-Phase Compressor Terminals ................. 509 25.9 Identifying Motor Problems .............510 25.10 Motor Bearings and Lubrication ....511 25.11 Fans and Blowers .......................513 Chapter 26 Electromagnetic Control Devices .........................................517 26.1 Magnetism and Electromagnetism ...517 26.2 Control Devices ............................518 26.3 Wiring Diagrams .......................... 542 Chapter 27 Motor Controls ............................. 549 27.1 Primary Controls .......................... 549 27.2 Thermostats ................................ 549 27.3 Pressure-Type Motor Controls ........ 555 27.4 Low-Pressure Safety Control .......... 560 27.5 Head-Pressure Safety Control ........ 563 27.6 Pumpdown Cycle ......................... 567 27.7 Oil Pressure Safety Control ............ 571 Chapter 28 Defrost Cycles .............................. 575 28.1 Physical Properties of Air .............. 575 28.2 Defrost Systems .......................... 577 Chapter 29 Ductwork ........................................ 605 29.1 Furnace Classifications ................ 605 29.2 Distribution Systems .................... 607 29.3 Distribution System Components ....610 29.4 System Efficiency .........................613 29.5 Ductwork Tools ............................614 29.6 How to Lay Out a Duct System .......615 29.7 Installing Starting Collars and Takeoffs ................................615 29.8 Working with Round Metal Pipes ....616 29.9 Extended Plenum System ..............618 29.10 Duct Support ............................. 621 29.11 Working with Insulated Flexible Duct ............................... 621 29.12 Wall Stack ................................ 623 29.13 Registers and Diffusers ............... 623 29.14 Return Air System ...................... 625 29.15 Insulation ................................. 626 29.16 How to Use Mastic ..................... 628 xvii Copyright Goodheart-Willcox Co., Inc.