23.8 Equipment Grounding Conductor . . . . 459 23.9 Power Circuit Devices . . . . . . . . . . . . 463 C H A P T E R 2 4 Power Transmission and Circuits . . . . . . . . . . . . . . . . 469 24.1 Power Transmission . . . . . . . . . . . . . 469 24.2 Transformers . . . . . . . . . . . . . . . . . . . 471 24.3 Overcurrent . . . . . . . . . . . . . . . . . . . . 474 24.4 Circuit Protection . . . . . . . . . . . . . . . 476 24.5 Electrical Connections . . . . . . . . . . . 481 C H A P T E R 2 5 Motors . . . . . . . . . . . . . . . . . . . . 485 25.1 Induction-Type Motors . . . . . . . . . . . 485 25.2 Single-Phase Motors . . . . . . . . . . . . 489 25.3 Types of Induction Motors . . . . . . . . . 494 25.4 Capacitors . . . . . . . . . . . . . . . . . . . . . 502 25.5 Dual-Voltage Motors . . . . . . . . . . . . . 507 25.6 Multi-Speed Motors . . . . . . . . . . . . . 509 25.7 Three-Phase Motors . . . . . . . . . . . . . 509 25.8 Identifying Single-Phase Compressor Terminals . . . . . . . . . . . . . . . . . . . . . 513 25.9 Identifying Motor Problems . . . . . . . . 514 25.10 Motor Bearings and Lubrication . . . . 515 25.11 Electronically Commutated Motors (ECMs). . . . . . . . . . . . . . . . . . . . . . . . 517 25.12 Fans and Blowers . . . . . . . . . . . . . . . 518 C H A P T E R 2 6 Electromagnetic Control Devices . . . . . . . . . . . . . . . . . . . 521 26.1 Magnetism and Electromagnetism . . . 521 26.2 Control Devices . . . . . . . . . . . . . . . . 522 26.3 Wiring Diagrams . . . . . . . . . . . . . . . . 546 C H A P T E R 2 7 Motor Controls . . . . . . . . . . . . . 553 27.1 Primary Controls . . . . . . . . . . . . . . . . 553 27.2 Thermostats . . . . . . . . . . . . . . . . . . . 553 27.3 Pressure-Type Motor Controls . . . . . 559 27.4 Low-Pressure Safety Control . . . . . . 564 27.5 Head-Pressure Safety Control . . . . . 567 27.6 Pumpdown Cycle . . . . . . . . . . . . . . . 571 27.7 Oil Pressure Safety Control . . . . . . . 575 C H A P T E R 2 8 Defrost Cycles . . . . . . . . . . . . . 579 28.1 Physical Properties of Air . . . . . . . . . 579 28.2 Defrost Systems . . . . . . . . . . . . . . . . 581 C H A P T E R 2 9 Ductwork . . . . . . . . . . . . . . . . . 609 29.1 Furnace Classifications . . . . . . . . . . . 609 29.2 Distribution Systems . . . . . . . . . . . . . . 611 29.3 Distribution System Components . . . 614 29.4 System Efficiency . . . . . . . . . . . . . . . 617 29.5 Ductwork Tools . . . . . . . . . . . . . . . . . ⤀ 618 29.6 How to Lay out a Duct System . . . . . 619 29.7 Installing Starting Collars and Takeoffs . . . . . . . . . . . . . . . . . . . 619 29.8 Working with Round Metal Pipes . . . 620 29.9 Extended Plenum System . . . . . . . . 622 29.10 Duct Support . . . . . . . . . . . . . . . . . . . 625 29.11 Working with Insulated Flexible Duct . . . . . . . . . . . . . . . . . . . . . . . . . 625 29.12 Wall Stack . . . . . . . . . . . . . . . . . . . . . 627 29.13 Registers and Diffusers . . . . . . . . . . 627 29.14 Return Air System . . . . . . . . . . . . . . . 629 29.15 Insulation . . . . . . . . . . . . . . . . . . . . . 630 29.16 How to Use Mastic . . . . . . . . . . . . . . 632 C H A P T E R 3 0 Gas Heat with Air Conditioning . . . . . . . . . . . . . . . 635 30.1 Air Distribution System . . . . . . . . . . . 636 30.2 Blower Section . . . . . . . . . . . . . . . . . ⤀ 636 30.3 Air Filter . . . . . . . . . . . . . . . . . . . . . . 637 30.4 Heating Section . . . . . . . . . . . . . . . . 638 30.5 Low-Voltage Heating Thermostat . . . 646 30.6 Add-On Air Conditioning . . . . . . . . . . 648 30.7 Heating and Cooling Thermostat . . . 648 30.8 Digital Thermostats . . . . . . . . . . . . . . 652 30.9 Blower Motor . . . . . . . . . . . . . . . . . . . 653 30.10 Troubleshooting Gas Furnaces . . . . . 654 C H A P T E R 3 1 Oil Heat with Air Conditioning . . . . . . . . . . . . . . . 659 31.1 Oil-Fired Furnaces . . . . . . . . . . . . . . 659 31.2 Gun-Type Burner Assembly . . . . . . . 660 xvii