Fundamentals of HVAC control systems : [a course reader] SI ed.

Contents Foreword ix 1 Introduction to HVAC Control Systems 1 1.1 Why Do We Need Controls? 2 1.2 A Brief History of Controls 3 1.3 Control Loops 4 1.4 Control Modes 9 Two-position Control 10 Floating Control 14 Modulating Control 16 Pulse-width Modulating, and Time-proportioning Control 20 1.5 Gains and Loop Tuning 21 1.6 Control Actions and Normal Position 24 1.7 Control Range, and Sequencing 27 1.8 Controls Documentation, Maintenance, and Operations 29 The Next Step 30 2 Basics of Electricity 31 2.1 Simple Circuits and Ohm’s Law 32 2.2 AC Circuits 36 2.3 Transformers and Power Services 40 2.4 Relays 43 2.5 Motors and Motor Starters 46 2.6 Variable Speed Drives 52 2.7 Relay Logic and Ladder Diagrams 55 The Next Step 61 3 Control Valves and Dampers 62 Introduction 62 3.1 Two-way Control Valves 63 Styles and Principles of Operation 63 3.2 Three-way Control Valves 73 3.3 Selecting and Sizing Valves 77 Flow Characteristic Selection 82 Close-off Pressure 85 3.4 Control Dampers 88 Styles and Principles of Operation 88 3.5 Selecting and Sizing Dampers 91 Two-position Duty 92 Capacity Control Duty 94 Mixing Duty 99 The Next Step 106 4 Sensors and Auxiliary Devices 107 4.1 Introduction to Terms 108 Accuracy 108 Range 108 Reliability 109 Repeatability, Precision 109 Transmitter 109 4.2 Temperature Sensors 110 Bimetal 110 Fluid Expansion 112 Electrical, Self-powered 113 Electrical Resistance 114 4.3 Humidity and the Psychrometric Chart 119 Indoor Air is a Mixture of Dry Air and Water Vapor 119 Relative Humidity 120 4.4 Moisture Sensors 130 Relative Humidity Sensors 130 4.5 Pressure Sensors 135 4.6 Flow Sensors and Meters 138 4.7 Auxiliary Devices 149 The Next Step 161 5 Self- and System-powered Controls 162 5.1 Principles of Operation – Self-powered Controls 162 5.2 Examples of Self-Powered Controls 163 Thermopile Controls 163 Hot Water Control Valve 164 Self-powered VAV Diffuser 164 5.3 System-powered Controls 166 System-powered Air Valves 166 System-powered Water System Valves 167 The Next Step 168 6 Electric Controls 169 6.1 Sensors 169 6.2 Controllers, Two-position 171 6.3 Controllers, Modulating 173 6.4 Example Application 176 6.5 Actuators 179 6.6 Auxiliary Devices 180 The Next Step 181 vi Contents 7 Pneumatic Controls 182 7.1 Principles of Operation 183 7.2 Sensors 185 7.3 Controllers 186 7.4 Actuators 190 7.5 Auxiliary Devices 192 7.6 Compressed Air Supply 198 7.7 Example Applications 200 The Next Step 206 8 Analog Electronic Controls 207 8.1 Principles of Operation 207 8.2 Sensors 208 8.3 Controllers 208 8.4 Actuators 213 8.5 Auxiliary Devices 214 8.6 Example Applications 214 The Next Step 217 9 Control Diagrams and Sequences 218 9.1 Control Systems Design Criteria 219 9.2 Control Systems Design Process 220 9.3 Control Diagrams and Symbols 220 9.4 Control Sequences 222 9.5 Example Applications 224 Typical Single-Zone System 224 Typical Constant Air Volume System with Face and Bypass Dampers 228 Typical Constant Air Volume System with Multiple Zones or Reheat 229 Typical Variable Air Volume System 229 Typical Constant Air Volume System, with Variable Speed Fan for Filter Loading 239 Chiller Plant, Pumps, and Boilers – Monitoring and Control 241 Temperature and Humidity Monitoring and Control 242 Carbon Dioxide Control 243 Exhaust Fan Control 244 Fume Hood Control 245 Condensate Management and Control 247 Ventilation Monitoring and Control 247 Filtration Monitoring and Control 248 Outside Air Monitoring and Control 248 DX – Direct Expansion Systems 248 Water Source Heat Pumps 249 Contents vii 10 DDC Introduction to Hardware and Software 252 10.1 Introduction, and Input and Output Points 252 10.2 I/O Point Characteristics 256 10.3 Control Sequences 260 10.4 Software Introduction 262 10.5 Specific Programming System Features and Parameters 270 10.6 Operator Terminal 280 11 DDC Networks and Controls Protocols 287 11.1 Interoperability 288 11.2 System Hardware Architecture 290 Sample Controllers 297 11.3 Network Standards 300 Ethernet (IEEE 802.3) 300 ARCNET 301 RS-485 301 Wireless 301 11.4 BACnet 304 What is a PICS? 305 1. Devices – Groups of Objects to Manage Activity 306 2. Objects – To Represent Information 306 3. Services – Making and Responding to Requests 308 4. Network – Transporting Request and Responses 309 11.5 LonWorks 311 The Next Step 313 12 Digital Controls Specification 314 12.1 Benefits and Challenges of DDC 315 12.2 Design 319 12.3 Bidding and Interoperability 326 12.4 Monitoring 328 12.5 Wiring 334 Network Wiring 334 Fiber Optic Cable 336 Power Wiring 336 12.6 Commissioning and Warranty 337 12.7 Resources 339 Index 342