ENGINEERING MANUAL OF AUTOMATIC CONTROL
v
PREFACE
The purpose of this manual is to provide the reader with a fundamental understanding of controls and how
they are applied to the many parts of heating, ventilating, and air conditioning systems in commercial buildings.
Many aspects of control are presented including air handling units, terminal units, chillers, boilers, building
airflow, water and steam distribution systems, smoke management, and indoor air quality. Control fundamentals,
theory, and types of controls provide background for application of controls to heating, ventilating, and air
conditioning systems. Discussions of pneumatic, electric, electronic, and digital controls illustrate that applications
may use one or more of several different control methods. Engineering data such as equipment sizing, use of
psychrometric charts, and conversion formulas supplement and support the control information. To enhance
understanding, definitions of terms are provided within individual sections. For maximum usability, each section
of this manual is available as a separate, self-contained document.
Building management systems have evolved into a major consideration for the control engineer when evaluating
a total heating, ventilating, and air conditioning system design. In response to this consideration, the basics of
building management systems configuration are presented.
The control recommendations in this manual are general in nature and are not the basis for any specific job or
installation. Control systems are furnished according to the plans and specifications prepared by the control
engineer. In many instances there is more than one control solution. Professional expertise and judgment are
required for the design of a control system. This manual is not a substitute for such expertise and judgment.
Always consult a licensed engineer for advice on designing control systems.
It is hoped that the scope of information in this manual will provide the readers with the tools to expand their
knowledge base and help develop sound approaches to automatic control.
ENGINEERING MANUAL OF AUTOMATIC CONTROL
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ENGINEERING MANUAL OF AUTOMATIC CONTROL
vii
CONTENTS
Foreward iii
Preface v
Control System Fundamentals 1
Control Fundamentals 3
Introduction 5
Definitions 5
HVAC System Characteristics 8
Control System Characteristics 15
Control System Components 30
Characteristics And Attributes Of Control Methods 35
Psychrometric Chart Fundamentals 37
Introduction 38
Definitions 38
Description of the Psychrometric Chart 39
The Abridged Psychrometric Chart 40
Examples of Air Mixing Process 42
Air Conditioning Processes 43
Humidifying Process 44
ASHRAE Psychrometric Chart 53
Pneumatic Control Fundamentals 57
Introduction 59
Definitions 59
Abbreviations 60
Symbols 61
Basic Pneumatic Control System 61
Air Supply Equipment 65
Thermostats 69
Controllers 70
Sensor-Controller Systems 72
Actuators and Final Control Elements 74
Relays and Switches 77
Pneumatic Control Combinations 84
Pneumatic Centeralization 89
Pneumatic Control System Example 90
Electric Control Fundamentals 95
Introduction 97
Definitions 97
How Electric Control Circuits Classified 99
Series 40 Control Circuits 100
Series 80 Control Circuits 102
Series 60 Two-Position Control Circuits 103
Series 60 Floating Control Circuits 106
Series 90 Control Circuits 107
Motor Control Circuits 114
ENGINEERING MANUAL of
AUTOMATIC
CONTROL
ENGINEERING MANUAL OF AUTOMATIC CONTROL
viii
Electronic Control Fundamentals 119
Introduction 120
Definitions 120
Typical System 122
Components 122
Electtonic Controller Fundamentals 129
Typical System Application 130
Microprocessor-Based/DDC Fundamentals 131
Introduction 133
Definitions 133
Background 134
Advantages 134
Controller Configuration 135
Types of Controllers 136
Controller Software 137
Controller Programming 142
Typical Applications 145
Indoor Air Quality Fundamentals 149
Introduction 151
Definitions 151
Abbreviations 153
Indoor Air Quality Concerns 154
Indoor Air Quality Control Applications 164
Bibliography 170
Smoke Management Fundamentals 171
Introduction 172
Definitions 172
Objectives 173
Design Considerations 173
Design Principles 175
Control Applications 178
Acceptance Testing 181
Leakage Rated Dampers 181
Bibliography 182
Building Management System Fundamentals 183
Introduction 184
Definitions 184
Background 185
System Configurations 186
System Functions 189
Integration of Other Systems 197
ENGINEERING MANUAL OF AUTOMATIC CONTROL
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Control System Applications 199
Air Handling System Control Applications 201
Introduction 203
Abbreviations 203
Requirements For Effective Control 204
Applications-General 206
Valve and Damper Selection 207
Symbols 208
Ventilation Control Processes 209
Fixed Quantity of Outdoor Air Control 211
Heating Control Processes 223
Preheat Control Processes 228
Humidification Control Process 235
Cooling Control Processes 236
Dehumidification Control Processes 243
Heating System Control process 246
Year-Round System Control processes 248
ASHRAE Psychrometric Charts 261
Building Airflow System Control Applications 263
Introduction 265
Definitions 265
Airflow Control Fundamentals 267
Airflow Control Applications 281
References 292
Chiller, Boiler, and Distribution System Control Applications 293
Introduction 297
Abbreviations 297
Definitions 297
Symbols 298
Chiller System Control 299
Boiler System Control 329
Hot And Chilled Water Distribution Systems Control 337
High Temperature Water Heating System Control 376
District Heating Applications 382
Individual Room Control Applications 399
Introduction 401
Unitary Equipment Control 412
Hot Water Plant Considerations 428
ENGINEERING MANUAL OF AUTOMATIC CONTROL
x
Engineering Information 429
Valve Selection and Sizing 431
Introduction 432
Definitions 432
Valve Selection 436
Valve Sizing 441
Damper Selection and Sizing 451
Introduction 453
Definitions 453
Damper Selection 454
Damper Sizing 463
Damper Pressure Drop 468
Damper Applications 469
General Engineering Data 471
Introduction 472
Weather Data 472
Conversion Formulas And Tables 475
Electrical Data 482
Properties Of Saturated Steam Data 488
Airflow Data 489
Moisture Content Of Air Data 491
Index 494
ENGINEERING MANUAL OF AUTOMATIC CONTROL
CONTROL FUNDAMENTALS
1
CONTROL
SYSTEMS
FUNDMENTALS
Contents
Introduction 5
Definitions 5
HVAC System Characteristics 8
General 8
Heating 9
General 9
Heating Equipment 10
Cooling 11
General 11
Cooling Equipment 12
Dehumidification 12
Humidification 13
Ventilation 13
Filtration 14
Control System Characteristics 15
Controlled Variables 15
Control Loop 15
Control Methods 16
General 16
Analog And Digital Control 16
Control Modes 17
Two-Position Control 17
General 17
Basic Two-Position Control 17
Timed Two-Position Control 18
Step Control 19
Floating Control 20
Proportional Control 21
General 21
Compensation Control 22
Proportional-Integral (Pi) Control 23
Proportional-Integral-Derivative (Pid) Control 25
Enhanced Proportional-Integral-Derivative (epid) Control 25
Adaptive Control 26
Process Characteristics 26
Control
Fundamentals
ENGINEERING MANUAL OF AUTOMATIC CONTROL
CONTROL FUNDAMENTALS
4
Load 26
Lag 27
General 27
Measurement Lag 27
Capacitance 28
Resistance 29
Dead Time 29
Control Application Guidelines 29
Control System Components 30
Sensing Elements 30
Temperature Sensing Elements 30
Pressure Sensing Elements 31
Moisture Sensing Elements 32
Flow Sensors 32
Proof-Of-Operation Sensors 33
Transducers 33
Controllers 33
Actuators 33
Auxiliary Equipment 34
Characteristics And Attributes Of Control Methods 35
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