ENGINEERING MANUAL OF AUTOMATION CONTROL
BUILDING AIRFLOW SYSTEM CONTROL APPLICATIONS
263
Building Airflow System
Control Applications
Contents
Introduction ............................................................................................................ 265
Definitions ............................................................................................................ 265
Airflow Control Fundamentals ............................................................................................................ 267
Need For Airflow Control ..................................................................... 267
What Is Airflow Control ........................................................................ 267
Types Of Airflow Systems.................................................................... 267
Variable Air Volume ......................................................................... 267
Constant Air Volume ....................................................................... 268
Variable Versus Constant Air Volume ............................................. 269
Ventilation ............................................................................................ 269
Pressurization...................................................................................... 270
Building Pressure Balance .............................................................. 270
Containment Pressurization ............................................................ 271
Wind Pressure Effects .................................................................... 271
Stack Effect ..................................................................................... 271
Characteristics Of Fans And Fan Laws ............................................... 272
General ........................................................................................... 272
Fan Types ....................................................................................... 272
Fan Performance Terms ................................................................. 273
Fan Laws ........................................................................................ 273
Fan Horsepower ............................................................................. 273
Duct System Curves ....................................................................... 274
Fan Curve And System Curve Comparison .................................... 274
Characteristics Of Airflow In Ducts ...................................................... 274
General ........................................................................................... 274
Pressure Changes Within A Duct .................................................... 274
Effects of Fittings ............................................................................ 276
Effects Of Dampers......................................................................... 277
Effects Of Air Terminal Units ........................................................... 277
Measurement Of Airflow In Ducts ........................................................ 278
General ........................................................................................... 278
Pressure Sensors ........................................................................... 278
Pitot Tube Sensors.......................................................................... 279
Total And Static Pressure Sensors .................................................. 279
Airflow Measuring Devices.............................................................. 279
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