Honeywell AUTOMATIC CONTROL Engineering Manual page 305

CHILLER, BOILER, AND DISTRIBUTION SYSTEM CONTROL APPLICATIONS
Methods Of Controlling Distribution Systems ...................................... 350
Three-Way Coil Bypass And Two-Way Valve Control ..................... 350
Valve Selection Factors .................................................................. 350
Flow And Pressure Control Solutions ............................................. 350
Single Pump, Pressure Bypass, Direct Return ........................... 351
Valve Location and Sizing ...................................................... 351
Differential Pressure Sensor Location .................................... 351
Single Pump, Pressure Bypass, Reverse Return ....................... 352
Dual Pumps, Dual Chillers, Pressure Bypass,
90 Percent Chiller Flow, Direct Return ..................................... 354
AHU Valve High Differential Pressure Control ............................ 354
Variable Speed Pump Control ......................................................... 355
Decoupled Variable Speed Pump Control, Direct Return ........... 355
Pump Speed Valve Position Load Reset .................................... 357
Balancing Valve Considerations ................................................. 359
Balancing Valve Effects .......................................................... 359
Balancing Valve Elimination ................................................... 359
Differential Pressure Sensor Location Summary ........................ 359
Pump Minimum Flow Control ...................................................... 359
Decoupled Variable Speed Pump Control, Reverse Return ....... 360
Hot Water Distribution Systems .......................................................... 360
General ........................................................................................... 360
Hot Water Converters ..................................................................... 360
Hot Water Piping Arrangements ...................................................... 361
General ....................................................................................... 361
Primary-Secondary Pumping ...................................................... 362
Control Of Hot Water Systems ........................................................ 362
General ....................................................................................... 362
Modulating Flow Control ............................................................. 362
Supply Hot Water Temperature Control ...................................... 363
Supply Hot Water Temperature Control With Flow Control ........ 363
Hot Water Reset ......................................................................... 363
Hot Water Converter ............................................................... 363
Three-Way Valve .................................................................... 366
Coordinating Valve Selection and System Design ...................... 366
Hot Water Control Method Selection .......................................... 366
Chilled Water Distribution Systems ..................................................... 366
General ........................................................................................... 366
System Objectives ...................................................................... 367
Control of Terminal Units ............................................................ 367
Dual Temperature Systems ............................................................. 367
Changeover Precautions ............................................................ 367
Multiple-Zone Dual-Temperature Systems ...................................... 367
Steam Distribution Systems And Control ............................................ 368
Introduction ..................................................................................... 368
Advantages Of Steam Systems vs Hot Water Systems .................. 368
Steam System Objectives ............................................................... 368
Properties Of Steam ............................................................................ 368
Steam System Heat Characteristics ............................................... 369
Steam Pressure, Temperature, and Density ................................... 369
Steam Quality ................................................................................. 369
Steam Distribution Systems ................................................................ 370
Steam Piping Mains ........................................................................ 370
Steam Traps .................................................................................... 370
Pressure Reducing Valve Station ................................................... 371
Types Of Low Pressure Steam Distribution Systems ..................... 372
One-Pipe Steam Systems .......................................................... 372
Two-Pipe Steam Systems ........................................................... 372
Types Of Condensate Return Systems ........................................... 372
Variable Vacuum Return Systems ................................................... 373
295 ENGINEERING MANUAL OF AUTOMATIC CONTROL