Honeywell AUTOMATIC CONTROL SI Edition Engineering Manual page 302

CHILLER, BOILER, AND DISTRIBUTION SYSTEM CONTROL APPLICATIONS
Boiler System Control
Hot and Chilled Water Distribution Systems Control ...................................................................................... 335
............................................................................................................ 327
Introduction .......................................................................................... 327
Boiler Types ......................................................................................... 327
Cast Iron and Steel Boilers ............................................................. 327
Modular Boilers ............................................................................... 327
Electric Boilers ................................................................................ 328
Boiler Ratings and Efficiency ............................................................... 328
Combustion in Boilers ......................................................................... 329
Principles of Combustion ................................................................ 329
Flue Gas Analysis ........................................................................... 329
Oil Burners ...................................................................................... 329
Gas Burners .................................................................................... 329
Boiler Controls ..................................................................................... 330
Boiler Output Control ...................................................................... 330
Combustion Control ........................................................................ 330
Flame Safeguard Control ................................................................ 330
Flame Safeguard Instrumentation ................................................... 331
Application of Boiler Controls .......................................................... 331
Multiple Boiler Systems ....................................................................... 332
General ........................................................................................... 332
Dual Boiler Plant Control ................................................................. 333
Modular Boilers ............................................................................... 335
Introduction .......................................................................................... 335
Classification of Water Distribution Systems ................................... 335
Typical Water Distribution System ................................................... 335
Control Requirements for Water Distribution Systems .................... 336
Centrifugal Pumps Used in Hot and Chilled Water Systems ............... 336
Pump Performance ......................................................................... 337
Pump Power Requirements ........................................................ 338
Pump Performance Curves......................................................... 338
Pump Efficiency .......................................................................... 338
Pump Affinity Laws ..................................................................... 339
Matching Pumps to Water Distribution Systems ............................. 340
System Curves ........................................................................... 340
Plotting a System Curve ............................................................. 340
Combining System and Pump Curves ........................................ 340
Variable Speed Pumps .................................................................... 342
Pumps Applied to Open Systems ................................................... 343
Multiple Pumps ............................................................................... 343
Operation .................................................................................... 344
Dual Pump Curves ..................................................................... 345
Distribution System Fundamentals ...................................................... 345
Direct Vs Reverse Return Piping Systems ...................................... 346
Coupled Vs Decoupled Piping Systems .......................................... 347
Methods of Controlling Distribution Systems ....................................... 348
Three-Way Coil Bypass and Two-Way Valve Control ...................... 348
Valve Selection Factors ................................................................... 348
Flow and Pressure Control Solutions .............................................. 348
Single Pump, Pressure Bypass, Direct Return ........................... 349
Valve Location and Sizing ...................................................... 349
Differential Pressure Sensor Location .................................... 349
Single Pump, Pressure Bypass, Reverse Return ....................... 351
Dual Pumps, Dual Chillers, Pressure Bypass,
90 percent Chiller Flow, Direct Return .................................... 352
AHU Valve High Differential Pressure Control ............................ 352
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ENGINEERING MANUAL OF AUTOMATIC CONTROL