Engineering Manual o.. - HVAC.Amickracing

INDIVIDUAL ROOM CONTROL APPLICATIONSIndividual Room Control ApplicationsENGINEERING MANUAL OF AUTOMATIC CONTROLCONTENTSIntroduction ............................................................................................................ 397Graphic Symbols ................................................................................. 398Abbreviations ....................................................................................... 399Air Terminal Unit Control ..................................................................... 399Variable Air Volume ATU...................................................................... 399Pressure-Dependent and Pressure-Independent ATU ................... 399Single-Duct VAV ATU ...................................................................... 400System Configuration ................................................................. 400Throttling VAV ATU ..................................................................... 400Variable Air Volume ATU ............................................................. 401Variable Air Volume ATU with Electric Reheat ............................ 402Constant Air Volume ATUs .......................................................... 402Induction VAV ATU ...................................................................... 402Parallel Fan ATU ......................................................................... 404Series Fan ATU ........................................................................... 404Dual-Duct ATU ................................................................................ 406Dual Duct Pressure Independent VAV ATU ................................ 406Dual Duct Pressure Independent Constant Volume ATU ............ 407Unitary Equipment Contr ol ............................................................................................................ 408General................................................................................................ 408Natural Convection Units ..................................................................... 408Radiant Panels .................................................................................... 409Unit Heaters ........................................................................................ 409General ........................................................................................... 409Control ............................................................................................ 410Two-Position Control ................................................................... 410Modulating Control...................................................................... 410Down-Blow Unit Heater ................................................................... 410Gas- or Oil-Fired Unit Heater .......................................................... 411Unit Ventilators .................................................................................... 411General ........................................................................................... 411Control ............................................................................................ 412ASHRAE Control Cycles............................................................. 412Standby/Warmup Stage ......................................................... 412Cycle I–Fixed Maximum Percentage of Outdoor Air............... 413Cycle II–Fixed Minimum Percentage of Outdoor Air............... 413Cycle III–Variable Outdoor Air ................................................ 414Day/Night Setback Control ......................................................... 414Unit Ventilator Digital Control ...................................................... 415Precautions and Conditions for Successful Operation .................... 418Blocked Airflow ........................................................................... 418Power Failure .............................................................................. 418Coil Freeze-Up ............................................................................ 418ENGINEERING MANUAL OF AUTOMATIC CONTROL 395