Engineering Manual o.. - HVAC.Amickracing

INDIVIDUAL ROOM CONTROL APPLICATIONSONWALL MODULE5575TEMPERATUREFAN0073HEATINGSETPOINTPERCENTOPEN75COOLINGSETPOINTOARA00PERCENT OPENTO BYPASS77PERCENT OPENTO OUTSIDE AIRCONTROLPROGRAM24MINIMUMVENTILATIONDAMPERSETPOINT46DISCHARGETEMPERATURESETPOINTHEATINGLOADPERCENTDISCHARGETEMPERATURESETPOINTCOOLINGLOADPERCENT55075010510055100OPENFAN ONHOT WATER VALVEFACEDAMPEROUTSIDE AIRDAMPERMINIMUMCLOSEDRECIRCULATESETPOINTHEATINGSETPOINTCOOLINGSETPOINT100 0 0100HEATING LOADPERCENTOCCUPIED MODECOOLING LOADPERCENTOPEN/ONFACE DAMPERHOT WATER VALVEOA DAMPERCLOSEDCLOSED/OFFFANFAN ONSETPOINTUNOCCUPIED MODECONVECTIONSETPOINTM10547Fig. 28. Cycle II with Enhanced Digital Control.On morning occupancy startup, the fan operates with the hotwater valve open, the face damper open, and the OA damperclosed; and as the room warms to a vent/recirculate setpoint,the OA damper opens to a minimum ventilation position. Asthe heating load drops, the face and bypass dampers modulateto maintain the room heating temperature setpoint. As the roomtemperature rises to a value midpoint between the heating andcooling setpoints, the heating valve closes. If the roomtemperature rises to the cooling setpoint, the OA dampermodulates to maintain the cooling setpoint.Although the discharge air sensor could be used as a lowlimit only, Figure 28 shows it as the primary controller resetfrom the demands of the room sensor.In the unoccupied mode, the valve is controlled in a twopositionmanner to maintain an unoccupied convection heatingroom temperature setpoint. If the room temperature cannot bemaintained by convection heating, the fan is cycled to maintainthe unoccupied heating fan-on setpoint. The face damper isopen and the OA damper is closed.Figure 29 adds a chilled water coil to Figure 28.ENGINEERING MANUAL OF AUTOMATIC CONTROL 392