Daikin MPS015 F Installation And Maintenance Manual

Contents

seqUenCe of oPeraTIonOperating StatesThe transition from any operating state to another is graphicallyrepresented in Figure 78Figure 78: State DiagramStart UpWith a “start up” command from the “Off” State the unit willdefault into the “Start Up” state of operation for 3 minutes.During this time, the fan is off.RecirculationNext, the unit will transition into the “Recirculation” state ofoperation for another 3 minutes. During this time, the outsideair damper will close and the fan will turn on, thereby mixingthe air in the ductwork and the space.Fan OnlyThe outside air damper will modulate to the minimum positionand based upon the sensor inputs, the unit will go into one ofthe four running states - “Heating,” “Cooling,” “Economizing,”or “Minimum DAT.” If the control temperature is between itssetpoint and its dead band, the unit will remain in the “FanOnly” state.HeatingThe unit's heating mode of operation is controlled by thecontrol temperature and the heating setpoint temperature. Theunit goes into the heating mode of operation by analyzing thecontrol temperature.The control temperature can be either the return temperatureor the space temperature.The return temperature is typically used for VAV units and thespace temperature is typically used for CAV units.The unit goes into the heating mode of operation when thecontrol temperature (return or space temperature) is below theheating setpoint by more than ½ the deadband.Example – If the heating setpoint is 68.0°F and the deadbandis 1.0°F, the unit will not go into the heating mode of operationuntil the control temperature reaches 67.4°F.When this takes place, the heating mode of operation willbegin and the 1st stage of heating operation will start. Thenext stage, up or down, will take place after 4 minutes. This“4 minutes” is called the stage timer. The gas or electricheat module will continue to stage up as long as the controltemperature is below the heating setpoint by more than ½the heating setpoint deadband. The unit will stage down if themaximum discharge air temperature of 120°F is reached. Gasunits with one gas valve have 2 stages of heating and unitswith two gas valves have 4 stages of heating.Minimum DATThis control mode is designed to temper the air in the ductworkwhen in heating mode. When the unit is in the “Fan Only” stateand the Discharge Air Temperature is less than the minimumdischarge air temperature limit, “Minimum DAT” control isinitiated. The unit will turn on minimum heat until the dischargeair temperature exceeds the limit.MechanicalCoolingHeatingEconomizerFan OnlyMinimum DATAny Other StateOFFStart UpRecirculationIM 1058-8 • MAVERICK II ROOFTOP SYSTEMS 90 www.DaikinApplied.comseqUenCe of oPeraTIon