Daikin MicroTech III DPS Installation And Maintenance Manual

Contents

Daikin MicroTech III DPS Installation And Maintenance Manual Manual pdf 55 page image

Operator’s Guidewww DaikinApplied com55 OM 1263 • MICROTECH UNIT CONTROLLERNormal CoolingIn the Normal Cooling state the following are accomplished:• Indoor coil expansion value is modulated to maintain the suction superheat at the suction superheat set point• Outdoor coil expansion valve is controlled to maintain outdoor coil subcooling at the outdoor coil subcooling set point (heatpump)• Outdoor fan(s) are modulated to maintain the discharge saturation temperature at the discharge saturation temperature setpointWhen in the Normal Cooling state the action of the cooling control devices is as follows:Table 38: Normal Cooling StateDevice ActionCompressorsInverter Compressor Speed Controlled with PI Loop to Maintain DAT SetpointComp 3: Turned On when inverter speed is at MaximumComp 3: Turned Off when inverter speed is at MinimumOutdoor Fan Outdoor Fan Capacity Controlled With PI Loop to Maintain condensingtemperature setpoint4 Way Valve(Heat Pump) OFFOutdoor Coil Expansion Valve (EVO) (Heat Pump only) ASVR (Heat Pump only) ClosedSVBSVB is normally closed during the Normal Cooling stateexcept in the following cases:SVB is opened for one second before and after Comp 3 is stoppedDuring Low Pressure Unloading Control SVB is opened if PTS< 21 psiIt is closed again when PTS> 43 psiIndoor Coil Expansion Valve (EVI) EVI Controlled With PI Loop to Maintain Suction Superheat SetpointTime Duration While in Normal Cooling stateA The outdoor expansion valve position is either driven fully open (100%) or varied based on outdoor coil subcooling as follows:• When the outdoor expansion valve Method is set to 100%, the outdoor expansion valve is driven to the 100% openposition• When the outdoor expansion valve Method is set to subcooling, the outdoor expansion valve is controlled to maintainthe outdoor coil subcooling temperature set pointNormal Cooling Outdoor Fan (OA Fan PI_Loop)ControlOne or two outdoor fans are controlled via Modbusconnections to the Inverter Compressor Board via the IFBcommunication boardThe outdoor fan control PI_Loop is active only during theNormal Cooling and Cooling Pumpdown operating states andthe loop maintains the discharge saturation temperature at theset point between a minimum value of 86°F and a maximumvalue of 131°F EER values will be improved by allowing thelower set points when appropriateNormal Heating OA Fan ControlDuring the Normal Heating state the outdoor fan speed is firstset at the maximum value and is then controlled as follows:• If discharge pressure is low (below 107 psi) or the INVBoard (fin) Temp is high [above 176°F (172°F for 208/230volt units) continuously for 15 seconds] the outdoor fanspeed is increased by 2% No further changes are madefor 15 seconds• If discharge pressure is high (above 162 psi) or the INVBoard (fin) Temp is low [below 172°F (169°F for 208/230volt units) continuously for 15 seconds] the outdoor fanspeed is decreased by 2% No further changes are madefor 30 secondsOutdoor Fan Fault ProtectionIf a unit is equipped with only one outdoor fan and it is shut offon one of its internal faults, compressor operation enters theStandby for Restart stateIf a unit is equipped with two outdoor fans and either outdoorfan 2 or both outdoor fans shut off on one of their internalfaults, compressor operation enters the Standby for Restartstate Note: In the case of two fans outdoor fan 2 providescritical cooling for the inverter compressor/outdoor fan controlboardsOnce compressor operation finishes the Standby for Restartstate and if there is a call for cooling, compressor operationis allowed to sequence to the Normal operating state in thenormal manner If this cycle is repeated three times in a thirtyminute period an OA Fan: Problem alarm is generated, lockingout compressor operation, requiring a manual reset.