Daikin MicroTech III DPS Installation And Maintenance Manual

Contents

Daikin MicroTech III DPS Installation And Maintenance Manual Manual pdf 44 page image

OM 1263 • MICROTECH UNIT CONTROLLER 44 wwwCompressor ProtectionCompressor ProtectionCompressor Protection Unloading ControlThere are a number unloading control functions that limitthe staging and speed control of the compressors to protectthem from damage under abnormal operating conditions Thefollowing unload functions are provided:• Cooling High Pressure Unloading Control• Cooling Low Pressure Unloading Control• Heating High Pressure Unloading Control• Heating High Protection Control [anticipating highpressure]• Heating Low Pressure Unloading Control• Inverter Compressor High Discharge Line TemperatureUnloading Control• Standard Compressor High Discharge Line TemperatureUnloading Control• Inverter Compressor High Current Unloading Control• Inverter Compressor Request for Unloading Control• Compression Ratio Unloading Control• Inverter Compressor Board Temperature UnloadingControl• Low Differential Pressure Protection ControlCooling High Pressure Unloading ControlNormal compressor operation is limited during cooling operationwhen high discharge pressure conditions occur When thedischarge pressure rises above 503 psi the inverter compressoris immediately reduced by three steps* and then reduced afurther step every 10 seconds in an attempt to keep the pressurefrom rising above 515 psi If reducing the compressor capacityfails to keep the pressure below 515 psi the inverter compressoris reduced to minimum and any fixed speed compressor runningis stopped If the discharge pressure continues to rise above 527psi, compressor operation is forced to the Standby state where itremains for a cooling stage time period before being allowed torestart If the unit is forced to Standby in this manner 3 times ina 30 minute period, a high pressure alarm is generated requiringmanual resetOnce active this limiting function remains active until thedischarge pressure falls back below 469 psiCooling Low Pressure Unloading ControlNormal compressor operation is limited during coolingoperation when low suction pressure conditions occur Whenthe suction pressure falls below 50 psi the inverter compressorcapacity is held at its current valve and the bypass solenoidvalve (SVB) is opened in an attempt to keep the pressure fromfalling below 36 psi If the pressure continues to fall below 36psi the inverter compressor is slowed to minimum speed andany fixed speed compressor running is stopped. If the pressurecontinues to fall below 10 psi, compressor operation is forcedto the Standby state where it remains for a cooling stage timeperiod before being allowed to restart If the unit is forced toStandby in this manner 3 times in a 30 minute period, a lowpressure alarm is generated requiring manual reset.Once active this limiting function remains active until thesuction pressure rises back above 57 psiHeating High Pressure Unloading ControlNormal compressor operation is limited during heatingoperation when high discharge pressure conditions occurWhen the discharge pressure rises above 481 psi the invertercompressor capacity is immediately reduced by seven stepsand then reduced a further step every 10 seconds in anattempt to keep the pressure from rising above 497 psi Ifthe pressure continues to rise above 497 psi the invertercompressor is slowed to minimum speed and any fixed speedcompressor running is stopped If the pressure continues torise above 527 psi, compressor operation is forced to theStandby state where it remains for a heating stage time periodbefore being allowed to restart If the unit is forced to Standbyin this manner 3 times in a 30 minute period, a high pressurealarm is generated requiring manual reset.Once active this limiting function remains active until thedischarge pressure falls back below 427 psi* See page 50 for more information about what is acompressor “step”.