Special Control SiBE31-801_C107 Function8.2 Oil Return OperationThis function is used to recover refrigerant oil that flows out from the compressor to the system side by conducting oilreturn operation in order to prevent the compressor from running out of refrigerant oil.8.2.1 Cooling Oil Return Operation[Start conditions]Referring to the following conditions, start cooling oil return operation.• Integral oil rise rate (*1) is reached to specified level.• When cumulative compressor operating time exceeds 8 hours (2 hours when the power supply turns ON forthe first time)*1 The integral oil rise rate:The higher the compressor operating step No., the cumulative refrigerant oil consumption increases.*1: In case of multi outdoor unit system:Master unit: It conducts the operation listed in the table above.Slave units: Operating units conduct the operation listed in the table above.Non-operating units conduct the operation listed in the table above after the "Oil returning" process.(Non-operating units stop while in "Preparation" mode.)State of function units is same as “Cooling operation” of 6.1.2 “Function Unit” (P.90)Outdoor unit actuator Elect.symbol Oil return preparationoperation Oil return operation Operation after oil returnCompressor 1 M1CTake the current step as theupper limit.52Hz+ON+ON(Subsequently, constant lowpressure control)Maintain the number ofcompressors that were usedbefore oil return operation)52Hz+ON+ON(Subsequently, constant lowpressure control)Compressor 2 M2CCompressor 3 M3COutdoor unit fan 1 M1F Fan control Fan control Fan controlOutdoor unit fan 2 M2FElectronic expansionvalve (main) Y1E 480 pls 480 pls 480 plsElectronic expansionvalve (subcooling) Y3E SH control 0 pls 0 plsElectronic expansionvalve (refilling refrigerant) Y2E 80 pls 80 pls 80 plsSolenoid valve (gaspurging pipe of refrigerantregulator) Y1S OFF OFF OFFFour way valve (for heatexchanger selection) Y3S OFF OFF OFFSolenoid valve (liquidpipe of refrigerantregulator) Y4S OFF OFF OFFSolenoid valve (hot gas) Y5S OFF OFF OFFSolenoid valve (mainbypass) Y6S ON ON ONSolenoid valve (dischargepipe of refrigerantregulator) Y7S OFF OFF OFFSolenoid valve (dischargepipe of refrigerantregulator) Y8S OFF OFF OFFFour way valve (for highand low pressure gas pipeselection) Y2S ON ON ONEnd conditions 20 sec. • After a lapse of 3 min.• TsA - Te<5°C• After a lapse of 3 min.• Pe<0.59MPa• Pc>3.53MPa• HTdi>110°CORor or
