SiUS34-801A_b Special ControlVRVIII R-410A Heat Recovery 60Hz 199conditions of indoor units with thermostat ON, thus maximizing the equipment capacity.[Starting conditions]•The system starts heating operation with thermostat ON at a high load.•The system completes defrosting operation.•The system switches the operation mode from cooling to heating or simultaneouscooling and heating operation.[Control]1. Start multiple INV compressors in the system at one time.2. Start multiple STD compressors in the system at intervals of 15 seconds.7.3 Oil Return OperationThis function is used to recover refrigerant oil that flows out from the compressor to the system side by conducting oil returnoperation in order to prevent the compressor from running out of refrigerant oil.7.3.1 Cooling Oil Return Operation[Start conditions]Referring to the following conditions, start cooling oil return operation.• Integral oil rise rate is reached to specified level.• When cumulative compressor operating time exceeds 8 hours (2 hours when the power supply turns ON for thefirst time)Furthermore, the integral oil rise rate is calculated by Tc, Te, and compressor loads.Start up STD compressors at intervals of 15 seconds.INVSTD071142285213356psiPressure PcPeTimeNumber ofcompressorsOROR
