Refrigerant Circuit SiUS331604E9 Refrigerant Circuit1.2 RXTQ48TAVJUNo. inpipingdiagramSymbol Name Function(1) M1C Inverter compressor Inverter compressor is operated on frequencies between 36Hz and 195Hz by using theinverter.(2) M1F Inverter fan Because the system is of an air heat exchange type, the fan is operated at 8-step rotationspeed by using the inverter.(3) Y1E Electronic expansion valve(Main) While in heating operation, PI control is applied to keep the outlet superheated degree ofair heat exchanger constant.(4) Y1S Four way valve Used to switch the operation mode between cooling and heating.(5) Y3S Solenoid valve (Unload circuit) Used for unloading operation of compressor.(6) S1NPH High pressure sensor Used to detect high pressure.(7) S1NPL Low pressure sensor Used to detect low pressure.(8) S1PH High pressure switch In order to prevent the increase of high pressure when an error occurs, this switch isactivated at high pressure of 4.0 MPa (580 psi) or more to stop the compressor operation.(9) — Fusible plugIn order to prevent the increase of pressure when abnormal heating is caused by fire orothers, the fusible part of the plug is molten at a temperature of 70 ~ 75°C (158 ~ 167°F) torelease the pressure into the atmosphere.(10) — Pressure regulating valve 1(Receiver to discharge pipe)This valve opens at a pressure of 4.0 MPa (580 psi) or more for prevention of pressureincrease, thus resulting in no damage of functional parts due to the increase of pressure intransportation or storage.(11) R1T Thermistor (Outdoor air) Used to detect outdoor air temperature, correct discharge pipe temperature, and others.(12) R2T Thermistor (Discharge pipe) Used to detect discharge pipe temperature, make the temperature protection control ofcompressor, and others.(13) R3T Thermistor (Suction pipe 1) Used to detect suction pipe temperature, keep the suction superheated degree constant inheating operation, and others.(14) R4T Thermistor (Heat exchangerdeicer)Used to detect liquid pipe temperature of air heat exchanger, determine defrost operation,and others.(15) R5T Thermistor (Suction pipe 2) Used to the calculation of an internal temperature of compressor etc.(16) R7T Thermistor (Liquid pipe) Used to detect refrigerant overcharge in check operation, and others.(17) FINTH Thermistor (Radiation fin)• Used for outdoor unit fan speed control.• Used for inverter radiation fin temperature control.• Used for pressure difference control.
