Check SiUS371614E277 Service Diagnosis4.3 Superheat Operation CheckIdentify the defective points referring to the failure factor analysis (FTA) as follows.Note: ∗1. Refer to “Low pressure protection control” for hot gas bypass control.∗2. Refer to “Subcooling electronic expansion valve control”.∗3. “Superheating temperature control” in cooling is conducted by indoor unit electronic expansion valve.∗4. Superheating temperature control in heating is conducted by outdoor unit electronic expansionvalve (main).∗5. Judgement criteria of superheat operation:(1) Suction gas superheated degree: 10°C (50°F) and over. (2) Discharge gas superheated degree: 45°C(113°F) and over, except immediately after compressor starts up or is running under drooping control.(Use the above values as a guide. Depending on the other conditions, the unit may be normaldespite the values within the above range.)CHECK 3Abnormal piping lengthBent or crashed pipe(Including moisture choke)Stop valve closed.Defective valve coilDefective valve bodyDefective valve coilDefective valve body←Are the coil resistance and insulation normal?←Are the electric characteristics normal?←Are the coil resistance and insulation normal?←Is the connector properly connected?Are the thermistor resistance characteristics normal?←Is the connector properly connected?Are the thermistor resistance characteristics normal?←Are the coil resistance and insulation normal?←Are the electric characteristics normal?←Refer to CHECK 7←Does the piping length fall in the permissible range?←Conduct visual checks.←Eliminate moisture by vacuum operation. (Refer to CHECK 8 )←Check if the stop valve is open.DefectivedischargepipetemperaturecontrolDefective hotgas bypasscontrolHot gas circuit cloggingDefective solenoidvalve coilDefective solenoidvalve bodyDefective servicemonitor PCBDefective servicemonitor PCBDefective valve coilDefective lowpressure sensorDefective subcoolingheat exchanger outletthermistorDefective valvebodyDefectivesubcoolingelectronicexpansionvalve controlSuperheat due toshaft damageSuperheat due todefective compressorDefective indoorunit electronicexpansion valveDefectivecontrolDefectivecontrolDefectiveoutdoor unitelectronicexpansion valveDefective fourway valveoperation[In cooling only](∗1)(∗2)CompressoroverheatRefrigerantshortageHigh piperesistanceDefectivesuperheateddegreecontrol.[In cooling]If the indoor unitelectronicexpansion valve isthrottled too much:(∗3)[In heating]If the outdoor unitelectronicexpansion valveexcessivelythrottled: (∗4)Temperatureincrease ofdischargepipeDefectivesubcoolingelectronicexpansionvalve←Are the coil resistance andinsulation normal?←Is the connector properly connected?Are the thermistor resistance characteristicsnormal?←Is the pressure value checked with theService Checker corresponding to themeasurement value of the pressure sensor?←Check if the piping temperature connectedto the four way valve is normal.Four way valve is in themiddle position.Leak from hot gas bypassvalveDefectivecontrolDefective gas pipethermistor of indoor unitDefective thermistor forindoor unit liquid pipeDefective servicemonitor PCBDefective low pressuresensorDefective suction pipethermistorDefective servicemonitor PCB ←Is the pressure value checked with the ServiceChecker corresponding to the measurementvalue of the pressure sensor?←Is the connector properly connected?Are the thermistor resistance characteristics normal?
