Midea M-Thermal Series - Page 69

M‐ThermalSplit 
68 201909
MideaM‐ThermalSplitServiceManual
RefrigerantSystem,InverterModule").
2. BackupelectricheaterwateroutlettemperaturesensorandwatersideheatexchangerwateroutlettemperaturesensorconnectionsareportCN6onthe
hydronicboxmainPCB(labeled11inFigure4‐2.1inPart4,2.2"MainPCBforHydronicSystem").
Domestichotwatertanktemperaturesensorconnection
isportCN13onhydronicboxmainPCB(labeled12inFigure4‐2.1inPart4,2.2"MainPCBforHydronicSystem"). 
3. Measuresensor resistance.If the resistanceis too low, the sensorhasshort‐circuited.Iftheresistanceisnotconsistentwith the sensor’s resistance
characteristicstable,thesensorhasfailed.RefertoPart2,1“LayoutofFunctionalComponents”andtoTable5‐5.1or5‐5.2inPart5,5.1“Temperature
SensorResistanceCharacteristics”.
4. HighpressureswitchconnectionisportCN13onthemainPCB(labeled 10in Figure 4‐2.2 in Part4, 2.3 "Main PCBsforRefrigerantSystem,Inverter
Module").PressuresensorconnectinisportCN4onthemaincontrolboard(labeled15inFigure4‐2.2inPart4,2.3"MainPCBsforRefrigerantSystem,
InverterModule")
5. Measuretheresistanceamongthethreeterminalsofthepressuresensor.IftheresistanceisoftheorderofmegaOhmsorinfinite,thepressuresensor
hasfailed.
6. Highpressuresideblockagecausesdischargetemperaturetobehigherthannormal,dischargepressuretobehigherthannormalandsuctionpressureto
belowerthannormal.
7. Checkairsideheatexchanger,fanandairoutletsfordirt/blockages.
8. Checkthewatersideheatexchanger,waterpiping,circulatorpumpsandwaterflowswitchfordirt/blockages.
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