Daikin · A major brand in the UK. 343 codes across 9 product families, each taken from the manufacturer’s manuals. Daikin technical support ↗
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343 codes
| Code | Meaning | Stops? | Homeowner check? |
|---|---|---|---|
| 7H | Flow abnormality | Not stated | Yes |
| 7H-01 | Water flow problem | Yes | Yes |
| 7H-04 | Water flow problem during domestic hot water production | Yes | Yes |
| 7H-05 | Water flow problem during heating/sampling | Yes | Yes |
| 7H-06 | Water flow problem during cooling/defrost | Yes | Yes |
| 7H-07 | Water flow problem. Pump deblocking active | No | Yes |
| 7H-08 | Pump abnormality during operation (pump feedback) | No | Yes |
| 7H-09 | Abnormal flow during emitter defrost | Yes | Yes |
| 7H-10 | Abnormal flow during tank defrost | Yes | Yes |
| 7H-11 | Flow abnormality during 4-way valve in cooling | Yes | Yes |
| 7H-12 | Main zone pump blocked abnormality | Partly | Yes |
| 7H-13 | Main zone pump electrical fault abnormality | Partly | Yes |
| 7H-14 | Add. zone pump communication error | No | Yes |
| 7H-15 | Add. zone pump blocked abnormality | Partly | Yes |
| 7H-16 | Add. zone pump electrical fault abnormality | Partly | Yes |
| 7H-17 | Main zone pump communication error | No | Yes |
| 7H-18 | Water flow requirement problem at space cooling request | Not stated | Yes |
| 7H-19 | Water flow requirement problem at tank heat-up request | Not stated | Yes |
| 7H-20 | Water flow requirement problem on emitter hydraulic circuit | Not stated | Yes |
| 7H-21 | Water flow requirement problem on tank hydraulic circuit | Not stated | Yes |
| 7H-22 | Water flow requirement problem at space heating request or during Water pipe freeze prevention | Not stated | Yes |
| 7H-23 | Main zone pump communication error | Yes | Yes |
| 7H-24 | Add. zone pump communication error | Yes | Yes |
| 8C-03 | Undercooling of the space cooling water circuit | Partly | Yes |
| 8C-04 | Undercooling of the main zone water circuit (e.g. stuck or broken mixing valve) | Partly | Yes |
| 8F-00 | Abnormal increase outlet water temperature (DHW) | Yes | Yes |
| 8H | Outlet water temperature too high | Not stated | Yes |
| 8H-00 | Abnormal increase outlet water temperature | Yes | Yes |
| 8H-01 | Overheating mixed water circuit | No | Yes |
| 8H-02 | Overheating mixed water circuit (thermostat) | Yes | Yes |
| 8H-03 | Overheating water circuit (thermostat) | Partly | Yes |
| 8H-08 | Overheating water circuit | Yes | Yes |
| 8H-09 | Backup heater stuck detection ongoing | Yes | Yes |
| 8H-10 | Overheating mixed water safety thermostat (mixing kit) | Partly | Yes |
| 8H-11 | Overheating/undercooling mixed water circuit (mixing kit) | Partly | Yes |
| 80 | Inlet water temperature thermistor abnormality | Not stated | Yes |
| 80-00 | Returning water temperature sensor problem | Yes | Yes |
| 80-01 | Returning water temperature sensor problem | Yes | Yes |
| 80-03 | Entering water temperature thermistor main zone abnormality | No | Yes |
| 80-04 | Entering water temperature thermistor add. zone abnormality | No | Yes |
| 81 | Outlet water temperature thermistor abnormality | Not stated | Yes |
| 81-00 | Leaving water temperature sensor problem | Yes | Yes |
| 81-01 | Mixed water thermistor abnormality | No | Yes |
| 81-04 | Leaving water temperature sensor not properly mounted | Not stated | Yes |
| 81-05 | Loose hanging tank thermistor | Yes | Yes |
| 81-06 | Entering water temperature thermistor abnormality (indoor unit) | Yes | Yes |
| 81-07 | Exit water temperature thermistor after tank valve abnormality | Yes | Yes |
| 81-10 | Mixed water thermistor abnormality (mixing kit) | Partly | Yes |
| 89 | Water heat exchanger freeze-up abnormality | Not stated | Yes |
| 89-01 | Heat exchanger freeze-up protection activated during defrost (error) | Yes | Yes |
| 89-02 | Heat exchanger freeze-up protection activated during heating / DHW operation. (warning) | Varies by model | Yes |
| 89-03 | Heat exchanger freeze-up protection activated during defrost (warning) | Varies by model | Yes |
| 89-04 | Interruption defrost during tank defrost | Yes | Yes |
| 89-05 | Heat exchanger freeze-up protection activated during cooling operation. (error) | Yes | Yes |
| 89-06 | Heat exchanger freeze-up protection activated during cooling operation. (warning) | No | Yes |
| 89-09 | Heat exchanger freeze-up protection activated during 4-way valve in cooling | Yes | Yes |
| 89-10 | Heat exchanger freeze-up protection activated during 4-way valve in cooling | Yes | Yes |
| 89-11 | Heat exchanger freeze-up protection activated during defrost operation | Yes | Yes |
| A0-02 | Indoor unit gas sensor detection | Yes | Yes |
| A1 | PC board defect, E2 PROM defect | Not stated | Yes |
| A1-00 | Zero cross detection problem | Yes | Yes |
| A1-01 | EEPROM reading error | Yes | Yes |
| A5 | Freeze-up protection or High pressure control | Not stated | Yes |
| A5-00 | OU: High pressure peak cut / freeze protection problem | Yes | Yes |
| A6 | Pump error | Not stated | Yes |
| A9 | Malfunction of moving part of electronic expansion valve (Y1E) | Not stated | Yes |
| AA | Back-up heater thermal protector is open | Not stated | Yes |
| AA-00 | Back up heater safety error | Yes | Yes |
| AA-01 | Backup heater overheated or BUH power cable not connected | Yes | Yes |
| AA-02 | External backup heater overheated | Yes | Yes |
| AA-07 | Diverter valve is blocked or incorrect valve type is selected | Yes | Yes |
| AA-08 | Mixing valve is blocked or incorrect valve type is selected | Yes | Yes |
| AA-09 | Diverter valve is broken or incorrect valve type is selected | Yes | Yes |
| AA-10 | Mixing valve is broken or incorrect valve type is selected | Yes | Yes |
| AA-11 | Tank valve is blocked or incorrect valve type is selected | Yes | Yes |
| AA-12 | Bypass valve is blocked or incorrect valve type is selected | Yes | Yes |
| AA-13 | Tank valve is broken or incorrect valve type is selected | Yes | Yes |
| AA-14 | Bypass valve is broken or incorrect valve type is selected | Yes | Yes |
| AC | Booster heater thermal protector is open | Not stated | Yes |
| AC-00 | Booster heater overheated | No | Yes |
| AE | Water Circuit Error | Not stated | Yes |
| AH-00 | Tank disinfection function not completed correctly | No | Yes |
| AJ | Malfunction of capacity setting | Not stated | Yes |
| AJ-03 | Too long DHW heat-up time required | No | Yes |
| C0 | Flow switch abnormality | Not stated | Yes |
| C0-00 | Flow sensor malfunction | Yes | Yes |
| C0-01 | Flow switch malfunction | Yes | Yes |
| C0-02 | Flow switch malfunction | Yes | Yes |
| C0-14 | Indoor gas sensor has a malfunction | Yes | Yes |
| C0-15 | Indoor gas sensor is disconnected | Yes | Yes |
| C1 | Failure of transmission (between indoor unit PC board and fan PC board) | Not stated | Yes |
| C1-10 | ACS communication malfunction | Not stated | Yes |
| C1-11 | ACS communication malfunction | Not stated | Yes |
| C4 | Malfunction of thermistor (R3T) for R-410A liquid/indoor unit (loose connection, disconnection, short circuit, failure) | Not stated | Yes |
| C4-00 | Heat exchanger temperature sensor problem | Yes | Yes |
| C5 | Malfunction of thermistor (R2T) for tank thermistor (loose connection, disconnection, short circuit, failure) | Not stated | Yes |
| C5-00 | Heat exchanger thermistor abnormality | Yes | Yes |
| C8-01 | Current sensor abnormality | Not stated | Yes |
| C9 | Malfunction of thermistor (R4T) for return water thermistor (loose connection, disconnection, short circuit, failure) | Not stated | Yes |
| CA | Malfunction of thermistor (R5T) for leaving water temperature (loose connection, disconnection, short circuit, failure) | Not stated | Yes |
| CJ | Malfunction of thermostat sensor in remote control | Not stated | Yes |
| CJ-02 | Room temperature sensor problem | No | Yes |
| E0-06 | Outdoor unit leakage detection error | Yes | Yes |
| E1 | PC board defect | Not stated | Yes |
| E1-00 | OU: PCB defect | Yes | Yes |
| E2-00 | Leakage current detection error | Yes | Yes |
| E2-01 | Leakage current detection error | Yes | Yes |
| E2-06 | Leakage current detection error | Yes | Yes |
| E3 | Code shown on the remote controller for the installation error(s): Stop valve left closed; refrigerant overcharge (Flex outdoor installation manual, test-operation table) | Not stated | Yes |
| E3-00 | OU: Actuation of high pressure switch (HPS) | Yes | Yes |
| E3-19 | OU: Actuation of high pressure switch (HPS) | Yes | Yes |
| E3-24 | High pressure sensor abnormality | Yes | Yes |
| E4 | Code shown on the remote controller for the installation error(s): Stop valve left closed; insufficient refrigerant (Flex outdoor installation manual, test-operation table) | Not stated | Yes |
| E4-00 | Abnormal suction pressure | Yes | Yes |
| E4-07 | Low evaporating temperature | Not stated | Yes |
| E5 | Compressor motor lock | Yes | Yes |
| E5-00 | OU: Overheat of inverter compressor motor | No | Yes |
| E6 | Standard compressor lock or over current | Yes | Yes |
| E6-00 | OU: Compressor startup defect | No | Yes |
| E7 | Code shown on the remote controller for the installation error(s): Fan motor junction connectors (X1A-X4A) not reconnected after inverter service (Flex outdoor installation manual, test-operation table) | Yes | Yes |
| E7-00 | OU: Malfunction of outdoor unit fan motor | Yes | Yes |
| E7-01 | OU: Malfunction of outdoor unit fan motor | Yes | Yes |
| E7-05 | OU: Malfunction of outdoor unit fan motor | Yes | Yes |
| E7-61 | OU: Malfunction of outdoor unit fan motor | Yes | Yes |
| E7-63 | OU: Malfunction of outdoor unit fan motor | Yes | Yes |
| E8 | Input over current | Yes | Yes |
| E8-00 | OU: Power input overvoltage | Yes | Yes |
| E9 | Malfunction of moving part of electronic expansion valve (Y1E, Y3E) | Not stated | Yes |
| E9-00 | Malfunction of electronic expansion valve | Yes | Yes |
| E9-01 | Malfunction of electronic expansion valve | Yes | Yes |
| E9-02 | Electronic expansion valve error due to wetness | Yes | Yes |
| E9-03 | Malfunction of electronic expansion valve | Yes | Yes |
| EA | Heating / Cooling switching failure | Not stated | Yes |
| EA-00 | OU: Cool/heat switchover problem | No | Yes |
| EA-01 | 4WV switching error | Yes | Yes |
| EC | Domestic hot water temperature too high | Not stated | Yes |
| EC-00 | Abnormal increase tank temperature | No | Yes |
| EC-04 | Tank preheating | No | Yes |
| EJ-01 | Brine circuit pressure low | Not stated | Yes |
| F3 | Code shown on the remote controller for the installation error(s): Stop valve left closed; insufficient refrigerant (Flex outdoor installation manual, test-operation table) | Yes | Yes |
| F3-00 | OU: Malfunction of discharge pipe temperature | No | Yes |
| F3-01 | OU: Malfunction of discharge pipe temperature | Yes | Yes |
| F3-02 | OU: Malfunction of discharge pipe temperature | Yes | Yes |
| F3-20 | OU: Malfunction of discharge pipe temperature | Yes | Yes |
| F3-24 | Compressor shell temperature error | Yes | Yes |
| F6 | Code shown on the remote controller for the installation error(s): Stop valve left closed; refrigerant overcharge (Flex outdoor installation manual, test-operation table) | Not stated | Yes |
| F6-00 | OU: Abnormal high pressure in cooling | No | Yes |
| FA-00 | OU: Abnormal high pressure, actuation of HPS | No | Yes |
| H0 | Sensor abnormality | Not stated | Yes |
| H0-00 | OU: Voltage/current sensor problem | Yes | Yes |
| H0-02 | Outdoor unit gas sensor malfunction | Yes | Yes |
| H0-04 | Outdoor unit gas sensor disconnection | Yes | Yes |
| H1-00 | External temperature sensor problem | No | Yes |
| H3-00 | OU: Malfunction of high pressure switch (HPS) | Yes | Yes |
| H3-01 | OU: Malfunction of high pressure switch (HPS) | Yes | Yes |
| H3-08 | OU: Malfunction of high pressure switch (HPS) | Yes | Yes |
| H4-00 | Malfunction of low pressure switch | Yes | Yes |
| H5-00 | Malfunction of compressor overload protection | Yes | Yes |
| H6 | Compressor start up failure | Yes | Yes |
| H6-00 | OU: Malfunction of position detection sensor | No | Yes |
| H7-01 | OU: Malfunction of outdoor unit fan motor | Yes | Yes |
| H7-31 | Fan motor operation hours | Yes | Yes |
| H8 | CT or related abnormality | Yes | Yes |
| H8-00 | OU: Malfunction of compressor input (CT) system | No | Yes |
| H9 | Malfunction of thermistor (R1T) for outdoor air (loose connection, disconnection, short circuit, failure) | Not stated | Yes |
| H9-00 | OU: Malfunction of outdoor air thermistor | Yes | Yes |
| H9-01 | OU: Malfunction of outdoor air thermistor | Yes | Yes |
| HC | Domestic hot water temperature thermistor abnormality | Not stated | Yes |
| HC-00 | Tank temperature sensor problem | No | Yes |
| HC-01 | Second tank temperature sensor problem | No | Yes |
| HC-02 | Lower tank thermistor abnormality | No | Yes |
| HC-09 | Tank temperature sensor problem | No | Yes |
| HJ-10 | Water pressure sensor abnormality | No | Yes |
| HJ-11 | Boiler abnormality detection Check boiler Refer to boiler manual | Not stated | Yes |
| HJ-12 | Bypass valve turning error | Not stated | Yes |
| J2 | Current sensor malfunction | Not stated | Yes |
| J3 | Malfunction of discharge pipe thermistor (R2T, R6T) (loose connection, disconnection, short circuit, failure) | Not stated | Yes |
| J3-00 | OU: Malfunction of discharge pipe thermistor | Yes | Yes |
| J3-01 | Discharge pipe Thermistor Abnormality | Yes | Yes |
| J3-10 | Compressor port thermistor abnormality | Yes | Yes |
| J3-47 | Compressor shell thermistor abnormality | Yes | Yes |
| J5 | Malfunction of thermistor (R3T, R5T, R7T) for suction pipe (loose connection, disconnection, short circuit, failure) | Not stated | Yes |
| J5-00 | Malfunction of suction pipe thermistor | Yes | Yes |
| J5-23 | Malfunction of suction pipe thermistor | Yes | Yes |
| J6 | Malfunction of thermistor (R6T) for heat exchanger (loose connection, disconnection, short circuit, failure) | Not stated | Yes |
| J6-00 | OU: Malfunction of heat exchanger thermistor | Yes | Yes |
| J6-07 | OU: Malfunction of heat exchanger thermistor | Yes | Yes |
| J6-31 | Inlet water temperature Thermistor abnormality | Yes | Yes |
| J6-32 | Leaving water temperature thermistor Abnormality (outdoor unit) | No | Yes |
| J6-33 | Sensor communication error | Yes | Yes |
| J6-36 | OU: Malfunction of injection thermistor | Yes | Yes |
| J6-42 | OU: Malfunction of injection thermistor | Yes | Yes |
| J7 | Malfunction of thermistor (R7T) for outdoor unit liquid pipe | Not stated | Yes |
| J7-00 | Malfunction of intermediate heat exchanger thermistor | Yes | Yes |
| J7-12 | Brine inlet thermistor abnormality | Not stated | Yes |
| J8-00 | Malfunction of refrigerant liquid thermistor | Yes | Yes |
| J8-07 | Brine outlet thermistor abnormality | Not stated | Yes |
| J9 | Malfunction of subcooling heat exchanger gas pipe thermistor (R4T) | Not stated | Yes |
| J9-23 | Heat pipe thermistor abnormality | Yes | Yes |
| JA | Malfunction of high pressure sensor IU/OU | Not stated | Yes |
| JA-00 | OU: Malfunction of high pressure sensor | Yes | Yes |
| JA-01 | OU: Malfunction of high pressure sensor | Yes | Yes |
| JA-17 | Refrigerant pressure sensor abnormality | Yes | Yes |
| JC | Malfunction of low pressure sensor IU/OU | Not stated | Yes |
| JC-00 | Low pressure sensor abnormality | Not stated | Yes |
| JC-01 | Evaporator pressure abnormality | Yes | Yes |
| L1 | Malfunction of PC board | Not stated | Yes |
| L1-00 | Malfunction of INV PCB | Yes | Yes |
| L1-01 | Malfunction of INV PCB | Yes | Yes |
| L1-02 | Malfunction of INV PCB | Yes | Yes |
| L1-03 | Malfunction of INV PCB | Yes | Yes |
| L1-04 | Malfunction of INV PCB | Yes | Yes |
| L1-05 | Malfunction of INV PCB | Yes | Yes |
| L1-06 | Malfunction of INV PCB | Yes | Yes |
| L1-27 | Malfunction of INV PCB | Yes | Yes |
| L1-31 | Malfunction of INV PCB | Yes | Yes |
| L1-54 | Malfunction of INV PCB | No | Yes |
| L1-55 | Malfunction of INV PCB | Yes | Yes |
| L3 | Switch box temperature rise | Not stated | Yes |
| L3-00 | OU: Electrical box temperature rise problem | Yes | Yes |
| L4 | Malfunction of inverter radiating fin temperature rise | Yes | Yes |
| L4-00 | OU: Malfunction of inverter radiating fin temperature rise | Yes | Yes |
| L4-01 | OU: Malfunction of inverter radiating fin temperature rise | Yes | Yes |
| L4-06 | OU: Malfunction of inverter radiating fin temperature rise | Yes | Yes |
| L4-07 | OU: Malfunction of inverter radiating fin temperature rise | Yes | Yes |
| L5 | Inverter compressor abnormal | Yes | Yes |
| L5-00 | OU: Inverter instantaneous overcurrent (DC) | Yes | Yes |
| L8 | Inverter current abnormal | Not stated | Yes |
| L8-00 | Malfunction triggered by a thermal protection in the inverter PCB | Yes | Yes |
| L8-01 | Malfunction triggered by a thermal protection in the inverter PCB | Yes | Yes |
| L8-02 | Malfunction triggered by a thermal protection in the inverter PCB | Yes | Yes |
| L8-03 | Malfunction triggered by a thermal protection in the inverter PCB | Yes | Yes |
| L8-04 | Malfunction triggered by a thermal protection in the inverter PCB | Yes | Yes |
| L8-05 | Malfunction triggered by a thermal protection in the inverter PCB | Yes | Yes |
| L8-14 | Malfunction triggered by a thermal protection in the inverter PCB | Yes | Yes |
| L9 | Inverter start up error | Not stated | Yes |
| L9-00 | Prevention of compressor lock | Yes | Yes |
| L9-01 | Malfunction in transmission system of outdoor unit | Yes | Yes |
| L9-02 | Malfunction in transmission system of outdoor unit | Yes | Yes |
| L9-03 | Malfunction in transmission system of outdoor unit | Yes | Yes |
| L9-13 | Malfunction in transmission system of outdoor unit | Yes | Yes |
| LC | Code shown on the remote controller for the installation error(s): No power supplied to outdoor or indoor unit (including phase interruption) (Flex outdoor installation manual, test-operation table) | Not stated | Yes |
| LC-00 | Malfunction in communication system of outdoor unit | Yes | Yes |
| LC-01 | Malfunction in communication system of outdoor unit | Yes | Yes |
| LC-02 | Malfunction in transmission system of outdoor unit | Yes | Yes |
| LC-03 | Malfunction in transmission system of outdoor unit | Yes | Yes |
| LC-05 | Malfunction in transmission system of outdoor unit | Yes | Yes |
| LC-33 | Malfunction in transmission system of outdoor unit | Yes | Yes |
| LH | Converter Error | Not stated | Yes |
| LH-01 | Converter error | No | Yes |
| P1 | High voltage of capacitor in main inverter circuit | Not stated | Yes |
| P1-00 | Open-phase power supply imbalance | Yes | Yes |
| P3-00 | Abnormal direct current | Yes | Yes |
| P3-01 | Abnormal direct current | Yes | Yes |
| P3-04 | Abnormal direct current | Yes | Yes |
| P4 | Radiation fin thermistor or related abnormality | Not stated | Yes |
| P4-00 | OU: Malfunction of radiating fin temperature sensor | Yes | Yes |
| P4-01 | Fin thermistor abnormality | Yes | Yes |
| P4-02 | Fin thermistor abnormality | Yes | Yes |
| P4-03 | Fin thermistor abnormality | Yes | Yes |
| PJ | Faulty combination of PCB | Not stated | Yes |
| PJ-00 | Capacity setting mismatch | Yes | Yes |
| PJ-01 | Capacity setting mismatch | Yes | Yes |
| PJ-04 | Inverter PCB mismatch | Yes | Yes |
| PJ-09 | Capacity setting mismatch | Yes | Yes |
| U0 | Low pressure drop due to refrigerant shortage or electronic expansion valve failure | Yes | Yes |
| U0-00 | OU: Shortage of refrigerant | Yes | Yes |
| U0-04 | OU: Shortage of refrigerant | Yes | Yes |
| U0-12 | Refrigerant cooling dew condensation error | Yes | Yes |
| U0-13 | OU: Shortage of refrigerant | Yes | Yes |
| U0-14 | OU: Shortage of refrigerant | Yes | Yes |
| U0-23 | OU: Shortage of refrigerant | Yes | Yes |
| U0-36 | Low refrigerant pressure | Yes | Yes |
| U1 | Code shown on the remote controller for the installation error(s): Phases of the outdoor power supply reversed; no power / phase interruption (Flex outdoor installation manual, test-operation table) | Not stated | Yes |
| U1-00 | Malfunction by reverse phase/open-phase | Yes | Yes |
| U1-01 | Malfunction by reverse phase/ open-phase | Yes | Yes |
| U2 | Power supply insufficient or instantaneous failure | Yes | Yes |
| U2-00 | OU: Defect of power supply voltage | Yes | Yes |
| U2-01 | Supply voltage error | Yes | Yes |
| U2-02 | Supply voltage error | Yes | Yes |
| U2-03 | Supply voltage error | Yes | Yes |
| U2-04 | Supply voltage error | Yes | Yes |
| U2-07 | Supply voltage error | Yes | Yes |
| U2-31 | Supply voltage error | No | Yes |
| U2-35 | Supply voltage error | Yes | Yes |
| U2-36 | Supply voltage error | Yes | Yes |
| U2-37 | Supply voltage error | Yes | Yes |
| U2-42 | Supply voltage error | Yes | Yes |
| U2-43 | Supply voltage error | Yes | Yes |
| U2-44 | Supply voltage error | Yes | Yes |
| U3 | Code shown on the remote controller for the installation error(s): Test operation not performed, interrupted, or run outside -20~35 C ambient so initial refrigerant detection failed (Flex outdoor installation manual, test-operation table) | Not stated | Yes |
| U3-00 | Underfloor heating screed dryout function not completed correctly | Yes | Yes |
| U4 | Code shown on the remote controller for the installation error(s): No power supplied to outdoor or indoor unit (including phase interruption) (Flex outdoor installation manual, test-operation table) | Not stated | Yes |
| U4-00 | Indoor/outdoor unit communication problem | Yes | Yes |
| U5 | Malfunction of transmission between remote control and indoor unit / failure of remote control PC board or setting during control by remote control | Not stated | Yes |
| U5-00 | User interface communication problem | Yes | Yes |
| U6-36 | Boiler standby abnormality Check boiler Refer to boiler manual | Not stated | Yes |
| U6-38 | Extension/hydro communication problem | No | Yes |
| U7 | Malfunction of transmission outdoor unit | Not stated | Yes |
| U7-00 | OU: Transmission malfunction between main CPU- INV CPU | Yes | Yes |
| U8 | Malfunction of transmission between main and sub remote controls (malfunction of sub remote control) | Not stated | Yes |
| U8-01 | Connection with LAN adapter lost | Yes | Yes |
| U8-02 | Connection with room thermostat lost | No | Yes |
| U8-03 | No connection with room thermostat | No | Yes |
| U8-04 | Unknown USB device | No | Yes |
| U8-05 | File malfunction | No | Yes |
| U8-06 | MMI/bizone kit communication problem | Yes | Yes |
| U8-07 | P1P2 communication error | No | Yes |
| U8-08 | Boiler communication malfunction | Not stated | Yes |
| U8-09 | MMI software version {version_MMI_software} / Indoor unit [version_IU_modelname] compatibility error | Yes | Yes |
| U8-11 | Connection with the Wireless gateway lost | No | Yes |
| U8-22 | Display PCB in bootloader | No | Yes |
| U8-23 | Display PCB communication issue | No | Yes |
| U8-24 | Display PCB in back port mode | No | Yes |
| U8-25 | Display PCB in self-test mode | No | Yes |
| U8-26 | Room thermostat software version compatibility error | Partly | Yes |
| U8-27 | Connection with multistep backup heater PCB lost | Yes | Yes |
| U8-28 | Invalid DB error Error only possible when there is a new software upload | No | Yes |
| U8-29 | EEPROM loaded with errors Error only possible when there is a new software upload | No | Yes |
| UA | Communication error between outdoor unit and indoor unit | Not stated | Yes |
| UA-00 | Indoor unit, outdoor unit matching problem | Yes | Yes |
| UA-05 | Indoor/outdoor combination abnormality | Yes | Yes |
| UA-07 | Indoor/outdoor combination abnormality | Yes | Yes |
| UA-09 | Indoor/outdoor combination abnormality | Yes | Yes |
| UA-16 | Extension/hydro communication problem | No | Yes |
| UA-17 | Tank type problem | Yes | Yes |
| UA-21 | Extension/hydro mismatch problem | Yes | Yes |
| UA-22 | Communication problem between control box and option box | Yes | Yes |
| UA-48 | Outdoor unit standby power connector connection error | No | Yes |
| UA-52 | Boiler, indoor unit matching problem | Not stated | Yes |
| UA-59 | HPSU/hydro combination abnormality | Yes | Yes |
| UA-60 | PCB combination malfunction | Yes | Yes |
| UF | Code shown on the remote controller for the installation error(s): Stop valve left closed; incorrect interconnections between units (piping and wiring inconsistent); refrigerant overcharge (Flex outdoor installation manual, test-operation table) | Not stated | Yes |
| UF-00 | Reversed piping or bad communication wiring detection | Yes | Yes |
| UF-01 | Indoor/outdoor miswiring detection | Yes | Yes |
| UF-02 | Reversed piping or bad communication wiring detection | Yes | Yes |
| UH | Malfunction of system, refrigerant system address undefined | Not stated | Yes |
| UH-17 | Indoor unit locked (R290) | Not stated | Yes |
| UH-18 | Outdoor unit locked (R290) | Yes | Yes |
| UH-19 | Too many attempts to unlock the unit | No | Yes |
| UJ-14 | AF communication error | No | Yes |
| UJ-20 | AF warning | No | Yes |
| UJ-26 | AF caution | No | Yes |