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Fault codesMeaningPossible cause
F.00Fault: Flow temperature sensorNTC plug not plugged in or has come loose, multiple plug on the PCB not plugged in correctly, interruption in cable harness, NTC sensor defective
F.01Fault: Return temperature sensorNTC plug not plugged in or has come loose, multiple plug on the PCB not plugged in correctly, interruption in cable harness, NTC sensor defective
F.10Short circuit: Flow temperature sensorNTC sensor defective, short circuit inthe cable harness, cable/casing
F.11Short circuit: Return temperature sensorNTC sensor defective, short circuit in the cable harness, cable/casing
F.12 and F.91Short circuit: Cylinder temperature sensorNTC sensor defective, short circuit in the cable harness, cable/casing
F.13Short circuit: Domestic hot water cylinder temperature sensorNTC sensor defective, short circuit in the cable harness, cable/casing
F.20Safety switch-oft. Overheating temperature reachedIncorrect earth connection between cable harness and product, flow or return NTC defective (loose connection), black discharge viaignition cable, ignition plug or ignition electrode
F.22Safety switch-oft. Low water pressure in the boilerNo or insufficient water in the product, water pressure sensor defective, cable lo the pump or to the water pressure sensor loose/not connected/defective
F.23Safety switch-oft. Temperature difference too great (NTC1/NTC2)Pump blocked, insufficient pump output, air in product, flow and return NTC sensoni connected the wrong way round
F.24Safety switch-oft. Temperature rise too fastPump blocked, insufficient pump output, air in product, system pressure too low, non-return valve blocked/incorrectly installed
F.25Safety switch-off. Flue gas temperature too highBreakin plug connection for optional flue gas safety temperature limiter (STB), break in cable harness
F.27Safety switch-off. Fault in flame detectionMoisture on the electronics, electronics (flame monitor) defective. gas solenoid valve leaking
F.28Fault: Ignition unsuccessful when starting upGas meter defeclive or gas pressure monitor has triggered, air in gas, gas flow pressure too low, thermal isolator device (TAE) has triggered, incorrect gas restrictor,incorrect spare gas valve, fault on the gas valve, multiple plug on PCB incorrectly plugged in, break in cable harness,ignition system (ig-
nition transformer, ignition cable, ignition plug, ignition electrode) defective, ionisation current interrupted (cable, electrode), incorrect earthing of product. electronics defective
F.29Fault: Flame lossGas supply temporarily stopped, flue gas recirculation, incorrect earthing of product, ignition transformer has spark fallure
F.32Fan frost protection function active: Fan speed outside the tolerance valuesPlug on fan not correctly plugged in, multiple plug on PCB not correCUy plugged in, breakin cable harness, fan blocked, Hall sensor defective, electronlcs defective
F.33Fan frost protection function active: Air pressure switch faultPressure monitor has not switched or has switched at a fan speed value that is too high (insufficient air supply)
Pressure monitor plug not correctly plugged in, pressure monitor defective, hose removed from between the pressure monitor and silencer, air/flue pipe blocked
FA9eBUS fault: Voltage too lowShort circuit on eBUS. eBUS overload or two power supplies with different polarities on the eBUS
F.61Fault: Gas valve control systemShort circuit/short to earth in cable harness for the gas valve, gas valve defective (colls shorted to earth), electronics defective
F.82Fault: Gas valve switch-off controlDelayed switch-off of gas valve, delayed extinguishing of flame signal,gas valve leaking, electronics defective
F.83Fault: EEPROMElectronics defective
F.64Fault: Electronics/sensor/analogue-to-digital converterFlow or return NTC short circuited, electronics defective
F.85Fault: Electronics temperature too highElectronics overheating due to external influences, electronics defective
F.67Value sent back by ASIC is incorrect (flame slgnal)Implausible flame signal, electronics defective
F.88Fault: Unstable flame (analogue input)Air in gas, gas flow pressure too low, incorrect air ratio, incorrect gas restricter, ionisation flow interruption (cable, electrode)
F.70Invalid product code (DSN)Display and PCB replaced alsame time and Device Specific Number not reset, wrong or missing output range coding resistance
F.71Fault: Flow/return temperature sensorFlow temperature sensor signaling constant value: Flow temperature sensor incorrectly positioned on supply pipe, flow temperature sensor defective
F.72Fault: Deviation in the water pressure sensor/return temperature sensorFlow/return NTC temperature difference too great -> flow and/or return temperature sensor defective
F.73Fault: Water pressure sensor not connected or has short-circuitedInterruption/short circuit of water pressure sensor, lntarrupaon/short circuit to GND in supply line to water pressure sensor or water pressure sensor defective
F.74Fault: Electrical problemin the water pressure sensorLine to water pressure sensor has a short circuit to 5 V/24 V or internal fault in the water pressure sensor
F.75Fault: Pressure sensorPressure switch defective
F.78The safety cut-out in the primary heat exchanger is defectiveSafety cut-out feedback does not match the gas valve feedback
F.77Fault: Condensate or smokeNo response, flue non-return flap defective
F.78Interruption to DHW outlet sensor at external controllerUK ink box is connected, but hot water NTC not bridged
F.83Fault: Burner temperature sensorBurner temperature sensor is defective
When the burner starts, the temperature change registered at the flow or retum temperature sensor is non-existent or too small: insufficient water in the product, the flow or retum temperature sensor is not in the correct position on the pipe
F.84Fault: Flow/return temperature sensorValues not consistent, difference < -6 K
Flow and return temperature sensors signalling implausible values: Flow and return temperature sensors have been inverted, flow and return temperature sensors have not been correctly Installed
F.85Fault: Temperature sensorThe flow and/or return temperature sensors have been installed on the same pipe/incorrect pipe
Temperature sensor not connected or is connected incorrectly
F.88Fault: Underfloor heating contactUnderfloor heating contact open, sensor disconnected or defective
F.87Fault: ElectrodesElectrodes not connected or they are connected incorrectly, short circuit in the cable harness
F.88Fault: Gas valveGas valve not connected or it is connected incorrecUy, short circuit in the cable harness
F.89Fault: PumpPump not connected or it is connected incorrectly, incorrect pump connected, short circuit in the cable harness
ConnectionNo communication between the PCB and the user interfaceElectronics defective