Identify the warning, do not guess the part.
If you Baxi Neodens iPlus show a code, copy the complete message and check the model. Here you will find the warnings from its manual and what information to provide for a review. A code guides: it does not confirm by itself which spare part is needed.
Models and version of the manual
24/24 F, 28/28 F and 33/33 F. This guide corresponds to iPlus. The codes from Neodens Plus ECO do not transfer to this generation.
Consulted edition: 7861627-05 · 13/03/2025 · manufacturer's manualThe control options, accessories, and versions may limit which notifications appear in each installation.
Locate the code on your screen.
These accesses lead to their entry in the table. They are not a classification of the most common faults: the manual does not provide incidence statistics.
- A02.06
Low pressure in the heating circuit
- H02.07
Low pressure in the heating circuit (water filling required).
- H01.18
There is no water circulation (temporarily).
- E01.17
There is no water circulation (permanent).
- E04.10
The burner has not ignited after five attempts.
- E04.29
Maximum allowed number of resets reached
What to do without opening the boiler
- Note what you see.
Complete code, message, and pressure displayed by the equipment. Indicate whether it occurs when opening hot water, requesting heating, or in both cases.
- Identify the device.
Take a photo of the screen and the identification accessible without disassembling anything. Brand, model, and version help avoid confusing tables from different ranges.
- Describe how it started.
Determine whether the fault is continuous or intermittent and if there was a supply interruption or a recent intervention. If it reappears after a reset allowed by the user manual, do not chain resets.
Do not open the casing or manipulate gas, wiring, combustion, or flue gas outlet. If you smell gas, avoid flames and switches, leave the area, and notify the distributor's emergency service from a safe location; in case of immediate danger, call 112.
Documented codes table
The meaning of the warning is provided, not the repair operations reserved for qualified personnel. When the manufacturer groups several codes, the grouping is maintained; it is not interpreted as a range of numbers.
| Code | What does · source indicate? |
|---|---|
| A00.34 | External sensor missing PDF |
| A02.06 | Low pressure in the heating circuit PDF |
| A02.18 | Incorrect configuration PDF |
| A02.33 | Maximum filling duration fault exceeded PDF |
| A02.34 | For automatic filling, the minimum interval time between the two requests was not reached. PDF |
| A02.36 | Functional device disconnected PDF |
| A02.37 | Disconnected passive functional device PDF |
| A02.45 | Connection error PDF |
| A02.46 | Device priority error PDF |
| A02.48 | Error in the unit's operating configuration. PDF |
| A02.49 | Node initiation fault PDF |
| A02.55 | The serial number is missing or incorrect. PDF |
| A02.76 | Internal memory reserved for complete customization of settings. No further changes can be made. PDF |
| A02.80 | No termination resistor on the bus PDF |
| A05.29 | Gas pressure below the limit PDF |
| A05.30 | Gas pressure check fault PDF |
| A05.95 | A brief flame interruption signal has been detected. PDF |
| A08.02 | Shower elapsed time error PDF |
| H00.42 | Open/defective pressure sensor or pressure too high PDF |
| H00.81 | Ambient temperature sensor missing PDF |
| H01.00 | Temporary communication error in the PCB PDF |
| H01.05 | The maximum temperature difference between the inlet and the return has been reached. PDF |
| H01.08 | Increase in supply temperature in the heating system, too fast PDF |
| H01.14 | The maximum value of the supply or return temperature has been reached. PDF |
| H01.18 | There is no water circulation (temporarily). PDF |
| H01.21 | Too rapid an increase in the supply temperature during operation as domestic hot water. PDF |
| H02.00 | Reset in progress. PDF |
| H02.02 | Waiting for the introduction of configuration adjustments (CN1, CN2) PDF |
| H02.03 | The configuration settings (CN1, CN2) have not been entered correctly. PDF |
| H02.04 | The settings of the main PCB cannot be read. PDF |
| H02.05 | Memory adjustment not compatible with the boiler's PCI type. PDF |
| H02.07 | Low pressure in the heating circuit (water filling required). PDF |
| H02.12 | Fault in the RL lockout input (discharge) of the boiler PDF |
| H02.31 | The device requires an automatic filling of the system due to low pressure. PDF |
| H02.38 | Maximum number of automatic filling cycles reached PDF |
| H02.70 | Error during the test of the external heat recovery unit PDF |
| H03.00 | There is no identification data for the boiler safety device. PDF |
| H03.01 | Communication failure in the comfort software (internal fault in the PCB of the boiler) PDF |
| H03.02 | Temporary flame loss PDF |
| H03.05 | Internal stop PDF |
| H03.08 | False flame PDF |
| H03.09 | Low voltage PDF |
| H03.17 | Gas control system fault PDF |
| H03.26 | Boiler calibration request PDF |
| H03.28 | Synchronization fault PDF |
| H03.31 | Blocked flue error PDF |
| H03.54 | Unknown fault PDF |
| H20.36 | Manual calibration error PDF |
| H20.39 | Without primary calibration PDF |
| H20.40 | No gas configuration PDF |
| E00.04 | Return temperature sensor not connected to the boiler ignition (when the boiler is turned on, the PCB detects if the sensor is present and connected) PDF |
| E00.05 | Short circuit in the return temperature sensor PDF |
| E00.06 | The return sensor is not connected during the operation of the boiler (the PCB has detected that the sensor has been disconnected during operation). PDF |
| E00.07 | Return temperature sensor temperature too high PDF |
| E00.16 | Domestic hot water accumulator temperature sensor not connected PDF |
| E00.17 | Short circuit in the temperature sensor of the domestic hot water accumulator. PDF |
| E00.40 | Water pressure sensor inlet open PDF |
| E00.41 | Water pressure sensor input closed PDF |
| E00.44 | Open DHW sensor PDF |
| E00.45 | Short circuit in the DHW sensor PDF |
| E01.12 | Return temperature measured by the sensor is higher than the supply temperature. PDF |
| E01.17 | There is no water circulation (permanent). PDF |
| E01.20 | The combustion gas has reached the maximum temperature. PDF |
| E02.15 | Minimum time for the recognition of the central storage unit key exceeded PDF |
| E02.17 | Permanent communication error on the PCB. PDF |
| E02.32 | Time elapsed for automatic filling PDF |
| E02.35 | Critical safety device disconnected PDF |
| E02.39 | Insufficient pressure increase after automatic filling PDF |
| E02.47 | The connection to an external device has failed. PDF |
| E04.00 | Security configuration fault PDF |
| E04.01 | Short circuit in the flow temperature sensor PDF |
| E04.02 | Flow temperature sensor disconnected PDF |
| E04.03 | The maximum supply temperature has been exceeded. PDF |
| E04.04 | Short circuit in the combustion gas sensor PDF |
| E04.05 | The combustion gas sensor has been disconnected. PDF |
| E04.06 | The combustion gas has reached a critical temperature. PDF |
| E04.07 | The maximum difference between the supply temperatures has been reached. PDF |
| E04.10 | The burner has not ignited after five attempts. PDF |
| E04.11 | Gas valve VPS test failed PDF |
| E04.12 | Ignition failure due to a false flame detection PDF |
| E04.13 | Fan blade blocked PDF |
| E04.14 | Combustion fault PDF |
| E04.15 | Fault due to exhaust gas blockage PDF |
| E04.17 | Fault in the control circuit of the gas valve PDF |
| E04.18 | The supply temperature is below the minimum. PDF |
| E04.23 | Internal communication blockage PDF |
| E04.24 | Gas family error not found PDF |
| E04.25 | Flame loss error during safety time PDF |
| E04.26 | Ignition fault PDF |
| E04.27 | Gas valve open fault with flame detection PDF |
| E04.28 | Gas valve information fault PDF |
| E04.29 | Maximum allowed number of resets reached PDF |
| E04.50 | Faulty gas valve PDF |
| E04.54 | Unknown fault PDF |
Is there a problem, but no fault code appears?
The absence of a warning does not rule out a fault. For a boiler that does not heat, does not deliver hot water, loses pressure, or operates intermittently, describe the symptom and the moment it occurs. Do not assume that the PCB, the pump, or a sensor is faulty without checking the equipment and the installation.
Request a review of the boiler. · Consult maintenance
Before requesting a repair
Does the code identify the spare part I need to buy?
No. A single warning can have multiple causes. The spare part reference requires identifying the appliance and confirming the fault; the code or a generic photograph is not sufficient.
Can it be reset again if the fault returns?
It is not advisable to chain resets. Follow only what is outlined for the user in your version's manual. A persistent or recurring lockout requires inspection.
When does it make sense to compare a new boiler?
When you have a diagnosis and a budget, compare repair, availability of the spare part, and replacement according to your installation. An isolated fault code does not justify changing the equipment.
Models of this guide in the catalog
See new boilers · Consult installation or replacement
The technical sheet of each product provides information on its price and availability. Installation is quoted separately depending on the case.
Documentation and other guides
Official manual for Baxi Neodens iPlus · 7861627-05 · 03/13/2025. The page references in the table correspond to the PDF viewer, whose numbering may differ from the printed version.
Consult fault guides by brand and model. · Return to the blog