Short answer
In the Baxi Neodens Plus ECO 24/24 F and 28/28 F, the user manual identifies 118 as insufficient pressure in the hydraulic circuit and 133 as a failure to ignite after five automatic attempts. The code indicates the next step, but does not identify on its own a faulty pump, sensor, electrode, or gas valve. This guide does not cover Neodens iPlus.
Confirm model and code.
Check if the board indicates Neodens Plus ECO and note the variant 24/24 F or 28/28 F ECO. Photograph the display and keep the complete symbol and number. Do not interchange codes 117 and 118: the manual separates excessive pressure from insufficient pressure. The codes from the iPlus range belong to another guide and another platform.
118: low pressure in heating
The 118 refers to the pressure of the heating circuit, not to the pressure of the hot water tap or gas. Observe the pressure gauge from the outside. To determine if the user can refill water, follow the procedure and limits outlined in the user manual for your model. Do not use a generic figure taken from another boiler. If you cannot identify the control, the pressure drops again, or the warning repeats, stop and request a review: a recurring drop requires investigating its cause.
133: the boiler did not ignite
The manual describes five automatic ignition attempts that have failed; it does not indicate that you should perform five manual resets. Only follow the reset that the user manual allows. If the lockout persists or returns, report the fault code and the moment it appears. Do not open the boiler or manipulate gas, electrodes, wiring, or flue.
If another number appears
Check the user manual table of the same generation before interpreting a different warning. A symptom like "no hot water" is not enough to deduce that the fault is a specific part. Provide the model, full code, pressure you see, and affected service when requesting a spare part. boiler inspectionMaintenance and repair are different tasks; the maintenance information it does not diagnose a present fault.
Primary sources: official BAXI Neodens Plus ECO technical sheet and official user manual BAXI Neodens Plus ECO 24/24 F, 28/28 F and 33/33 F, ref. 7731457 (01-04/19). The manual indicates that 118 is too low pressure and 133 is ignition failure after five automatic attempts; follow the user action indicated for the fault code that appears.
