| F.22 | Safety shutdown: lack of water | A blocked/defective circulator pump or one with insufficient performance reduces the flow rate, and the boiler interprets it as a lack of water; check by forcing the pump from service mode and verifying electrical supply and rotation/flow rate. |
| F.23 | Safety shutdown: excessive temperature variation | If the pump is blocked or underperforming, the ΔT flow/return increases and the block overheats differentially; check the actual rotation of the rotor, bleed air, and ensure the ΔT normalises after unblocking/replacing the pump. |
| F.24 | Safety shutdown: temperature rise too fast | The lack of circulation due to a blocked/faulty pump causes a sudden rise in temperature; verify by activating the pump in service test and confirming that there is flow and the temperature does not spike when the pump is restored. |
| F.75 | Fault: no pressure change detected when the pump starts | At the start, the electronics expect a pressure jump created by the pump; if it is faulty or not moving water, there is no variation and F.75 appears; check by forcing the pump and observing that the pressure does not change, and measuring the pump's power supply/consumption. |
| F.89 | Error: pump | The boiler detects a pump fault (not connected, poorly connected, incorrect model, or short circuit); check continuity and wiring, pump reference/brand, and ensure it receives the correct signal/voltage. |
