| E125 | Baxi: lack of circulation in the primary circuit/air in the system. | If the Wilo RS15/5-3C pump is blocked or not rotating, there is no flow and the equipment detects a lack of circulation. Verify by forcing the pump to run (test mode), checking voltage at terminals and shaft rotation through the bleed screw. |
| F.75 | Vaillant: when the pump starts, sufficient pressure increase is not detected. | A seized or unpowered Wilo RS15/5-3C pump does not generate the expected pressure increase at the start. Check the pump (blockage/noise/consumption), voltage, and run program P.0 to see if there is a pressure jump. |
| F.75 | Saunier Duval: insufficient pressure/pressure increase not detected when the pump starts. | If the Wilo RS15/5-3C pump fails, the equipment does not detect the pressure increase generated by the circulator's start-up. Check system pressure, bleed, and test the pump (voltage/rotation). |
| A1 281 | Junkers/Bosch: the heating pump does not generate pressure (blocked or with air). | A Wilo RS15/5-3C blocked or with a seized rotor prevents generating pressure/flow. Check circuit pressure, bleed and test the pump (voltage at terminals, continuous service operation); replace if it does not rotate. |
