BoilerFaultCodesTechnical description
Return-Sensor check is running, demand (DHW or heating) is blocked
What causes this fault?
This occurs when the boiler's control board detects a potential discrepancy between the flow and return temperature sensors and needs to verify their accuracy. It is often caused by a sensor that is starting to drift out of its calibrated range or a slight delay in the water temperature changing when the pump starts. While usually a brief self-test, persistent pauses suggest the internal sensors are no longer providing consistent readings to the computer.
DIY fix possible
Wait up to 15 minutes for the internal test to completeEnsure all radiator valves are open to help water flowCheck if the system pressure is between 1.0 and 1.5 bar
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