BoilerFaultCodesAtag 154 Fault Code
The Atag 154 fault code means: your boiler has detected that water is heating up too quickly or moving in the wrong direction, which usually means the water isn't circulating properly through your radiators.. It appears on 4 Atag models in our database.
Technical description: Flow increases too fast / return temperature greater than flow temperature
DIY fix possible
Check that your boiler pressure is between 1.0 and 1.5 barEnsure all radiator valves and isolation valves are fully openBleed your radiators to remove any trapped air pocketsReset the boiler once circulation is confirmed
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Atag models that show the 154 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Atag 154 fault code information on this page is sourced and cross-checked against the official Atag service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 31 August 2026