BoilerFaultCodesAtag 11 Fault Code
The Atag 11 fault code means: your boiler has detected that the water inside the heating system is getting too hot too quickly, likely because the water is not circulating properly through your radiators.. It appears on 3 Atag models in our database.
Technical description: Maximum (cid:39)T of flow and return sensor in central heating has repeatedly been exceeded. During the block normal operation of the hot water supply is possible. The pump continues to operate at minimum capacity during the block.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Atag models that show the 11 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Atag 11 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 7 July 2026