154 Medium

Atag 154 Fault Code

The Atag 154 fault code means: your boiler has detected an abnormal temperature difference between the water leaving it and the water returning, which usually indicates a circulation problem inside the system.. It appears on 3 Atag models in our database.

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description: Flow increases to fast ∆T to large, return > flow
Typical repair cost £150-350 (including labour)

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 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