b30 High

Atag b30 Fault Code

Also written as B30 — same fault.

The Atag b30 fault code means: your boiler has temporarily stopped because the water is heating up too quickly or isn't circulating around your radiators fast enough.. It appears on 1 Atag model in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Boiler block: Difference between flow and return too high
Typical repair cost £100-£350 (including labour)

DIY fix possible

Check that all radiator valves (TRVs) are turned to the highest settingEnsure the boiler pressure gauge is between 1.0 and 1.5 barCheck that any external valves on the pipework leading to the boiler are fully open

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Atag models that show the b30 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Atag b30 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 27 April 2026