StBY Low

Atag StBY Fault Code

Also written as STBY — same fault.

The Atag StBY fault code means: your boiler is currently in standby mode and is working exactly as it should, waiting for a signal from your thermostat or hot water tap to start operating.. It appears on 3 Atag models in our database.

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

Technical description: Standby mode.

DIY fix possible

Check your room thermostat is set to a higher temperature than the current room temperatureEnsure your heating timer or programmer is set to 'On'Turn on a hot water tap to see if the boiler fires up

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Atag models that show the StBY fault code

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

Source

Atag StBY 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