29 High

Alpha 29 Fault Code

The Alpha 29 fault code means: your boiler has detected a problem with the sensor that monitors exhaust gases, and it has shut down for safety purposes.. It appears on 24 Alpha models 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: Flue sensor fault

What causes the Alpha 29 fault?

This fault occurs when the sensor responsible for measuring the temperature of the exhaust gases signals that it is failing or providing an unrealistic reading. The most common reason is that the sensor has developed an electrical fault due to age, or the internal wiring has become damaged over time. Because this sensor is a critical safety component that prevents the boiler from overheating, the system will shut down immediately to prevent damage.

Typical repair cost £120-220 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Alpha models that show the 29 fault code

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

Source

Alpha 29 fault code information on this page is sourced and cross-checked against the official Alpha service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026