28 High

Main 28 Fault Code

The Main 28 fault code means: your boiler has detected an issue with the sensor that reads the temperature of the water flowing out of the unit, meaning it has safely shut down to prevent damage.. It appears on 10 Main 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: Possible faulty components
Typical repair cost £150-250 (including labour)

Engineer required

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

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Main models that show the 28 fault code

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

Source

Main 28 fault code information on this page is sourced and cross-checked against the official Main service / installation manuals for each affected model.

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