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Autofrostat Function on Worcester Bosch 28 i SI

Your boiler has detected that it is in a cold environment and has briefly activated its built-in protection mode to prevent the internal pipes from freezing.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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.

What the manual says

Manufacturer manual

No demand and primary temperature below 8°C. Monitor central heating sensor: Below 5°C / 5°C to 9°C / Above 9°C

From this model's manual
Verified against the Worcester Bosch Greenstar 25si installation & service manual.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

Engineer required

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

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