Medium
Vitotronic 300 on Viessmann Vitola Biferral

Your heating system is struggling to adjust correctly to freezing outdoor temperatures because a sensor is sending the wrong information.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

Technical description

Activates after 0°C / 32°F outdoor temperature

Engineer required

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

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