Medium Warning
6F:100 on Viessmann Vitodens 200-W

Your boiler is telling you that it has defaulted to its maximum power setting for heating your hot water because it has encountered a configuration memory error.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

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

Max. output during DHW loading 100%, defaulted by the boiler coding card

What causes this fault?

This fault occurs because the boiler's internal memory chip, which stores its specific performance settings, has failed or lost communication with the main computer. Without these specific instructions, the boiler enters a 'safe mode' where it lacks the data to modulate its power, leading it to default to maximum output when heating your water. It is usually caused by a physical hardware failure in the coding card or a fault on the main control board.

Engineer required

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

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