Medium Warning
72:2 on Viessmann Vitodens 333-F

Your boiler has detected that hot water is being heated when it shouldn't be, which is usually caused by a faulty sensor or a sticking internal valve.

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

ON during DHW loading to set value 2

What causes this fault?

This fault occurs when the boiler detects an unexpected rise in temperature within the hot water system, suggesting heat is flowing where it shouldn't. The most common reason is a faulty temperature sensor providing incorrect readings or an internal diverter valve that has become stuck, allowing heat to leak into the water cylinder even when the boiler is only supposed to be heating your radiators.

Engineer required

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

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