Medium Warning
60:10 on Viessmann Vitodens 300-W

Your boiler is getting much hotter than expected while trying to heat your water, which usually suggests the heat isn't transferring properly or a sensor is misreading.

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

During DHW loading, the boiler water temperature is up to 20K higher than the set DHW temperature

What causes this fault?

This fault happens because the water inside the boiler is getting significantly hotter than the target temperature for your hot water tank. It is usually caused by a blockage or a mechanical failure that prevents the heat from flowing smoothly out of the boiler and into your cylinder. The most common culprits are a buildup of limescale in the heat exchanger or a diverter valve that is stuck and restricting the water flow.

Engineer required

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

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