Medium Warning
53:1 on Viessmann Vitodens 300-W

Your boiler has detected a technical issue with the internal pump responsible for circulating hot water around your taps.

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

Function connection 28 of the internal extension: DHW circulation pump

What causes this fault?

This fault occurs when the boiler's control board loses its connection with the pump responsible for moving hot water to your taps. It is usually caused by a failure in the internal electronic expansion module or a loose connection in the wiring harness that bridges these components. In some cases, the pump itself may have developed an electrical fault, preventing it from reporting its status back to the main system.

Engineer required

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

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Related fault codes

53:2View →53:3View →

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