BoilerFaultCodesViessmann 30 Fault Code
The Viessmann 30 fault code means: your boiler has stopped heating because a internal sensor that monitors water temperature has developed an electrical fault and is preventing the burner from firing.. It appears on 9 Viessmann models in our database.
Technical description: Burner blocked. Short circuit - boiler water temperature sensor.
What causes the Viessmann 30 fault?
This fault occurs when the boiler's internal thermometer, which monitors how hot the water is getting, fails to send a correct electrical signal to the main control board. The most common reason is that the sensor has suffered an internal electrical short circuit or the connecting wires have become damaged or loose. Because the boiler no longer knows the exact temperature of the water inside, it shuts down the burner as a primary safety precaution to prevent overheating.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Gas Safe Register →Viessmann models that show the 30 fault code
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Source
Viessmann 30 fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026