BoilerFaultCodesViessmann 52:0 Fault Code
Also written as 520 — same fault.
The Viessmann 52:0 fault code means: your boiler has lost communication with a sensor that monitors water temperature moving through your heating system, which may prevent it from heating your home efficiently or at all.. It appears on 5 Viessmann models in our database.
Technical description: Without flow temperature sensor for low loss header
What causes the Viessmann 52:0 fault?
This fault occurs when the boiler loses communication with the sensor responsible for tracking water temperature in the main mixing chamber of your plumbing. The most common reason is that the sensor itself has failed internally or the wiring connecting it to the boiler's main control board has become loose or damaged. Without this data, the boiler cannot accurately balance the heat output for your home.
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 52:0 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann 52:0 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