BoilerFaultCodesViessmann 63:0 Fault Code
Also written as 630 — same fault.
The Viessmann 63:0 fault code means: your boiler is struggling to correctly communicate with its internal control system regarding how it should heat your hot water tank.. It appears on 5 Viessmann models in our database.
Technical description: Without auxiliary function for DHW loading
What causes the Viessmann 63:0 fault?
This fault occurs when the boiler's main control board loses its electronic connection with the components responsible for heating your hot water cylinder. The most common reason is a breakdown in the communication module or a faulty sensor that prevents the boiler from knowing the water temperature in the tank. Without this data link, the boiler stops heating the cylinder as a safety precaution.
DIY fix possible
Turn the boiler's power switch off for 30 secondsSwitch the power back on and wait for the system to rebootCheck if the hot water function operates normally
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Gas Safe Register →Viessmann models that show the 63:0 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann 63:0 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