BoilerFaultCodesViessmann F.980 Fault Code
Also written as F980 — same fault.
The Viessmann F.980 fault code means: your boiler has detected that the water pressure in your system is too low to safely heat your hot water, so it has stopped the hot water function to protect itself.. It appears on 1 Viessmann model in our database.
Technical description: No DHW heating. Minimum system pressure before the start of DHW heating is too low.
DIY fix possible
Locate the external filling loop connected to your boiler pipework.Open the filling valve slowly to allow water into the system until the pressure gauge reads between 1.0 and 1.5 bar.Close the valve tightly to prevent over-pressurisation.
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Viessmann models that show the F.980 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann F.980 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 7 July 2026