BoilerFaultCodesViessmann 7b:0 Fault Code
Also written as 7B0 — same fault.
The Viessmann 7b:0 fault code means: your boiler is having difficulty communicating the correct time over its internal network system, which might affect your heating schedules.. It appears on 5 Viessmann models in our database.
Technical description: Do not send time to LON
What causes the Viessmann 7b:0 fault?
This fault occurs when there is a configuration error in the boiler's communication settings, specifically regarding how it shares time and date information with other linked components. It usually happens because the control system is trying to send a time signal to a network module that isn't set up to receive it, or there is a minor data mismatch between the internal boards.
DIY fix possible
Check that the date and time settings on the main boiler control panel are correctPerform a simple reset of the boiler using the power buttonIf you have a Vitotrol room thermostat, ensure it is powered and showing the correct time
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Gas Safe Register →Viessmann models that show the 7b:0 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann 7b: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