92
FAULT CODE
Viessmann
Air/Gas Mixture Setting Error
High Severity
Engineer Required
The combustion air/gas ratio is not within the acceptable range. The boiler is not burning fuel efficiently or safely.
Step-by-Step Fix Guide
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Step 1
A Gas Safe engineer must perform a flue gas analysis
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Step 2
The gas restrictor, venturi, or fan may need adjustment or replacement
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Step 3 Engineer only
Check for flue gas recirculation at the terminal
Gas Safe Reminder
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.