A3
FAULT CODE
Viessmann
Flue Gas Temperature Limiter
High Severity
Engineer Required
The flue gas temperature has exceeded the safety limit. The boiler has shut down to protect the flue system.
Step-by-Step Fix Guide
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Step 1
Allow the boiler to cool and reset
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Step 2
A Gas Safe engineer should check the heat exchanger for blockage or scaling
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Step 3 Engineer only
The flue gas sensor may also need testing
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.