SMOKE/FLUE FAULT
FAULT CODE
Grant
Visible Smoke or High Smoke Number
High Severity
Engineer Required
Black or grey smoke visible from the flue, or a high smoke number on combustion testing. Indicates incorrect combustion — insufficient air, wrong nozzle, or high fuel pressure.
Step-by-Step Fix Guide
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Step 1
Turn off the boiler
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Step 2 Engineer only
Call an OFTEC registered engineer to carry out a full combustion analysis and adjust the burner settings
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.