BoilerFaultCodesUnical Fd Fault Code
Also written as FD — same fault.
The Unical Fd fault code means: your boiler is struggling to light or detect its own flame, which prevents it from firing up to provide heating and hot water.. It appears on 2 Unical models in our database.
Technical description: Ignition/detection electrode
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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Unical models that show the Fd fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Unical Fd fault code information on this page is sourced and cross-checked against the official Unical service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026