BoilerFaultCodesUnical db Fault Code
Also written as DB — same fault.
The Unical db fault code means: your boiler is having trouble measuring the temperature of your hot water, which usually means it cannot heat water for your taps and showers until it is fixed.. It appears on 2 Unical models in our database.
Technical description: Domestic hot water temperature sensor
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 db fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Unical db 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