5 Emergency

Unical 5 Fault Code

The Unical 5 fault code means: your boiler has automatically shut down because a safety sensor detected that exhaust gases are getting too hot near the flue collector.. It appears on 2 Unical models in our database.

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

Technical description: FLUE GAS COLLECTOR SAFETY THERMOSTAT Intervention of the flue gas collector safety thermostat (23). Rearm the thermostat manually and press the unblock button on the panel. Check the connections.
Typical repair cost £100-250 (including labour)

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 5 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Unical 5 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 31 August 2026