Red LED illuminated (TTB) Emergency

Potterton Red LED illuminated (TTB) Fault Code

Also written as REDLEDILLUMINATEDTTB — same fault.

The Potterton Red LED illuminated (TTB) fault code means: your boiler has detected potentially dangerous exhaust fumes backing up into your home due to a blocked or obstructed chimney or flue, and has safely shut itself off to prevent carbon monoxide poisoning.. It appears on 1 Potterton model 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: Products Discharge Safety Device (TTB) - CFL Only: In the case of flue blockage this device will operate and the boiler will go to lockout. Repeated shutdown should be investigated.
Typical repair cost £120-250 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Potterton models that show the Red LED illuminated (TTB) fault code

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

Source

Potterton Red LED illuminated (TTB) fault code information on this page is sourced and cross-checked against the official Potterton service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026