Boiler Fault Code TTB Downdraught Thermostat

Also written as TTBDOWNDRAUGHTTHERMOSTAT — same fault.

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

Fault code TTB Downdraught Thermostat appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has shut down because wind or a blockage is pushing harmful exhaust fumes back down the chimney instead of letting them escape outside. (As reported on Ideal Mexico Super CF3 40-80)