BoilerFaultCodesTechnical description
The Products Discharge Safety Device (TTB) has operated in the case of flue blockage and the boiler has gone to lockout.
What causes this fault?
This fault occurs when a safety sensor detects that combustion gases are blowing back into the room instead of escaping through the chimney. The most common reasons are a blockage in the chimney, such as a bird's nest or debris, or severe atmospheric conditions preventing the natural flow of exhaust. The boiler shuts down immediately to prevent harmful carbon monoxide from entering your home.
This fault is more frequent during periods of high winds or extreme cold, which can create pressure imbalances or 'downdraughts' in the chimney flue.
Engineer required
This is a emergency severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.