Atag Block 81 Fault Code

Also written as BLOCK81 — same fault.

The Atag Block 81 fault code means: your boiler has detected that a critical safety sensor responsible for monitoring exhaust gases has become disconnected, so it has safely shut itself down to prevent operation.. It appears on 8 Atag models in our database.

Technical description: The flue gas sensor is not connected although it was connected to the control. The burner is blocked until the flue gas sensor is reconnected.