Atag Block 12 Fault Code

Also written as BLOCK12 — same fault.

The Atag Block 12 fault code means: your boiler has temporarily stopped heating your hot water because the temperature difference between the water leaving and returning to the boiler is too high, often caused by a blockage or flow issue.. It appears on 6 Atag models in our database.

Technical description: Maximum ΔT of flow and return sensor in domestic hot water has repeatedly been exceeded. During the block normal operation of the central heating installation is possible. During the block the pump continues to operate at minimum capacity.