How much does it cost to fix Atag error code Block 01?

Typical repair cost for the Atag Block 01 fault is £120-250 including labour.

Block 01 High

Atag Block 01 Fault Code

Q: What does the Atag Block 01 fault code mean?

Your boiler has been automatically shut down because an external safety device, such as a separate room thermostat or a smoke alarm link, has triggered a signal to stop the system.

Also written as BLOCK01 — same fault.

The Atag Block 01 fault code means: your boiler has been automatically shut down because an external safety device, such as a separate room thermostat or a smoke alarm link, has triggered a signal to stop the system.. It appears on 6 Atag models in our database.

Technical description: External safety contact cut out

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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Atag models that show the Block 01 fault code

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

Source

Atag Block 01 fault code information on this page is sourced and cross-checked against the official Atag service / installation manuals for each affected model.

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