How much does it cost to fix Chaffoteaux error code 8.11?

Typical repair cost for the Chaffoteaux 8.11 fault is £120-350 including labour.

8.11 Emergency

Chaffoteaux 8.11 Fault Code

Q: What does the Chaffoteaux 8.11 fault code mean?

Your boiler is not burning gas correctly, which means it may be producing dangerous carbon monoxide and needs to be switched off immediately.

Also written as 811 — same fault.

The Chaffoteaux 8.11 fault code means: your boiler is not burning gas correctly, which means it may be producing dangerous carbon monoxide and needs to be switched off immediately.. It appears on 3 Chaffoteaux models in our database.

Technical description: Yellow Flames - Soot Formed

Typical repair cost £120-350 (including labour)

Engineer required

This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Chaffoteaux models that show the 8.11 fault code

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

Source

Chaffoteaux 8.11 fault code information on this page is sourced and cross-checked against the official Chaffoteaux service / installation manuals for each affected model.

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