How much does it cost to fix Saunier Duval error code 30.?

Typical repair cost for the Saunier Duval 30. fault is £120-250 including labour.

30. High

Saunier Duval 30. Fault Code

Q: What does the Saunier Duval 30. fault code mean?

Your boiler has detected that the water leaving the unit is significantly hotter than the water returning to it, suggesting a blockage or poor water flow through your heating system.

Also written as 30 — same fault.

The Saunier Duval 30. fault code means: your boiler has detected that the water leaving the unit is significantly hotter than the water returning to it, suggesting a blockage or poor water flow through your heating system.. It appears on 4 Saunier Duval models in our database.

Technical description: There is excessive temperature difference between the flow and return thermistors.

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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Saunier Duval models that show the 30. fault code

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

Source

Saunier Duval 30. fault code information on this page is sourced and cross-checked against the official Saunier Duval service / installation manuals for each affected model.

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