205 Emergency

Navien 205 Fault Code

The Navien 205 fault code means: your boiler has detected an issue with the air intake or exhaust system, meaning it cannot safely vent gases and has shut down to protect your home.. It appears on 5 Navien models in our database.

Act immediately

Turn off your boiler and stop using gas appliances. Call a Gas Safe engineer now. This fault can be dangerous if ignored.

Technical description: Error 205
Typical repair cost £150-£300 (including labour)

Engineer required

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

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Navien models that show the 205 fault code

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

Source

Navien 205 fault code information on this page is sourced and cross-checked against the official Navien service / installation manuals for each affected model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026