294 Emergency

Navien 294 Fault Code

The Navien 294 fault code means: your boiler has detected dangerously high temperatures inside its cooling system and has shut down to prevent permanent damage or a fire hazard.. It appears on 1 Navien model 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: 294:WCS + eng head overt: Water cooled seal thermostat has operated and engine head temperature thermocouple measurement exceeds 584 degrees C
Typical repair cost £250-450 (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 294 fault code

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

Source

Navien 294 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