Emergency
E18 on Navien NCB 35 HE

Your boiler has detected that the temperature of the gases leaving the flue is higher than it should be, so it has safely shut itself down to prevent damage.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

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

Exhaust gas sensor overheat error

Engineer required

This is a emergency severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

E016View →E110View →

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