High
E291 on Navien NCB 28 HE

Your boiler has detected that the water flow pipes are connected in the wrong order or that the heat is moving in the wrong direction, causing the system to shut down to prevent damage.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Supply/Return inversion limit

Engineer required

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

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