Emergency
E046 on Navien NCB

Your boiler has sensed that the water inside it has become dangerously hot and has shut itself down to prevent damage or fire risk.

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.

What the manual says

Manufacturer manual

High water temperatures (> 105°C) in the heat exchanger or high limit switch activation

From this model's manual
Verified against the Navien Ncb installation & service manual, page 74.
Plain-English guidance below. Severity, DIY steps, costs and parts are our interpretation to help you act, not text from the manual.

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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