Emergency
E05 on Navien NCB

Your boiler has detected an issue with the internal ventilation system that prevents it from safely clearing exhaust gases, so it has stopped working to keep your home safe.

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

Fan 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.

Find a Gas Safe engineer
Search the official register →

Related fault codes

E03View →E04View →

Related guides you might find useful

Banging / kettling / whistling noise

Each noise points to a different fault.

Read →

When to replace your boiler

7 signs repair isn't worth it anymore.

Read →

Is boiler cover worth it?

Break-even maths on monthly cover.

Read →