High
E762 on Navien NCB-40LDWE

Your boiler is struggling to detect the exhaust vent, likely because the flue pipe is not fitted securely or is the wrong size for your home.

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.

What the manual says

Manufacturer manual

Vent installation detector error; can appear if the vent pipe is not correctly sized or has not been inserted properly.

From this model's manual
Verified against the Navien Ncb 28ldwe installation & service manual, page 60.
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 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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