High
E302 on Navien NCB H

Your boiler has stopped working because the water pressure inside the heating system has dropped too low.

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

If the pressure is lower than the minimum pressure set (1 bar by default), error code E302 will appear on the display.

From this model's manual
Verified against the Navien Ncb H installation & service manual, page 78.
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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