Medium
E787 on Navien NCB

Your boiler has detected a temporary internal memory or logic error and needs to be restarted to clear the fault.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Book a service

This fault should be looked at by a Gas Safe engineer within the next week or two. It may get worse if left.

What the manual says

Manufacturer manual

Abnormal operation: Reset device

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.

DIY fix possible

Locate the 'Reset' button on the boiler control panelPress and hold the button for 3 to 5 secondsWait 5 minutes while the boiler restarts and attempts to reignite

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