Low
E788 on Navien NCB500 NCB500-15K System

Your boiler is showing an error because a setting was accidentally changed on the display to the wrong gas type.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Monitor it

This is a minor fault. Keep an eye on it and mention it at your next annual boiler service. Reset the boiler and see if it clears.

What the manual says

Manufacturer manual

The error code E788 will appear if you try to change the gas type on the front panel.

From this model's manual
Verified against the Navien/Navien Ncb500 System Service Manual En 250331 Pdf installation & service manual.
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 fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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All 52 fault codes on the NCB500 NCB500-15K System

Seeing a different code? Every code this model can display, in one place.

001003004012016030031046047109205218302352353515517593594615740782E001E003E004E012E016E030E031E046E047E109E110E205E218E291E302E351E352E353E480E515E517E593E594E598E615E740E782E783E787

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