Emergency
E016 on Navien NCB500 NCB500-1S+/30K

Your boiler has detected dangerously high water temperatures inside the heat exchanger and has locked out for safety because it cannot reliably control or sense the overheating condition.

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.

What the manual says

Manufacturer manual

Unable to detect high water temperature conditions if the switch malfunctions / Unable to shut down the boiler if the water temperature from the heat exchanger exceeds 105°C.

From this model's manual
Verified against the Navien/Navien Ncb500 Combi Service Manual30k 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 is a emergency severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.

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Related fault codes

E012View →E014View →E015View →

All 60 fault codes on the NCB500 NCB500-1S+/30K

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

001003004012016030031046047109205218302352353407421515517593594615740782E001E003E004E012E030E031E046E047E109E110E205E218E291E302E351E352E353E407E421E434E439E441E445E480E515E517E593E594E598E615E740E782E783E787E788

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