BoilerFaultCodesWhat the manual says
Manufacturer manualThe system checks the fan speed signal when the fan starts. The error message 109E (cleared manually) is displayed in the following cases: 1. If fan speed is low or close to 0... 2. If a low speed signal or one that is close to 0 is detected for 3 sec during combustion...
From this model's manual
Verified against the Navien/Navien Ncb300 Combi Service Manual30k 250328 Pdf installation & service 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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Related fault codes
All 56 fault codes on the NCB300
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