Navien unit displays E110; often associated with high exhaust or flue temperature.

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Blocked exhaust vent, Scale buildup in heat exchanger, Failed flue temperature sensor, Incorrect gas/air ratio causing high flue temps

Safety: Turn OFF power and allow the unit to cool fully before inspection.

Steps:

1. Inspect exhaust vent: Check for obstructions and ensure proper venting per Navien guidelines.
2. Descale heat exchanger: Perform a full descaling flush if maintenance is overdue.
3. Check condensate drainage: Ensure condensate is draining freely and not pooling in the heat exchanger or vent.

If E110 persists, the flue temperature sensor or combustion settings may be at fault and should be evaluated by a technician.

Hard 4/5

Flue Temperature Sensor

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