Navien e351 error code

E351 – Abnormal Auto feeder valve

If the water pressure sensor senses low water level as the heating pipe pressure is low, the system stops operation of the boiler, and refills water automatically.

If water is supplied by auto feeder valve open over 5 minutes, the error(E351) is detected and displayed on the front panel. If this occurs, the boiler initiates shutdown.

Check items:

1. Water is not refilled.
   • Check if the cold water valve is closed or frozen.
   • Check if the auto feeder valve works normally.
2. Water overflows through condensed water hose.
   • Check the left drain valve of the main heat exchanger.
   • Check if water leaks due to a defective heat exchanger.
3. Check if water leaks from the heating pipe.
4. Check the auto feeder.
5. Check the water supplied pipe open.
6. Check the water pressure.