351Error - Navien NCB-150E Service Manual

5.2.14 351Error

Error conditions and Check Items
Error
E351
Abnormal Auto feeder valve
Check items
1. Check DHW cold water pressure
2. Check connecter
(#1,#2 and #3 of CN 22)
3. Check the water pressure sensor
116 NCB-E Service Manual
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.
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.
Leaking in unit
No
Is the auto feeder valve
normal?
Yes
Is the DHW cold water
valve open?
Yes
Description
Yes
Check leaking in unit
NO
Replace the auto feeder valve
NO
Open the DHW cold water valve
Version 1.4