Navien NCB-180 Service Manual page 82

Error Code
Abnormal Auto feeder valve (make-up water)
E351
High water pressure
E352
Abnormal operation: water pressure sensor
E353
Hot water outlet: thermistor open or short
E407
Cold water inlet: thermistor open or short
E421
Abnormal PCB
E515
Abnormal dip switch setting
E517
Abnormal operation: EEPROM
E594
Abnormal input & memory
E615
Abnormal operation: outdoor temperature sensor
(appears only when the outdoor reset curve is
E740
enabled).
Abnormal operation: LWCO
E777
Abnormal Main-Panel communication
E782
If any of the above solutions do not resolve the problem with the Boiler, contact Navien's Technical department at 1-800-519-8794.
There will be error codes displayed on the front panel and recorded on the PCB board (within the unit) of any problems or failures that
occur with the Boiler.
IMPORTANT
To reset the Boiler, either press the [Reset] button on the front panel or disconnect, then reconnect electrical power to the boiler.
Function Self-diagnostic/Action
Check the auto feeder valve
Check the auto feeder valve
Check the water pressure sensor.
1. Check the thermistor.
2. Replace the thermistor.
1. Check the thermistor.
2. Replace the thermistor.
Check the PCB
Check the dip switches on the front panel and PCB.
Check the PCB
Check the PCB.
1. Ensure that the outdoor reset curve is configured
properly.
2. Check the outdoor temperature sensor wiring
connection.
1. Check the LWCO wiring connection
2. Ensure that the system water level is appropriate.
3. Add make-up water to the system if necessary.
Check the PCB.