Navien NCB-180, Service Manual

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Error Code Function Self-diagnostic/Action
E351
Abnormal Auto feeder valve (make-up water) Check the auto feeder valve
E352
High water pressure Check the auto feeder valve
E353
Abnormal operation: water pressure sensor Check the water pressure sensor.
E407
Hot water outlet: thermistor open or short
1. Check the thermistor.
2. Replace the thermistor.
E421
Cold water inlet: thermistor open or short
1. Check the thermistor.
2. Replace the thermistor.
E515
Abnormal PCB Check the PCB
E517
Abnormal dip switch setting Check the dip switches on the front panel and PCB.
E594
Abnormal operation: EEPROM Check the PCB
E615
Abnormal input & memory Check the PCB.
E740
Abnormal operation: outdoor temperature sensor
(appears only when the outdoor reset curve is
enabled).
1. Ensure that the outdoor reset curve is configured
properly.
2. Check the outdoor temperature sensor wiring
connection.
E777
Abnormal operation: LWCO
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.
E782
Abnormal Main-Panel communication Check the PCB.
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.