Understanding Error Codes - Navien NFB-301C User's Information Manual

5.2 Understanding Error Codes

When an error code appears on the front panel, refer to the following chart for a definition and possible remedy for the situation.
Error Code Reason
E001 Heat exchanger over temperature
E003 Ignition failure
E004 False flame detection
E012 Flame loss
E016 Heat exchanger overheat
E030 Abnormal operation: exhaust temperature
E031 Burner overheating
E046 Abnormal operation: heat exchanger overheating sensor
E047 Abnormal operation: exhaust thermostat
E060 Abnormal operation: dual venturi
E109 Abnormal operation: fan motor
E110 Exhaust vent closed
E127 Abnormal operation: APS
E205 Abnormal operation: heating supply thermistor
E218 Abnormal operation: heating return thermistor
E278 Abnormal operation: system supply thermistor
E279 Abnormal operation: system return thermistor
E291 Supply/Return inversion limit
E302 Low water pressure
E352 High water pressure
E353 Abnormal operation: water pressure sensor
E480 Abnormal operation: DHW tank temperature sensor
E515 Abnormal operation: PCB component
E517 Abnormal operation: DIP switch setting (PCB)
E594 Abnormal operation: EEPROM (PCB)
E615 Abnormal operation: MCU
E736 Abnormal operation: Cascade communication
E740 Abnormal operation: outdoor temperature sensor
E765 Abnormal external-pump
E774 Manual reset limit
E775 Auto reset limit
E777 Abnormal operation: LWCO limit (external device)
E782 Abnormal operation: boiler communication
E784 Abnormal operation: zone controller communication (external device)
If these remedies do not resolve the problem, contact Technical Support at 1-800-519-8794.
Self-diagnostic/Action
Auto reset/Manual reset/Power On reset
Manual reset/Power On reset
Auto reset
Manual reset/Power On reset
Manual reset/Power On reset
Auto reset/Manual reset/Power On reset
Manual reset
Auto reset
Auto reset/Manual reset/Power On reset
Alarm
Manual reset/Power On reset
Manual reset/Power On reset
Alarm
Auto reset
Alarm
Alarm
Alarm
Manual reset/Power On reset
Manual reset
Auto reset
Auto reset
Alarm
Alarm/Manual reset/Power On reset
Manual reset/Power On reset
Alarm
Alarm/Auto reset/Manual reset/Power On
reset
Alarm
Alarm
Alarm
Manual reset
Auto reset
Auto reset
Alarm
Alarm
Troubleshooting 19