Navien NBH Series, User'S Information Manual

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22 Troubleshooting
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 Self-diagnostic/Action
E001 Heat exchanger over temperature Auto reset/Manual reset/Power On reset
E003 Ignition failure Manual reset/Power On reset
E004 False flame detection Auto reset
E012 Flame loss Manual reset/Power On reset
E016 Heat exchanger overheat Manual reset/Power On reset
E030 Abnormal operation: exhaust temperature Auto reset/Manual reset/Power On reset
E046 Abnormal operation: heat exchanger overheating sensor Auto reset
E047 Abnormal operation: exhaust thermostat Auto reset/Manual reset/Power On reset
E060 Abnormal operation: dual venturi Alarm
E109 Abnormal operation: fan motor Manual reset/Power On reset
E110 Exhaust vent closed Manual reset/Power On reset
E205 Abnormal operation: heating supply thermistor Auto reset
E218 Abnormal operation: heating return thermistor Alarm
E271 Temperature differential limit Alarm
E278 Abnormal operation: system supply thermistor Alarm
E279 Abnormal operation: system return thermistor Alarm
E291 Supply/Return inversion limit Manual reset/Power On reset
E302 Low water pressure Manual reset
E352 High water pressure Auto reset
E353 Abnormal operation: water pressure sensor Auto reset
E515 Abnormal operation: PCB component Alarm/Manual reset/Power On reset
E517 Abnormal operation: DIP switch setting (PCB) Manual reset/Power On reset
E594 Abnormal operation: EEPROM (PCB) Alarm
E615 Abnormal operation: MCU
Alarm/Auto reset/Manual reset/Power On
reset
E736 Abnormal operation: Cascade communication Alarm
E740 Abnormal operation: outdoor temperature sensor Alarm
E777 Abnormal operation: LWCO limit (external device) Auto reset
E782 Abnormal operation: boiler communication Alarm
E784 Abnormal operation: zone controller communication (external device) Alarm
If these remedies do not resolve the problem, contact Technical Support at 1-800-519-8794.