Product troubleshooting
Navien NFB700-800C troubleshooting and error codes
These codes are matched from manufacturer documentation to this model's series or control platform. Keep checks visible and safe; do not open electrical, refrigerant, gas, combustion, or sealed equipment compartments.
Source-backed code set
34 matched codes
| Code | Meaning | System area | Priority |
|---|---|---|---|
| E001 | Heat exchanger overheat | Equipment control | Urgent |
| E003 | Ignition failure | Combustion / venting | Urgent |
| E004 | False flame detection | Combustion / venting | Urgent |
| E012 | Flame loss | Combustion / venting | Urgent |
| E016 | Heat exchanger overheat | Equipment control | Urgent |
| E030 | Exhaust overheat | Combustion / venting | Urgent |
| E031 | Burner overheat | Combustion / venting | Urgent |
| E046 | Abnormal operation: heat exchanger limit or thermistor | Temperature / sensor | Service |
| E047 | Exhaust thermostat or thermistor open/short | Combustion / venting | Urgent |
| E060 | Abnormal operation: dual venturi | Combustion / venting | Urgent |
| E109 | Abnormal operation: fan motor | Airflow / fan | Service |
| E110 | Abnormal air pressure or exhaust blockage | Combustion / venting | Urgent |
| E127 | Abnormal operation: air pressure sensor or air volume control | Combustion / venting | Urgent |
| E205 | Heating supply temperature sensor | Temperature / sensor | Service |
| E218 | Heating return temperature sensor | Temperature / sensor | Service |
| E278 | External supply sensor not detected | Temperature / sensor | Service |
| E279 | External return sensor not detected | Temperature / sensor | Service |
| E291 | Return temperature exceeds supply temperature | Temperature / sensor | Service |
| E302 | Low water pressure | Water flow / hydronics | Urgent |
| E352 | High water pressure | Water flow / hydronics | Urgent |
| E353 | Water pressure sensor issue | Temperature / sensor | Urgent |
| E480 | Domestic hot water tank temperature sensor not detected | Temperature / sensor | Service |
| E515 | Abnormal operation: PCB | Controls / communication | Urgent |
| E517 | Abnormal operation: DIP switch setting | Controls / communication | Service |
| E594 | Abnormal operation: EEPROM | Controls / communication | Urgent |
| E615 | Abnormal operation: input and memory | Controls / communication | Service |
| E736 | Abnormal operation: cascade communication | Controls / communication | Service |
| E740 | Abnormal operation: outdoor temperature sensor | Temperature / sensor | Service |
| E765 | Abnormal external pump operation | Water flow / hydronics | Service |
| E774 | Manual reset limit | Equipment control | Service |
| E775 | Auto reset limit | Equipment control | Service |
| E777 | Low water cutoff activated | Water flow / hydronics | Service |
| E782 | Abnormal operation: front/main panel communication | Controls / communication | Service |
| E784 | Abnormal operation: zone controller communication | Controls / communication | Service |
No matching error codes found.