Navien NHB Error Codes
Mar 23, 2025
22
Error code list for the Navien NHB boilers
| Error Code | Reason | Recommended Action |
|---|---|---|
| E001 | Heat Exchanger Overheat | Check for proper system flow. |
| E003 | Ignition Failure | Check gas supply valve and igniter. |
| E004 | False Flame | Check electric ground. |
| E012 | Flame Loss | Check gas, venting, and condensate trap. |
| E016 | Heat Exchanger Overheat | Check flow, clean system filters. |
| E030 | Exhaust Overheat | Check flow, clean system filters. |
| E046 | Heat Exchanger Thermistor | Check thermistor connector. |
| E047 | Exhaust Thermistor | Check thermistor connector. |
| E060 | Abnormal Dual Venturi | Check dual venturi. |
| E109 | Abnormal Fan Motor | Check fan and venting. |
| E110 | Exhaust Blockage | Check exhaust venting. |
| E205 | Heating Supply Temp. Sensor | Check flow, thermistor connector. |
| E218 | Heating Return Temp. Sensor | Check thermistor connector. |
| E278 | Ext. Supply Sensor Not Detected | Check sensor connections. |
| E279 | Ext. Return Sensor Not Detected | Check sensor connections. |
| E291 | Return Temp. Exceeds Supply | Check for reversed piping. |
| E302 | Low Water Pressure | Check water pressure. |
| E352 | High Water Pressure | Check water pressure. |
| E353 | Water Pressure Sensor | Check WPS. |
| E480 | DHW Tank Sensor Not Detected | Check sensor connections. |
| E515 | Abnormal PCB | Check PCB connections. |
| E517 | Abnormal DIP Switch | Check DIP switch settings. |
| E594 | Abnormal EEPROM | Check the PCB. |
| E615 | Abnormal Memory | Check PCB connections. |
| E736 | Cascade Communication | Check cascade cable. |
| E740 | Outdoor Sensor Not Detected | Check sensor connections. |
| E762 | Vent Pipe Not Fully Inserted | Insert pipe 2" (70 mm) into exhaust collar. |
| E777 | Low Water Cutoff Activated | Check supply water. |
| E782 | Front Panel Communication | Check panel connections. |
| E784 | Zone Controller Communication | Check wiring and settings. |
| E786 | Improper Front Panel Detected | Check for correct panel version. |
| E788 | Incorrect Gas Type Setting | Check DIP switch setting. |
