Navien Fault Codes
Comprehensive reference table of all Navien boiler error codes. Click any code for detailed troubleshooting steps.
Pro Tip
Check your boiler's digital display panel (usually behind a drop-down cover) to find the current active fault code.
| Error Code | Description | Applies To |
|---|---|---|
| E001 | Overheating of heat exchanger | NCB-CE, NCB300, NCB500, NCB700, LCB700 |
| E001 | Error Display on Smart Plus - Error code on boiler | Smart Plus |
| E002 | Communication Error with Coms module and Smart Plus | Smart Plus |
| E003 | Ignition failure | NCB-CE, NCB300, NCB500, NCB700, LCB700, NPE |
| E004 | False flame detection | NCB-CE, NCB300, NCB500, NCB700, LCB700, NPE |
E008 | Communication Error with Coms module and boiler | Smart Plus |
| E012 | Flame loss | NCB-CE, NCB300, NCB500, NCB700, LCB700, NPE |
| E016 | Heat exchanger overheat | NCB-CE, NCB300, NCB500, NCB700, LCB700, NPE |
| E030 | Abnormal exhaust temperature | NCB-CE, NCB300, NCB500, NCB700, LCB700, NPE |
| E031 | Overheating of Burner | NCB300, NCB500, NCB700, LCB700 |
E046 | Abnormal operation: Heat exchanger overheating sensor | NCB-CE, NCB300, NCB500, NCB700, LCB700 |
E047 | Abnormal operation: Exhaust thermostat | NCB-CE, NCB300, NCB500, NCB700, LCB700, NPE |
E056 | Abnormal operation: Oil pump | LCB700 |
E060 | Abnormal operation: Dual venturi limit switch | NCB-CE, NCB700, NPE |
E109 | Abnormal operation: Fan | NCB-CE, NCB300, NCB500, NCB700, LCB700, NPE |
E110 | Exhaust blockage (Condensate blockage) | NCB-CE, NCB700, LCB700, NBE |
E127 | Abnormal operation: APS | NCB-CE, NCB700, LCB700, NPE |
E144 | Burner thermistor open or short circuit | LCB700 |
E157 | Abnormal operation: APS Hose | LCB700 |
E205 | Heating supply thermistor open or short circuit | NCB-CE, NCB300, NCB500, NCB700, LCB700 |
E218 | Heating return thermistor open or short circuit | NCB-CE, NCB500, NCB700 |
E291 | Supply/Return inversion limit | NCB500, NCB700 |
| E302 | Low water pressure | NCB-CE, NCB300, NCB500, NCB700, LCB700 |
E352 | High water pressure | NCB-CE, NCB500, NCB700, LCB700 |
E353 | Abnormal operation: water pressure sensor | NCB-CE, NCB500, NCB700, LCB700 |
E407 | DHW Outlet thermistor Open or Short Circuit | NCB-CE, NCB300, NCB500, NCB700, LCB700, NPE |
E421 | DHW Inlet thermistor Open or Short Circuit | NCB-CE, NCB500, NCB700, LCB700, NPE |
E432 | Abnormal Cold water inlet2:thermistor (Open/short) | NPE |
E434 | Abnormal operation: Flow control value | NCB500, NCB700, NPE |
E438 | Abnormal circulation pump. ("A" models only) | NPE |
E439 | Abnormal flow sensor | NPE |
E441 | DHW Outlet 2 thermistor open or short circuit | NCB500, NCB700, LCB700, NPE |
E445 | Abnormal operation: Mixing valve | NCB500, NCB700, LCB700, NPE |
E480 | DHW tank thermistor open or short circuit | NCB500, NCB700, LCB700 |
E515 | Abnormal operation: Relay feedback (PCB) | NCB-CE, NCB300, NCB500, NCB700, LCB700, NPE |
E517 | Abnormal operation: DIP switch setting (PCB) | NCB-CE, NCB300, NCB500, NCB700, LCB700, NPE |
E593 | Abnormal operation: Touch IC (Panel PCB) | NCB700, NPE |
E594 | Abnormal operation: EEPROM (PCB) | NCB-CE, NCB300, NCB500, NCB700, LCB700, NPE |
E598 | Abnormal operation: Panel real time clock | NCB300, NCB500, NCB700, LCB700 |
E615 | Abnormal operation: Input and memory (MCU) | NCB-CE, NCB300, NCB500, NCB700, LCB700, NPE |
E736 | Abnormal cascade communication | NPE |
E740 | Abnormal operation: Outdoor temperature sensor | NCB-CE, NCB300, NCB500, NCB700, LCB700, NPE |
E760 | Flushing/service alarm | NPE |
E782 | Abnormal operation: Main panel communication | NCB-CE, NCB300, NCB500, NCB700, LCB700, NPE |
E783 | Abnormal operation: OpenTherm remote control | NCB-CE, NCB300, NCB500, NCB700 |
E785 | Abnormal Flow Switch Operation | NPE |
E787 | Abnormal operation: Reset device Manual/Power | NCB-CE, NCB300, NCB500, NCB700, LCB700 |
E788 | Abnormal operation: Gas type settings | NCB300, NCB500, NCB700 |
E792 | Abnormal operation: DHW circulation | NCB700 |
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