HeatingCodesNavien NPN tankless water heater error codes
Navien shows an E-prefixed error code on the front panel. The manual's chart gives a reason and a self-diagnostic action for each one, and for many codes the action is simply to contact technical support.
What this table coversThe main table is section 5.2 of Navien's NPN non-condensing water heater User's Information Manual. The comparison table below adds the most common codes from three more Navien owner's manuals: NPE-2 and NPE condensing water heaters and NCB-H combi-boilers. Condensing models have additional codes not shown here; use the chart in your own manual.
How to read the display
The code appears on the front panel. Some codes (like E003) have a few safe owner checks. Others say only to contact technical support, which you should do rather than opening the unit.
Navien code table
| Code | Meaning | What the document says |
|---|---|---|
| E003 | Ignition failure | Ensure the main gas supply valve is open. Ensure the gas manifold and the fuel DIP switch setting match the supplied gas type. Full explanation |
| E004 | False flame detection | Ensure the electrical cord is properly grounded. |
| E012 | Flame loss | Clean the intake air filter. Ensure the electrical cord is properly grounded. Ensure the gas manifold and fuel DIP switch setting match the supplied gas type. Full explanation |
| E016 | Overheating of heat exchanger | Turn the system off for at least 30 minutes, then restart it. Clean the cold water inlet filter. Flush the heat exchanger. |
| E046 | Abnormal operation: limit control | Contact Navien technical support. |
| E056 | Abnormal operation: modulating gas valve | Contact Navien technical support. |
| E109 | Abnormal operation: fan motor | Contact Navien technical support. |
| E110 | Abnormal air pressure | Ensure the vent pipe is free of obstructions. Full explanation |
| E127 | Abnormal operation: air volume open / short / default value / no answer | Contact Navien technical support. |
| E157 | Abnormal operation: air volume control | Contact Navien technical support. |
| E170 | Antifreeze heater open / short | Contact Navien technical support. |
| E407 | Hot water outlet: thermistor open or short circuit | Contact Navien technical support. |
| E421 | Cold water inlet: thermistor open or short circuit | Contact Navien technical support. |
| E434 | Abnormal operation: water adjustment valve | Contact Navien technical support. |
| E438 | Abnormal operation: circulation pump | External: ensure all water supply and return lines are open. |
| E439 | Abnormal operation: flow sensor | Contact Navien technical support. |
| E441 | Hot water inlet: thermistor open or short circuit | Contact Navien technical support. |
| E445 | Abnormal operation: bypass mixing valve | Contact Navien technical support. |
| E515 | Abnormal operation: PCB | Ensure the electrical cord is properly grounded. |
Source: Navien NPN User's Information Manual, chart in section 5.2.
E003, E012 and E110 across four Navien manuals
These three codes, each with owner-level actions, appear in every Navien owner's manual we read:
| Code | NPN (non-condensing) | NPE-2 and NPE (condensing water heaters) | NCB-H (combi-boiler) |
|---|---|---|---|
| E003 Ignition failure | Ensure the main gas supply valve is open; ensure gas manifold and fuel DIP switch match the gas type | Ensure the main gas supply valve is open | Ensure the main gas supply valve is open |
| E012 Flame loss | Clean the intake air filter; ensure the cord is properly grounded; ensure gas manifold and DIP switch match the gas type | Clean the intake air filter; ensure the cord is properly grounded | Clean the intake air filter; ensure the cord is properly grounded |
| E110 | Abnormal air pressure: ensure the vent pipe is free of obstructions | Abnormal air pressure: ensure the exhaust pipe is free of obstructions; clean the intake air filter | Exhaust blockage: ensure the exhaust pipe is free of obstructions; clean the intake air filter |
The NPE-2 manual adds that a clogged air intake filter will stop the heater and show error 110, and asks owners to clean the filter every 3 to 4 months. On the NPE-2 you reset the heater with the Back button on the front panel.
Detailed explanations
- Navien tankless water heater error E003: ignition failure
- Navien tankless water heater error E110: abnormal air pressure
- Navien error code E012: flame loss
SafetyThese tables describe what the manufacturer documents say. Gas, combustion, refrigerant and line-voltage repairs are for licensed professionals. If you smell gas, leave the building and call your gas utility or 911. Safety disclaimer.
Sources
- User's Information Manual: NPN Non-Condensing Water Heaters, section 5.2 Understanding Error Codes (Navien) Covers: Navien NPN-series non-condensing tankless water heaters (NPN-120E through NPN-199U). Condensing NPE/NCB models have their own manuals.
- User's Information Manual: NPE-2 Condensing Water Heaters (NPE-180/210/240A2 and S2), section 5.2 Understanding Error Codes (Navien) Covers: Navien NPE-180A2, NPE-210A2, NPE-240A2, NPE-180S2, NPE-210S2 and NPE-240S2 condensing tankless water heaters.
- User's Information Manual: NPE Condensing Water Heaters (NPE-180/210/240A and NPE-150/180/210/240S), section 5.2 Understanding Error Codes (Navien) Covers: Navien first-generation NPE-A and NPE-S condensing tankless water heaters.
- User's Information Manual: NCB-H Condensing Combi-Boilers, section 5.2 Understanding Error Codes (Navien) Covers: Navien NCB-190/060H, NCB-190/080H, NCB-240/110H, NCB-240/130H and NCB-250/150H combi-boilers.