Navien Tankless Water Heater Error Codes Guide
Navien tankless water heaters — including the NPE-A2 and NPE-S2 series — are among the most efficient and feature-rich units on the market. They provide endless hot water on demand, but like all sophisticated appliances, they can develop faults that trigger error codes. The good news: Navien's diagnostic system is very specific, which usually means faster and more accurate repairs when something goes wrong. This guide explains the most common Navien tankless water heater error codes and what you should do about each one.
Where Navien Error Codes Appear
Error codes appear on the front panel display of the Navien unit. The code (e.g., "E003") appears along with a short description. Many Navien units are also compatible with the NaviLink Wi-Fi module, which sends error code notifications to the NaviLink app on your phone. This is particularly useful for monitoring units in vacation homes or rental properties. The unit logs up to 20 recent fault codes, accessible through the service menu.
Common Navien Tankless Water Heater Error Codes
| Error Code | Meaning | What to Do |
|---|---|---|
| E003 | Ignition failure — no flame after 3 attempts | Check gas; check vent for ice; one reset |
| E004 | False flame detection | Technician required — flame sensor or gas valve |
| E007 | Hot surface igniter fault | Technician required — igniter replacement |
| E009 | Heat exchanger outlet temperature sensor fault | Technician required — sensor replacement |
| E011 | Heat exchanger inlet temperature sensor fault | Technician required |
| E012 | Flame loss during operation | Check gas supply and pressure; call technician |
| E016 | Overheating — high limit activated | Check for scale buildup; call technician |
| E030 | Exhaust temperature too high | Check vent for blockage; call technician |
| E033 | Inlet gas pressure too low | Contact gas utility; call technician |
| E047 | Inlet thermistor temperature abnormal | Technician required |
| E109 | Fan motor speed abnormal | Technician required — fan or control board |
| E110 | Vent blockage or exhaust temperature fault | Check exterior vent for ice/debris; call tech |
| E302 | Low water pressure (system pressure fault) | Check incoming water pressure; call if low |
| E351 | Domestic hot water flow sensor fault | Technician required |
E003: Navien's Most Common Error Code
E003 (ignition failure) accounts for a large percentage of all Navien service calls in Wisconsin. There are several causes:
- Iced vent termination: In cold weather, the PVC exhaust pipe exit on the exterior wall can become coated with ice, starving the unit of combustion air. This is by far the most common cause of E003 in winter. Inspect the exterior vent termination and carefully clear any ice. Reset the unit after clearing.
- Low gas pressure: If other gas appliances also have low or no gas, contact your gas utility company. If only the Navien is affected, the gas supply line to the unit may be undersized or partially closed.
- Dirty igniter or burner: Over time, the igniter and burner can accumulate deposits that prevent reliable ignition. This typically requires a technician with the correct tools to clean or replace.
E110: Vent Blockage in Wisconsin Winters
E110 is almost synonymous with Wisconsin winters for Navien units. The condensing exhaust produces moist air that tends to ice over at the vent termination when outdoor temperatures drop sharply. After clearing the ice blockage, reset the unit by pressing the power button or cycling power at the breaker. If E110 recurs repeatedly, ask a technician about installing extended vent terminations with ice guards.
Scale and Hard Water Maintenance
Southeastern Wisconsin has moderately hard water. Navien recommends annual maintenance — including a heat exchanger descale — for units in hard water areas. Signs that scaling is building up include reduced hot water flow, longer wait times for hot water, and increased frequency of E016 (overheating) codes. Annual descaling typically costs less than $200 and extends the life of the heat exchanger significantly.
When to Call a Professional
All sensor faults, gas valve faults (E004, E012 recurring), fan motor faults (E109), and flow sensor faults (E351) require professional diagnosis and repair. Navien units use high-efficiency condensing combustion and require technicians trained specifically on this platform. Using unqualified service providers on Navien units can void warranties and cause additional damage.
Burkhardt Heating, Cooling, Plumbing & Electric is a Navien-trained service provider serving Southeastern Wisconsin. We stock common Navien parts and offer 24/7 emergency service for hot water outages.
Navien Tankless Repair in Southeastern Wisconsin
Navien's detailed error codes make diagnosis efficient and repairs faster than on older equipment. When you call with an error code in hand, Burkhardt's technicians can often bring the right part on the first visit.
If you see any of these codes, call Burkhardt at 414-206-3049. Our NATE-certified technicians can diagnose and repair the issue — usually in a single visit.
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