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Tankless water heater error codes tell you what the unit detected. Here’s what the most common codes mean across brands, and what to check before calling for service.
Before looking up a specific code, check the basics. They solve a large share of errors:
Tankless water heater code 11 is the most searched error code across brands.
Seen on Rinnai, Rheem, Richmond, Noritz and others. The unit attempted ignition but didn’t detect flame.
The burner lit but the flame went out.
Common on Rinnai and Rheem units. Check the vent and intake terminals, vent joints and length. Persisting codes need a technician.
These are the most common Navien tankless water heater error codes.
| Code | Meaning | What to check |
|---|---|---|
| E003 | Ignition failure | Gas supply, gas valve open, propane level, gas pressure |
| E012 | Flame loss | Gas pressure, venting, burner and flame rod |
| E016 | Heat exchanger overheat | Scale buildup, low flow, recirculation settings |
| E030 | Exhaust overheat | Venting and exhaust temperature sensor |
| E110 | Exhaust blockage or air pressure problem | Vent and intake terminals, vent length and joints |
Navien models use many more codes, such as E4xx codes for sensors and water-related faults. Look up codes like E438 or E110-01 in the manual for your exact model, available on Navien’s website.
Noritz units also use 11 for ignition failure and 12 for flame failure. Other codes cover combustion, airflow, sensor and scale conditions. Many Noritz units have a code chart printed inside the front cover; the owner’s manual has the full list.
Richmond tankless units share many codes with Rheem units: 11 (no ignition), 12 (flame failure), and model-specific codes such as 17 and 29. Check the manual or the code chart inside the cover for your model.
RV tankless water heaters from Furrion, Girard and others use their own code systems. Many issues come from low propane, low 12V battery voltage, low water flow or freezing. See our RV tankless water heater guide and your owner’s manual.
Call a licensed technician if a code returns after the basic checks, if you smell gas, or if the code involves combustion, overheating, the fan, gas valve or control board. Read our repair and troubleshooting guide.
Scale-related codes clear after a proper flush. Get a kit and descaler.
On Rinnai, Rheem, Richmond, Noritz and several other brands, code 11 means the unit tried to light but did not detect a flame. Common causes are a closed gas valve, empty propane tank, air in a new gas line, low gas pressure, a dirty flame rod or a faulty igniter.
Code 12 usually means flame failure, meaning the burner lit but the flame was lost during operation. Causes include low gas pressure, vent or air intake blockage, wind at the vent terminal, or a dirty flame sensor.
Navien publishes installation and user manuals with full error code tables on its website. Search for your exact model number, such as NPE-240A2.
Fix the cause first, then turn the unit off and on with the controller or by cycling power. Some codes clear automatically. If the code returns, call a technician.
This guide is general information for U.S. homeowners, not professional advice. Gas, electrical and venting work must follow the manufacturer’s instructions and local codes, and in most areas requires a licensed plumber, electrician or gas fitter and a permit. Specifications and prices change; always confirm details on the product page and in the installation manual.
