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Rinnai tankless water heater code 11 is the most common Rinnai code, but there are many more. Here’s what each common code means and what to check.
| Code | Meaning | What to check first |
|---|---|---|
| 10 | Air supply or exhaust blockage | Vent and intake terminals for snow, debris or nests; vent joints and length |
| 11 | No ignition | Gas valve open, propane level, air in gas line, gas pressure |
| 12 | Flame failure | Gas pressure, venting, wind at terminal, flame rod |
| 14 | Thermal fuse | Overheating, often from scale, venting or burner issue; technician needed |
| 16 | Over-temperature warning | Scale buildup, low flow, recirculation settings |
| 19 | Electrical grounding | Power supply and grounding; technician needed |
| 25 | Condensate drain blocked (condensing models) | Condensate line, trap and neutralizer for clogs or freezing |
| 32 | Outgoing water temperature sensor fault | Sensor and wiring; technician needed |
| 33 | Heat exchanger outgoing temperature sensor fault | Sensor and wiring; technician needed |
| 52 | Modulating solenoid valve signal abnormal | Gas valve; technician needed |
| 61 | Combustion fan failure | Fan and wiring; technician needed |
| 65 | Water flow control fault | Flow control valve; technician needed |
| 71 | Solenoid valve circuit fault | Gas valve circuit; technician needed |
| 72 | Flame sensing device fault | Flame rod; technician needed |
| 79 | Water leakage detected (models with leak detection) | Look for leaks inside the cabinet; shut off water |
| LC | Scale buildup detected | Flush the unit |
| FF | Maintenance has been performed | Informational |
Code meanings can differ slightly between model generations. Codes not listed here, such as 17 or 63 on some models, should be checked in the manual for your exact model.
Code 11 is the most common Rinnai code. It means the unit tried to light but didn’t sense a flame.
The burner lit but the flame went out. Check that the vent and intake are clear and that wind isn’t blowing directly at the termination. Low gas pressure and a dirty flame rod are common causes. Repeated code 12 needs a technician to measure gas pressure under load.
Rinnai tankless water heater code 12 often appears when gas pressure drops as other appliances start.
Inspect the vent termination outside for snow, ice, leaves, insect nests or bird nests. Make sure the vent system meets Rinnai’s length and elbow limits. Damaged or disconnected vent pipes need immediate professional repair.
Rinnai tankless water heater code 10 is common after snowstorms when the vent terminal is buried.
LC (sometimes followed by a number) means the unit detected scale in the heat exchanger. Flush the unit with descaler or vinegar as the manual allows. If you have hard water, consider a scale inhibitor or softener.
After fixing the cause, press the power button on the controller to turn the unit off and on, or cycle power at the outlet. If the code returns, contact a Rinnai-authorized service provider. Your unit may still be under warranty; see Rinnai tankless water heaters for warranty basics.
A flush kit and descaler clear LC codes and keep your Rinnai efficient.
Make sure the gas supply valve is open, the propane tank isn’t empty, and other gas appliances work. After new installation, air in the gas line can cause code 11. Turn the unit off and on and try again. If code 11 continues, a technician should check gas pressure, the igniter and flame rod.
Flame failure. The burner lit but the flame was lost. Check for low gas pressure, a blocked vent or intake, and strong wind at the termination. Persistent code 12 needs a technician.
LC indicates scale buildup in the heat exchanger. Flush the unit with descaler following the manual. On many models you can temporarily continue using hot water by turning the controller off and on, but the code will return until the unit is flushed.
Your Rinnai owner’s manual and installation manual list the codes for your model. Many units also have a diagnostic chart inside the front cover.
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.
