Rinnai Water Heater Error Code 20: How to Fix It

Q: What does error code 20 mean on a Rinnai tankless water heater?

Error code 20 on a Rinnai tankless water heater means the unit has detected that the burner flame is too high. This can be caused by excessive gas supply pressure, a faulty gas valve, a dirty flame sensor, or venting issues. The unit shuts down as a safety precaution to prevent overheating or damage.

Q: Can I reset a Rinnai error code 20 myself?

Yes, you can attempt a reset by turning the unit off, shutting off the gas supply for at least 5 minutes, then turning everything back on. If the error code 20 does not return, the issue may have been a temporary gas pressure fluctuation. However, if the code comes back repeatedly, you will need to investigate the root cause rather than continuing to reset the unit.

Q: Is error code 20 on a Rinnai dangerous?

Error code 20 is rated as a medium-severity issue. The unit automatically shuts off when it detects this condition, which is a built-in safety feature. As long as you do not override or repeatedly ignore this error, it is not immediately dangerous. However, you should address it promptly because running the heater with an abnormally high flame can damage the heat exchanger or gas valve over time, and could pose a safety risk if left unresolved.

Q: How much does it cost to fix Rinnai error code 20?

If a simple reset or flame sensor cleaning resolves the issue, the cost is minimal — just your time. If the gas supply pressure needs adjustment, your gas utility may handle that at no charge. If the gas valve needs to be replaced, expect to pay between $200 and $600 or more in parts and labor depending on your location and the specific model. A service call from a licensed technician typically starts at $100 to $150 before parts.

Q: Why does my Rinnai keep showing error code 20 after resetting?

If error code 20 keeps coming back after you reset the unit, it means the underlying cause has not been fixed. The most common culprits for a recurring error code 20 are inconsistent or high gas supply pressure, a gas valve that is failing to regulate fuel flow correctly, or a flame sensor that is still dirty or damaged. Continued resets without fixing the root cause can lead to more serious damage, so it is best to work through the troubleshooting steps or call a professional.

Abstract

Rinnai Error Code 20 indicates that the burner flame inside your tankless water heater is burning higher than it should be, which can lead to overheating and potential safety hazards. This error is typically triggered by a problem with the gas supply pressure, a faulty gas valve, or a dirty or malfunctioning flame sensor. Addressing this promptly is important — running the unit with an excessively high flame can damage internal components or create a safety risk.