Rinnai Error Code 18: Gas valve air/fuel adjustment limit reached (Tankless)
Rinnai error code 18 on a tankless water heater means: Gas valve air/fuel adjustment limit reached. It is also called Rinnai diagnostic code 18.
Homeowner? What Rinnai code 18 means for you
Call a technician Your tankless water heater is reporting: Gas valve air/fuel adjustment limit reached. The tankless water heater has locked out or cannot run properly. One reset is fine; if the code comes back, it needs a licensed technician to find the cause.
Safe things you can check yourself
- Check that gas reaches the house: other gas appliances work, or the propane tank is not empty.
- Make sure the heater is plugged in and its breaker is on. In winter, keep the power on: it protects the unit from freezing.
- Outside, make sure the intake and exhaust pipes or vent cap are not blocked by snow, ice, leaves or a nest.
- Check that the hot and cold water valves under the heater are fully open.
- If you have a remote controller, turn it off and on once. If the code comes back, call a technician.
Call (647) 657-2977Book a service call
Licensed technicians serving Vaughan, Toronto and the GTA.
What does Rinnai error code 18 mean?
The Smart-Sense gas valve has hit its rich or lean air/fuel adjustment limit for the selected gas type, which should not happen in normal operation.
Applies to: SENSEI RX/CX Series
Common causes of Rinnai code 18
- Wrong gas being supplied to the unit
- Parameter 10 (Gas Type) set incorrectly
- Incorrect gas valve parameters entered
A technician checks these and 1 other possible causes on site before replacing any part.
Rinnai models that use code 18
CX160iCX199iCXP160iCXP199iRX130iRX160iRX180iRX199iRXP160iRXP199i
Other Rinnai Tankless codes
All Rinnai Tankless Water Heater error codes →
Rinnai code 18: homeowner questions
What does Rinnai code 18 mean?
Gas valve air/fuel adjustment limit reached. The Smart-Sense gas valve has hit its rich or lean air/fuel adjustment limit for the selected gas type, which should not happen in normal operation.
Is it safe to keep using my tankless water heater with code 18?
It depends on the cause. The tankless water heater has locked out or cannot run properly. One reset is fine; if the code comes back, it needs a licensed technician to find the cause.
Can I reset Rinnai code 18 myself?
You can try one reset (power off for 30 seconds, then on). If Rinnai code 18 comes back, the cause is still there and a licensed technician should check it.
Who can fix Rinnai code 18 near me?
Aurora Star Tech Inc. repairs Rinnai tankless water heaters in Vaughan, Toronto and across the GTA. Call (647) 657-2977 or book a service call online.
Homeowner help: Tankless Water Heater No Hot Water: What to Check
Troubleshooting guides
- No hot water All brands · Tankless Water Heater
- Water temperature fluctuates All brands · Tankless Water Heater
Source: Rinnai Troubleshooting TWH Diagnostic Codes (100000652), p.30. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.