Code 12 differs from code 11. With 11 the heater never lights; with 12 it lights and then loses the flame, which often points to a gas supply or venting problem.
Safety first
If you smell gas, do not light anything or touch electrical switches. Leave the house and call SDG&E or 911 from outside. Manufacturers reserve gas, burner, venting and internal electrical work for qualified technicians.
Causes Rinnai lists for code 12
- Gas turned off at the heater or meter.
- A blocked flue outlet or exhaust.
- A gas line or meter too small for the heater.
- Wrong gas type or gas pressure.
- Air in the gas lines.
- Fan motor wiring.
What you can safely check
- The gas valve at the heater is fully open and the meter is on.
- The exhaust and intake terminations outside are clear of debris, nests or anything stacked against them.
When to call a plumber
If the code repeats, call a licensed plumber or Rinnai service provider. Gas line sizing, pressure testing and fan wiring are technician jobs. A heater that loses flame when other gas appliances run may have an undersized gas supply, which a plumber can measure.
Common questions
What is the difference between Rinnai code 11 and code 12?
Code 11 is no ignition: the heater never lights. Code 12 is flame failure: it lights, then the flame goes out.
General information, not professional or legal advice; follow your manufacturer's manual, and your installer and local permit office have the final word. Sources:Rinnai RL75i/RL94i technical sheet (diagnostic codes); Rinnai, Troubleshooting Tankless Water Heater Diagnostic Codes. SD Water Heaters is not affiliated with any manufacturer; brand names are used only to identify products, and codes can differ by model, so confirm in your own manual.
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