Rinnai Non-SENSEI Code 16
Outlet water temperature too high. A safety shutdown: the water leaving the unit passed 203°F (95°C). Rinnai's causes are all on the combustion side — restricted air flow around the vent terminal, a fan not running properly, a check valve behind the fan motor stuck, foreign material in the combustion chamber or exhaust, or a blocked heat exchanger — followed by the wrong gas type, and finally the gas valve or fan motor themselves.
Call a proThe verdict
Call a licensed plumber
Scalding-hot water reached a fixture before the unit stopped itself. Do not reset and carry on using it. This is combustion and gas work.
Typical cost: $150–$1,100
US estimate for parts and labor. Prices vary by region and by who does the work — see how we estimate costs.
What the manual says
The meaning above is transcribed from the manufacturer's diagnostic documentation for the Non-SENSEI — not averaged across the brand.
Source: Rinnai Troubleshooting Tankless Water Heater Diagnostic Codes (100000652) (p. 27), read Aug 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
Before anything else: if you smell gas, stop here, leave, and call your gas utility.
- Stop using hot water until this is diagnosed — the unit shut down because the water was hot enough to scald.
- Check the vent terminal outside for anything restricting air flow.
- Book a licensed professional. The remaining causes are the fan, the combustion chamber and the gas valve.
Code 16 on other Rinnai series
The same code number can mean something different on another series — make sure you're reading the page for your exact unit: