Rinnai SENSEI Code 15
Venturi control fault. The PC board is not getting the response it expects from the venturi control on the gas valve — the assembly that meters the air-to-gas ratio. On the SENSEI, Rinnai's diagnosis is a set of resistance and voltage readings at connector D (35-41 ohms across two coil pairs, 12-14 VDC on the supply), then the fan motor and airflow, then replacing the gas valve or the fan.
Call a proThe verdict
Call a licensed plumber
One free thing first: Rinnai's step one is a full power reset. If the code returns, this ends in a gas valve or fan motor replacement decided by readings taken at the board — professional work on the gas train either way.
Typical cost: $0–$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 SENSEI — not averaged across the brand.
Source: Rinnai Troubleshooting Tankless Water Heater Diagnostic Codes (100000652) (p. 26), 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.
- Reset the main power: switch the heater off at the breaker, wait a minute, switch it back on.
- If the code returns immediately, leave the unit off and book a licensed professional.
- If you smell gas at any point, leave and call your gas utility from outside.
Frequently asked questions
Do older, non-condensing Rinnai units have a code 15?
No. Rinnai lists code 15 for the SENSEI and SENSEI RX/CX series only — it belongs to the gas valves that actively control the air-fuel ratio.
Code 15 on other Rinnai series
Other Rinnai series report code 15 under the same fault name, but each manual is transcribed separately and they do not read alike:
Don't confuse this with
One other Rinnai SENSEI code points at the venturi too. They are different components in different places, and ordering a part against the wrong one is the most common way this fault gets expensive: