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
The same code number can mean something different on another series — make sure you're reading the page for your exact unit: