Rinnai RH180 Hybrid Code 30
Flammable vapour sensor fault. The flammable vapour sensor — the one behind code FE — is not reporting correctly. Rinnai's remedy is short: check the sensor wiring for damage, measure the resistance of the sensor. What makes this matter more than a typical sensor code is which sensor it is. While code 30 is showing, the appliance's ability to detect flammable vapours around it cannot be relied on.
Call a proThe verdict
Call a licensed plumber
The part is not expensive and the diagnosis is two steps, but this is the safety sensor, and both steps are inside the cabinet on a gas appliance. Do not defer it on the grounds that the unit still makes hot water — the thing that is broken is the thing that watches for petrol vapour.
Typical cost: $150–$600
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 RH180 Hybrid — not averaged across the brand.
Source: Rinnai RH180 Operation and Installation Manual (100000319) (p. 36), read Sep 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.
- Move any gasoline, solvents, paint thinner or adhesives out of the room while the sensor is unreliable.
- Call a licensed professional and say it is code 30 on an RH180 — the flammable vapour sensor, not a temperature sensor.
Frequently asked questions
My Rinnai tankless heater has a code 30 too. Same thing?
No. Rinnai's general diagnostic document lists code 30 for the RH180 only, and here it is the FV sensor. If you are reading a code 30 page written for a tankless Rinnai, it is not describing your appliance.
Don't confuse this with
5 other Rinnai RH180 Hybrid codes point at a sensor 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: