Rinnai RH180 Hybrid Code 32
Heat exchanger outgoing temperature sensor fault. The sensor reading the water temperature leaving the heat exchanger is out of range. Rinnai's list has four steps: check the sensor wiring for damage, measure the sensor's resistance, clean scale build-up off the sensor, and replace it. The third one is the useful one — on this appliance Rinnai expects scale on the sensor itself to be a cause, not just a background condition.
Call a proThe verdict
Call a licensed plumber
Cheap part, and there is a real chance the sensor is fine and just scaled. That makes water hardness the thing to raise with whoever comes out — if the sensor is furred, the heat exchanger is too, and fixing one without the other buys you a few months.
Typical cost: $150–$700
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.
- Find out how hard your water is, and when the unit was last flushed, before the technician arrives.
- Call a licensed professional. The sensor is on the heat exchanger outlet inside the cabinet.
Frequently asked questions
The RH180 has no scale warning code. How do I know when to flush it?
You do not get told, which is exactly why this code matters. Rinnai lists SS on the SENSEI generations and LC on the Non-SENSEI tankless range, but there is no scale code in the RH180 table. Go by water hardness instead — our guide on how often to flush works from hardness rather than a calendar.
Code 32 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:
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: