Rinnai RH180 Hybrid Code 16
Over temperature warning. The RH180 shut itself down because it got too hot. Rinnai's checklist is short and all of it is professional: restrictions in the air flow around the unit and the vent terminal, foreign material in the combustion chamber or exhaust piping, a clogged heat exchanger, and whether the gas type in use is the right one for the unit.
Call a proThe verdict
Call a licensed plumber
The one homeowner-side cause is clearance — something stacked against the unit or the terminal. Everything else is inside the combustion path. A clogged heat exchanger on this list is also a maintenance signal worth acting on regardless of what the technician finds.
Typical cost: $0–$900
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.
- Clear anything stored against or on top of the heater, and check the vent terminal outside is not obstructed.
- Note how long the unit runs before it trips and tell the technician — a fast trip and a slow one point at different causes.
- Call a licensed professional. Rinnai marks the whole of this code professional-only.
Frequently asked questions
Is 16 the same thing as 14?
They share causes but not consequences. Code 16 is the over-temperature warning; code 14 is the thermal fuse having actually opened, which is a physical part that has to be replaced. Repeated 16s are the warning that 14 is coming.
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: