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
Code 16 is a different fault on every other Rinnai series that documents it, which is exactly why this page is written for the RH180 Hybrid alone: