Rinnai Non-SENSEI Code 14
Overheat switch or thermal fuse tripped. An overheat protection device opened. On this generation that is the more expensive version of the fault, because Rinnai names two different devices: a bi-metal switch on the heat exchanger, which resets itself once things cool down, and thermo-fuses wrapped around the heat exchanger, which are one-shot — once blown they must be replaced, and reaching them means removing the heat exchanger. Rinnai also asks the technician to look for blackened discolouration where the copper meets the combustion box.
Call a proThe verdict
Call a licensed plumber
Take this one seriously. If the unit starts working again on its own it was the self-resetting switch, and the cause behind it has not been fixed. If it stays dead, a thermo-fuse has blown and the repair involves pulling the heat exchanger — the top of the cost range here is a real outcome, not a worst case.
Typical cost: $150–$1,400
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 Non-SENSEI — not averaged across the brand.
Source: Rinnai Troubleshooting Tankless Water Heater Diagnostic Codes (100000652) (p. 23), 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.
- Stop using the unit and leave it off until someone has looked at it. It is telling you it overheated.
- Note whether it recovers on its own after cooling — that distinguishes the resettable switch from a blown fuse, and it is the first thing a technician will ask.
- Note when the heat exchanger was last flushed. Scale is a common route to an overheat on these units.
- Book a licensed professional. Do not bypass or jumper the switch to get hot water back.
Frequently asked questions
The unit started working again by itself. Is it fixed?
No. Rinnai states the bi-metal switch resets on its own once the heat exchanger cools, and that it will trip again whenever the underlying fault reappears. A code 14 that clears itself is a warning with a delay on it, not a repair.
Why is a code 14 more expensive on an older Rinnai?
Because of the thermo-fuses. On the Non-SENSEI generation Rinnai lists them alongside the bi-metal switch as a cause, and they are one-shot devices wrapped around the heat exchanger — replacing one means removing the heat exchanger, which is most of the labour in the repair.
Code 14 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
2 other Rinnai Non-SENSEI codes point at a switch 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: