Heat exchanger overheat
Displayed as: 14
Rinnai's RU series installation and operation manual lists diagnostic code 14 as "Heat Exchanger Overheat". The manual's checks are: measure the resistance of the overheat switch; check the heat exchanger surface for hot spots that indicate blockage due to scale build-up; refer to the manual's instructions for flushing the heat exchanger, since hard water must be treated to prevent scale build-up or damage; and ensure the unit is not in the forced-high setting.
Hot water and scalding
- Water above 49 °C at a tap can scald in seconds, and children and older adults are at most risk. BC's plumbing code limits shower and bathtub water to 49 °C.
- Storage tanks are normally kept hotter (Health Canada advises 60 °C) to limit Legionella growth, with a thermostatic mixing valve tempering the water to the fixtures.
- Never bypass or remove a mixing valve, thermostat or high-limit control to get hotter water.
Official guidance: Government of Canada on water temperature and scalds and HealthLinkBC.
Applies to
This code and wording come from manual 100000467 for the RU series. The cross-series document 100000652 applies the same code family across SENSEI and non-SENSEI generations.
- Rinnai SENSEI RU (Super High Efficiency Plus condensing)
- Rinnai RU130iN
- Rinnai RU160iN
- Rinnai RU180iN
- Rinnai RU199iN
Control platform: Rinnai PC board with digital controller display. Source manual: 100000467 (rev. 07 on rinnai.ca) (2020–2021).
Why a code is not a diagnosis
Code 14 means the overheat sensor has seen temperatures above its limit. The manual points at two directions: scale build-up inside the heat exchanger (visible as hot spots and the reason flushing is a warranty condition) and controls forcing too much heat. The overheat switch measurement separates a failed sensor from a genuine overheat.
Same code, other equipment
- Rinnai non-SENSEI series: The same code means the same overheat family per troubleshooting document 100000652. Source
Safe things to observe
- Note whether the water at the taps was unusually hot before the code appeared.
- Consider how long it has been since the last descaling flush; scale is the usual suspect on unmaintained units.
Do not
- Do not repeatedly reset the unit and keep drawing hot water.
- Do not run the unit on the forced-high setting to work around the code.
- Do not attempt to flush the heat exchanger without following the manual's isolation-valve procedure.
How professional service helps
- A technician measures the overheat switch resistance and checks the heat exchanger for hot spots and scale.
- The heat exchanger is flushed by the manual's procedure using the isolation valves, or replaced if scale damage is beyond flushing.
Diagnostic visit
Repair visits carry a diagnostic service fee that CANRO states is credited toward the repair if you proceed. The amount is confirmed by phone; it is not published. Source, checked September 7, 2026.
Where CANRO provides on-site service
On-site service is currently offered across Metro Vancouver: Vancouver, Burnaby, Richmond, Surrey, Coquitlam, North Vancouver, West Vancouver, New Westminster, Delta, Langley, Port Moody, Port Coquitlam, Maple Ridge, Pitt Meadows, White Rock, Tsawwassen; plus Anmore, Belcarra, Lions Bay, Bowen Island, Abbotsford with travel or ferry arrangements confirmed by phone. Everything else on this site is reference information you can use anywhere in Canada.
Frequently asked questions
Can hard water cause code 14?
Yes. Scale build-up inside the heat exchanger blocks heat transfer and creates hot spots, which the manual calls out directly. Metro Vancouver's soft water slows this, but flushing is still a warranty condition.
Is code 14 an emergency?
The unit has shut down for its own protection. If water was dangerously hot before the trip, treat the unit as unsafe until checked; otherwise book the flush and inspection.
Locked out with no hot water? Call with the code ready.
The brand, model and this code are passed along when you request service online, so the technician arrives prepared.
On-site service in Metro Vancouver, BC. Call to check availability.
Sources and verification
- Rinnai RU series Installation and Operation Manual, section 5.6 Diagnostic Codes · 100000467 · accessed September 7, 2026
- Rinnai Troubleshooting Tankless Water Heater Diagnostic Codes · 100000652 · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.