Rinnai i-Series (previous generation) 140 — Heat Exchanger Overheat
140
Heat Exchanger Overheat. • Overheat switch is tripped. • Measure the resistance of the Overheat Switch. • Check the heat exchanger surface for hot spots which may indicate blockage due to scale buildup. • Ensure the boiler pump is not locked up. • Ensure that all of the valves in the CH circuit are open. • Ensure the boiler and CH circuit does not have a freezing condition. • The surface of the heat exchanger may turn to a black color as stainless steel is tempered even in normal conditions. This does not indicate an abnormal condition. • Check for damage on the exhaust, seal, and venting. • Ensure the parameter A0 corresponds to the gas type the unit is installed in. • Ensure the gas orifice is the proper orifice for the gas type in use. • Ensure deaeration has been performed. The table classifies it as Diagnostic Code.
If you smell gas
- Stop what you are doing. Do not use phones, switches, matches or anything that can spark inside.
- Go outside and leave the door open behind you.
- Call the FortisBC 24-hour emergency line at 1-800-663-9911 or dial 911.
Only after that, call ROMA about the boiler. Official guidance: FortisBC gas leaks and odour.
Applies to
This gas-train fault code is displayed by the I-Series control (numeric diagnostic codes) on Previous-generation I-Series combi models (i060CN, i090CN, i120CN), as documented in Rinnai I-Series Condensing Combi Boiler Installation and Operation Manual, doc 800000111 (hosted on the Rinnai Canada i060CN product page), Section 12.8 Diagnostic Codes (800000111). Codes can differ between controller generations, so always check the manual that matches your unit.
- Rinnai i-Series (previous generation)
- Rinnai i060CN
- Rinnai i090CN
- Rinnai i120CN
- Rinnai i060SN
- Rinnai i090SN
- Rinnai i120SN
- Rinnai i150SN
Controller: I-Series control (numeric diagnostic codes). Source manual: 800000111.
Why a code is not a diagnosis
A gas-train code involves the gas valve or its electrical circuit. It does not mean there is a leak; the circuit, coils and wiring must be measured by a licensed technician.
Safe things to observe
- If you smell gas, stop, go outside and call your gas utility's emergency line or 911 before anything else.
- Note the exact code and what the appliance was doing when it appeared.
- Check whether other gas appliances in the building are working.
Do not
- Do not reset or run the appliance while the gas valve circuit is suspect.
- Do not touch the gas valve.
How professional service helps
- A technician verifies harness connections and coil resistances against the manual before replacing parts.
- Combustion and safety devices are verified with an analyser and the manufacturer's procedure after any repair.
Where ROMA provides on-site service
On-site service is currently offered in Greater Vancouver, BC, including Vancouver, Burnaby, Richmond, Surrey, Coquitlam, North Vancouver, West Vancouver, New Westminster, Port Coquitlam, Port Moody, Delta, Langley, Maple Ridge, Abbotsford, Chilliwack, White Rock, Pitt Meadows, Tsawwassen, Anmore, Lions Bay, Belcarra, Bowen Island, Mission. Everything else on this site is reference information you can use anywhere in Canada.
Parts and service
Parts commonly involved
These parts appear in the documented text for this alert. A code reports a condition, not a failed part — a technician confirms the cause by testing before anything is replaced.
Heat exchanger
The heat exchanger is where a boiler transfers heat from the burner flame to the water that heats your home.
What a technician checks →Gas orifice
A gas orifice is the precisely sized opening that meters gas into each burner, and its size must match the fuel and altitude the boiler was set up…
What a technician checks →Boiler venting (flue and air intake)
A condensing boiler vents cool, wet flue gases through dedicated plastic pipe that must meet ULC S636 in Canada and the boiler manufacturer's own…
What a technician checks →Circulator pump
The circulator is the pump that moves heated water from a boiler out to the radiators, baseboards or in-floor loops and back again.
What a technician checks →
Service for this alert
- Gas Boiler Repair
Licensed gas technicians from ROMA Heating & Cooling diagnose and repair residential and light-commercial gas boilers across…
- Gas Boiler Replacement
ROMA replaces old, failed or inefficient gas boilers in Greater Vancouver, handling removal, venting and gas-supply changes,…
Every boiler part explained — what it does, how it fails and what a technician checks.
Documented for Rinnai i-Series (previous generation).
Frequently asked questions
Does this code mean I have a gas leak?
Not by itself. If you smell gas, stop, leave the building and call your gas utility's emergency line or 911 from outside before anything else. Otherwise the code points to a fault a technician confirms on site.
Can I clear this code myself?
Clearing a code without fixing its cause usually just brings it back. Note the code, check the safe items on this page, then call a licensed technician. If your appliance manual describes a user reset for this exact code and it stays away, no call may be needed.
Boiler locked out? Call with the alert text ready.
The brand, model and this alert are passed along when you request service online, so the technician arrives prepared.
On-site service in Greater Vancouver, BC. ROMA lists “Open 7 days” on its site; call to confirm same-day availability.
Sources and verification
- Rinnai I-Series Condensing Combi Boiler Installation and Operation Manual, doc 800000111 (hosted on the Rinnai Canada i060CN product page), Section 12.8 Diagnostic Codes · 800000111 · accessed September 9, 2026
Facts checked September 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.