Rinnai i-Series (previous generation) 443 — Low Water Cut-off (LWCO)
443
Low Water Cut-Off (LWCO). • Ensure the LWCO device is working correctly. • Ensure the LWCO jumper is connected properly when LWCO is not in use. • Ensure the output is 24 VAC on the PCB. If it is not, check the transformer harness and output of transformer. The table classifies it as Diagnostic Code.
Applies to
This low-water or pressure protection 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 water-pressure or low-water code can mean a genuine leak or empty system, a failed expansion tank, a faulty fill valve, or a sensor problem. The appliance does not distinguish these.
Safe things to observe
- Read the pressure gauge and compare it with the normal cold-system pressure your installer set.
- Look for drips or wet spots near the appliance, pipes and the relief-valve discharge.
Do not
- Do not keep re-pressurizing a system that keeps losing water.
- Do not cap a relief-valve discharge pipe.
How professional service helps
- A technician finds and repairs the leak, checks the expansion tank and fill assembly, and verifies the sensor circuit.
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.
Control board / PCB
The control board — also called the PCB, or printed circuit board — is the boiler's main computer.
What a technician checks →Transformer
The transformer is the small component inside the boiler that steps household 120-volt power down to the low voltage the controls use — typically 24…
What a technician checks →Low-water cutoff
A low-water cutoff is the safety device that stops a boiler from firing when there is not enough water inside it.
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…
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
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.