Lochinvar Crest Low Water Cutoff Open — Low Water Cutoff is not Making
Low Water Cutoff Open
Low water cutoff is not making. The low water cutoff is not making, so reset the LWCO from the RESET button on the front control panel, verify the system is full of water and all air has been purged, and check for loose or misplaced jumpers if the flow switch or LWCO is not installed. The table classifies it as Lockout (manual reset).
Applies to
This low-water or pressure protection code is displayed by the Crest control (text faults) on Crest with Hellcat models (FCB1000 through FCB6000), as documented in Crest with Hellcat (FCB) Service Manual, 100343237 Rev D — Table 3G fault codes (100343237 Rev D). Codes can differ between controller generations, so always check the manual that matches your unit.
- Lochinvar Crest (FB / Hellcat FCB)
- Lochinvar Crest FBN0751
- Lochinvar Crest FBN1001
- Lochinvar Crest FBN1251
- Lochinvar Crest FBN1501
- Lochinvar Crest FBN1751
- Lochinvar Crest FBN2001
- Lochinvar Crest FBN2501
- Lochinvar Crest FBN3001
- Lochinvar Crest FBN3501
- Lochinvar Crest FBN4001
- Lochinvar Crest FBN5001
- Lochinvar Crest FBN6001
- Lochinvar Crest FCB1000
- Lochinvar Crest FCB1500
- Lochinvar Crest FCB2000
- Lochinvar Crest FCB2500
- Lochinvar Crest FCB3000
- Lochinvar Crest FCB4000
- Lochinvar Crest FCB5000
- Lochinvar Crest FCB6000
Controller: Crest control (text faults). Source manual: 100343237 Rev D (2025-07).
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.
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 →Flow switch
A flow switch proves that water is actually moving through the boiler before it fires and while it runs.
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…
- Emergency Boiler Repair
Priority gas boiler repair for homes and buildings in Greater Vancouver with no heat, no hot water, a locked-out boiler or a leak.
Every boiler part explained — what it does, how it fails and what a technician checks.
Documented for Lochinvar Crest (FB / Hellcat FCB).
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
- Crest with Hellcat (FCB) Service Manual, 100343237 Rev D — Table 3G fault codes · 100343237 Rev D · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.