Lochinvar Crest Manual Reset High Limit Open — Outlet Water Temperature Exceeded the Setting of the High Limit
Manual Reset High Limit Open
Outlet water temperature exceeded the setting of the high limit. The outlet water temperature has exceeded the setting of the high limit, so verify the system is full of water and all air has been purged, verify the boiler is piped properly, check voltage to the boiler pump motor on a call for heat, check the MRHL set point and the high limit device, check the resistance of the water sensors against Table 3B, and replace the high limit (if equipped) or the main control board. The table classifies it as Lockout (manual reset).
Applies to
This overheating 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
An over-temperature code protects the heat exchanger or venting; it does not reveal whether the cause is low water flow, a failed pump, trapped air, fouling or a sensor fault.
Safe things to observe
- Note the code and whether rooms or hot water are still working.
- If you see steam, melted wiring or smell burning, switch the appliance off at its service switch and call a technician.
Do not
- Do not reset the appliance repeatedly while the cause is unknown.
- Do not remove covers or bypass any high-limit device.
How professional service helps
- A technician checks pump operation, flow, system pressure and the cleanliness of the heat exchanger.
- 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.
High-limit switch
A high-limit switch shuts the burner off when boiler water gets hotter than it should, protecting the heat exchanger and the system from overheating.
What a technician checks →Boiler sensors (thermistors)
Boiler sensors are small temperature probes, usually thermistors, that tell the control how hot the water and flue gases are so it can fire safely…
What a technician checks →Control board / PCB
The control board — also called the PCB, or printed circuit board — is the boiler's main computer.
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…
- 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.