Slant/Fin All LEDs + temperature display (blinking alternately) — Safety High Limit Over-temperature Lockout
All LEDs + temperature display (blinking alternately)
Safety high limit over-temperature lockout. If the LED lights and the temp display are blinking alternately, the control has sensed a boiler temperature of 250°F. The control pulses the burner relay and then shuts down and locks out the burner until the temperature falls below 210°F. Analyze the system for the cause of overheating; check that the sensor is fully inserted in the well, system wiring and operation, and the control's high limit setting; replace the control if the cause cannot be determined. The table classifies it as lockout.
Applies to
This overheating code is displayed by the HydroStat 3200-Plus (LED diagnostics) on Sentry, Sentinel and Galaxy GG cast-iron models, as documented in HydroStat 3200-Plus control instructions (Sentry / Sentinel / Galaxy GG LED diagnostics). Codes can differ between controller generations, so always check the manual that matches your unit.
- Slant/Fin Sentry (S-34 to S-150)
- Slant/Fin Sentinel (SE-70 to SE-210)
- Slant/Fin Galaxy (GXH/GXHA, GXH-II and GG Series)
Controller: HydroStat 3200-Plus (LED diagnostics). Source manual: see sources.
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.
Burner assembly
The burner assembly is where gas and air meet and burn inside a boiler, and its condition decides whether combustion is clean or makes carbon…
What a technician checks →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 →
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 Slant/Fin Sentry (S-34 to S-150), Slant/Fin Sentinel (SE-70 to SE-210) and Slant/Fin Galaxy (GXH/GXHA, GXH-II and GG Series).
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
- HydroStat 3200-Plus control instructions (Sentry / Sentinel / Galaxy GG LED diagnostics) · accessed September 9, 2026
Facts checked September 9, 2026. Last updated September 9, 2026. Technical reviewer: not yet assigned.