IBC Technologies · Error codes
IBC SL G3 “Vent High Limit” alert
Error: Vent High Limit
The manual lists this alert when the exhaust (flue) gas temperature exceeds the venting material's limit — 248°F for six seconds or 232°F for 60 seconds with CPVC or polypropylene venting — and the boiler enters a hard lockout. The temperature ceiling protects the vent pipe material from softening or failing.
If a carbon-monoxide alarm sounds
- Leave the building immediately and get fresh air.
- Call 911. Do not go back inside until emergency services say it is safe.
- Have every fuel-burning appliance inspected before use.
Only after that, call ROMA about the boiler. Official guidance: Health Canada on carbon monoxide.
Applies to
This alert is shown by the V-10 touchscreen controller on SL Series G3 residential boilers (SL 10-85 G3, SL 14-115 G3, SL 20-160 G3 and SL 30-199 G3), as documented in IBC Installation & Operating Manual — SL 10-85 G3 / SL 14-115 G3 / SL 20-160 G3 / SL 30-199 G3, doc 120-276E13, sections 9.2–9.4.
Controller: V-10 touchscreen controller. Source manual: 120-276E13 (2026-08-11).
Why a code is not a diagnosis
The alert does not say why the flue gas is too hot. Possible causes include a return water temperature that is too high (the boiler is not condensing), a blocked or restricted vent or combustion-air path, a fan fault, or improper combustion. Each must be tested on site.
Safe things to observe
- Note the alert text and whether the boiler locked out during a heating call or on its own.
- From outside or a safe distance, check whether the vent terminal is blocked by snow, leaves, a bird nest, a cover left on after service, or debris.
- If a carbon-monoxide alarm sounds anywhere in the building, treat it as an emergency: leave, then call 911 from outside.
- Turn the boiler off at its service switch if you can do so safely and call a licensed technician.
Do not
- Do not keep resetting the boiler while the vent temperature problem is unresolved.
- Do not remove, extend or modify vent pipe yourself.
- Do not run the boiler with a suspected blocked vent to 'see if it clears'.
How professional service helps
- A technician checks return water temperature and the system design temperatures (a condensing boiler must receive cool return water).
- The vent and combustion-air paths are inspected for blockage, restriction or sagging, including the terminal.
- Combustion is measured with an analyser and the fan and venting are verified before the boiler is returned to service.
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 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 →
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 IBC Technologies SL Series G3.
Frequently asked questions
Does the vent high limit mean carbon monoxide is leaking?
Not necessarily, but a vent problem can create a CO risk, so treat any CO alarm as an emergency and call 911 from outside. A technician investigates the flue temperature fault before the boiler runs again.
What temperatures trip the vent high limit?
With CPVC or polypropylene venting the manual lists 248°F for six seconds or 232°F for 60 seconds; the VX manual adds lower limits of 205°F / 189°F where PVC venting is used.
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
- IBC Installation & Operating Manual — SL 10-85 G3 / SL 14-115 G3 / SL 20-160 G3 / SL 30-199 G3, doc 120-276E13, sections 9.2–9.4 · 120-276E13 · accessed September 7, 2026
Facts checked September 7, 2026. Last updated September 7, 2026. Technical reviewer: not yet assigned.