IBC boilers are generally reliable modulating units, but modulation-related faults, condensate issues, and sensor drift account for most of our service calls.
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Quick answer
The issues we see most often on IBC gas boilers involve the modulation and outdoor reset controls drifting out of expected behaviour, condensate drainage blockages, low or fluctuating system pressure from a failing expansion tank, and sensor or control faults that trigger a lockout. Most of these are maintenance-related or tied to water quality and system condition rather than the boiler's core design being unreliable.
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IBC is commonly documented as manufacturing modulating condensing boilers, often paired with outdoor reset controls that adjust supply water temperature based on outdoor conditions. This gives excellent comfort and efficiency when it's working as intended, but it also means there are more sensors and settings involved than on a simple on/off boiler, and any one of them drifting or failing can produce symptoms that look confusing to a homeowner, uneven heat, a boiler that seems to run constantly at low output, or temperatures that don't match the thermostat setting.
Diagnosing a modulation issue usually starts with reviewing the outdoor reset curve settings against actual conditions, then checking the outdoor and supply sensors for accurate readings before assuming a bigger fault.
Like other condensing boilers, an IBC unit produces acidic condensate that needs to drain reliably, usually through a small trap and line to a floor drain or condensate pump. Over time, sediment or biological growth can partially block this path, and because many boilers monitor condensate flow as a safety measure, a blockage often shows up as a shutdown or fault condition rather than a visible leak first.
A slowly dropping system pressure, or pressure that fluctuates as the system heats and cools, often points to a failing expansion tank rather than a leak in the piping itself. The expansion tank absorbs the water's expansion as it heats; when its internal bladder or pre-charge fails, the system pressure swings more than it should, sometimes tripping a low-pressure fault.
A modulating boiler relies on several temperature sensors, supply, return, outdoor, and sometimes a flue sensor, and any one of these giving an inaccurate reading can trigger a protective lockout even when the underlying combustion process is fine. This is one area where a technician's diagnostic tools matter, since confirming which specific sensor is out of range is far more useful than guessing based on symptoms alone.
| Symptom | Likely Cause | What Gets Checked |
|---|---|---|
| Uneven heat, unexpected output | Modulation/outdoor reset drift | Reset curve settings, sensor accuracy |
| Boiler shuts down, condensate-related fault | Drainage blockage | Trap and line condition |
| Pressure fluctuates or drops | Expansion tank or small leak | Pre-charge, visible fittings |
| Unexplained lockout | Sensor fault | Individual sensor readings against expected range |
Safety note
If you ever smell gas, hear hissing near a gas line or appliance, or suspect a leak, leave the home immediately and call from outside. Do not flip switches, light anything, or use a phone inside the house. Call FortisBC at 1-800-663-9911 to report a suspected gas leak or carbon monoxide concern before doing anything else. Gas piping, venting, and combustion appliance work in BC must be done by a Technical Safety BC licensed gas fitter; CANRO holds gas licence LGA0043870 and boiler licence LBP0046450.
This is often normal modulating behaviour on a mild day, but if it's paired with rooms not reaching set temperature, it's worth having the outdoor reset settings and sensors checked.
It's not an immediate emergency, but it does indicate a pressure problem that should be looked at soon rather than ignored, since it usually points to an expansion tank or overpressure issue.
Many boilers allow a manual reset, but if it locks out again shortly after, that's a sign of an underlying fault that needs diagnosis rather than repeated resetting.
There's no fixed schedule we'll promise, but a tank that's losing pre-charge is a common age-related failure worth checking during annual service.
Metro Vancouver's municipal water is generally soft, but any hydronic system can accumulate scale or sediment over years, which is part of why water quality gets checked periodically.
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