A homeowner's comparison of the Rinnai i-Series and the Lochinvar Noble Boiler, a condensing fire-tube heat-only boiler, with a focus on hot-water planning.
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The Rinnai i-Series is a condensing wall-hung boiler offered in solo (heat-only) and combi versions, and the Lochinvar Noble Boiler (NKB) is a condensing fire-tube heat-only boiler. Because the Noble Boiler only heats the house, the practical comparison is between a heat-only approach with separate hot water and an i-Series that can also be a combi. Sizing by heat-loss calculation, the hot-water plan and local service support decide the fit.
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Some boilers are built to do one job. The Lochinvar Noble Boiler, listed as NKB, is a condensing fire-tube heat-only boiler: it heats the water that circulates through radiators, baseboard or radiant floors, and leaves domestic hot water to something else. The Rinnai i-Series is a condensing wall-hung boiler that comes in a solo (heat-only) version and a combi version that also makes hot water.
That contrast frames the whole comparison. If you want a heating-only boiler, the i-Series solo and the Noble Boiler are the natural pair to compare. If you would like one unit to do both jobs, the i-Series combi is the only one of the two described as offering that. We describe both by type only, and we leave out outputs, sizes and efficiency figures because they depend on the exact model and belong to the manufacturers.
Heat-only boilers separate heating from hot water, and that separation has real advantages. Hot water comes from a stored source, so a household with several bathrooms is not limited by what a boiler can heat instantly. If the existing gas water heater is still in good shape, it can stay in service. If it is not, an indirect tank heated by the boiler is a common upgrade. The heating boiler then has one clear job, and problems with hot water do not automatically become problems with heating.
The trade-off is more components: a tank, extra piping and controls that give hot water priority. A combi reduces that parts list. Which side of the trade-off suits you depends on your household and your room.
| Consideration | Rinnai i-Series | Lochinvar Noble Boiler (NKB) |
|---|---|---|
| Type | Condensing wall-hung boiler | Condensing fire-tube heat-only boiler |
| Versions | Solo (heat-only) and combi | Heat-only |
| Hot water | Combi on demand, or solo with an indirect tank | Through an indirect tank or an existing water heater |
| Design description | See the manufacturer | Fire-tube heat exchanger |
| Best for | Compact homes wanting one unit, or heat-only with a tank | Homes wanting a dedicated heating boiler with separate hot water |
| Service and parts | Ask about local support | Ask about local support |
The similarity between the i-Series solo and the Noble Boiler is greater than the difference. The real fork appears when you consider the combi.
Homeowners who start with the boiler and work backwards to hot water often end up with an arrangement that frustrates them. Starting with hot water avoids that.
A heat-only boiler is sized from the heat-loss calculation alone, plus any allowance the designer makes for heating an indirect tank. Because there is no on-demand hot water load in the boiler itself, sizing tends to be cleaner. Outdoor reset control matters here as it does for any condensing boiler, because the more often return water is cool enough, the more often it condenses. We set the curve for your emitters and record it.
Both boilers serve all three emitter types. Radiant floors and baseboard run at gentle temperatures that suit condensing operation. Older cast-iron radiators need hotter water in the coldest weather, so the boiler condenses less on those days. That is normal and is one reason we check each radiator's output against its room. Radiant floors often need mixing arrangements to keep the floor supply within safe limits, and we design those alongside the boiler.
As condensing boilers, both generally vent through sealed pipe out an exterior wall and drain condensate through a trapped line. The manufacturers' manuals define approved materials, lengths and clearances. A heat-only boiler paired with an indirect tank adds no extra venting, but the tank needs floor space near the boiler. If an old boiler leaves a shared chimney, any remaining gas appliance's venting is reviewed as its own safety item.
Ask any installer what happens after they leave. Who services the boiler? Where do parts come from? How is the indirect tank, if there is one, maintained? A fire-tube heat-only boiler and a compact wall-hung boiler each have their own service considerations, and a technician who works on the equipment regularly will find faults faster. CANRO is not an authorized or factory dealer for Rinnai or Lochinvar. We are a licensed Metro Vancouver gas contractor with gas licence LGA0043870 and boiler licence LBP0046450, and we advise on the arrangement that fits the house.
A heat-only boiler with an indirect tank means a second insulated tank stands or hangs near the boiler and is heated by water from it. The installer arranges piping, a circulator or zone valve and controls so hot water gets priority when the tank calls for heat. It is a well-understood arrangement and a good one, but it needs floor or wall space for the tank, a permitted arrangement for its relief valve discharge and an eye on the mechanical room layout. In older Vancouver basements, where the room is already crowded, we measure before we promise anything.
If you are replacing a boiler and a gas water heater together, this arrangement can also let the old water heater and its vent go, simplifying the room. If the water heater is still sound, there is no need to remove it.
Because a heat-only boiler is not asked to make instant hot water, its heating performance does not compete with showers. Some homeowners find that reassuring, especially during the cold snaps that arrive in the Lower Mainland a few times a winter. Others are perfectly happy with a combi. The point is that the arrangement should match the way the household lives, not a brochure.
When we visit, we check the mechanical room, the gas supply, the route for vent and condensate, and the emitters in the house. We ask about hot-water habits and note whether a suite shares the system. We look at the state of the system water, the expansion tank and the piping around the current boiler. Those observations, plus the heat-loss calculation, let us describe the heat-only or combi arrangement that fits, and give a written quote with permit details.
We name no overall winner. The house and household decide. This comparison carries no pricing; the CANRO office gives a written quote after a short assessment.
Safety note
If you smell gas, leave the home immediately without touching switches, then call FortisBC at 1-800-663-9911 from outside. If a carbon monoxide alarm sounds, get everyone out and call 911. Boiler selection, installation and venting must be handled by a Technical Safety BC licensed gas fitter, following the manufacturer's installation manual.
It is described as a heat-only boiler, so hot water is typically provided through an indirect tank or an existing water heater.
Yes, the solo version heats the house only and, like any heat-only boiler, can be paired with an indirect tank or an existing water heater.
A combi suits compact homes and moderate hot-water use. Households with several bathrooms or overlapping use often prefer stored hot water.
Both are serviceable by a qualified technician. Ask how each is supported locally and how easy it is to reach the parts that need attention.
No. Condensing boilers generally vent through sealed pipe, though any other appliance left on a chimney must be reviewed.
No. CANRO is an independent licensed gas contractor that advises on which type suits each home.
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