Rinnai i-Series vs NTI FTV: Boiler Comparison

Need a licensed gas fitter for your gas boiler? Call CANRO at (604) 359-1081 — residential natural-gas heating and hot water across Metro Vancouver since 1999.

The realistic reader of this comparison

The people who search for this comparison usually own an FTV already. The NTI FTV is a discontinued condensing fire-tube boiler, so a new buyer cannot simply choose it; an owner is instead asking whether to keep it running or move to something current like the Rinnai i-Series. The i-Series is a condensing wall-hung boiler with solo (heat-only) and combi versions.

We describe both by type only, and we leave out outputs and efficiency numbers because they belong to the manufacturers' documents and vary by model. What we can share is what we see in the field when an FTV reaches the point where its owner starts asking questions.

Common ground: both are condensing boilers

Because the FTV is already a condensing boiler, a replacement with the i-Series does not change the basic idea. Both recover extra heat from the exhaust when the water returning from the house is cool enough, both produce condensate that must run to a drain, and both generally vent through sealed pipe. That is helpful, because it means much of the existing installation, the vent route and the condensate drain, may already suit a condensing replacement, unlike a swap from an old chimney-vented boiler where everything changes.

The differences are in format and features. The i-Series hangs on a wall and can be a combi that makes domestic hot water on demand. Whether your FTV is wall-mounted or floor-mounted, the mounting arrangement is part of the assessment, and the manufacturer's documentation for the specific unit tells you.

How service and parts look for a discontinued FTV

We are open about the limits of servicing a discontinued boiler. CANRO services FTV boilers and sources parts where they are available. Ordinary wear parts such as ignition components, flame sensors, pumps and condensate trap parts are generally the easier repairs. Major items such as a leaking heat exchanger or an unavailable control board are where a repair may become impractical, and that is the moment to talk about replacement.

Comparing the two side by side

The similarities are stronger than the differences, which is why an FTV replacement can often be a tidier job than a swap from an older, non-condensing boiler.

What replacing an FTV involves

1. Assess the boiler, its mounting, the piping, vent, condensate and gas supply.
2. Calculate heat loss room by room, since the house may have changed since the FTV was sized.
3. Decide the hot-water plan: combi, indirect tank, or an existing water heater.
4. Check the existing vent and condensate arrangements against the new boiler's manual.
5. Quote in writing, arrange the gas permit through Technical Safety BC.
6. Remove the FTV, install, commission and check combustion.

In many FTV replacements the vent and condensate work is reused or lightly modified, but we confirm with the new boiler's installation manual rather than assuming the old arrangement is acceptable.

Piping and system health matter more than the box

A boiler replacement is the best moment to fix the things around the boiler. We look at air separation, dirt removal, isolation valves, the expansion tank and the condition of the system water. A condensing boiler that has run for years on unprotected, dirty water often shows it in its heat exchanger, and putting a new boiler onto the same dirty water repeats the problem. Cleaning and protecting the system at replacement is part of a sound job, not an upsell.

Radiators, baseboard and radiant floors

The system the FTV serves stays. The i-Series is compatible with baseboard, radiant floors and cast-iron radiators, with the water temperature managed by controls so that it condenses as often as the emitters permit. Homes with older radiators that need hotter water in the coldest weather should expect somewhat less condensing on those days, which is normal.

A short case: the FTV that outlived its parts

A typical story goes like this. A homeowner has had their FTV serviced regularly, and it has run without much fuss. One winter the control board fails. The technician checks whether the board can be found, and it turns out to be slow or impossible to source. The rest of the boiler is sound, but there is now a choice between waiting and hoping, or replacing the boiler on a planned schedule. Because the FTV is already a condensing boiler, the venting and condensate arrangements are often reusable, so the replacement is tidier than it would have been from an older, non-condensing unit.

We share this not to alarm anyone but to explain why we suggest keeping a service record, noting which parts have already been replaced, and thinking ahead about the day a major part cannot be found.

What a good service record looks like

A useful record lists the date of each service, the combustion readings, the condition of the burner, sensors and condensate trap, any parts replaced, the system pressure, and anything the technician flagged for follow-up. Photos of the boiler's data plate and settings are helpful too. If you ever change contractors, or if the boiler is replaced, that record shows exactly what the system has been through and helps the next technician avoid repeating the diagnosis from scratch.

Timing the change around the heating season

Owners of a discontinued boiler often ask when to act. If the FTV is healthy, there is no rush. If it has begun to show signs of age, such as recurring lockouts, moisture near the heat exchanger or a pump that groans, the sensible window is the warm part of the year, when the house can go without heat for a day or two and there is time to arrange the permit and equipment. In the Lower Mainland, where winters are wet and mild with occasional cold snaps, that window is long. Waiting for a failure in the middle of a cold week narrows every option, including the choice of equipment and the date.

Deciding whether to keep or replace

A serviced FTV that runs well does not need replacing because of its status. When repairs pile up, parts become hard to find or a heat exchanger fails, planning the swap in mild weather beats a January emergency. We give owners an honest view either way. CANRO is not an authorized or factory dealer for Rinnai or NTI; we are a licensed Metro Vancouver gas contractor with gas licence LGA0043870 and boiler licence LBP0046450. This comparison carries no pricing; the CANRO office gives a written quote after a short assessment.

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