Canadian homeowners rarely choose between “a heat pump” and “no heat pump”. They choose between three retrofit paths, and the difference is mostly about what stays in the basement. Distributors who can frame that choice clearly win the quote; distributors who lead with an efficiency number usually end up arguing about price.
Here is how we at the factory describe the three paths, and the questions we ask before quoting one.
The three paths
Add-on. A heat pump outdoor unit is added to the existing furnace, which stays in place and continues to run as the primary or secondary heat source. The furnace’s blower, cabinet and ductwork are reused. This is the lowest-disruption path and the one most often taken when the furnace is mid-life and the air conditioner has failed.
Dual-fuel. A heat pump is matched with a furnace under a control strategy that switches between them. The heat pump carries the load in milder weather; the furnace takes over when capacity or cost favours it. In practice, add-on and dual-fuel blur together — the difference is how deliberately the changeover is designed and controlled.
Full replacement. The furnace and the cooling equipment are both replaced, typically when the furnace is near end of life, when the ductwork needs work anyway, or when the electrical service is being upgraded. The result is a single integrated system rather than two appliances sharing a cabinet.
What changes in each path
| Add-on | Dual-fuel | Full replacement | |
|---|---|---|---|
| Outdoor unit | New heat pump | New heat pump | New heat pump |
| Indoor coil | Usually replaced | Replaced | Replaced |
| Furnace | Kept | Kept, re-controlled | Replaced |
| Blower and airflow | Existing, often fixed-speed | Existing, verified against heat pump airflow needs | Selected for the new system |
| Controls | Changeover setpoint or lockout | Explicit dual-fuel logic | Designed together |
| Ductwork | Reused | Reused, often rebalanced | Reused or corrected |
| Electrical service | Frequently unchanged | Frequently unchanged | Often upgraded |
| Refrigerant lines | Reused where viable | Reused where viable | New lines |
| Documentation burden | Existing furnace data needed | Existing furnace data needed | One clean system file |
| Main risk | Mismatched indoor coil | Bad changeover logic | Cost and scope creep |
The single most common technical failure in the first two columns is the indoor coil. A heat pump runs in two directions; an old coil selected for cooling-only duty may not have been rated with the new outdoor unit, and a coil that was fine for air conditioning is not automatically part of a matched heat pump system. If the pairing cannot be documented, the honest options are to replace the coil or to describe the installation as unmatched.
The second most common failure is the controls. A heat pump that is set to hand over to the furnace too early spends much of the winter as an oversized air conditioner. One that is set to run too long in extreme cold will be fighting its own capacity curve. Dual-fuel logic exists precisely to make that decision deliberately, and it needs a thermostat that supports auxiliary and alternative heat staging.
Questions to settle before the design
Work through these in order. The answers usually make the path obvious.
- What is the age and condition of the furnace? Check heat exchanger condition and blower type. A furnace with several years of life left changes the economics of full replacement.
- What is the electrical service? Heat pump retrofits often add load. Confirm panel capacity and whether an upgrade is required before promising a scope.
- What is the existing coil, and can it be matched? Get the model number off the data plate. If it cannot be matched to the new outdoor unit, plan for a coil change.
- What is the ductwork capable of? Undersized ducts behind a variable-capacity system produce noise and comfort complaints that get blamed on the equipment.
- Where does the changeover happen? Set the balance-point strategy explicitly and record it in the commissioning notes.
- How cold does the design day actually get? Capacity and output fall as outdoor temperature falls. Determine the outdoor design temperature for the location and confirm the heat pump’s published capacity at that condition — per model, from the submittal sheet.
- What documentation will the homeowner need? Provincial and utility programmes, where they exist, ask for specific documents. Confirm what is required before installation, not after.
- What is the outdoor unit’s siting? Clearance, snow accumulation and defrost water drainage all affect a Canadian installation.
Where our own catalogue sits
We build both sides of the decision, which is unusual for a supplier and useful for a distributor.
- The furnace family covers 2, 3, 4 and 5 ton capacities at 95% AFUE, on R-454B, and is designed to pair with heat pump outdoor units for dual-fuel and add-on retrofits.
- The side-discharge outdoor unit is an inverter heat pump from 1.5 to 5 ton, up to SEER2 18, 220V/60Hz single phase, with 24V control. It is built to adapt to cassette, floor-ceiling, ducted and air-handling indoor units on one platform, and to work with multiple 24V controllers for field replacement of an aging condensing unit.
- Our A-Coil family is matched to our own outdoor units in three coil sizes, which removes the third-party compatibility guesswork from the retrofit.
- For the line set, the PEXFit multilayer pipe system covers 9,000–36,000 Btu and light commercial systems up to 5 ton, with a compression connection that adapts both to screw-valve and copper-tube-outlet equipment.
One thing we will not do is hand you a payback figure. Comparative energy and cost claims for a specific house depend on climate, envelope, fuel price, and existing equipment, and in Canada environmental and cost claims need testing to support them. Instead, evaluate any proposal on these four measures: the modelled heating load at the outdoor design temperature, the equipment’s published capacity at that temperature, the changeover strategy and its setpoints, and the documentation package the installer will hand over. If a proposal cannot show all four, it is a price, not a design.
Documentation to insist on
- Submittal sheets for both the outdoor unit and the indoor coil, with capacity at the relevant outdoor conditions, not only at rating conditions.
- The matched-system reference number for the exact combination being installed, where one exists.
- The Canadian certification mark on each nameplate — the “c” prefix version, or a combined mark — and the certificate details behind it.
- NRCan energy efficiency registration status for the models being imported.
- A commissioning record: airflow, refrigerant charge per the manufacturer’s method, changeover setpoints, and static pressure.
- A written statement of what was reused: furnace, coil, line set, thermostat.
For the wider picture on specification and compliance, the heat pump solutions hub and the A2L-ready overview are the next stops. If you have a project with a specific furnace and a specific outdoor unit in mind, send the models and the load calculation through our RFQ form and we will answer against that pairing rather than a generic catalogue page.