Installation of a GREE FLEXX R32 ULTRA central heat pump in a Dual Fuel configuration in Saint-Barnabé-Sud, MRC des Maskoutains

A central heat pump, a propane tank, and an old condenser lying in the yard: what a photo taken after nightfall reveals

In this photo, the new appliance is not the most informative element. What truly tells the story of the project is what surrounds it: a propane tank on the right, a yellow gas line running along the foundation, and the old air-conditioning condenser lying on its side, waiting to be loaded onto the truck.

These three elements define the type of installation carried out in Saint-Barnabé-Sud: a GREE FLEXX R32 ULTRA central heat pump installed in a Dual Fuel configuration, paired with an existing propane heating system.

Saint-Barnabé-Sud: no natural gas, propane, and bills that follow the market

Saint-Barnabé-Sud, in the Maskoutains RCM, is an agricultural municipality in the Saint-Hyacinthe area. The natural gas distribution network does not serve residences in the rural area. Homeowners who wanted something other than electric baseboards therefore historically turned to heating oil or propane, with a tank on the property and periodic deliveries.

Propane has a structural disadvantage that electricity does not: its price follows the market. One heating season can cost significantly more than the previous one without anything changing in the house. This is very often what prompts the call, more than comfort or environmental concerns.

Dual Fuel: two heat sources, one thermostat

How it works

A Dual Fuel system — literally dual-fuel — combines an electric heat pump with a fuel-burning heating appliance, in this case propane. The two never operate simultaneously. A control determines which one heats, based on the outdoor temperature.

Above a defined threshold, the heat pump heats on its own, with an efficiency of around 300% — it moves three units of heat for every unit of electricity consumed. Below this threshold, the control shuts off the heat pump and lets the propane furnace take over entirely.

The FLEXX ULTRA range is explicitly designed for this type of installation: it is advertised as compatible with Dual Fuel systems and works with a conventional 24 VAC thermostat, without requiring a proprietary controller. This is what makes it possible to integrate it with an existing heating unit from another brand.

The changeover point is economic, not merely technical

Here is the nuance that almost no contractor explains, and it is what determines whether the customer actually saves money.

With a heat pump + electric heating system, the changeover threshold is a technical balance point: the system switches over when the heat pump is no longer sufficient to cover the home's heat loss.

With a Dual Fuel system, that is not the right criterion. The heat pump may very well continue providing heat at -18 °C—but if, at that temperature, its efficiency has dropped enough that the delivered kilowatt-hour costs more than the propane equivalent, the system must switch over even though the unit could continue operating. Conversely, if propane is expensive that year, the threshold shifts lower.

The optimal changeover point is therefore an economic balance point that depends on three variables:

1. The electricity rate applicable to the customer.
2. The price of propane per litre, which varies from one year to the next and from one supplier to another.
3. The heat pump's actual performance curve based on the outdoor temperature.

How we determine it

We calculate this threshold during commissioning using the propane price the customer actually pays—not a provincial average—and program it into the control system. Then we invite the customer to call us after the first full season, or whenever there is a significant change in the propane price, so we can readjust it.

A threshold programmed once to the manufacturer's default value and never reviewed means a customer pays more than necessary for ten years without ever knowing it.

What Dual Fuel changes about system sizing

Here is one dual-fuel advantage that few homeowners know about—and one that has a direct impact on the project cost.

In a home heated solely with electricity, the heat pump is sized to target the lowest possible balance point, which drives capacities and costs upward. In a Dual Fuel system, the existing propane furnace already covers the entire load during very cold weather on its own—that is what it did before.

The heat pump therefore does not need to be sized for the design day. It should be sized for the mid-season load, meaning the temperature range in which the vast majority of the year's heating hours in Quebec occur—roughly between +10 °C and -12 °C.

The result: a more modest capacity, a lower investment, finer modulation, and coverage of the same proportion of heating hours. This is the reasoning that led us to a combination of 24,000 BTU/h here rather than an oversized unit.

Clearances around the propane tank

This is the central safety point of the project, and it is visible in the photo: the propane tank is a few metres from the outdoor unit, and the yellow gas line runs along the foundation beneath the unit.

The tank's relief valve

Every propane tank is equipped with a relief valve that, in the event of overpressure, vents gas into the atmosphere. The propane installation code (CSA B149.2) prescribes minimum distances between the discharge point of this valve and any ignition source, as well as any opening through which gas could enter a building.

An outdoor heat pump unit contains a contactor, an electronic control board, and a connection compartment. These are potential ignition sources under the code. The equipment location must therefore be planned with the tank's position and the direction of its discharge in mind—not the other way around.

The gas piping

The line supplying the house must not be crushed, used as a support, or exposed to a point where defrost water could fall and create an ice load. We check its route before securing the equipment supports, and we leave sufficient clearance for a gas technician to service it without removing the heat pump.

Two flammable gases on the same wall

The refrigerant R32 is classified A2L : mildly flammable. Propane is classified as highly flammable. The two present no risk of interaction in a compliant installation—they are completely separate circuits in distinct equipment—but their coexistence requires the installer to be familiar with both codes rather than just one.

This is a question to ask anyone proposing a heat pump for a property supplied by propane, in Saint-Barnabé-Sud as throughout Montérégie.

The old condenser on the ground: what happens to it after we leave

The old air-conditioning condenser, visible lying on its side to the right in the photo, is not ordinary scrap metal.

It still contains refrigerant—most often R22 or R410A, depending on its age. In Quebec, the Halocarbons Regulation prohibits releasing these substances into the atmosphere and requires their recovery by a qualified person using dedicated recovery equipment before any dismantling or disposal.

In practical terms, our procedure for every removal:

1. Recovery of the refrigerant into a labeled recovery cylinder before any piping is cut.
2. Removal of the unit and transport to a metal recycling facility that accepts refrigeration equipment.
3. Documentation in the customer file.

A contractor who cuts a refrigerant line with a pipe cutter and lets the gas escape—saving ten seconds—commits an environmental violation. It is an invisible detail on a quote, and that is exactly why you need to ask about it.

Anchoring to a concrete block wall

The wall is clad with concrete blocks, which simplifies part of the work compared with brick or vinyl siding: the block is a structural material capable of supporting a suspended load.

That does not eliminate the need for proper technique. A concrete block is hollow, and an anchor installed in an empty cell holds nothing. Anchoring must be done either in the block’s solid webs or with hardware specifically designed for hollow masonry—never in the mortar joints. The joints are the weak point of a block wall, and a vibrating load deteriorates them.

The vibration-isolating pads between the unit’s feet and the support arms complete the installation. On a masonry wall, vibration transmission is particularly effective: the material is dense and rigid, and it conducts the low frequencies from a compressor very well.

The gold-coated fins

Through the side grille, you can see the coil's gold-coated fins. In an agricultural area, this detail has practical value: ammonia fumes from livestock buildings are corrosive to aluminum, and a protective coating significantly slows fin deterioration.

Nevertheless, for properties located in the immediate vicinity of livestock facilities, we recommend rinsing the outdoor coil with clean water in spring and fall—at low pressure, never with a pressure washer, which irreversibly bends the fins.

The installed combination

Pricing, subsidies, and follow-up after the first season

Hydro-Québec's dual-energy rate

A Dual Fuel installation opens a door that a heat pump + electric heating installation does not: access to Hydro-Québec's dual-energy rate, designed specifically for buildings equipped with an electric heating system paired with a fuel-based system with automatic changeover.

The principle: electricity is billed at an advantageous rate above a threshold temperature and at a significantly higher rate below it—precisely when the customer heats with propane and therefore uses very little electricity for heating.

Eligibility, connection requirements, and the required metering equipment are validated directly with Hydro-Québec for each application. We prepare the necessary technical information, but we never promise eligibility that we do not control.

LogisVert: the propane incentive

Hydro-Québec's LogisVert program determines the incentive for an air-source heat pump based on its heating capacity at -8 °C, according to a rate of approximately $120 per 1,000 BTU/h, with a maximum of about $6,700. Enhanced amounts apply when the installation replaces heating oil or propane heating—exactly this home's profile, as well as that of many row houses in the MRC des Maskoutains.

Conditions: be a residential homeowner and a Hydro-Québec customer, have the work performed by a contractor holding an RBQ licence, and install an approved system that is ENERGY STAR certified and bears an AHRI number corresponding to the combination actually installed. Since the rates change periodically, we confirm the applicable amount for the project before including it in a quote.

What we measure after one winter

A Dual Fuel installation is evaluated based on figures, not impressions. After the first full season, we compare:

• The number of litres of propane consumed, compared with previous seasons.
• The electricity used for heating, available in the Hydro-Québec customer portal.
• The number of hours during which the system switched to propane, as shown in the equipment monitoring data.

These three figures allow us to adjust the changeover threshold for the following season. It is a fifteen-minute follow-up that makes the installation cost-effective year after year.

Our service area

At AirGreen, we install and maintain central heat pumps, wall-mounted heat pumps, and central air conditioning systems in Saint-Barnabé-Sud, Saint-Hyacinthe, and the MRC des Maskoutains, as well as in Longueuil, Boucherville, Châteauguay, and the Sorel-Tracy area. We also serve Montreal, Laval, the North Shore, and the South Shore.

If your home is heated with propane or heating oil and you want to know at what price per litre a heat pump becomes cost-effective for you, that is a calculation we perform before proposing anything—with your bills, not averages.