In Saint-Damase, a triple-zone heat pump integrated into the heart of an interior renovation
Some multizone heat pump installations take place in fully finished homes, while others must be integrated into a construction site where the walls, coverings, and interior layout are still changing. This is precisely what this installation by our AirGreen team in Saint-Damase shows: a Fujitsu Aquila XLTH triple-zone heat pump, installed in a residence where renovation work was still visible when we carried out the installation.
The photo of one of the indoor units tells much of the story. The Fujitsu wall-mounted unit is positioned very high on a section of wall undergoing renovation, between a decorative block surface and a finished side wall. Beneath the unit, the wall covering is not yet complete, and some areas of the wall remain exposed. This context is important to us: it shows that an HVAC installation does not necessarily have to wait until the very last stage of a renovation. However, it must be planned early enough so that the location of the units, refrigerant lines, electrical supply, and drainage can be coordinated with the work that follows.
In this Saint-Damase home, the goal was to create three distinct heating and cooling zones while keeping a single Fujitsu outdoor unit. This approach makes it possible to treat different areas of the residence according to their actual needs rather than trying to control the entire home from a single point.
Why a multizone system was particularly relevant for this project
A home undergoing renovation often offers an opportunity to completely rethink how comfort is distributed.
In a conventional single-zone system, the temperature set in one room generally becomes the reference for a large part of the building. Yet, needs are almost never identical everywhere. A space with massive walls, a room exposed to the sun, and a bedroom on another floor can react very differently.
With a Fujitsu three-zone heat pump, we can distribute comfort across three distinct areas.
Fujitsu documentation for the AIRSTAGE H Series Aquila confirms that multi-zone systems can be paired with several types of indoor units: wall-mounted units, Slim Duct units, compact cassettes, or Mid Static Duct ducted units. The outdoor units offered in this family are available in nominal capacities of 18,000, 24,000, 36,000, and 45,000 BTU/h, depending on the number and type of indoor units to be connected.
For a three-zone configuration, the document notably shows that the outdoor unit AOUH24KWAS3 / AOUH24KWAH3 can accommodate up to three indoor units. Higher-capacity platforms allow more connections, depending on the selected combination.
However, the important point for a homeowner is not to look for the combination with the highest possible number of BTUs. Indoor capacities must be selected based on the actual rooms.
An indoor unit placed very high to promote air circulation
In the Saint-Damase photo, the wall-mounted unit is installed near the ceiling.
This location is generally advantageous for a wall-mounted heat pump because the conditioned air can be projected into the room rather than being immediately blocked by furniture or occupants.
However, positioning must take several details into account:
- the clearance required above and beside the unit;
- the ability to open the front panel to clean the filters;
- the direction of the airflow;
- the refrigerant line path;
- the condensate drain route;
- the presence of mouldings, beams, doors, or other obstacles.
In this installation, the unit was positioned on the upper portion of the wall that was available, leaving the lower area free for finishing and the room’s future layout.
This is something we often encounter during renovation and heat pump installation work: the chosen location must work today, but also after new materials, furniture, and decorative elements have been installed.
Installing during renovations can make for a cleaner finish
When a client consults us before the walls are fully closed, we often have more options for organizing the lines.
A wall-mounted heat pump requires several connections between the indoor unit and the outdoor unit: refrigerant lines, communication wiring and power supply depending on the configuration, as well as a condensate drain.
In a fully finished home, these components sometimes have to be concealed in visible line-hide covers. During a renovation, certain sections can sometimes be integrated or planned as part of the work.
The Saint-Damase photo clearly shows why coordination between the HVAC contractor and the finishing work can be advantageous. The wall around the unit was not finished when the photo was taken, allowing other trades to complete their work around a predefined HVAC location.
A zone should never be sized simply according to its area
When a homeowner tells us they want three indoor units, the next question is not automatically: “three units of how many BTUs?”
We start by looking at the three spaces.
A 300-square-foot room with several sun-exposed windows may have a very different load from a room of the same size located in the basement.
We consider, among other factors:
insulation, window dimensions, building orientation, ceilings, floors, solar gains, heat losses, and the actual use of each space.
Fujitsu documentation lists several wall-mounted unit capacities that can be included in multi-zone combinations: 7,000, 9,000, 12,000, 15,000, 18,000, and 24,000 BTU/h, depending on the configuration selected.
This means that, in certain permitted configurations, a triple-zone installation may combine three different capacities rather than three identical units.
Fujitsu tables are compatibility tables, not a load calculation
This distinction deserves particular attention.
In its own documentation, Fujitsu specifies that its combination tables are not intended to select system capacity. The manufacturer recommends using its Design Simulator software to select equipment for AIRSTAGE H series systems.
In other words, the fact that three units can technically be connected together does not automatically mean that this combination will be optimal for a given home.
At AirGreen, we apply this approach in our projects in Saint-Damase, Montreal, Laval, Longueuil, on the North Shore and South Shore: we always distinguish mechanical compatibility from actual sizing.
A high-performance HVAC installation begins with this distinction.
Three zones, three adjustable temperatures, but one outdoor system
The true advantage of individual zoning
According to Fujitsu documentation, each indoor unit in an AIRSTAGE multizone system can be controlled independently.
For occupants, this completely changes how temperature is managed.
A rarely used zone can be set differently from a living room occupied all evening. A bedroom can maintain a cooler temperature. A floor that tends to heat up more during the summer can have its own setpoint.
This principle is particularly appealing in a renovated property where the layout of the spaces is no longer necessarily the one planned during the original construction.
The Fujitsu Aquila XLTH triple-zone heat pump thus makes it possible to create more targeted comfort without adding multiple outdoor units to the façade or around the house.
What “independent control” does not mean
There is, however, an important nuance.
The indoor units can have their own settings, but they are all connected to the same outdoor unit.
Fujitsu states in its documentation that the system provides heating and cooling, but not simultaneously.
Therefore, one zone cannot be asked to actively heat while another simultaneously requests cooling.
For the vast majority of residences, this limitation is not problematic because the different rooms generally have the same seasonal needs. In January, all zones essentially need heating. In July, they primarily need cooling.
Nevertheless, we explain how this works before installation so that the owner knows exactly how the multizone system operates.
A combined capacity that can exceed the outdoor unit’s rated capacity
For certain configurations, Fujitsu tables allow a combined capacity of the indoor units greater than 100% of that of the outdoor unit. The documentation mentions a multizone connection capacity of up to 130%.
This figure must be properly understood.
This does not mean that a condenser with a given capacity suddenly produces 30% more power.
Fujitsu expressly specifies that exceeding 100% combined capacity does not increase the system's production capacity.
This connection flexibility instead takes into account the fact that all zones in a residence do not normally require their maximum capacity at exactly the same time.
This is one of the reasons why sizing a multi-zone system requires more thought than simply adding up the BTUs listed on the indoor units.
Inverter modulation adapted to variations between zones
The Fujitsu AIRSTAGE series described in the manufacturer's document uses an Inverter technology compressor.
For a three-zone system, this technology is particularly relevant.
The load varies continuously throughout the day. A single room may require heating upon waking. A few hours later, a second zone calls for heating. Then the sun warms one area of the home and demand decreases.
The compressor can adjust its operation to these changes rather than operating solely according to an on-off, full-capacity logic.
For the homeowner, this contributes to more gradual regulation and operation better suited to the varying needs of a multi-zone system.
A design intended for cold temperatures
The Fujitsu document presented with this project describes the Aquila and Aquila CTEB family and indicates, for the documented CTEB versions, cold-climate heating capacity down to -26 °C. It also indicates cooling operation up to 50 °C for these versions.
This data is particularly relevant in Quebec, where a heat pump must do more than provide effective cooling for a few weeks in summer.
For our heat pump installations in Montreal, Laval, Longueuil, Montérégie, on the North Shore, and on the South Shore, winter performance is an integral part of the selection process.
However, it is important to distinguish the general capabilities of the product line presented in the documentation from the exact specifications of each model and installed combination. Precise performance must always be confirmed using the technical data corresponding to the outdoor unit and indoor units actually selected.
An indoor installation that must also remain accessible
A wall under renovation can make you want to conceal as many elements as possible.
Nevertheless, we must maintain a balance between aesthetics and maintenance.
The wall-mounted unit must remain accessible so the owner can remove and clean its filters. A technician must also be able to open the casing during future HVAC maintenance, perform diagnostics, and access the internal components without having to dismantle part of the wall.
In the Saint-Damase project, the unit remains fully accessible from the front and top.
This accessibility may seem trivial when a unit has just been installed. It becomes much more important after five, ten, or fifteen years of operation.
What to plan around a wall-mounted unit during finishing work
When a room is still under construction, like the one shown in the photo, we recommend that subsequent work take several factors into account.
Do not block the unit’s air intake with molding that is too high, install a cabinet directly beneath the air outlet, or build a finish that would prevent the unit from being opened.
Painters and contractors must also avoid contaminating the unit with a significant amount of drywall or sawdust.
During major renovations, temporarily protecting the unit during very dusty work may be appropriate, provided, of course, that it is not operated while its air intakes or outlets are covered.
A visible detail in the photo that changes the entire way the project is perceived
The photographed room in Saint-Damase features textured blocks, an open section of wall, and several surfaces that have not yet been made uniform.
Rather than viewing this as a visual flaw, we see it as the precise moment when a heat pump installation can be integrated intelligently into a renovation.
Once the work is complete, much of the technical complexity disappears visually.
But they must have been resolved beforehand.
The drain must have the proper slope. The refrigerant lines must be correctly sized and connected. The openings must be positioned logically. The unit must be at the right height and in the right location before the final finishing work.
A mistake made at this stage may force the client to redo part of the wall later.
The errors we avoid on a triple-zone installation
A multi-zone project requires more coordination than a single-zone system.
Among the errors we seek to avoid are:
installing an indoor unit based on aesthetics alone, without considering airflow projection;
installing the same capacity in every room, without calculating the requirements;
choosing a combination solely because it appears in a Fujitsu table, without performing a sizing calculation;
forgetting the drainage slope, particularly when trying to conceal all the lines during a renovation;
positioning a unit too close to a ceiling, trim, or future piece of furniture;
closing the walls before confirming the routing of the HVAC lines;
and assuming that the sum of the indoor capacities automatically represents the capacity actually available simultaneously.
These are precisely the details that distinguish a simple appliance installation from a truly professional HVAC installation.
A single outdoor unit to reduce clutter around the house
In a triple-zone system, the homeowner could theoretically install three separate single-zone heat pumps.
This solution would require three outdoor units.
A multi-zone system, by contrast, allows several indoor units to be connected to a single compatible condenser. Fujitsu documentation indicates that the AIRSTAGE H Series platform can accommodate up to five indoor units, depending on the capacity of the selected outdoor unit.
In a home where preserving outdoor space is a priority, limiting the number of condensers can be a significant advantage.
This also reduces the number of visible elements around the property, which is often appreciated during a renovation when the homeowner is also investing in the building’s overall appearance.
The choice of indoor units can go beyond wall-mounted models
Even though the project photo shows a wall-mounted unit, the Fujitsu platform described in the document also allows for various integration options.
Fujitsu offers Slim Duct units, compact cassettes, and Mid Static Duct units, in addition to conventional wall-mounted units.
This can be beneficial in more complex renovation projects.
A bedroom can accommodate a wall-mounted unit, while a space where the homeowner wants to avoid a visible appliance could, depending on the combination’s technical possibilities, be served by a ducted or concealed solution.
This flexibility is one of the major benefits of a well-planned multi-zone system.
Our AirGreen approach to a multi-zone heat pump in Saint-Damase
For this installation, as with our other projects in Greater Montreal and the surrounding municipalities, we never consider the heat pump as an isolated appliance.
We look at:
the building, the rooms, the zones, the line routes, the areas being renovated, future maintenance, and how the occupants will actually use their system.
In a house undergoing renovations, this planning work is even more important.
The installation of this Fujitsu Aquila XLTH triple-zone heat pump in Saint-Damase illustrates this approach well: positioning the units before the final finishing work, coordinating the installation with the realities of the construction site, and creating three comfort zones from a suitable multi-zone outdoor system.
A heat pump should never be chosen solely based on a BTU rating
For a homeowner currently comparing systems in Saint-Damase, Montreal, Laval, Longueuil, on the North Shore or the South Shore, the technical specifications are important, but they tell only part of the story.
You should also ask:
What capacity will be installed in each zone?
Why were these capacities selected?
Are the exact combinations approved by Fujitsu?
How will the lines be routed?
Where will the drain run?
Will the indoor unit remain accessible after the renovation?
Where will the outdoor unit be installed, and how will it be protected against winter accumulation?
These questions make it possible to compare two quotes much more intelligently than by looking only at the price or the total number of BTUs.
At AirGreen, these are precisely the details we focus our work on. A Fujitsu triple-zone heat pump must be designed as a complete system, from the room where the indoor unit will be placed to the outdoor unit, which will have to operate during Quebec's cold days.
In this Saint-Damase project, the renovation gave us a particular context, but also an interesting opportunity: to integrate the HVAC system into the building at the right time, before everything was closed in and finished.
The desired result is simple to describe, even though it requires extensive technical preparation: three well-distributed zones, a clean installation, an accessible system for maintenance, and comfort adapted to the different areas of the house.