A Fujitsu multi-zone installation designed for three spaces, with a protected and perfectly integrated outdoor unit
At Saint-Roch-de-Richelieu, we completed an installation that clearly illustrates what a Fujitsu AIRSTAGE AQUILA XLTH three-zone heat pump can provide when a residence requires more precise comfort control in several rooms without multiplying the number of outdoor units. The principle appears simple: a single outdoor heat pump supplies three distinct indoor zones. In practice, however, the success of such a project depends greatly on choosing the right capacities, positioning the equipment, routing the refrigerant lines, and ensuring high-quality installation.
In the photo of this installation, the Fujitsu AIRSTAGE unit operating with R32 refrigerant is installed beneath a concrete slab, in a relatively confined side area. Rather than simply placing the unit on the ground, we mounted it on sturdy wall brackets, at a height that better protects it from water, ground-level accumulations, debris, and winter conditions.
This detail is especially important in Quebec. A heat pump operating during cold periods must maintain good airflow around the heat exchanger and have a suitable environment for its defrost cycles. The chosen location must therefore take the building into account, as well as what will happen around the unit in January and February—not just on the day of installation.
Why a three-zone heat pump was particularly well suited here
A multi-zone heat pump allows several indoor units to be connected to a single outdoor unit. In a three-zone configuration, three spaces can each have their own indoor unit and temperature setting.
This offers several advantages in a home where needs are not the same everywhere:
- A room exposed to the sun may require more air conditioning;
- a space on a lower level may require less cooling;
- a common area may have a much higher heating or cooling load than a small bedroom;
- some rooms may be occupied all day while others are occupied only in the evening.
With the Fujitsu multi-zone system, each indoor unit can be controlled individually. The documentation for the AIRSTAGE H Series Aquila and Aquila CTEB line also indicates that a single outdoor unit can supply multiple indoor units, with a connection capacity of up to 130%, depending on the authorized combinations. It also specifies that the system provides heating and cooling, but not both simultaneously in different zones.
This is an important distinction for a homeowner comparing a triple-zone heat pump with three separate single-zone systems. The three rooms have individual controls, but they share the outdoor unit’s overall operating mode.
Sizing a multi-zone system is not a matter of adding up three numbers
One of the most common mistakes when selecting a multi-zone system is thinking that it is enough to add up the rated capacity of three indoor units and choose the outdoor unit corresponding to the total.
Fujitsu provides authorized combination tables for its H series. For example, the documentation includes:
- the AOUH18KWAS2 / AOUH18KWAH2, which can connect up to two indoor units;
- the AOUH24KWAS3 / AOUH24KWAH3, which can connect up to three indoor units;
- the AOUH36KWAS4 / AOUH36KWAH4, which can connect up to four indoor units;
- the AOUH45KWAS5, which can connect up to five indoor units.
For a three-zone installation, several configurations may therefore be possible depending on the capacity required in each room. However, Fujitsu clearly states that its combination tables should not, by themselves, be used to select the system’s actual capacity and recommends using its Design Simulator to select AIRSTAGE equipment.
At AirGreen, this is exactly the distinction we make between a technically permitted combination and one that is genuinely suited to the building.
An outdoor installation beneath a slab that required careful planning
The configuration visible in Saint-Roch-de-Richelieu presented an interesting challenge: the space available for the outdoor unit was bounded by the home's wall, the upper concrete slab, and the nearby guardrail.
In such a situation, a few centimetres can make a significant difference.
We must consider, among other things:
Clearance around the coil
A heat pump must draw in and expel a significant amount of air. The outdoor unit should therefore not be treated as a simple appliance that can be placed in any available space.
In this installation, the front of the fan remains largely unobstructed. The positioning also keeps the unit accessible for future HVAC servicing, cleaning, and diagnostics.
The unit's height
We used a wall-mounted installation rather than installing the unit directly on the ground. This arrangement keeps the bottom of the unit away from the surface below.
In Quebec, this precaution can help reduce problems associated with snow accumulation, ice, and water produced during defrost cycles.
The supports and vibrations
The metal brackets are secured to the structure, and the unit rests on support points designed to limit direct vibration transmission.
With an Inverter compressor heat pump, the operating speed varies continuously. Properly installed mounting therefore contributes as much to equipment stability as it does to the occupants' acoustic comfort.
The line finish
The photo also shows the refrigerant lines protected by white outdoor line-hide covers. This finish is important for several reasons: it protects the lines, provides a much cleaner installation, and allows the mechanical routing to blend into the façade instead of leaving the lines exposed.
For a heat pump installation in Saint-Roch-de-Richelieu, this part of the work directly affects the project's durability and final appearance.
What this Fujitsu AQUILA XLTH installation delivers for the homeowner
A single outdoor unit for three comfort zones
One of the greatest advantages of this installation is immediately apparent: three indoor zones can operate with a single outdoor unit.
In some properties, installing three separate outdoor units would be technically possible but undesirable. They would take up more space, multiply the electrical connections, create more visible elements on the facade, and complicate the outdoor layout.
The Fujitsu triple-zone heat pump shown here centralizes heating and cooling production while maintaining separate control in each zone.
Inverter technology at the heart of operation
According to Fujitsu documentation for the H series, AIRSTAGE multi-zone systems use an inverter-driven compressor, commonly known as Inverter technology. The compressor can therefore modulate its operation rather than operating solely according to an on-off logic.
In a residence, this can allow the system to adjust its output more closely to actual demand.
This is particularly relevant in a three-zone system. If only one room requires a temperature adjustment, the demand placed on the system is not necessarily the same as when all three zones are operating at high capacity simultaneously.
R32: a new generation of Fujitsu systems
The visible marking on the outdoor unit of this installation clearly identifies the R32 refrigerant.
This point is worth mentioning, since the HVAC market in Quebec is moving toward new generations of refrigerants and equipment. Using a recent system also means that the installer must be familiar with the requirements applicable to the product, refrigerant connections, evacuation, and commissioning.
A successful installation therefore depends not only on the brand chosen. Even an excellent heat pump can deliver disappointing results when the refrigerant lines are improperly prepared, a connection leaks, or evacuation is neglected.
Interesting corrosion protection for the outdoor unit
Fujitsu documentation indicates that systems in this family use a blue-fin heat exchanger, designed to provide better corrosion resistance and help extend the coil’s service life.
This type of feature is particularly relevant in Greater Montreal and on the South Shore, where outdoor equipment is exposed for years to humidity, temperature fluctuations, snow, and contaminants in the environment.
Cold-weather heating: pay attention to the exact model reference
The documentation provided for Fujitsu Aquila and Aquila CTEB systems mentions heating operation for CTEB versions down to -26 °C. It also indicates cooling operation for these units up to 50 °C.
For this installation, the project is identified as a Fujitsu AQUILA XLTH triple-zone. However, the outdoor unit's complete model number is not sufficiently legible in the photo to attribute all the characteristics listed for each CTEB variant to this particular unit without reservation. At AirGreen, we always prefer to confirm exact performance using the model number and corresponding technical data sheet rather than automatically associating the characteristics of an entire product line with a specific unit.
The indoor units do not necessarily have to be identical
Another advantage of the Fujitsu platform is the ability, depending on the selected combination, to use several styles of indoor units.
The H series documentation notably presents:
Wall-mounted units
- ASUH07KPAS
- ASUH09KPAS
- ASUH12KPAS
- ASUH15KPAS
- ASUH18KPAS
- ASUH24KPAS
Slim Duct units
- ADUH07KUAS
- ADUH09KUAS
- ADUH12KUAS
- ADUH18KUAS
- ADUH24KUAS
The lineup also includes compact cassette and Mid Static Duct units in certain configurations.
This flexibility makes it possible, for example, to use a wall-mounted unit in a bedroom, another in an open area, and, when the building structure allows, a concealed unit in another part of the residence.
The mistakes we take particular care to avoid in a multi-zone installation
A triple-zone installation requires more planning than a simple system. Among the mistakes that can prove costly in the long term, we pay particular attention to:
- Oversized indoor units. An oversized unit does not automatically mean greater comfort.
- Incorrect capacity combinations. Not all indoor unit combinations are permitted with all outdoor units.
- Poor outdoor unit placement. An overly enclosed space can hinder airflow.
- Unnecessarily long or inadequately protected refrigerant lines.
- An improperly planned condensate drain.
- An installation that is too low for Quebec’s winter conditions.
- Insufficient access for future maintenance.
The Saint-Roch-de-Richelieu configuration clearly demonstrates the importance of considering all these elements before securing the first wall bracket.
An Approach Applicable in Montreal, Laval, Longueuil, the North Shore, and the South Shore
We carry out this type of HVAC installation in very different buildings throughout Montreal, Laval, Longueuil, the North Shore, and the South Shore. The technical principles remain the same, but each property imposes its own constraints.
In Montreal, we often have to work with extremely narrow side passages and façades where available space is limited. In Laval or on the North Shore, the distances between the rooms and the outdoor unit can be greater. In Longueuil and on the South Shore, we frequently encounter configurations where patios, balconies, foundations, and outdoor landscaping determine the best location for the unit.
In every case, our goal is not simply to “fit” a heat pump into the available space. Instead, we seek a configuration that remains logical for operation, maintenance, aesthetics, and everyday use.
The Result in Saint-Roch-de-Richelieu
This project brings together several elements we look for in a well-executed multi-zone heat pump installation: elevated equipment, sturdy mechanical supports, unobstructed airflow, protected lines, accessible equipment, and clean integration in a challenging location.
For the homeowner, the result is above all practical: a single Fujitsu outdoor system serves three spaces with individual control of the indoor units, while minimizing the amount of equipment around the residence.
This is precisely the type of project where a Fujitsu AIRSTAGE AQUILA XLTH triple-zone heat pump makes perfect sense. The unit is important, but the final quality also depends on sizing, combination selection, positioning, and execution details.
At AirGreen, we pay the same attention to these details for our installations of heat pumps, wall-mounted air conditioners, and multi-zone systems in Saint-Roch-de-Richelieu, Montreal, Laval, Longueuil, the North Shore, and the South Shore.