Installation of a Fujitsu AIRSTAGE Aquila XLTH dual-zone heat pump in Saint-Constant, on Montreal’s South Shore

A wall-mounted unit precisely installed in a simple, functional residential space

In Saint-Constant, we installed a Fujitsu AIRSTAGE Aquila XLTH dual-zone heat pump to improve the comfort of two distinct areas of the property using a single outdoor unit. This configuration makes it possible to heat and cool two zones from the same compressor while providing individual control of each indoor unit.

The photograph shows one of the wall-mounted units installed in a room with light-coloured walls, a standard ceiling, and few visible architectural features. This type of environment may seem simple, but it still requires careful planning. The choice of location directly affects air circulation, ease of maintenance, acoustic comfort, and the visual quality of the result.

The Fujitsu unit was positioned high on the wall, slightly to the left of the centre of the available section. This arrangement keeps the lower part clear for furniture while ensuring sufficient air coverage in the room. A wall controller is visible on the right, making it easier to access the settings without constantly having to handle a remote control.

This project illustrates our approach at AirGreen: we do not simply install a machine. We adapt each HVAC installation to the reality of the building, the occupants’ habits, and the physical constraints of the space.

Why a dual-zone heat pump was suitable for this property

A dual-zone heat pump connects two indoor units to a single outdoor unit. This solution is particularly suitable for homes where two areas have different needs.

For example:

• of a living room and a bedroom;
• of a ground floor and an upper floor;
• of an open-concept area and an office;
• of an older section and an addition;
• of two rooms with different sun exposure;
• of a main living area and a less frequently used zone.

In Saint-Constant, many properties combine open-concept rooms with enclosed bedrooms or finished basements. A single wall-mounted unit is not always enough to distribute air evenly throughout the house. A dual-zone configuration can therefore treat each area more precisely.

Fujitsu documentation for AIRSTAGE H Series multi-zone systems indicates that a single outdoor unit can power several indoor units. Each indoor unit can be controlled independently, allowing the temperature to be adjusted according to the specific needs of each room.

A high installation to promote air distribution

The unit visible in the photo is installed near the ceiling while maintaining clearance above the cabinet. This clearance is essential because room air enters the appliance through its upper section before passing through the filters and heat exchanger.

Installing the unit too close to the ceiling can reduce air intake and impair performance. It can also make it more difficult to open the front panel and remove the filters.

In this project, the installation height allows for:

• good air intake above the unit;
• wider air distribution throughout the room;
• an unobstructed lower louver;
• reasonable access to the front panel;
• discreet integration into the wall;
• preserving usable space for furniture.

The high mounting position also promotes cooling. Cool air naturally descends, which helps distribute the temperature throughout the occupied area. In heating mode, the louver should be directed farther downward to prevent warm air from remaining near the ceiling.

The importance of airflow direction

A properly sized heat pump can still cause discomfort if its airflow is poorly directed.

We therefore assess the unit’s position based on:

• the location of the bed or sofa;
• the direction of movement in the room;
• doors and openings;
• the height of the furniture;
• the presence of a workstation;
• the distance between the appliance and the occupants.

In the photo, the unit is installed on a relatively unobstructed wall. This position allows the airflow to travel through the room without being immediately blocked by a bookcase or tall piece of furniture.

During commissioning, we check different louver positions and several fan speeds. The goal is to find a setting that promotes an even temperature without creating a direct draft.

An easily accessible wall-mounted control

To the right of the unit, a small wall-mounted control can be seen. Depending on the exact configuration, this type of device can provide convenient access to the main settings.

Its location was chosen at an accessible height and at a distance from the indoor unit. A control should not be placed in an area directly affected by airflow, sunlight, or another heat source, as this could distort the perceived temperature.

A good control location should notably avoid:

• the unit’s direct airflow;
• a very sunny window;
• an exterior door;
• a heat-producing appliance;
• a cold or damp wall;
• an inaccessible area.

The presence of this controller makes the system easier to use, particularly for a unit installed high up.

Choosing the capacities for the two zones

The photograph does not show the complete model number or the indoor unit’s exact capacity. Several Fujitsu AIRSTAGE wall-mounted units may have similar cabinets while offering different capacities.

We therefore never determine the BTU capacity solely from appearance.

To choose each indoor unit, we consider:

• area;
• ceiling height;
• room volume;
• number of windows;
• solar orientation;
• insulation level;
• floor;
• exterior walls;
• air infiltration;
• number of occupants;
• daily use;
• heat-producing appliances.

Selecting a heat pump should not be based on an approximate square-footage formula. Two rooms of the same size may have very different requirements if one has a large south-facing window and the other is in the center of the building.

Combinations permitted by Fujitsu

The Fujitsu AIRSTAGE Aquila series is available with several outdoor unit capacities, including 18,000, 24,000, 36,000, and 45,000 BTU/h. Depending on the model, an outdoor unit can power two to five indoor units.

For an 18,000 BTU/h outdoor unit designed for a dual-zone configuration, the Fujitsu tables list the following combinations, among others:

• 7,000 + 7,000 BTU/h;
• 7,000 + 9,000 BTU/h;
• 7,000 + 12,000 BTU/h;
• 7,000 + 15,000 BTU/h;
• 9,000 + 9,000 BTU/h;
• 9,000 + 12,000 BTU/h;
• 9,000 + 15,000 BTU/h;
• 12,000 + 12,000 BTU/h.

These data are used to verify compatibility between the units, but they do not replace a thermal load analysis.

Fujitsu also specifies that its combination tables are not intended to be used on their own to select the system capacity. The manufacturer recommends using its Design Simulator software to select AIRSTAGE H series equipment.

Why the total capacity of the indoor units can exceed the outdoor unit’s capacity

In some multi-zone systems, the sum of the indoor units’ nominal capacities may be greater than that of the outdoor unit.

For example, an 18,000 BTU/h outdoor unit can be connected to two indoor units totaling 21,000, 22,000, or 24,000 BTU/h, depending on the permitted combinations.

This possibility is explained by the fact that the two zones do not always require their full capacity at the same time.

An open area may have greater demands in the afternoon, while a bedroom becomes the priority at night. In this context, some oversizing may be permitted.

However, it is important to understand that this configuration does not create additional capacity. Fujitsu clearly states that exceeding 100% in a combination does not increase the system’s heating or cooling capacity.

When both zones simultaneously call for maximum output, the available capacity is divided between them.

A multi-zone system with a shared mode

Each indoor unit can be controlled separately, but the two zones generally share the same main mode.

The system can:

• heat both zones;
• cool both zones;
• operate only one unit;
• maintain different temperatures;
• use different fan speeds.

However, it cannot actively heat one zone while the other is simultaneously operating in cooling mode.

Fujitsu documentation specifies that the system provides heating and cooling, but not both at the same time.

This feature is important to explain, especially during the transition periods in spring and fall. One room may become warm in the sun while another remains cooler. In this case, occupants must choose a consistent shared mode or temporarily use another heat source in a specific zone.

A system designed to provide consistent comfort throughout Quebec’s seasons

Heating down to -26 °C for cold-climate models

In Saint-Constant, as elsewhere on the South Shore of Montreal, winter heating is an essential criterion when choosing a heat pump.

Fujitsu documentation indicates that the Aquila CTEB cold-climate models can operate in heating mode down to -26 °C. It also states that they can operate in cooling mode up to 50 °C.

However, it is important to distinguish the minimum operating temperature from the capacity actually available at that temperature. Like all heat pumps, the system’s performance varies according to outdoor conditions.

To assess the role of the heat pump during the winter, we consider:

• the capacity available at low temperatures;
• the heat loss of each zone;
• window quality;
• insulation;
• airtightness;
• the presence of supplemental heating;
• the requested temperature;
• exposure to wind.

A low-temperature heat pump can significantly reduce the use of electric baseboard heaters or another existing heating system, but it must be selected based on the actual building.

Variable-speed technology

The Fujitsu system’s compressor uses inverter technology. This allows it to adjust its speed according to the demand from both zones.

When temperatures are far from the setpoints, the system can increase its output. As the rooms approach the desired temperature, it can reduce its operation rather than shut down completely.

This modulation helps to:

• maintain a more stable temperature;
• reduce frequent start-ups;
• improve acoustic comfort;
• adapt consumption to the load;
• limit sudden fluctuations;
• respond more precisely to the needs of both zones.

The Fujitsu documentation also mentions a blue-fin heat exchanger designed to improve corrosion resistance, as well as several built-in protections for the circuits, fan motor, and compressor.

The refrigerant line routing

Each indoor unit in a dual-zone system has its own circuit to the outdoor unit.

This circuit generally includes:

• a liquid line;
• a gas line;
• insulation;
• a communication cable;
• a condensate drain.

In the photo, no significant line-set cover route is visible around the unit. This integration suggests a discreet passage to the side or rear of the wall, depending on the property’s configuration.

When the building allows it, we favor a short, orderly route. This reduces the visual impact and limits the number of changes in direction.

Refrigerant connections must be made precisely. A slow leak can cause:

• reduced capacity;
• extended cycles;
• ice formation;
• increased energy consumption;
• poor heating;
• error codes;
• potential damage to the compressor.

We therefore perform leak tests and pull a vacuum before commissioning.

Condensate drainage

In air conditioning, the indoor unit removes moisture from the air. This water must be discharged through a drain.

When gravity drainage is possible, we aim to maintain a continuous slope. A proper installation must avoid upward bends, crushed sections, and improperly secured connections.

A drainage problem can cause:

• a leak on the wall;
• odors;
• a gurgling noise;
• an overflowing drain pan;
• a safety shutdown;
• damage to interior finishes.

In a room with light-colored walls like the one in the photo, a leak would quickly become visible. A complete drain inspection is therefore an integral part of commissioning.

Validation steps before handing the system over to the customer

A dual-zone heat pump installation is not complete when the units are merely mounted on the wall.

We check in particular:

1. the strength of the supports;
2. the level of the indoor units;
3. the tightness of the connections;
4. the quality of the vacuum;
5. the operation of each zone;
6. communication between the units;
7. drainage;
8. the movement of the louvers;
9. the response of the controls;
10. the absence of vibration or unusual noise.

We then explain to the owner how the system works in general, the limitations of multi-zone mode, and basic maintenance tasks.

Mistakes to avoid in a similar installation

Install the unit too close to the ceiling

Air must enter freely through the top. Insufficient clearance can reduce airflow.

Position the unit without considering the furniture

A sofa, wardrobe, or bed may receive the airflow directly or block its distribution.

Choose capacity based solely on floor area

Glazing, insulation, exposure, and floor level strongly influence requirements.

Confusing indoor capacity with outdoor capacity

A higher indoor reading does not mean that the compressor produces more.

Forgetting access to the filters

The front panel must be easy to open, and the filters must remain accessible.

Placing the wall control in the airflow

The temperature reading may be affected if the control receives hot or cold air directly.

Maintaining the Fujitsu indoor unit

The visible unit is installed at a height. The owner must therefore provide safe access for cleaning the filters.

Routine maintenance includes:

• regular filter cleaning;
• checking the airflow;
• monitoring unusual noises;
• checking for any signs of water;
• clearance above the unit;
• gentle cabinet cleaning.

Professional HVAC maintenance goes further by cleaning:

• the heat exchanger;
• the tangential fan;
• the condensate pan;
• the drain;
• the louvers;
• the internal surfaces.

A dirty fan can reduce airflow even when the filters appear clean. The system may then seem less efficient even though its cooling capacity is still available.

Eligibility for financial assistance

Eligibility for a subsidy cannot be confirmed solely from the photo or the Aquila XLTH name.

Verification generally requires:

• the complete model of the outdoor unit;
• the models of both indoor units;
• the AHRI number of the combination;
• the recognized capacity at the required temperature;
• the installation date;
• the detailed invoice;
• the criteria specific to the building;
• the rules of the program in effect.

Since the nameplate is not legible in the photo, no precise amount can be attributed to this installation based solely on the image.

A project adapted to the property's actual needs

This installation in Saint-Constant demonstrates that a multi-zone heat pump can integrate discreetly into a residential interior while providing precise control of two areas.

The Fujitsu AIRSTAGE unit was installed high on a clear wall, with good air circulation, accessible controls, and discreet visual integration. The dual-zone configuration allows the owner to control two spaces separately without multiplying the number of outdoor units.

For us, the work involved coordinating the positioning, capacity, airflow, drainage, refrigerant lines, and future access for maintenance.

At AirGreen, we install wall-mounted heat pumps, multi-zone systems, and HVAC solutions in Montréal, Laval, Longueuil, the North Shore, and the South Shore. Each project is adapted to the architecture, thermal loads, and actual use of the rooms.