Installation of a Fujitsu AIRSTAGE Aquila XLTH dual-zone heat pump in Rivière-des-Prairies–Pointe-aux-Trembles, Montréal

A multizone solution integrated into an attic bedroom with particularly tight clearances

This installation of a Fujitsu AIRSTAGE Aquila XLTH dual-zone heat pump in Rivière-des-Prairies–Pointe-aux-Trembles perfectly illustrates the type of project where the quality of the result depends as much on the choice of equipment as on the precision of its positioning.

The photograph shows one of the indoor units installed in a bedroom beneath a sloped roof. The available wall space was limited by three major elements: a large window, a sloped ceiling, and a ceiling fan. It was therefore necessary to find a location that would ensure good air circulation without interfering with the windows opening, directing the airflow straight toward the bed, or compromising future access to the filters.

We installed the Fujitsu wall-mounted unit on the section of wall above the window. This choice preserves the available side surfaces, distributes the air toward the center of the room, and visually integrates the equipment into the attic architecture.

The visible result is simple and functional. The white unit stands out slightly against the blue-gray wall while remaining aligned with the window frame. Despite the ceiling slope on the right, the clearance required for the appliance's operation and maintenance was preserved.

An attic bedroom that required planning down to the centimeter

In a conventional room, a wall-mounted unit can generally be installed on several wall sections. In this bedroom, the options were much more limited.

The steep ceiling slope quickly reduces the available height on the right side. The ceiling fan occupies part of the central space, while the window covers most of the exterior wall. The positioning therefore had to meet several constraints simultaneously:

• maintain sufficient clearance above the unit;
• prevent the sloped ceiling from interfering with air intake;
• do not obstruct the window;
• keep the unit perfectly level;
• allow the front panel to be opened;
• distribute the air throughout the room rather than against the slope;
• limit the visual impact on the interior design;
• plan a logical route for the refrigerant lines and drain.

In this type of HVAC installation, a difference of a few centimeters can alter air circulation or make maintenance much more difficult. We therefore check the unit’s actual dimensions, the ceiling height, and the path of the louver before securing the wall plate.

Why the location above the window was the most logical

Installing an indoor unit above a window requires careful analysis, but this position can provide excellent results when it is technically feasible.

In this bedroom, this location offered several advantages:

• the exterior wall made it easier to route the piping;
• the air could be directed toward the back of the room;
• the side walls remained free for furniture;
• the unit was not directly above the bed;
• the window remained fully functional;
• the unit was installed in the highest available section of the wall.

The window is often an area of greater heat loss than insulated walls. In winter, the unit’s proximity helps better compensate for the cold-wall sensation around the glazing. In summer, the unit can also address the solar heat entering through the windows before it spreads throughout the bedroom.

The final choice, however, is never based solely on this principle. We must first confirm the available structure, the clearance required by the manufacturer, access to the drain, and the possibility of creating a clean opening.

Complete protection of the bedroom during the work

The photograph clearly shows that the furniture was covered before the work began. A large cover protects the bed or main piece of furniture, while a drop cloth has been placed on the floor beneath the work area.

This preparation is an integral part of our work method. A heat pump installation generally involves:

• drilling through the wall;
• securing a metal plate;
• handling copper piping;
• cutting certain materials;
• installing the cables and drain;
• sealing the openings;
• the final cleaning of the area.

Even when drilling is done carefully, small amounts of dust or debris may be produced. Protecting the furniture and floors reduces the risk of soiling and makes it possible to leave the room clean after the installation.

The presence of the stepladder, tools, and materials visible on the floor indicates that the photo was taken during the active construction phase. The indoor unit has already been installed, but the final checks and finishing work are still underway.

A dual-zone heat pump suited to the needs of two distinct spaces

Choosing a dual-zone heat pump makes it possible to serve two rooms or areas from a single outdoor unit.

This configuration is particularly relevant when the two zones have different thermal behaviors. An upstairs or attic bedroom, like the one shown here, can become much hotter in summer than a room on the ground floor. Heat naturally accumulates on the upper levels, and proximity to the roof sometimes increases heat gain.

A second zone can then be installed in a main living area, office, living room, or another bedroom. Each indoor unit has its own control, allowing the temperature to be adjusted according to the actual use of each room.

Fujitsu documentation for H-series multizone systems indicates that Aquila outdoor units can be connected to different types of indoor units, including wall-mounted models, compact cassettes, and ducted units. The outdoor model intended for two zones can power up to two indoor units.

Independent comfort in the two zones

Each indoor unit can be adjusted separately. In a family home, this independence makes it possible, for example, to keep the bedroom cooler at night without imposing the same temperature throughout the house.

Occupants can generally adjust:

• the set temperature;
• the fan speed;
• the louver direction;
• the operating mode;
• the timer;
• certain comfort features specific to the controller.

Nevertheless, an important rule applies to multizone systems: the two indoor units connected to the same compressor must operate in compatible modes.

Fujitsu documentation specifies that the system can provide heating or cooling, but not both simultaneously. One zone therefore cannot call for heating while the other calls for cooling.

This feature should be explained to the homeowner, especially during the shoulder seasons. In a home where an attic bedroom receives a great deal of sunlight, it can become hot while a lower room remains cooler. The mode selection must then be coordinated between the zones.

Fujitsu Aquila XLTH: a design intended for cold climates

In Rivière-des-Prairies–Pointe-aux-Trembles, a heat pump must be selected to operate under Montréal’s actual conditions, not merely to provide cooling for a few weeks in summer.

The Fujitsu Aquila series designed for cold climates is engineered to provide low-temperature heating. The documentation supplied for the CTEB models indicates heating operation down to -26 °C. It also states that the system can operate in cooling when the outdoor temperature reaches up to 50 °C.

This operating range is particularly relevant for a bedroom located beneath a roof, as the room may experience both extremes:

• substantial heat buildup on sunny days;
• significant heat loss during cold nights;
• faster temperature changes than on lower floors;
• greater discomfort near sloped surfaces.

A cold-climate heat pump helps maintain a more stable temperature, but it must always be sized according to the building’s actual heat losses.

Capacity should not be selected based solely on floor area

Estimates based solely on square footage are common. This method is too approximate for properly selecting a heat pump.

In an attic bedroom, several factors can increase the heat load:

• the roof area directly above the room;
• insulation in the attic or sloped walls;
• the size and orientation of the windows;
• sun exposure;
• air infiltration;
• the ceiling height and shape;
• the number of occupants;
• the electrical appliances in the room.

A modest-sized room may require special attention if it overheats significantly in summer. Conversely, an oversized unit can cause short cycling, cool the room too quickly without adequately dehumidifying it, and produce comfort fluctuations.

At AirGreen, we view the property as a whole. For a dual-zone heat pump, we assess not only each room’s load but also the simultaneous demand of both zones.

Fujitsu combinations must be approved

The fact that an outdoor unit has two connections does not mean that all indoor capacities can be combined arbitrarily.

For Fujitsu 18,000 BTU/h outdoor units designed for two zones, the combination table includes the following nominal 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 combinations indicate the technical compatibility of the units, but they do not, on their own, determine the appropriate capacity for the home. Fujitsu states in its documentation that the tables should not be used directly to select system capacity and recommends using its Design Simulator software for H-series AIRSTAGE equipment.

A higher indoor capacity does not create additional outdoor capacity

Certain permitted combinations have a nominal capacity greater than that of the outdoor unit. This practice may be appropriate when the two zones do not require their full capacity at the same time.

However, Fujitsu clearly states that exceeding 100% of the connected capacity does not increase the system’s output capacity.

For example, if both indoor units simultaneously call for maximum capacity, the compressor must distribute the actually available capacity between the two zones. That is why sizing must take into account usage patterns, room orientation, and the periods when demand may overlap.

In this project, the attic bedroom represents a zone that may experience high cooling demand. The second zone therefore had to be analyzed in parallel to avoid an unbalanced selection.

Inverter modulation improves temperature stability

The Fujitsu AIRSTAGE series uses an inverter-controlled variable-speed compressor.

This technology allows the system to adjust its output according to demand. Instead of operating only at full capacity and then stopping, the compressor can reduce or increase its speed.

In a bedroom, this modulation offers several benefits:

• a more stable temperature;
• fewer abrupt changes during the night;
• a more consistent noise level;
• fewer repeated starts;
• better adaptation when only one zone requires heating or cooling.

Fujitsu documentation associates this inverter-driven compressor with improved comfort and energy efficiency. It also mentions built-in protection for the circuits, fan motor, and compressor.

Air distribution in a room with a sloped ceiling

The sloped ceiling influences how air moves through the bedroom.

In cooling mode, cold air tends to descend. A unit installed high above the window can therefore project the air toward the center before it gradually spreads throughout the occupied area.

In heating mode, warm air naturally rises. The louver’s direction is therefore important to push the air downward and prevent it from accumulating near the ceiling.

During commissioning, we check:

• the complete opening of the louver;
• the absence of obstacles in front of the air outlet;
• airflow reach;
• the room’s response;
• comfort near the bed;
• the effect of the ceiling fan on air circulation.

The fan visible in the photo can also help even out the temperature when used at low speed and with the correct direction of rotation. However, it must not directly disrupt the unit’s air outlet.

An installation above a window requires impeccable drainage management

In cooling mode, the indoor unit removes moisture from the air. This water is collected in a drain pan and then carried away through a drain.

When the unit is placed above a window, a leak could damage:

• the frame;
• the paint;
• the trim;
• the window mechanism;
• the wall beneath the unit.

The drain must therefore be installed with an appropriate slope and tested before the work is completed.

We check, in particular:

1. the wall plate’s level;
2. the unit’s position on its hooks;
3. the drain slope;
4. no kinks in the hose;
5. a watertight connection;
6. drainage to the outlet;
7. sealing around the exterior penetration.

A slightly tilted indoor unit can disrupt drainage in the pan. That is why leveling is a technical step, not merely an aesthetic one.

The details that distinguish a clean installation from an improvised one

Choosing the line route

A dual-zone heat pump requires a separate route between the outdoor unit and each indoor unit.

This route generally includes:

• the refrigerant lines;
• the communication cable;
• the required wiring;
• the condensate drain;
• exterior or interior protection.

In this bedroom, the presence of an exterior wall behind the unit made a relatively direct route possible. A short route can reduce the amount of visible trim and facilitate gravity drainage.

However, drilling must avoid the studs, electrical cables, and structural elements around the window. In older buildings in Rivière-des-Prairies–Pointe-aux-Trembles, the actual wall composition may vary depending on renovations carried out over the years.

Evacuating the refrigerant circuit

Once the lines are connected, the circuit must undergo a complete evacuation.

This step removes:

• air;
• moisture;
• non-condensable gases;
• contaminants present in the lines.

Residual moisture can react with compressor oil, reduce efficiency, and contribute to the formation of contaminants in the circuit. A heat pump may appear to work after improper commissioning, but develop premature problems several months or years later.

Professional commissioning also includes a leak test, checking the electrical connections, and testing both zones.

Common mistakes to avoid in an attic bedroom

Installing the unit too close to the sloped ceiling

The air intake on top can be restricted, reducing airflow and increasing noise.

Directing the air directly at the bed

A continuous cold draft can cause discomfort, even when the room’s overall temperature is comfortable.

Neglecting the front panel

The unit must be able to open for filter cleaning and HVAC maintenance.

Drill without checking the surrounding window structure

This area may contain lintels, reinforced studs, or wiring.

Install a drain without sufficient slope

Poor drainage can cause a leak onto the window or wall.

Choose excessive capacity to compensate for an insulation problem

A heat pump does not replace an adequate thermal envelope. Insufficient insulation should be taken into account in the calculation and, when possible, corrected.

Maintenance of a heat pump installed in a bedroom

An indoor unit installed in a bedroom must remain clean to preserve airflow and comfort quality.

The filters should be inspected regularly, particularly if the room contains textiles, pets, or a lot of dust.

Periodic maintenance includes:

• cleaning the filters;
• inspection of the heat exchanger;
• cleaning the fan when necessary;
• inspection of the drain pan and drain;
• checking for unusual noises;
• inspection of the outdoor unit;
• confirmation of the performance in both zones.

The fact that the unit is installed above the window must also be considered when planning the room in the future. Curtains, blinds, or decorations must not block the air intake or outlet.

A representative example of our work in Greater Montreal

This installation in Rivière-des-Prairies–Pointe-aux-Trembles shows that a complex room is not necessarily incompatible with a wall-mounted heat pump.

The sloped ceiling, window, fan, and furniture limited the options, but a precise assessment allowed us to identify a functional, clean installation location. The Fujitsu indoor unit fits into the upper part of the wall without obstructing the bedroom’s architecture.

At AirGreen, we install heat pumps, wall-mounted air conditioners, and multi-zone systems in Montreal, Laval, Longueuil, the North Shore, and the South Shore. Each project is adapted to the building’s constraints rather than reproduced according to a one-size-fits-all formula.

For this Fujitsu Aquila XLTH dual-zone heat pump, the essential considerations were clear:

• select a compatible combination;
• size both zones together;
• use the available space above the window;
• maintain clearances despite the sloped ceiling;
• ensure good air distribution;
• protect the bedroom during the work;
• perform a complete commissioning;
• ensure reasonable access for maintenance.

The result gives the occupants direct control over the comfort in this attic bedroom while using a single outdoor unit to serve two zones. This is a particularly relevant solution for homes where the upper floors overheat in summer or lose heat quickly during Montreal winters.