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

An interior installation designed around two openings, a ceiling molding, and a very precisely defined circulation area

In Kahnawake, we installed a Fujitsu Aquila XLTH dual-zone heat pump to serve two distinct areas of the residence from a single outdoor unit. This project stands out mainly because of the interior configuration visible in the photo: one of the Fujitsu AIRSTAGE wall-mounted units was installed above two door openings, just beneath a ceiling molding, in an area where every available inch was important.

This type of configuration requires more than simply identifying a location visually. The unit had to be positioned to maintain adequate clearance from the ceiling, remain accessible for maintenance, avoid obstructing the door frames, and above all distribute air toward a central area of the home.

The photo also shows an adjacent room used as a laundry room, with a washer and dryer, as well as another opening leading to a living area. The choice of location therefore allows the unit to treat the air in a central circulation area rather than blowing directly into an enclosed corner.

Why a dual-zone heat pump was suitable for this Kahnawake residence

A dual-zone heat pump consists of an outdoor unit connected to two indoor units. Each indoor unit can be installed in a different area of the home and controlled separately.

This configuration is particularly interesting when two spaces have different comfort needs, for example:

• an upper floor and a ground floor;
• a main living area and a bedroom;
• a central corridor and a more remote area;
• a renovated section and an older section;
• two rooms that are not connected enough to be served by a single wall-mounted unit.

In this Kahnawake project, the presence of several closely spaced openings made positioning a unit in a circulation area particularly relevant. The airflow can therefore contribute to the comfort of the central area while allowing the other indoor unit of the dual-zone system to serve a second area more specifically.

The main advantage is that a single unit is not asked to artificially cover the entire residence. Two well-placed units generally provide a more consistent distribution of heating and cooling.

A wall-mounted unit installed above door frames

The photo highlights an important constraint: the Fujitsu unit is installed above two openings, with very little wall space available in the lower section.

We therefore had to check several elements before securing the wall plate:

1. the clear height between the door frames and the trim;
2. the upper clearance required for air intake;
3. full opening of the front panel;
4. access to the filters;
5. the movement of the lower louver;
6. the presence of solid structure behind the wall;
7. the direction of the airflow;
8. the condensate drain route;
9. the route of the refrigerant lines.

The unit could not be installed too low, as it would have visually and mechanically encroached on the openings. Nor could it be placed too high, as the trim and ceiling would have reduced the upper clearance.

The final positioning is therefore a precise technical compromise between the structure, maintenance, and air distribution.

Ceiling trim completely changes how the installation is measured

Decorative trim is immediately visible above the unit. This detail directly affects the installation.

We cannot simply measure the distance between the top of the unit and the unfinished ceiling. The trim creates a protrusion that can affect:

• air intake;
• panel opening;
• visibility;
• the clearance required for cleaning;
• the perception of alignment.

In a room with trim, the installation must be planned in relation to the most restrictive part of the architectural profile.

We also aim to maintain a clean visual line. A unit positioned askew relative to the trim or door openings immediately draws the eye, even if it operates correctly.

Air directed toward a passageway

Positioning the unit above the doors allows the air to be directed toward the central area rather than straight toward a nearby wall.

This arrangement is particularly useful in a home where rooms are connected by several openings. The conditioned air can circulate more naturally toward adjacent spaces.

This does not mean that a single unit can automatically cool all the rooms. A closed door, a narrow corridor, or a change in level can quickly limit the reach of the air.

That is precisely why we have a dual-zone heat pump here: a second indoor unit makes it possible to cover another area without overloading the one visible in the photo.

The laundry room’s proximity: an important detail for comfort

The opening on the left leads to a room where a washer and dryer can be seen. A laundry room may produce more heat and humidity than other rooms, particularly when the appliances operate for long periods.

Even if the wall-mounted unit is not installed directly in the laundry room, its proximity can help stabilize the temperature in the area when the door remains open.

However, a unit should not be installed directly in an environment where textile dust, humidity, or laundry products could accelerate buildup.

Choosing an adjacent location can therefore offer a good compromise: the unit contributes to comfort without being placed at the heart of the laundry area.

Fujitsu Aquila XLTH: a multi-zone range for cold climates

The Fujitsu AIRSTAGE Aquila range is part of the H-series multi-zone systems. According to the supplied Fujitsu documentation, the outdoor units are available in several capacities and can power different types of indoor units.

Page 2 of the document notably shows 18,000, 24,000, and 36,000 BTU/h outdoor units, while page 3 adds the 45,000 BTU/h model. Compatible indoor units may be wall-mounted, Slim Duct, compact cassette, or Mid Static Duct units.

For a dual-zone configuration, an 18,000 BTU/h outdoor unit can be connected to two indoor units in several approved combinations, including indoor capacities of 7,000, 9,000, 12,000, or 15,000 BTU/h.

However, the photo alone does not confirm the exact capacity of the indoor unit installed in Kahnawake. The complete model number would be needed to identify it unambiguously.

Heating down to -26 °C according to the CTEB range

Fujitsu documentation indicates that the CTEB units in this family are designed to operate in heating mode down to -26 °C and in cooling mode up to 50 °C.

This information is particularly important in the Montreal and South Shore region, where a heat pump must be selected based on its winter heating capacity.

However, the minimum operating temperature must be distinguished from the capacity actually available. A machine may continue operating at -26 °C without necessarily covering all of a residence’s heat loss on its own.

We therefore also analyze:

• insulation;
• airtightness;
• floor area;
• windows;
• exposed walls;
• ceiling height;
• the existing supplemental heating;
• the occupants’ habits.

Inverter technology in a two-zone configuration

Fujitsu documentation mentions an inverter-driven compressor. This means that the system can adjust its speed according to demand rather than operating only at full capacity.

In a two-zone installation, this advantage is particularly useful.

When only one indoor unit requires heating or cooling, the system can reduce its output. When both zones require more power, it can gradually increase its output.

This modulation promotes:

• more stable temperatures;
• longer cycles;
• fewer abrupt starts;
• better comfort;
• quieter operation at partial load.

Two independent zones, but not two opposing modes

Each indoor unit can be controlled separately. Occupants can adjust the temperature and fan speed in each zone.

However, the two units share the same refrigeration circuit. Fujitsu documentation specifies that the system provides heating and cooling, but not simultaneously.

This means that the two zones can:

• heat at the same time;
• cool at the same time;
• have different setpoints;
• operate at different times.

They normally cannot heat one room while the other simultaneously requires cooling.

This feature is important to explain, especially in homes where one zone receives a lot of sunlight while another remains cold.

A connected capacity of up to 130%

Fujitsu documentation also specifies that the multi-zone outdoor unit can accept a connected capacity of up to 130 % depending on the permitted combinations.

This offers greater flexibility when pairing multiple indoor units.

However, the manufacturer also specifies that exceeding 100% does not increase the system’s output capacity.

In other words, two indoor units can have a combined nominal capacity greater than that of the outdoor unit, but the outdoor unit will not produce more than its own maximum capacity.

Why this nuance is essential

In a home where both zones rarely require their full capacity at the same time, this flexibility can be useful.

In a house where both zones are always heavily used simultaneously, much greater caution is required.

A combination authorized by the manufacturer is therefore not automatically the best combination for every project.

Fujitsu tables do not replace a load calculation.

The documentation clearly states that combination tables must not be used to select system capacity. Fujitsu recommends using its “Design Simulator” software to select equipment from the H series.

This precision is important.

We do not choose a heat pump based solely on an approximate square-footage rule.

We take the following factors into account:

• the type of construction;
• insulation;
• glazing;
• orientation;
• air infiltration;
• ceiling height;
• solar exposure;
• the number of occupants;
• heat-producing equipment.

An oversized unit may run cycles that are too short. An undersized unit may run constantly without reaching the desired temperature.

Drainage in an installation above a door.

Installation above an opening also requires particular attention to drainage.

In cooling mode, the indoor unit removes moisture from the air. This water must be discharged through a pipe installed with an adequate slope.

A faulty drain at this location could cause a leak directly above a passageway.

We must therefore check:

• the drain slope;
• the continuity of the route;
• the absence of any reverse slope;
• the outlet point;
• the final drainage test.

When gravity allows, we favor this solution. A condensate pump is added only when necessary.

Future maintenance influenced the positioning.

Even when the unit is installed high up, it must be serviceable without removing the trim or door frames.

The front panel must be able to open, and the filters must be removable.

We therefore check that:

• the trim does not block the opening;
• the unit is not wedged between the frames;
• a stepladder can be placed under the appliance;
• The lower flap remains accessible;
• The technician can work without removing permanent components.

An appliance that is difficult to access is often maintained less effectively.

The filters must be maintained in both zones.

A dual-zone system means two indoor units, and therefore two sets of filters.

We recommend checking the filters regularly during periods of intensive use.

A dirty filter can cause:

• reduced airflow;
• increased noise;
• reduced comfort;
• longer operation;
• fan fouling.

Even a unit that is used less frequently should be inspected.

Mistakes to avoid in a similar configuration

Installing the unit too close to the moulding

This can reduce air intake and make maintenance more difficult.

Placing the unit too low above a door

The unit could encroach on the openings both visually and mechanically.

Directing the airflow toward a nearby wall

The airflow must have enough space to develop.

Neglecting the adjacent laundry room

The heat and humidity in this room can affect the heating and cooling load.

Choosing the BTU capacity based solely on floor area

The openings, orientation, and insulation must also be considered.

Forgetting that both zones share the outdoor unit’s capacity

The available capacity is distributed among the active units.

Setting opposite modes

A multi-zone system does not operate like two completely independent heat pumps.

Our post-installation commissioning

Once the units are installed, we carry out a series of checks before handing the system over to the occupants.

We check, among other things:

• the tightness of the connections;
• vacuuming;
• communication between the units;
• the operation of both zones;
• drainage;
• supply-air temperature;
• the louvers;
• vibrations;
• unusual noises.

We then explain how to use the remotes and the best practices for avoiding incompatible settings between the two zones.

A multi-zone installation adapted to the home’s actual layout

This Fujitsu Aquila XLTH dual-zone heat pump installation in Kahnawake perfectly demonstrates why the placement of an indoor unit should never be improvised.

The visible unit was installed above two door openings, beneath a ceiling moulding, in a passageway where available wall space was limited. This choice keeps the openings clear, preserves the wall surface, and directs airflow toward a central area.

At AirGreen, we install wall-mounted heat pumps, multi-zone systems, and central solutions in Montreal, Laval, Longueuil, the North Shore, and the South Shore.

Each HVAC installation is adapted to the building’s practical constraints: doors, windows, mouldings, foundations, piping routes, electrical supply, and access for maintenance.