Installation of a Fujitsu Aquila XLTH dual-zone heat pump in Sainte-Thérèse, on Montreal’s North Shore

Two comfort zones combined in an understated wall-mounted installation adapted to the available space

At Sainte-Thérèse, we installed a Fujitsu Aquila XLTH dual-zone heat pump to heat and cool two distinct areas of a home using a single outdoor unit. The project required careful planning of the indoor units’ locations, since the photographed room has a large wall surface, an adjacent opening, and a window with a roller shutter in the neighboring space.

One of the Fujitsu AIRSTAGE wall-mounted units was installed high up, near the ceiling, on an unobstructed wall. This location keeps the entire lower portion of the wall available while directing airflow toward the occupied area. The unit’s white front panel and simple lines blend naturally with the light interior finish.

An installation that looks understated once completed is nevertheless based on several technical decisions. The right combination of equipment must be selected, clearances confirmed, the refrigerant line route anticipated, drainage organized, and the unit’s serviceability verified without having to modify the room.

In this Sainte-Thérèse home, the goal was therefore not simply to add two sources of heating and cooling. We had to create a cohesive multi-zone system capable of meeting the occupants’ actual needs while respecting the building’s existing layout.

Why a dual-zone system was the right choice for this project

A dual-zone heat pump consists of an outdoor unit connected to two indoor units. Each unit serves a specific area of the home and has its own control.

This solution is particularly relevant when a home has two areas that respond differently to temperature variations, for example:

• an upper floor and a ground floor;
• a living room and a bedroom;
• a room exposed to the sun and a more shaded area;
• an open area and an enclosed room;
• a renovated area and an older section;
• two separate areas that cannot be served efficiently by a single wall-mounted unit.

A single unit installed in a hallway cannot always circulate air through several doors, partitions, and changes in level. Instead, the dual-zone system makes it possible to place each unit where it can genuinely affect comfort.

In this project in Sainte-Thérèse, this approach also helps limit the number of outdoor units around the house. The two indoor units share the same outdoor equipment, reducing clutter and centralizing the system’s main refrigeration components.

A wall-mounted unit installed in the upper part of the wall

The photograph shows an indoor unit mounted near the ceiling, in a section of wall beside an opening leading to another room.

This type of positioning offers several advantages when properly planned:

• air can be directed toward the open part of the room;
• the appliance does not compete with the furniture;
• the wall remains usable beneath the unit;
• air is discharged above the traffic area;
• the unit is visually less dominant.

Nevertheless, sufficient clearance must be maintained above the appliance. Most wall-mounted units draw a significant portion of their air from the top. An installation too close to the ceiling can therefore impair airflow and make it difficult to open the front panel.

Before securing the wall plate, we check in particular:

1. the distance from the ceiling;
2. the space required on each side;
3. the strength of the support behind the finish;
4. the level of the mounting plate;
5. the airflow direction;
6. filter removal;
7. the drain route;
8. the location of the wall penetration.

For this project, the unit remains accessible with a suitable stepladder. Its lower flap can open freely, and no shelf, cabinet, or molding interferes with air distribution.

The adjacent opening directly influences air circulation

The visible unit is installed near an opening leading to another space. This detail has a real impact on comfort distribution.

The airflow from a wall-mounted air conditioner does not automatically follow the administrative boundaries of rooms. It moves according to the building’s geometry, the position of the doors, ceiling height, and temperature differences.

A unit placed near an opening can help moderate an adjacent area, but it does not necessarily replace a dedicated unit when that area is distant or frequently isolated by a door.

This is precisely one of the advantages of a dual-zone system: rather than asking a single unit to cover an excessive area, we distribute the workload between two indoor units.

A discreet integration in a room with light-colored surfaces

The white casing of the Fujitsu AIRSTAGE unit coordinates with the wall and ceiling. In a room with neutral colors, this continuity reduces visual contrast.

We also pay attention to elements that could make the installation unnecessarily visible:

• oversized line covers;
• diagonal runs;
• exposed cables;
• poorly aligned outlets;
• units installed without regard to the room's architecture.

A successful finish does not mean that technical constraints disappear. It means that the component routing was decided before drilling.

In many homes in Sainte-Thérèse and the North Shore, the lines must pass through an existing structure, run along a façade, or connect to an outdoor unit located on a different wall. The best indoor location must therefore be evaluated together with the outdoor routing, not separately.

Fujitsu Aquila XLTH: a multi-zone range suited to cold-weather heating

The Fujitsu AIRSTAGE Aquila range belongs to the H-series multi-zone systems. The manufacturer's documentation presents 18,000, 24,000, 36,000, and 45,000 BTU/h outdoor units that can power several types of indoor units.

Depending on the configuration, it is possible to connect:

• wall-mounted units;
• Slim Duct units;
• compact cassettes;
• Mid Static Duct units.

For a dual-zone installation, the 18,000 BTU/h outdoor unit can be connected to two compatible indoor units. The documentation specifically presents various combinations using 7,000, 9,000, 12,000, or 15,000 BTU/h indoor units.

The cold-climate version is advertised as operating in heating mode down to -26 °C, depending on the applicable model. This feature is particularly important in Sainte-Thérèse, where a heat pump must be selected for its winter performance as well as its summer performance.

Why we do not state a precise capacity based on the photo

The photograph identifies a Fujitsu AIRSTAGE wall-mounted unit, but it does not allow the exact installed capacity to be confirmed with certainty.

A 7,000, 9,000, or 12,000 BTU/h unit may look very similar. The capacity must be confirmed using:

• the model number;
• the nameplate;
• the quotation;
• the combination approved by Fujitsu;
• the load calculation performed for each zone.

We avoid estimating BTUs based solely on the unit's apparent width. This method can lead to inaccurate information and does not reflect the building's actual heating requirements.

Sizing a dual-zone system is not just about square footage

Floor area remains useful information, but it is not enough to select the capacity of a multi-zone heat pump.

We also analyze:

• the age of the home;
• the level of insulation;
• the number of windows;
• the type of glazing;
• solar orientation;
• ceiling height;
• air infiltration;
• the number of occupants;
• the presence of heat-generating appliances;
• the communication between rooms;
• the floor where each zone is located.

A 250 sq. ft. bedroom may require a different capacity than a living area of the same size. The former may be better insulated and receive little sunlight, while the latter may have several windows and an exterior door.

Each zone must therefore be evaluated separately before confirming the outdoor unit and the two indoor units.

Approved combinations and the outdoor output limit

Fujitsu documentation allows certain combinations in which the sum of the indoor units' rated capacities exceeds the capacity of the outdoor unit.

A multi-zone outdoor unit can accept a connected capacity of up to 130 % in certain configurations. This provides useful flexibility when both zones do not require their full capacity at the same time.

However, Fujitsu specifies that exceeding 100% does not increase the maximum capacity produced by the outdoor unit. The available power must always be distributed among the active zones.

What this means for occupants

If only one indoor unit is operating, the system can concentrate a significant portion of its output in that zone.

If both units request intense heating at the same time, the outdoor unit distributes its capacity. The two indoor units therefore do not necessarily receive their full rated capacity at the same time.

This distinction must be considered during the design phase. A technically approved combination is not automatically the best combination for every home.

The same operating mode for both zones

The two indoor units can be controlled separately, but they share the same refrigerant circuit.

They can have:

• different temperatures;
• different fan speeds;
• different schedules;
• one zone active and the other turned off.

However, they must operate in the same general mode. The system can heat both zones or cool them, but it normally cannot heat one room while the other simultaneously calls for cooling.

Fujitsu documentation confirms that the system provides heating and cooling, but not simultaneously in opposite modes.

We explain this feature to occupants during commissioning to avoid conflicting commands between the remote controls.

Inverter technology for adjusting output

The Fujitsu system uses an inverter-driven compressor, also known as an Inverter compressor.

This technology allows the compressor speed to be adjusted gradually according to demand, rather than operating only in a full-power on-off cycle.

When demand is low, the system can operate at a reduced output. When the outdoor temperature becomes more demanding or both zones require more capacity, it increases its output.

This modulation provides:

• a more stable temperature;
• longer cycles at low output;
• fewer abrupt starts;
• quieter operation;
• adaptation to the varying needs of the two zones.

Condensate drainage must be planned before installation

In cooling mode, the indoor unit removes moisture from the air. This moisture turns into water and must be drained away through a drain line.

In a high-mounted installation like the one shown in the photo, we must determine the drainage route before securing the unit.

When the configuration allows, we favor a continuous gravity slope. This avoids adding a pump and reduces the number of mechanical components requiring maintenance.

Inadequate drainage can cause:

• a leak on the wall;
• water accumulation in the unit;
• odors;
• draining noises;
• paint stains;
• damage to the interior finish.

After installation, we test the drainage to confirm that water is flowing properly.

Refrigerant lines: precision and leak-tightness

The indoor units are connected to the outdoor unit by insulated copper lines. These lines carry the refrigerant through the system.

A durable installation requires, among other things:

• diameters compliant with the model;
• clean flares;
• proper tightening;
• continuous insulation;
• a leak test;
• vacuum pumping;
• mechanical protection on exposed sections.

Vacuum pumping removes air and moisture from the system before commissioning. This step must not be shortened.

Moisture left in the lines can contaminate the system, damage the compressor oil, and affect long-term reliability.

Installation and usage choices that protect long-term comfort

Maintain clear access to the filters

The visible unit is installed high up, but its front panel must remain accessible.

The filters should be inspected regularly, especially during periods of intensive use.

A clogged filter reduces airflow and can lead to:

• reduced efficiency;
• increased noise;
• less even distribution;
• extended operation;
• a buildup of dirt on the evaporator.

In a dual-zone system, the filters in both units must be maintained. A less frequently used unit can still accumulate dust.

Avoid placing tall furniture below the unit

The large visible wall area could potentially accommodate a piece of furniture, but sufficient clearance must be maintained below the unit.

A cabinet that is too tall can block the airflow and create air recirculation around the unit. The system then measures a temperature that may not represent the temperature in the rest of the room.

We recommend keeping the airflow path clear.

Adjust the louvers according to the season

In cooling mode, cold air naturally falls. A more horizontal direction generally allows the airflow to reach farther.

In heating mode, warm air rises. It is often helpful to direct the louver farther downward to bring heat into the occupied area.

The setting should also take into account the position of beds, armchairs, desks, and passageways.

Avoid settings that are too far apart between zones

Even if each unit has its own remote control, extreme differences between the two zones can reduce system stability.

When the doors remain open, air naturally circulates between the rooms. A very hot zone and a very cold zone partially offset each other, forcing the units to work harder.

Reasonable settings suited to each room’s use generally provide a better balance.

Common mistakes we help avoid

Installing the unit too close to the ceiling

Insufficient clearance can restrict air intake and make maintenance more difficult.

Directing the airflow toward a nearby partition

The air needs sufficient space to circulate throughout the room.

Choosing BTUs based only on floor area

The quality of the building envelope, the windows, and the exposure can significantly affect requirements.

Assuming that each zone always receives its full capacity

The two indoor units share the outdoor unit’s capacity.

Programming opposite modes

One remote control set to heating and the other to cooling can result in incompatible operation.

Neglecting access to the filters

A unit that is difficult to maintain will gradually lose airflow if the filters are not cleaned.

Confusing compatibility with sizing

Fujitsu tables indicate the authorized combinations, but the manufacturer specifies that they are not intended to select the system capacity. Fujitsu’s design software must be used to validate H Series equipment.

Our post-installation commissioning

Once the components are installed, we carry out a series of checks.

We check, in particular:

• connection tightness;
• the vacuum level achieved;
• communication between the units;
• operation of each zone;
• remote control response;
• discharge air temperature;
• louver movement;
• drainage;
• vibrations;
• unusual noises.

We then explain how the system works to the occupants: mode selection, temperature adjustment, filter maintenance, and good seasonal practices.

This step is essential to ensure that a dual-zone heat pump is used as an integrated system rather than as two completely separate units.

An installation suited to homes in Sainte-Thérèse and the North Shore

This Fujitsu Aquila XLTH dual-zone heat pump installation in Sainte-Thérèse demonstrates that an indoor unit can be discreetly integrated into a room when positioned according to the architecture, airflow, and future maintenance requirements.

The visible unit was installed on a large wall surface, near an opening, with airflow directed toward an unobstructed area. Its location leaves the lower part of the wall clear and allows the room to be served efficiently without interfering with everyday movement.

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

Each project is based on a practical assessment:

• occupant needs;
• room layout;
• compatible capacities;
• building structure;
• piping route;
• electrical supply;
• outdoor access;
• long-term maintenance.

Our goal is to deliver an HVAC installation that functions properly, integrates with the building, and remains accessible throughout the system’s entire service life.