Installation of a Fujitsu AIRSTAGE Aquila XLTH dual-zone heat pump in Saint-Théodore-d’Acton

A compact outdoor installation integrated between the masonry, deck, and existing openings

At Saint-Théodore-d’Acton, our AirGreen team installed a Fujitsu AIRSTAGE Aquila XLTH dual-zone heat pump to serve two distinct zones of the property from a single outdoor unit.

The photograph of this project perfectly illustrates a situation we regularly encounter in HVAC installation: the equipment cannot be placed just anywhere. Here, the outdoor space is bordered by a brick façade, a large window, an elevated wooden deck, and several existing structural elements. The goal was therefore to find a location that preserved the required clearances, airflow, and access for maintenance, while avoiding inconvenience for the occupants.

The Fujitsu outdoor unit was installed beneath the window, slightly offset toward the deck. It is elevated on a metal bracket, keeping the cabinet well above ground level and creating the space needed for snow, defrost water, and future inspection.

The front of the unit also displays the AIRSTAGE R32 identification, along with an EnerGuide label visible on the cabinet. The accompanying Fujitsu documentation presents the H-series Aquila lineup as a multizone platform that allows several types of indoor units to be connected to a single outdoor unit.

An outdoor location chosen to avoid several long-term problems

The location of an outdoor heat pump directly affects:

• its airflow;
• its sound level;
• its ease of maintenance;
• its protection from snow;
• the management of defrost water;
• the length of the lines;
• its integration into the building.

In this project, the unit is located near a window, but low enough not to obstruct the opening. It is also close to the deck without being wedged underneath it.

This positioning keeps the area in front of the fan clear.

This is an essential detail. The large front fan must be able to discharge air without immediately encountering:

• a fence;
• a railing;
• a wall;
• furniture;
• a buildup of snow;
• another HVAC unit.

An obstruction that is too close can cause the discharged air to recirculate toward the outdoor coil. The system then operates under less favorable conditions and may lose efficiency.

A brick façade that requires thoughtful routing

The house shown in the photo has a masonry façade. When a heat pump is installed on a brick building, the routing of the lines must be planned carefully.

The route normally includes:

• refrigerant copper lines;
• insulation;
• interconnection wiring;
• control conductors;
• drainage from the indoor units.

Penetrations must be made in a location that avoids structural elements and makes it possible to maintain an adequate slope for condensate drainage when it occurs by gravity.

We must also limit unnecessary lengths. The more complex the route, the more the installation involves:

• of changes in direction;
• of points requiring protection;
• of exterior finishing;
• of support work;
• of potential future damage.

A proper heat pump installation therefore begins well before the final connection.

A dual-zone heat pump: one outdoor unit, two comfort zones

The system installed in Saint-Théodore-d’Acton is a dual-zone heat pump.

This means that two indoor units are connected to a single outdoor unit.

This configuration makes it possible to serve two spaces that may have very different needs.

For example:

• an open-plan area and a bedroom;
• an upper floor and a ground floor;
• a front room and a back room;
• two areas with different levels of sunlight;
• a main zone and a basement.

Each indoor unit can be controlled separately.

Fujitsu documentation indicates that H-Series multi-zone systems offer individual zoning, with independent control for each indoor unit. However, it specifies that heating and cooling cannot be produced simultaneously in different zones.

What independent zone control really means

Occupants can adjust separately:

• the temperature;
• the fan speed;
• the louver direction;
• the activation or shutdown of each zone.

It is therefore possible to heat one zone to 20 °C and the other to 22 °C, or to cool one room to a different setpoint than the other.

However, one zone cannot request heating while the other simultaneously requests cooling.

This feature is important to explain during commissioning, especially during the shoulder seasons, when a sun-exposed room may be warmer than another.

Fujitsu combinations available for a dual-zone configuration

Fujitsu documentation specifically lists the AOUH18KWAS2 and AOUH18KWAH2 outdoor units as capable of supplying up to two indoor units.

Several nominal combinations are permitted:

• 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 provide considerable flexibility when designing a system.

A main room may receive an indoor unit with a higher capacity than the one installed in a smaller bedroom.

The H series documentation also lists 24,000, 36,000, and 45,000 BTU/h outdoor units, capable of supplying more zones depending on the model selected.

Why an authorized combination is not automatically the right combination

A common mistake is to look at a compatibility table and conclude that a combination permitted by the manufacturer is necessarily suitable for the building.

That is not the case.

Fujitsu also specifies in its table on page 2 that the combinations shown are not intended to select the system capacity. The manufacturer recommends using its Design Simulator software to select equipment for the AIRSTAGE H series.

Sizing must take the building’s actual characteristics into account:

• area;
• ceiling height;
• insulation;
• window quality;
• air infiltration;
• solar orientation;
• number of occupants;
• wall exposure;
• room’s level in the building;
• zone usage.

A room with extensive glazing may require a very different capacity from another room of the same size.

Connected capacity up to 130%: an important nuance

Fujitsu documentation indicates that a multi-zone outdoor unit can accept a connected capacity of up to 130 %, depending on the configuration.

This means that, in some combinations, the sum of the nominal capacities of the indoor units may exceed the nominal capacity of the outdoor unit.

However, it is important to understand the difference between connected capacity and available capacity.

Fujitsu specifies that exceeding 100% in a combination does not increase the outdoor unit’s total production capacity.

For example, if both zones require their full capacity at the same time, the outdoor unit must share its output between them.

This flexibility remains useful when the two spaces do not reach their maximum load simultaneously.

Why install the unit on an elevated support

The outdoor unit visible in the photo is installed on a metal frame.

This elevation is particularly important in Quebec.

During heating operation, the outdoor heat exchanger can accumulate frost. The system then initiates defrost cycles.

This process produces water that drains beneath the unit.

If the heat pump is installed too low, this water can freeze and gradually create a block of ice beneath the unit.

The bracket helps to:

• keep the bottom of the cabinet away from ice;
• leave more space for drainage;
• reduce the risk of blockage by snow;
• facilitate inspection;
• protect certain connections;
• make maintenance more convenient.

The height must also take into account the usual level of snow accumulation around the building.

Proximity to the deck that required a thorough analysis of airflow

The wooden deck appears very close to the right side of the outdoor unit.

In this type of configuration, we must check not only the physical distance but also the airflow path.

The front fan must be able to discharge air freely outdoors. The sides and rear of the unit also need sufficient space to allow the heat exchanger to draw in outdoor air.

A heat pump should never be enclosed in a space that is too narrow between:

• a deck;
• a railing;
• two walls;
• a fence;
• a staircase;
• decorative panels.

The visible open space in front of the unit is therefore important for maintaining proper operation.

A unit beneath a window: what to check

Installing a heat pump beneath a window can be perfectly suitable when the clearances are respected.

However, we must verify:

• that the unit does not prevent the window from opening;
• that the fan does not blow air directly against a surface that is too close;
• that the noise remains acceptable for the room;
• that maintenance can be performed;
• that snow does not accumulate against the bottom of the window;
• that the lines do not obstruct the framing.

In this project, the unit is low enough to preserve the window and sufficiently clear to remain accessible.

Inverter technology at the heart of the Fujitsu system

Fujitsu documentation specifies that the range uses an inverter-driven compressor.

An inverter compressor adjusts its speed according to demand.

Instead of operating only at full power or being off, it can modulate its operation.

This modulation offers several advantages in a dual-zone system:

• adaptation when only one zone is operating;
• more stable temperature maintenance;
• more gradual operation;
• reduction of certain startup cycles;
• adjustment to changes in load.

In a property where the two zones have different needs at different times of day, this modulation capability is particularly useful.

Cold-climate heating

Fujitsu documentation for the Aquila and Aquila CTEB systems mentions heating operation down to -26 °C for CTEB units, as well as cooling operation up to 50 °C.

This ability to operate at low temperatures is important for a residence located in Saint-Théodore-d’Acton.

When a heat pump is used as a heating source in Quebec, we are not concerned only with its rated capacity under moderate conditions.

We must also analyze its behavior:

• below 0 °C;
• during periods of extreme cold;
• during defrost cycles;
• when both zones call for heating;
• when the compressor must operate for long periods.

The R32 visible in the photo

The front of the outdoor unit clearly displays the identification R32.

The choice of refrigerant is part of the system design and requires appropriate installation procedures.

During commissioning, several steps are essential:

• preparation of the lines;
• completion of the connections;
• leak test;
• vacuum evacuation;
• connection check;
• operational test.

The presence of R32 also requires compliance with the prescribed handling procedures for this type of refrigerant.

What commissioning must confirm

A HVAC installation is not finished as soon as the machine is secured.

Before handing the system over to the customer, we check in particular:

The support

The unit must be stable, level, and securely fastened.

Clearances

The fan and heat exchanger must have sufficient clearance.

Refrigerant connections

The lines must be properly prepared, insulated, and protected.

Leak tightness

There must be no leaks at the connections.

The vacuum

The circuit must be cleared of air and moisture before start-up.

Communications

Both indoor units must communicate properly with the outdoor unit.

Both zones

Each zone is tested individually, then the system is observed while both units are operating.

Heating and cooling

The available modes are tested according to the conditions at the time of installation.

Noise and vibrations

We check the operation of the fan, compressor, and support.

Errors to avoid in an installation like this

This installation highlights several common errors.

1. Install the heat pump directly on the ground
   Snow, water, and ice can quickly become problematic.
2. Place the unit too close to the patio
   The airflow must never be restricted.
3. Partially obstruct the window
   Existing openings must remain functional.
4. Choosing the location based solely on aesthetics
   Clearances and future service take priority.
5. Installing a combination of units without validating it
   The manufacturer’s tables must be consulted.
6. Confusing compatibility with sizing
   An approved combination is not automatically suitable for the building.
7. Assuming that 130% connected means 130% output
   The outdoor unit retains its own capacity.
8. Neglecting defrost water
   Poor drainage can create a significant accumulation of ice.
9. Setting the two zones to opposite modes
   The system shares a general operating mode.
10. Making the service panel inaccessible
    A durable installation must also be practical to maintain.

Recommended Maintenance After Installation

To maintain proper operation, a few habits are important.

Occupants should:

• keep the space in front of the outdoor unit clear;
• remove significant snow accumulations;
• avoid leaning objects against the unit;
• check that the deck or furniture is not blocking the fan;
• clean the indoor unit filters regularly;
• monitor for any unusual vibration or noise;
• schedule HVAC maintenance when necessary.

The outdoor coil must also remain clean so that air can pass properly through the heat exchanger.

An HVAC installation suited to a brick façade and limited outdoor space

This Fujitsu AIRSTAGE Aquila XLTH dual-zone heat pump project in Saint-Théodore-d’Acton shows how important the choice of outdoor location is.

The unit had to be integrated between a large window, a brick façade, and a wooden deck, while maintaining unobstructed air discharge and sufficient height for winter conditions.

The elevated stand, positioning beneath the window, and clearance in front of the fan keep the installation practical and accessible.

At AirGreen, we install wall-mounted heat pumps, dual-zone systems, and multi-zone systems in Montreal, Laval, Longueuil, on the North Shore and South Shore, as well as in several surrounding municipalities.

At AirGreen, we assess each project based not only on system capacity but also on the building itself: clearances, masonry, deck, windows, drainage, snow, maintenance access, and line-set routing.

At this Saint-Théodore-d’Acton property, the Fujitsu Aquila XLTH solution now provides two-zone comfort control from a single outdoor unit, installed in a compact space without compromising essential airflow and winter operation considerations.