Installation of a Fujitsu AIRSTAGE Aquila XLTH Dual-Zone Heat Pump in Mercier, on Montreal’s South Shore

An outdoor unit installed on a raised base, with protected connections and clearances designed for Quebec winters

This installation of a Fujitsu AIRSTAGE Aquila XLTH dual-zone heat pump in Mercier highlights a determining aspect of any multi-zone project: the location and preparation of the outdoor unit. In the photograph, the Fujitsu compressor is installed against a foundation wall, on a ground-level metal support equipped with anti-vibration pads. The refrigerant lines leave the right side of the unit and rise along a protected route, while the front of the fan remains completely unobstructed.

The site presented a clear constraint: the unit had to be placed in a relatively low area, beneath a structure, while retaining enough space around the cabinet to ensure air intake and discharge. The heat pump could not simply be placed on the ground. Snow, drainage during defrost cycles, vibrations, and access to the connections all had to be taken into account.

At AirGreen, we therefore installed the unit on a raised base to keep its bottom above the paving stones and debris. This configuration also facilitates the drainage of water produced in winter while limiting direct contact between the cabinet and ground moisture.

The photo also identifies the Fujitsu AIRSTAGE branding, the R32 designation, and our AirGreen label affixed to the unit. Together, these details attest to a recent installation designed for two comfort zones and prepared for the conditions in Mercier and Montreal’s South Shore.

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

A dual-zone heat pump allows a single outdoor unit to power two indoor units installed in separate spaces. This configuration is particularly suitable for homes where a single wall-mounted unit cannot distribute air effectively throughout the space.

The two zones may correspond to different layouts:

• a living room and a bedroom;
• a ground floor and an upper floor;
• an open-concept area and an office;
• a main room and a basement;
• two separate areas divided by doors or corridors.

Each indoor unit can be controlled separately. Occupants can therefore adjust the temperature, fan speed, and airflow direction according to how each room is used.

The Fujitsu H Series documentation presents multi-zone outdoor units rated at 18,000, 24,000, 36,000, and 45,000 BTU/h. Depending on the model, they can power up to two, three, four, or five indoor units. The systems can also be combined with wall-mounted units, compact ducted units, cassettes, and certain concealed duct units.

In this Mercier project, the dual-zone configuration made it possible to limit the installation to a single outdoor compressor while improving comfort in two areas of the property.

An elevated support to prevent a vulnerable ground-level installation

The outdoor unit visible in the photo rests on a four-legged metal support. Pads are installed between the cabinet’s feet and the structure.

This elevation serves several important purposes.

Protection against snow

A unit placed directly on paving stones can quickly become surrounded by accumulated snow or be shifted during snow removal. When the bottom of the cabinet is obstructed, defrost water drains less easily and may form a block of ice.

Protection from moisture and debris

Leaves, dirt, insects, and splashes can reach an appliance more easily when it is installed too low. The metal base creates a useful separation between the cabinet and the ground.

Drainage access

In heating mode, the outdoor heat exchanger may accumulate frost. The system periodically performs a defrost cycle, during which water drains beneath the unit. The clearance makes this drainage easier.

Installation stability

A properly levelled base distributes the weight across all four support points. The cabinet remains upright, reducing stress on the panels, connections, and support structure.

In Mercier’s climate, this preparation is not optional. A heat pump may operate for long hours during the winter, and its immediate surroundings must remain clear.

Anti-vibration pads to limit noise transmission

The small blue components visible beneath the unit’s feet help dampen vibrations.

An outdoor unit contains a compressor and a large-diameter fan. Even when operating normally, these components produce some vibration. If the cabinet is screwed directly onto a rigid base, some of this vibration can be transmitted to the support, floor, or building structure.

Anti-vibration pads help to:

• reduce vibrations transmitted to the base;
• limit certain resonance noises;
• avoid metal-to-metal contact;
• stabilize the support points;
• improve acoustic comfort around the house.

We also check that the lines do not directly touch a surface capable of transmitting noise. A refrigerant line resting against metal or concrete can become a vibration path, even when the unit itself is properly isolated.

Front clearance essential to fan operation

The large front fan occupies a significant portion of the outdoor unit. Its role is to circulate air through the heat exchanger.

The area in front of the grille must therefore remain clear. An obstacle placed too close can slow the discharge of air and cause recirculation. The unit may then re-aspirate some of the air it has just discharged.

This can lead to:

• reduced efficiency;
• increased operating time;
• increased pressures or operating stresses;
• more defrost cycles in winter;
• heat buildup around the unit in summer;
• reduced capacity in both indoor zones.

In the photo, the front of the unit is unobstructed. This area should not later be used to store objects, tires, patio furniture, or construction materials.

An installation beneath a structure also requires sufficient vertical clearance

The heat pump is installed beneath a surface located above the cabinet. This type of location can partially protect the unit from direct precipitation, but it must be carefully evaluated.

The presence of a ceiling, balcony, or deck must not create an enclosed space. The discharged air must be able to leave the area without becoming trapped above or around the cabinet.

We therefore check:

• the space between the top of the unit and the structure;
• the side openings;
• the available air volume;
• the risk of recirculation;
• access to the panels;
• the possibility of removing the cabinet or certain components in the event of a repair.

A covered location can be effective when it remains open. It becomes problematic if the sides are later enclosed with panels, walls, or storage.

Fujitsu Aquila XLTH: a heat pump designed for low-temperature heating

The Fujitsu Aquila XLTH range is designed for applications where winter heating is a priority.

The Fujitsu documentation for the Aquila and Aquila CTEB systems indicates heating operation down to -26 °C for versions intended for cold climates. It also mentions cooling operation down to an outdoor temperature of 50 °C for CTEB units.

This operating range suits the conditions in Mercier, Châteauguay, Longueuil, and other areas of the South Shore, where a heat pump may be called on to operate for long periods below freezing.

However, the advertised minimum temperature must be interpreted correctly. The fact that a unit can operate at -26 °C does not necessarily mean that it retains its full rated capacity at that temperature.

To select the system properly, we must consider:

• the building’s heat loss;
• insulation;
• windows;
• air infiltration;
• the area and volume of the two zones;
• available capacity at low temperatures;
• backup heating;
• the simultaneous demand.

The R32 refrigerant visible on the front of the unit

The marking R32 is clearly visible on the installed heat pump.

This information is important for installation and future service work. The refrigerant used determines the tools, procedures, and precautions to follow during commissioning.

A dual-zone heat pump’s refrigerant circuit includes several connections. Each indoor unit has its own pair of pipes, and each pair must be connected to the correct outdoor port.

The elements to be checked include:

• the pipe diameter;
• the total length;
• the height difference;
• the quality of the connections;
• insulation;
• mechanical protection;
• identification of each zone;
• circuit tightness.

Confusing the refrigerant circuits with the communication cables can create complex errors. That is why the zones are identified and tested separately before the system is put back into service.

Pipe bends made without excessive kinking

In the photo, the pipes exit from the right side of the heat pump and curve upward.

Copper pipes must not be bent abruptly. A curve that is too tight can deform the pipe, reduce its internal diameter, or weaken the metal.

We therefore pay attention to:

• the bending radius;
• insulation protection;
• the absence of voltage at the connections;
• support for the lines;
• contact with walls or structures;
• protection against UV rays.

The lines must be installed so that they remain stable despite temperature changes and normal equipment vibrations.

A two-zone capacity that must comply with Fujitsu combinations

A two-zone outdoor unit cannot accommodate just any combination of indoor units.

The Fujitsu table for the AOUH18KWAS2 and AOUH18KWAH2 models lists the following rated 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 confirm that the units can be connected together. However, they do not determine the appropriate capacity for a given home.

Fujitsu specifies that its tables should not be used alone to select system capacity and recommends using its Design Simulator software for H-series AIRSTAGE equipment.

Why the total capacity of the indoor units can exceed that of the compressor

Some approved combinations exceed 100% of the outdoor unit’s rated capacity.

This may seem contradictory, but the practice is based on the fact that both zones do not always demand their maximum capacity simultaneously.

Fujitsu nevertheless specifies that exceeding 100% connected capacity does not increase the system’s output capacity.

For example, two indoor units totaling 24,000 BTU/h may be compatible with an 18,000 BTU/h outdoor unit in certain configurations. When both zones operate at full demand, they must share the compressor’s actual capacity.

The choice must therefore take the thermal behavior of both spaces into account:

1. Do the two zones generally heat at the same time?
2. Is one zone much smaller?
3. Does one receive more sunlight?
4. Is one bedroom primarily used at night?
5. Is auxiliary heating available?
6. Do the peak demands occur at the same time?

Two independent controls, but one common mode

Each indoor unit can have its own setpoint temperature. One zone can be set to 21 °C and the other to 19 °C, for example.

However, the two zones cannot operate simultaneously in opposite modes. Fujitsu documentation specifies that the system provides heating and cooling, but not both at the same time.

This means that:

• both zones can heat;
• both zones can cool;
• one zone can operate while the other is off;
• one zone cannot heat while the other cools.

This limitation should be explained to occupants, particularly during the shoulder seasons.

Inverter modulation for enhanced comfort

The Fujitsu AIRSTAGE system uses an inverter-driven compressor.

This technology adjusts the compressor speed according to demand. It does not have to operate continuously at full capacity.

In a dual-zone configuration, this modulation can:

• reduce capacity when only one room requires little heating;
• gradually increase capacity when both zones are operating;
• limit stops and restarts;
• stabilize the indoor temperature;
• reduce certain noise variations;
• adapt consumption to demand.

Fujitsu documentation also mentions protections for the circuits, fan motor, and compressor, as well as a heat exchanger designed to provide better corrosion resistance.

The role of evacuation under vacuum in system reliability

Once the lines have been installed, the refrigeration circuit must be evacuated under vacuum.

This operation removes:

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

Residual moisture can react with the compressor oil, impair performance, and contribute to premature degradation of the circuit.

A complete commissioning generally includes:

• a leak test;
• evacuating the system;
• checking that the vacuum holds;
• opening the valves;
• validating the connections;
• testing both indoor units;
• checking temperatures;
• checking communications;
• checking for vibrations;
• explaining the controls to the customer.

Defrost drainage around the support

The ground visible around the unit contains leaves, dirt, and light debris. This situation highlights the importance of keeping the area clean.

In winter, defrost water can freeze between the feet of the support. If enough ice accumulates, it can reach the bottom of the unit or create a slope around the base.

The owner should:

• remove leaves in the fall;
• clear snow around the support;
• monitor ice buildup;
• avoid pushing snow against the fan;
• do not store objects under or in front of the unit;
• check that the lines remain intact.

Do not strike the ice with a metal tool near the coil or refrigerant lines.

Mistakes to avoid when installing an outdoor dual-zone system

Installing the unit directly at ground level

This increases the risks associated with snow, water, and debris.

Neglecting vibration-isolation pads

Noise can be transmitted to the support or the building structure.

Blocking the front of the fan

The air discharge must remain completely unobstructed.

Enclosing the unit beneath a structure

A covered space must maintain sufficient air circulation.

Leaving the lines unsupported

Weight and vibrations can place stress on the connections.

Misidentifying the two circuits

Each refrigerant line must correspond to the correct indoor unit and the correct cable.

Choosing the units solely based on their BTU rating

Compatibility, heating load, and simultaneous operation must all be verified.

Forgetting access to the service panel

A technician must be able to reach the connections and components without moving the machine.

A Fujitsu installation adapted to Mercier’s conditions

This installation shows that a successful dual-zone project begins with careful preparation of the outdoor unit.

The Fujitsu Aquila XLTH heat pump was installed on an elevated support, protected from vibrations, and positioned to maintain full front clearance. The lines were routed upward with gradual bends, while the cabinet remains accessible for HVAC maintenance.

This configuration provides occupants with two comfort zones from a single outdoor unit. It reduces clutter around the property while allowing individual control in the rooms served.

At AirGreen, we install heat pumps, wall-mounted air conditioners, and multi-zone systems in Mercier, Châteauguay, Brossard, Longueuil, Montréal, the North Shore, and the South Shore.

For this project, we focused on specific elements:

• support stability;
• snow protection;
• defrost drainage;
• vibration isolation;
• air circulation;
• protecting the lines;
• validating both zones;
• commissioning the R32 circuit.

The result is an HVAC installation designed to remain accessible, stable, and functional throughout the seasons, while providing the flexibility expected from a Fujitsu dual-zone heat pump.