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

An outdoor unit installed beneath an elevated structure, with a floor-mounted support, calculated clearances, and protected connections

This installation of a Fujitsu AIRSTAGE Aquila XLTH dual-zone heat pump in Oka stands out because of the location selected for the outdoor unit. The photograph shows the compressor installed beneath an elevated structure, likely a porch or deck, in a space partially protected from the elements but whose height and clearances required precise planning.

The Fujitsu unit is positioned against a concrete foundation wall, on a floor-mounted metal support equipped with anti-vibration pads. The refrigerant lines and cables are routed to the right through sections of white line-hide, while the electrical components are secured to the nearby wall.

At first glance, the installation may seem simple: place the unit under the deck, make the connections, and start the system. In reality, a covered location requires several essential checks. It is necessary to ensure that the fan can discharge air freely, that the unit does not reabsorb its own air, that defrost cycles do not create ice accumulation, and that the unit remains accessible for future HVAC maintenance.

At AirGreen, we therefore treated this space as a complete technical area. The positioning of the heat pump, the height of the support, the line-set routing, and the location of the accessories were coordinated to achieve a clean installation suited to Oka’s winter conditions.

Why installing the unit under the deck required special analysis

An elevated structure can offer some protection from direct rain, snow, and debris. However, it does not automatically constitute a good location for a heat pump.

The outdoor unit must absorb the energy present in the surrounding air. To operate properly, it needs sufficient air volume around its heat exchanger and clear space in front of the fan.

In this project, we had to verify:

• the distance between the top of the unit and the structure;
• the clearance in front of the fan grille;
• the available space behind and on the sides;
• the risk of air recirculation;
• the possibility of snow or ice accumulation;
• access to the service panels;
• the safe routing of the pipes and wiring;
• the drainage of water produced during defrosting.

A unit placed too far beneath a deck may operate in a pocket of colder air in winter or warmer air in summer. The discharged air may remain trapped and then be drawn back in by the coil. This recirculation reduces efficiency and can increase the demands placed on the compressor.

The positioning shown in the photograph leaves an open space in front of the fan. The unit is not enclosed in a cabinet and remains accessible from the front and right side.

A ground-mounted metal support rather than direct installation on the pavers

The outdoor unit rests on a raised metal base. It is not placed directly on the slabs or ground.

This decision offers several advantages for an installation located in Oka, where snow, frost, and ground movement must be taken into account.

The support provides, among other things:

• to keep the bottom of the heat pump above ground level;
• to reduce contact with moisture, dust, and leaves;
• to facilitate the drainage of defrost water;
• to limit the risk of obstructions beneath the unit;
• to provide more convenient access to the support points;
• to reduce the direct transmission of vibrations to the pavers.

A heat pump operating in heating mode naturally accumulates frost on its outdoor coil when conditions favor it. It then performs a defrost cycle that produces water. This water can freeze beneath the unit if it does not have enough space to drain.

The raised support helps delay the formation of an ice block directly against the base of the unit. Nevertheless, it remains important for the owner to keep this area clear during the winter.

Visible anti-vibration pads beneath the contact points

The photograph shows blue and white pads installed between the Fujitsu unit and its metal support.

These components help dampen vibrations generated by the compressor and fan. Their presence is particularly relevant in a space beneath a deck, as vibrations could otherwise be transmitted to the support, pavers, or surrounding structural elements.

A slight vibration at the machine can become more noticeable indoors when amplified by a structure. Acoustic problems are more common when:

• the unit is rigidly mounted without isolation;
• the support is not level;
• a foot is not bearing properly;
• a pipe touches the wall or structure;
• a panel is loose;
• the compressor operates at high speed in cold weather.

We therefore check not only for the presence of the pads, but also the stability of the entire assembly. All four support points must support the unit evenly to prevent cabinet twisting or irregular vibrations.

A dual-zone heat pump for serving two areas of the property

The Fujitsu Aquila XLTH dual-zone system can power two indoor units from a single outdoor unit.

This configuration is useful when two rooms have different needs. They may be a living area and a bedroom, two floors, or two areas with different sun exposure and occupancy patterns.

The main advantages are as follows:

• a single outdoor unit to integrate into the building;
• two distinct setpoint temperatures;
• use suited to each room;
• less outdoor space than two separate systems;
• a reduction in the number of independent refrigerant circuits;
• more precise comfort management.

Fujitsu documentation for the H series presents 18,000, 24,000, 36,000, and 45,000 BTU/h outdoor units capable of powering up to two, three, four, or five indoor units, respectively, depending on the model and selected combination. It also supports various indoor unit formats, including wall-mounted units, compact ducted units, cassettes, and certain concealed duct units.

In this Oka installation, the dual-zone configuration limits the number of outdoor units while providing independent control in two areas of the property.

Fujitsu Aquila XLTH: a solution designed for cold-climate heating

Selecting a heat pump for the North Shore of Montreal must take winter temperatures into account, not just summer cooling needs.

Fujitsu documentation for the Aquila and Aquila CTEB systems indicates heating operation down to -26 °C for models intended for cold climates. It also mentions cooling operation at outdoor temperatures up to 50 °C.

This operating range is relevant for Oka, where the system may be exposed to:

• extended periods below freezing;
• snow accumulation;
• repeated freeze-thaw cycles;
• winter humidity conducive to frost formation;
• significant variations between day and night.

However, it is important to distinguish between the minimum operating temperature and the heating capacity actually available. A heat pump can continue operating at very low temperatures without necessarily delivering its full rated capacity.

Sizing must therefore be determined based on:

• of the building’s heat loss;
• of the wall and roof insulation;
• of the window area;
• of air infiltration;
• of the desired indoor temperature;
• of the available auxiliary heating;
• of simultaneous demand in both zones.

The R32 refrigerant visible on the unit

The logo R32 is clearly visible on the front of the outdoor unit.

This indication is important for the installer and for future technicians who will work on the system. The circuit must be installed and serviced using the tools, procedures, and practices appropriate for the refrigerant used.

During installation, we must pay particular attention to:

• the quality of the refrigerant connections;
• performing a leak test;
• evacuation under vacuum;
• mechanical protection of the lines;
• compliance with the permitted lengths and elevation differences;
• identification of the circuits associated with each zone.

A dual-zone heat pump has several pairs of lines. Each indoor unit must be connected to the correct refrigerant port and communication wiring. Reversing them can cause errors, inconsistent responses, or operation in the wrong zone.

Lines protected by rigid line covers

In the photo, the lines leave the right side of the compressor, rise slightly, and then pass through white sections secured to the wall.

These line covers generally protect and bundle:

• insulated refrigerant lines;
• communication cables;
• some electrical conductors;
• sometimes the drains, depending on their route.

The finish offers several benefits:

• a more orderly appearance;
• protection against UV rays;
• reduced mechanical damage;
• better resistance to the elements;
• an easier-to-inspect route.

The curves are particularly important. A copper line must not be bent sharply, as deformation can restrict refrigerant flow or weaken the tubing.

The visible route forms a gradual curve before joining the horizontal section. The cables are also bundled to prevent them from hanging freely in the space beneath the deck.

A grouped, accessible electrical area

Two enclosures are installed on the wall to the right of the heat pump. Without claiming to identify their exact function from the image alone, their location shows that the electrical components associated with the system have been grouped near the unit.

A proper electrical installation should provide:

• access to the disconnecting device;
• wiring protection;
• circuit identification;
• proper clearances;
• safe access for maintenance;
• stable attachment to the building.

It is important that the cables do not touch the fan grille, wet ground, or surfaces that could damage them.

In a partially covered outdoor space, the enclosures and fittings must also be suitable for the environment and resistant to moisture.

Indoor unit combinations cannot be improvised

For a dual-zone heat pump, the choice of the two indoor units must comply with the combinations authorized by Fujitsu.

The table provided for 18,000 BTU/h outdoor units serving two zones lists 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 tables indicate compatible combinations but do not constitute a load calculation. Fujitsu specifies that they should not be used alone to select capacity and recommends using its Design Simulator software for H-series AIRSTAGE equipment.

Connected capacity and capacity actually available

Some combinations allow the sum of the indoor capacities to exceed the rated capacity of the outdoor unit.

This may be appropriate when the two zones do not use their full capacity at the same time. However, the manufacturer specifies that connected capacity above 100% does not increase the system’s production capacity.

For example, combining two indoor units totaling 24,000 BTU/h does not turn an 18,000 BTU/h compressor into a 24,000 BTU/h unit. If both zones demand high capacity simultaneously, the available outdoor output is divided between them.

To avoid a lack of comfort, we must analyze:

1. the peak demand of each room;
2. the likelihood that both zones will operate at high capacity at the same time;
3. low-temperature capacity;
4. sun exposure;
5. the occupants’ habits;
6. the available supplemental heating.

Independent controls with a shared mode

Each indoor unit can be adjusted separately. Occupants can adjust the temperature, fan speed, and louver direction according to the needs of each zone.

However, a multi-zone system cannot heat one room while cooling another. Fujitsu documentation specifies that the system provides heating and cooling, but not simultaneously.

The two zones can therefore have different setpoint temperatures, but they must remain in a compatible mode.

This distinction is important in spring and fall. A very sunny room may need cooling while another part of the house remains cold. The homeowner must then coordinate the system’s overall mode.

The role of the inverter compressor in a multi-zone system

Fujitsu documentation indicates that the system uses an inverter-driven compressor.

This technology allows the compressor speed to be modulated according to demand. The system therefore does not operate solely through a succession of full-power starts and stops.

Modulation can help:

• maintain a more stable temperature;
• reduce short cycles;
• serve one zone when the second is turned off;
• gradually adjust capacity;
• reduce certain sound fluctuations;
• improve comfort during periods of low demand.

In a dual-zone heat pump, this adjustment is particularly useful. The system can operate at a reduced level when only one room requires adjustment, then increase its output when both indoor units are being used.

The importance of airflow beneath a deck

The covered location partially protects the unit, but the deck must not act like a ceiling that is too close.

In cooling mode, the fan expels warm air. In heating mode, it expels air that is colder than the outdoor air. In both cases, this air must be able to leave the space.

The risks of inadequate clearance include:

• recirculation of discharged air;
• reduced efficiency;
• an increase in defrost cycles;
• operation at less favorable pressures;
• excessive heat buildup in summer;
• a very cold area beneath the deck in winter.

An installation should therefore never be evaluated solely according to the physical space occupied by the machine. The volume of air available around it must also be considered.

Managing defrost water

The visible ground surface beneath the heat pump consists of pavers and outdoor materials. This environment can become slippery if defrost water freezes in a passageway.

The positioning must take the water’s destination into account. It must not accumulate against the foundation, beneath the support feet, or in a frequently used passageway.

The owner must also monitor the area during the winter and remove ice buildup before it reaches the base of the unit.

Never break the ice with a tool that could damage:

• the coil;
• the bottom tray;
• the lines;
• the cables;
• the metal bracket.

Mistakes to avoid with a heat pump installed under a structure

Installing the unit too close to the underside of the deck

Insufficient clearance can restrict air exchange.

Enclose the sides of the space after installation

Adding panels, storage, or a covering in the future can turn an open location into an enclosed space.

Placing the unit directly on the ground

Snow, water, and ice can reach the base more quickly.

Neglecting vibrations

A stand without suitable pads can transmit noise to the structure or pavers.

Leaving the lines unprotected

Exposed insulation deteriorates more quickly under the effects of weather and UV rays.

Blocking the service panel

The connections, technical label, and components must remain accessible.

Storing objects in front of the fan

The front of the unit must remain clear in every season.

Commissioning that validates the complete system

After the mechanical installation, we perform a complete commissioning.

The checks generally include:

• checking the stability of the stand;
• tightening the support points;
• checking the refrigerant connections;
• performing a leak test;
• evacuating the lines;
• checking that the vacuum holds;
• opening the valves;
• checking the electrical connections;
• confirming communication with each zone;
• testing in cooling mode;
• testing in heating mode;
• checking the controls;
• inspecting vibrations and noise.

Evacuation removes air and moisture from the new lines before the refrigerant is circulated. This step directly affects the system’s reliability and must never be replaced by a simple purge.

A clean outdoor installation adapted to Oka’s conditions

This project in Oka shows how a heat pump can be integrated into a space beneath a deck rather than simply placed in the first available location.

The result is based on several coordinated decisions:

• using an elevated metal stand;
• adding anti-vibration pads;
• maintaining clearance in front of the fan;
• protecting the lines with line-hide covers;
• grouping the electrical components;
• preserving access for maintenance;
• taking defrost water into account;
• selecting a compatible Fujitsu dual-zone configuration.

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. In Oka, as in the other municipalities we serve, we adapt each project to the building’s characteristics and the actual environment surrounding the outdoor unit.

The Fujitsu Aquila XLTH installed here provides two comfort zones from a single compressor. Its location beneath the structure offers partial protection, while the ground stand and neatly organized connections support a durable, accessible installation better prepared for Quebec’s winter.