A multi-zone installation designed for the comfort of two distinct spaces
In many homes in Côte-des-Neiges–Notre-Dame-de-Grâce, heating and cooling needs vary considerably from one room to another. Buildings in the area often feature masonry walls, additions built at different times, floors that are difficult to balance, and spaces with uneven sun exposure. A single wall-mounted unit can therefore struggle to maintain a stable temperature throughout the home.
For this installation in Montréal, we installed a Fujitsu AIRSTAGE Aquila XLTH dual-zone heat pump. The system can power two indoor units from a single outdoor unit while allowing occupants to adjust the temperature of each zone separately.
The goal was therefore not simply to add an air-conditioning unit. It was necessary to design a solution capable of meeting several practical constraints:
- provide efficient heating during the Montréal winter;
- cool two spaces with different needs;
- limit the number of visible outdoor units;
- install the equipment in a relatively narrow passage;
- preserve access to the windows, wooden structure, and building elements;
- ensure a solid installation despite the masonry and the façade’s unique configuration.
The result is a compact, clean HVAC installation adapted to the existing architecture.
Why a dual-zone heat pump was particularly suitable
A multi-zone heat pump is often chosen when a homeowner wants to condition several rooms without installing a separate outdoor unit for each indoor unit. In this home in Côte-des-Neiges–Notre-Dame-de-Grâce, this approach made it possible to serve two zones while keeping a single Fujitsu outdoor unit.
Each indoor unit can be controlled independently. This makes it possible, for example, to maintain a cooler temperature in one bedroom and a different temperature in a living area. This independence improves comfort and reduces the need to heat or cool less-used spaces unnecessarily.
Fujitsu documentation states that H series AIRSTAGE multizone systems can power several types of indoor units, including wall-mounted units, slim duct units, compact cassettes, and certain ducted units. It also indicates that each indoor unit can be controlled separately, while the system provides heating or cooling according to the mode selected for the installation as a whole.
This distinction is important: in a conventional multizone system, the indoor units can have different set temperatures, but they generally must operate in the same overall mode. One zone cannot request heating while the other simultaneously requests cooling.
The Fujitsu Aquila XLTH: a configuration suited to Quebec’s climate
The choice of the Fujitsu Aquila XLTH is based in part on its design for multizone residential applications and harsh winter conditions. Fujitsu’s AIRSTAGE Aquila range includes outdoor units that can be paired with different combinations of indoor units, depending on the required capacity and number of zones.
The H series technical documentation lists 18,000, 24,000, 36,000, and 45,000 BTU/h outdoor units that can supply up to two, three, four, or five indoor units, respectively, depending on the model and authorized combinations. However, it specifies that the combination tables do not replace a complete technical selection and recommends using the Fujitsu Design Simulator to size the system correctly.
For this dual-zone installation, we therefore considered much more than the number of rooms. Choosing the appropriate capacity depends in particular on:
- the actual floor area of each zone;
- insulation quality;
- the number and size of the windows;
- the building’s orientation;
- ceiling height;
- heat loss;
- air circulation between the rooms;
- daily use of the spaces.
Simply adding the floor areas of two rooms and selecting an outdoor unit based on a rough rule of thumb can result in an oversized or undersized system. An oversized system may run shorter cycles, dehumidify less effectively in summer, and produce temperature fluctuations. An undersized system, on the other hand, may run continuously without achieving the desired comfort during the coldest periods.
An Outdoor Unit Installed on Sturdy Wall Brackets
The photograph of this project shows the Fujitsu AIRSTAGE with R32 refrigerant outdoor unit, installed on two metal brackets secured to the foundation wall. This installation method is particularly well suited when ground space is limited or when it is preferable to keep the heat pump above the snow accumulation level.
In this project, the location was between a window and an exterior wooden structure. The available space therefore required careful planning. Sufficient clearance had to be maintained around the unit to allow for:
- adequate airflow;
- air discharge by the fan;
- access to the refrigerant connections;
- future maintenance of the unit;
- cleaning the heat exchanger;
- safe service in the event of troubleshooting or repair.
We also had to take the proximity of the window into account. An outdoor unit should not be positioned solely based on the apparent available space. Its airflow, noise level, access to the service panels, and the clearances recommended by the manufacturer must be assessed before drilling.
Here, wall brackets keep the unit at a practical height while clearing the ground. They are secured to a structure capable of supporting the unit’s weight and vibrations. Vibration-damping elements are placed between the heat pump base and the brackets to limit the transmission of vibrations to the masonry.
Why the Height of the Outdoor Unit Matters in Montreal
In Montreal, a heat pump installed too close to the ground can be exposed to several problems:
- snow accumulation in front of the heat exchanger;
- partial blockage of airflow;
- ice formation around the base;
- prolonged contact with defrost water;
- more difficult access during winter;
- risk of damage caused by a shovel or snow blower.
During heating, a heat pump periodically produces water during its defrost cycles. This water must be able to drain away without forming a block of ice that could reach the underside of the unit. The wall-mounted installation shown in this project helps provide the necessary clearance beneath the appliance.
The height must nevertheless remain reasonable. A unit placed unnecessarily high makes maintenance more difficult and may require additional equipment during service work. Our role is to strike a balance between protection from snow, accessibility, and integration with the building.
Careful integration into a challenging architectural environment
Residences in Côte-des-Neiges–Notre-Dame-de-Grâce frequently feature brick facades, concrete foundations, exterior stairs, balconies, and narrow side passages. Each element affects the positioning of HVAC equipment.
For this installation, the outdoor unit is located near a wooden structure and beneath a large window. We chose a position that reduces obstruction in the passage while keeping the equipment sufficiently far from immediate obstacles.
The alignment of the supports, leveling of the unit, and quality of the anchors are particularly important. An improperly leveled heat pump can promote poor drainage, amplify certain vibrations, and complicate operation during defrost cycles.
We also pay particular attention to the routing of the refrigerant lines, communication wiring, and condensate drain. Even when these elements are not all visible in an exterior photograph, their installation directly affects system reliability.
Refrigerant lines must never be improvised
A multi-zone installation includes a pair of refrigerant lines for each indoor unit. The line diameter, total length, height difference, and any additional refrigerant charge must comply with the manufacturer’s requirements.
Among the errors we encounter on some installations carried out without sufficient planning are:
- pipes bent too sharply;
- damaged insulation;
- improperly prepared flared connections;
- the absence of an adequate leak test;
- a vacuum pull that is too short;
- unverified pipe lengths;
- communication wiring associated with the wrong zone.
On a dual-zone system, a mix-up between the electrical and refrigerant connections can cause inconsistent operation: one indoor unit calls for heating, but the outdoor unit supplies the circuit corresponding to the other room. A complete check of each zone is therefore carried out before final commissioning.
The R32 refrigerant visible on the unit
The label affixed to the outdoor unit clearly indicates the use of R32 refrigerant. This fluid is used in several recent HVAC systems because of its thermodynamic properties and lower global warming potential than R410A.
Its presence nevertheless requires adapted work methods. The tools, recovery procedures, pressure tests, and commissioning practices must be compatible with the refrigerant used. A professional installation does not consist solely of connecting the pipes: it includes a complete leak check, a measured evacuation, and verification of operation in every mode.
Cold-weather heating and seasonal operation
Fujitsu documentation associated with the Aquila H-series systems indicates that some versions designed for cold climates can provide heating down to -26 °C. It also mentions cooling operation at high outdoor temperatures, as well as an inverter-driven compressor design.
A variable-speed compressor adjusts its output according to demand rather than operating only at full power or being switched off. This modulation can provide a more stable temperature and reduce repeated starts when demand is moderate.
However, it is important to distinguish the minimum operating temperature from the capacity actually available at very low temperatures. A heat pump may continue operating at a given temperature while providing less heat than it would at a milder outdoor temperature. Sizing must therefore be based on the exact model’s performance data and the building’s heat loss.
In some properties, the heat pump can become the primary source of heating. In others, it works alongside electric baseboard heaters or an existing central system. We explain to the homeowner how to use supplemental heating sources without interfering with the heat pump’s operation.
What this installation provides in everyday life
Two setpoint temperatures, one outdoor unit
The main advantage of this installation is the ability to control two spaces separately. A bedroom upstairs may require less heating than a living room exposed to several windows. In summer, a room facing the sun may also require more air conditioning.
With two indoor units, occupants can adjust each zone according to its use. This approach is more precise than a single unit installed in a corridor with the hope that the air will naturally reach all the rooms.
Fujitsu documentation also emphasizes that an outdoor unit from the H series can accommodate different categories of indoor units. Depending on the project, it is therefore possible to combine a wall-mounted unit with a cassette or a compatible ducted unit. This flexibility can be useful in a building where the two zones do not have the same architectural constraints.
A less cluttered façade
Installing two single-zone heat pumps would have required two outdoor units, two sets of supports, two power supplies, and more space. The dual-zone configuration reduces visual clutter and makes integration easier on a wall already occupied by windows and a staircase.
This does not mean that a multi-zone heat pump is automatically preferable for every project. Two independent systems may sometimes provide greater redundancy or better serve zones that are very far apart. The right solution depends on the building, piping length, required capacities, and the owner’s priorities.
Mistakes to avoid before choosing a dual-zone system
Before accepting a quote, we recommend checking several specific points.
Choosing solely based on the number of BTUs stated in an advertisement
Nominal capacity is not enough. You must examine heating performance, the permitted combinations of indoor units, and the available capacity when both zones operate simultaneously.
Assuming that each indoor unit always receives its maximum nominal capacity
In a multi-zone system, the outdoor unit distributes its capacity among the active zones. When both indoor units demand their full output, the available capacity depends on the outdoor unit and operating conditions.
Fujitsu also specifies that combining indoor units exceeding 100% of the outdoor unit’s nominal connection capacity does not increase the outdoor unit’s output capacity.
Neglecting access for HVAC maintenance
An installation positioned very close to a fence, balcony, or wall may look discreet but become difficult to maintain. The technical panels, connections, and heat exchanger must remain accessible.
Place the unit directly in a snow accumulation area
Winter clearance must be planned from the outset of the installation. Adding a support afterward is often more complex and costly.
Ignoring indoor condensate management
Each indoor unit produces water in cooling mode. The drain must have a sufficient slope or be equipped with a condensate pump when gravity drainage is not possible. An improperly designed drain can cause leaks, odours, or damage to interior finishes.
Commissioning and final checks by AirGreen
After the mechanical installation, we carry out a series of checks before handing the system over to the customer:
- checking the tightness and stability of the supports;
- checking the clearances around the outdoor unit;
- leak testing of the refrigerant circuits;
- vacuuming the system according to a measured procedure;
- validation of the electrical and communication wiring;
- verifying that each circuit is correctly matched to its zone;
- testing the heating and cooling functions;
- checking the drainage of the indoor units;
- explanation of the remote controls and settings;
- presentation of maintenance guidelines.
We recommend regularly cleaning the indoor unit filters and keeping the outdoor heat exchanger clear. In winter, snow must not be allowed to accumulate in front of or behind the unit. However, striking the ice with a tool is not recommended, as this could damage the coil or chassis.
An HVAC installation adapted to Montreal’s realities
This project in Côte-des-Neiges–Notre-Dame-de-Grâce illustrates the importance of adapting each installation to the building rather than applying the same method everywhere. The brick wall, foundation, window, wooden staircase, and available side space all influenced our work.
The Fujitsu AIRSTAGE Aquila XLTH dual-zone heat pump provides a well-suited solution here: two independently controlled zones, a single outdoor unit, and a wall-mounted installation that protects the equipment from snow accumulation while preserving the passageway.
At AirGreen, we carry out multi-zone heat pump installations in Montreal, Laval, Longueuil, on the North Shore and the South Shore. Every project begins with an assessment of the property, heating and cooling needs, and installation constraints. This preparation allows us to propose a system whose capacity, location, and configuration truly match the spaces it must serve.