A high wall-mounted installation designed to free up ground space and serve three separate zones
At Rivière-des-Prairies–Pointe-aux-Trembles, we installed a HITACHI airHome Multi triple-zone multi-zone heat pump on the rear façade of a property where available ground space was particularly limited. The outdoor unit had to power three indoor units while fitting into a narrow passage bordered by a brick wall, vertical wood siding, an upstairs window, and several architectural elements.
Rather than placing the unit on a slab or ground-level base, we chose an installation on reinforced metal wall brackets. This approach keeps the passageway clear, distances the unit from accumulated snow, and keeps the refrigerant connections close to the routes leading to the three indoor zones.
The job-site photo clearly illustrates the complexity of this project. The HITACHI outdoor unit is installed at a considerable height between two sections of the building. Its fan remains oriented toward the open area, the refrigerant lines are grouped along the wall, and the electrical disconnect is accessible nearby.
This type of HVAC installation in Montreal requires more thorough planning than a traditional ground-level installation. The wall’s load-bearing capacity, fan clearance, vibrations, working height, piping route, and future access for heat pump maintenance must all be assessed.
Why install the outdoor unit at an elevated height
At this property in Rivière-des-Prairies–Pointe-aux-Trembles, the available space between the walls did not allow for easy placement of a ground-level unit without obstructing the passageway. A low installation would also have exposed the unit more to snow, ice, leaves, and debris.
The wall-mounted installation offers several practical advantages here:
- it preserves ground-level access;
- it reduces the risk of snow blockage;
- it keeps the unit away from puddles and ice buildup;
- it moves the unit away from paths leading to the upper floors;
- it facilitates the organization of the three sets of lines;
- it avoids occupying a useful section of the yard or passageway.
However, this solution is not automatically suitable for every building. Decorative cladding must never be considered the equipment’s sole support. The anchors must reach a sufficiently strong structure, and the mounting method must be suited to the unit’s weight and the vibrations generated by the compressor and fan.
In this installation, the two triangular brackets transfer the load to the masonry wall. Their depth keeps the unit away from the cladding, while the metal crossbars support the base of the outdoor unit.
A triple-zone heat pump for better comfort distribution
A triple-zone multi-zone heat pump allows three indoor units to be connected to a single outdoor unit. This configuration is advantageous when the areas to be treated are separated by walls, doors, or different levels.
A single wall-mounted unit installed in a central area is not always enough to cool bedrooms properly. In winter, the heat produced in one area does not necessarily spread to an upper floor or basement. A triple-zone system instead makes it possible to place an indoor unit directly in each priority area.
Each zone can have:
- its own temperature setting;
- its own fan speed;
- an appropriate airflow direction;
- its own operating schedule;
- independent control.
One unit can be turned off when its room is unoccupied while the other two continue to operate. This flexibility is useful in a residence where occupancy varies between bedrooms, living areas, and workspaces.
However, an important rule must be kept in mind: the three indoor units share the same outdoor unit. They must therefore operate in compatible modes. In summer, they can be used for cooling, dehumidification, or ventilation. In winter, they can operate in heating or ventilation mode. It is not possible to heat one room while another simultaneously requests cooling.
The HITACHI brochure states that the airHome Multi range can serve up to five indoor units, depending on the outdoor model. It also confirms that each unit can be controlled individually and that several indoor formats can be combined, including wall-mounted units, floor consoles, mini-cassettes, and ducted units.
The outdoor model designed for three indoor units
In the HITACHI airHome Multi range, the model associated with a configuration that can accommodate up to three indoor units is the RAM-G24N3HAA.
Its main published features for a ductless combination include:
- rated cooling capacity of 24,000 BTU/h;
- modulating cooling capacity of 7,000 to 28,000 BTU/h;
- rated heating capacity of 24,000 BTU/h;
- modulating heating capacity of 9,000 to 26,200 BTU/h;
- TRÉS2 of up to 22,0;
- region 5 CPSC2 of up to 7,8;
- advertised COP of 3.5 at 8 °C;
- heating operation down to -20 °C;
- cooling operation down to 46 °C;
- advertised outdoor sound level of 54 dB(A);
- refrigerant R32.
These figures vary depending on the exact combination of indoor units. To determine the certified performance of a specific combination, always check the AHRI reference corresponding to the models actually installed.
The outdoor capacity is not simply divided into three equal parts. The Inverter compressor distributes its output according to the demand of each zone. An indoor unit may receive more capacity when it is the only one operating. When all three zones simultaneously call for heating or cooling, the total capacity is distributed among them.
What the photograph reveals about our installation approach
A fan orientation toward an unobstructed area
The outdoor unit’s fan is directed toward the open space rather than the opposite wall. This positioning is essential to prevent the discharged air from being immediately drawn back in through the coil.
In cooling mode, the unit expels heat. If this hot air remains trapped in an overly enclosed space, system pressure may increase and efficiency may decrease. In heating mode, the unit extracts heat from the outdoor air and also requires a sufficient volume of air.
In a narrow passageway, we therefore assess:
- the distance in front of the fan;
- the space behind the coil;
- side obstacles;
- the clearance below the soffits;
- the presence of windows;
- natural air circulation;
- the location of the other equipment.
Brackets suitable for a multizone unit
A triple-zone unit is generally heavier than a small single-zone outdoor unit. The RAM-G24N3HAA model is listed with a net weight of approximately 121 lb, or nearly 55 kg.
This weight must be supported securely and stably, taking into account the forces generated during startup, operation, and defrost cycles. The brackets must also withstand temperature variations and humidity.
In the photo, the supports consist of:
- two vertical posts attached to the wall;
- horizontal arms beneath the unit;
- diagonal braces;
- multiple attachment points;
- supports beneath the unit base.
This triangulated geometry limits arm flexing. It also keeps the unit level, which is important for the drainage of defrost water.
An installation above the passageway
The selected height keeps the unit from obstructing movement at ground level. It also protects the fan from snowdrifts.
Installing the unit at height, however, introduces new responsibilities. The outdoor unit must remain accessible for:
- coil cleaning;
- pressure checks;
- access to the service valves;
- electrical inspection;
- compressor diagnostics;
- any potential component replacement.
We therefore avoid placing the unit under an inaccessible overhang or in a space where a ladder could not be used safely.
Three refrigerant circuits to organize without improvisation
The three-zone system requires three separate sets of refrigerant lines. For the RAM-G24N3HAA model, the outdoor unit has three liquid connections 1/4 po and three gas connections 3/8 po.
In the photo, the insulated lines are grouped along the wall before branching off toward the different zones. This arrangement reduces clutter and protects the pipes from accidental impacts.
Each circuit must be clearly identified to prevent a mix-up between:
- the refrigerant port;
- the communication cable;
- the corresponding indoor unit;
- the condensate drain.
A mix-up between two circuits can cause a startup fault. For example, the indoor unit in zone B could communicate with electrical port B while being connected refrigerant-wise to port C. The system would then not operate properly, even if each connection appears to have been completed correctly on its own.
We therefore identify the lines before closing them up and verify the connections during commissioning.
Piping limits for the three-zone system
HITACHI documentation specifies several limits for the RAM-G24N3HAA:
- maximum total piping length: 200 feet;
- maximum length between the outdoor unit and an indoor unit: 82 feet;
- maximum total height: 66 feet;
- minimum total length: 16 feet;
- maximum height difference between indoor units: 16 feet.
This data directly affects the project’s feasibility. In a multi-level property, routes must not be estimated in a straight line. Vertical rises, detours around windows, passages beneath soffits, and horizontal runs to each room must be measured.
A proper installation is also one in which the lines retain gradual bends. Bends that are too tight can crush the copper and restrict refrigerant flow.
Choosing R32 refrigerant
The HITACHI airHome Multi range uses R32 refrigerant. This refrigerant requires specific procedures during installation and commissioning.
Compatible indoor units may include a leak sensor. Depending on the configuration, an alert may be provided by an indicator light, an audible alarm, or a control accessory.
For our team, this means in particular:
- follow the manufacturer’s handling procedures;
- ensure the connections are leak-tight;
- carry out a pressure test;
- perform a proper evacuation;
- check the charge according to the line lengths;
- confirm that the planned alert systems are working.
Connection quality is particularly important in a multi-zone system because it has more connections than a single-zone unit. Each additional connection is a point that must be carefully prepared and inspected.
A complete commissioning to ensure the three zones operate properly
Leak test and evacuation
Before releasing the refrigerant into the lines, we check the connections for leaks. This step detects an imperfect flare, an insufficiently tightened nut, or a damaged line.
We then evacuate the system to remove air and moisture from the network. Residual moisture can react with the compressor oil, promote acid formation, and reduce the system’s service life.
In a triple-zone installation, the internal volume of the network is greater. The time required for evacuation may therefore be longer than for a single-zone installation.
Checking each indoor unit
We test all three units individually and then simultaneously. The procedure includes:
- starting the first zone;
- checking the supply air temperature;
- confirming drainage;
- checking the louvers;
- checking communication;
- repeating the process for the other two zones;
- testing combined operation;
- checking for abnormal vibrations;
- inspection of the outdoor unit;
- explaining how it works to the occupants.
This commissioning also confirms that the compressor modulates correctly when the zones turn on or off.
Cold-weather performance
The outdoor unit can operate in heating mode down to -20 °C, but its capacity decreases as the temperature drops.
For the RAM-G24N3HAA, the brochure specifically lists:
- a nominal heating capacity of approximately 16,000 BTU/h at -8 °C;
- a maximum capacity of approximately 18,500 BTU/h at -15 °C;
- a maximum capacity of approximately 13,000 BTU/h at -20 °C.
These values are important in eastern Montreal, where winter temperatures can remain very low for several hours. The system must be selected based on the building's heating load and the capacity available at cold temperatures, not solely on the nominal rating of 24,000 BTU/h.
Depending on the property's insulation and configuration, supplemental heating may still be necessary during the coldest periods.
Defrost water management
In heating mode, frost may accumulate on the outdoor coil. The system then initiates a defrost cycle that produces water beneath the unit.
Installing the unit high on the wall limits the risk of this water accumulating directly around the appliance. However, it must be ensured that its drainage does not create:
- a sheet of ice in a passageway;
- water accumulating on a step;
- water flowing toward a door;
- water seeping toward the wall;
- a hazard for occupants.
The position of the brackets and the space beneath the unit facilitate drainage, but the area below must remain monitored during winter.
Indoor functions available with airHome Multi
Depending on the indoor unit models selected, the HITACHI range offers several useful functions.
FrostWash
The FrostWash technology freezes and then melts moisture on the coil to carry away some of the accumulated dust and contaminants. It helps maintain the cleanliness of the heat exchanger and airflow.
This function does not replace periodic filter cleaning or professional maintenance of the fan and condensate drain pan.
Mold Guard
The Mold Guard function circulates air after cooling or dehumidification to help dry the internal components. The sequence can last approximately 60 minutes.
Filtration
Depending on the selected unit, the system may use:
- a PM2.5 activated carbon filter;
- a ViroSense S filter;
- a washable pre-filter;
- filtration suited to the wall-mounted, ducted, or cassette format.
The exact configuration must always be confirmed with the indoor unit model number.
airCloud Go Order
An optional interface enables use of the airCloud Go app. It can be used to schedule operation, control the temperature remotely, and monitor certain usage parameters.
Mistakes to avoid in a multi-zone wall-mounted installation
Attaching the unit only to the siding
Wood, vinyl, or decorative brick siding does not necessarily provide sufficient structural support. The anchors must reach a reliable support.
Underestimating the equipment's weight
A multi-zone unit imposes a significant load. The brackets must be selected according to the actual weight and installed level.
Positioning the fan facing a wall that is too close
An obstacle in front of the unit can cause air recirculation and reduce efficiency.
Leaving the lines exposed
Exterior insulation deteriorates under ultraviolet rays and the elements. The lines must be protected and secured.
Forgetting access to the service valves
A compact installation must not block the connections and panels required for maintenance.
Using the three zones in conflicting modes
All units share the same refrigeration cycle. They must be configured in compatible seasonal modes.
Choosing capacities without a load calculation
Three indoor units should not be selected solely based on approximate floor area. Windows, insulation, floors, and exposure must be considered.
An AirGreen installation adapted to the constraints of eastern Montréal
This HITACHI airHome Multi triple-zone heat pump installation in Rivière-des-Prairies–Pointe-aux-Trembles shows how a restricted outdoor space can be used efficiently without obstructing the passage.
The wall-mounted setup on metal brackets keeps the outdoor unit elevated, away from snow and traffic areas. The fan's orientation promotes unobstructed air discharge, while the three refrigerant circuits are routed in an organized manner to the indoor units.
We apply this same rigor to installations carried out in Montréal, Laval, Longueuil, on the North Shore, and on the South Shore. Every building requires a tailored solution: wall bracket, ground pad, rooftop, balcony, side passage, or narrow yard.
In this project, the main challenge was bringing together three comfort zones around a single outdoor unit while respecting the existing architecture. The result provides a compact layout, good technical accessibility, and a multi-zone heating and cooling solution suited to the property's daily use.