Three comfort zones powered by a single outdoor unit installed on wall brackets
For this multi-zone heat pump installation in Montréal-Nord, the challenge was not limited to choosing the capacity. We had to integrate an outdoor unit capable of powering three distinct zones into an already landscaped backyard, without sacrificing ground space or compromising the airflow required for the equipment to operate.
Our AirGreen team installed a Hitachi airHome Multi heat pump in a triple-zone configuration on the residence’s foundation wall. The system serves three indoor units from a single outdoor compressor, making it possible to heat and cool several areas of the house without multiplying the number of appliances around the building.
The project photo illustrates an installation particularly well suited to the urban setting of Montréal-Nord. The outdoor unit is mounted above a wooden deck on two sturdy wall brackets. It remains high enough not to occupy the usable yard space and to reduce its exposure to leaves, moisture, and snow accumulation.
The positioning also takes into account the abundant vegetation on the left, the exterior cladding, the foundation wall, an existing appliance nearby, and the electrical connection located to the right of the heat pump.
Why a triple-zone configuration was the right choice for this residence
A triple-zone heat pump makes it possible to connect three indoor units to a single outdoor unit. This solution is particularly well suited to a home where the temperature varies considerably from one floor or room to another.
The three zones could, for example, correspond to:
- an open-concept ground floor;
- a primary bedroom;
- a second floor or office;
- a home spread across several levels;
- a warmer back room in summer;
- a basement with different needs from the rest of the house.
Each indoor unit has its own temperature setting and fan speed. One zone can operate while the other two remain off. The homeowner therefore does not have to treat all three areas uniformly when certain spaces are unoccupied.
This independence improves comfort, but it must be clearly understood. The three units share the available capacity of the outdoor unit. When they operate simultaneously, the system distributes its output according to the demand from each zone.
The units must also operate in a compatible mode. In summer, they can be used for cooling, dehumidification or ventilation. In winter, they can heat or ventilate. One zone normally cannot be set to heating while another simultaneously requests cooling.
We always explain how this works before finalizing a multi-zone HVAC installation, because proper technical selection must be accompanied by realistic system use.
A wall-mounted installation to preserve the deck and yard
The most visible choice in this project was using metal wall brackets rather than a ground slab or a table placed on the deck.
This method was particularly well suited to the existing layout.
No floor space sacrificed
The surface beneath the unit remains clear. The homeowner therefore retains more space to move around, maintain the yard or use the deck.
In urban areas such as Montréal-Nord, Anjou, Saint-Léonard and Montréal-Est, backyards are often narrow and shared between several uses. An outdoor unit placed directly on the ground can quickly become an obstacle, especially when it is near a walkway or door.
The wall-mounted installation shown here clears the deck while maintaining convenient access to the unit.
Better protection against buildup
The heat pump is positioned well above the ground. It is therefore less exposed to:
- fallen leaves;
- mud;
- splashing;
- grass and plants;
- accumulated snow;
- standing water;
- the items stored in the yard.
The image shows leaves and natural debris on the wooden boards. A unit installed directly on this surface would have required much more frequent clearance and cleaning around its base.
Space under the unit for defrosting
In heating mode, an outdoor heat pump naturally accumulates frost on its heat exchanger. It periodically initiates a defrost cycle that produces water.
The free space under the unit makes it easier for this water to fall and drain away. It also reduces the risk of ice quickly reaching the underside of the unit.
The owner must nevertheless monitor accumulations during the winter. Defrost water may freeze on the patio, and the area beneath the heat pump must remain clear.
Reinforced metal supports and vibration-damping mounts
The Hitachi heat pump rests on two triangular brackets secured to the foundation wall. The shape of the braces allows the unit’s weight to be transferred to the anchor points.
Vibration-damping mounts are installed between the unit’s feet and the supports. This detail is essential when a heat pump is mounted directly to the building.
Without mechanical isolation, compressor and fan vibrations can be transmitted to the foundation and then felt inside the home. The supports help reduce this transmission while keeping the equipment stable.
Before choosing a wall-mounted installation, we check in particular:
- the type of wall;
- the condition of the foundation;
- the location of visible cracks;
- the capacity of the anchors;
- the weight of the outdoor unit;
- potential vibrations;
- access for maintenance;
- the clearances required around the unit.
For this project, the supports were installed in the foundation wall rather than in the lightweight cladding on the upper section. This distinction is important: exterior cladding is not necessarily an adequate structure for supporting a multi-zone unit.
A location that preserves clearance in front of the fan
The front of the outdoor unit remains completely unobstructed. The fan can therefore discharge air toward the yard without immediately encountering a wall, fence, or decorative screen.
This clearance promotes:
- good air circulation;
- reduced recirculation;
- more stable performance;
- better heat exchange;
- easier access for cleaning the grille.
The right side of the unit also remains accessible for connections and service work.
The unit must not later be surrounded by panels, storage bins, or patio furniture. Even when a decorative screen appears open, it can reduce the available airflow and complicate HVAC maintenance.
Abundant vegetation to monitor
The left side of the installation is bordered by climbing plants and dense landscaping. We positioned the heat pump far enough away to allow air to circulate, but the vegetation will need to be maintained throughout the seasons.
Branches, leaves, and stems must not reach the outdoor heat exchanger. They can:
- get caught in the fins;
- reduce air circulation;
- retain moisture against the casing;
- make cleaning more difficult;
- cause rubbing noises;
- increase coil fouling.
Periodic trimming around the heat pump is therefore recommended. However, tools or products that could damage the fins should be avoided.
To clean the area, the owner can remove leaves around the unit and keep the passage clear. Cleaning the coil itself must be done using a suitable method to avoid bending the fins or damaging the electrical components.
A short, visible, and accessible electrical connection
The electrical disconnect is installed on the foundation wall, to the right of the heat pump. A black conduit connects this enclosure to the outdoor unit.
This arrangement keeps the connection close to the unit and facilitates access during servicing. The technician can disconnect the power locally before opening the service panels.
A professional electrical connection must comply with:
- the voltage required by the manufacturer;
- the minimum circuit ampacity;
- the maximum permitted protection;
- the conductor size;
- the type of conduit;
- mechanical protection;
- the requirements applicable in Quebec.
Protection must never be determined solely by BTU capacity. Two units with similar capacities may have different electrical requirements.
A grouped piping route on the service side
The refrigerant pipes and communication cables enter the unit from the right side. Their route is grouped and supported before entering the enclosure.
In a triple-zone configuration, three circuits connect the outdoor unit to the three indoor units. Each pair of pipes must correspond to the correct unit and be properly associated with the electrical communication connections.
During commissioning, we verify that:
- zone A corresponds to the correct refrigeration circuit;
- zone B responds to the intended control;
- zone C communicates with the correct unit;
- the connections are leak-tight;
- the cables are neither pinched nor under tension;
- the pipes are properly insulated;
- the vacuum was completed in accordance with the requirements;
- the panels can be closed without obstruction.
Reversing the piping and communication wires can cause errors, inconsistent temperatures, or unstable operation. Identifying the circuits is therefore an essential step in a triple-zone heat pump installation.
The features of the Hitachi airHome Multi triple-zone system used to plan the project
The triple-zone outdoor model in the range
In Hitachi's documentation, the outdoor unit designed for three indoor connections is model RAM-G24N3HAA.
According to the technical table on page 4, this configuration offers, among other things:
- 24,000 BTU/h of rated cooling capacity;
- 24,000 BTU/h of rated heating capacity;
- a cooling range of up to 28,000 BTU/h with ductless units;
- a heating range of up to 26,200 BTU/h;
- a TRÉS2 rating of up to 22,0;
- a CPSC2 Region 5 rating of up to 7,8;
- a COP of 3.5 at 8 °C;
- heating operation down to -20 °C;
- a maximum heating capacity of 18,500 BTU/h at -15 °C;
- a maximum heating capacity of 13,000 BTU/h at -20 °C;
- a stated outdoor sound level of 54 dB(A) at high speed;
- a 208–230 V, single-phase, 60 Hz power supply;
- minimum circuit ampacity of 19 A;
- maximum overcurrent protection of 35 A.
The table also indicates dimensions of 33.5 inches wide, 31.5 inches high, and 11.7 inches deep, as well as a net weight of approximately 121 lb. These specifications explain why suitable supports and anchors are necessary rather than an improvised lightweight attachment.
Since the nameplate is not legible in the photograph, the exact installed reference must always be confirmed in the project's technical documentation. The RAM-G24N3HAA data correspond to the triple-zone model presented by the manufacturer.
Piping designed for routes distributed throughout the home
According to the manufacturer's specifications, the triple-zone model allows:
- up to 200 feet of total piping;
- up to 82 feet between an indoor unit and the outdoor unit;
- up to 66 feet of total height;
- three 1/4-inch liquid connections;
- three 3/8-inch gas connections.
These limits provide considerable flexibility in a multilevel building. However, they do not mean that long routes should always be used.
We focus instead on minimizing detours, protecting the lines, and keeping routes accessible. Excessive length may require refrigerant adjustments and increase the number of exposed sections.
Three indoor units suited to three different needs
The airHome Multi system can be paired with several indoor unit formats:
- airHome 400 wall-mounted units;
- airHome 650 wall-mounted units;
- airHome Floor consoles;
- ducted units;
- four-way cassettes.
Available capacities vary by model, generally from 7,000 to 24,000 BTU/h.
The three connected units do not necessarily have to be identical. An open-concept area may require a 12,000 or 18,000 BTU/h unit, while a bedroom may be better served by a lower capacity.
Sizing takes several factors into account:
- area and volume;
- fenestration;
- solar orientation;
- insulation;
- level of the house;
- doors and corridors;
- occupancy;
- heat-generating appliances;
- air distribution.
A simple rule based on square footage is not always sufficient. In a multi-zone system, we must also verify that the total and combination of indoor units remain compatible with the capacity of the outdoor unit.
Low-temperature performance: understanding remaining capacity
The Hitachi airHome Multi can continue operating in heating mode down to -20 °C. This does not mean that it provides its full rated capacity at that temperature.
For the triple-zone model, the documentation indicates approximately:
- 18,500 BTU/h maximum capacity at -15 °C;
- 13,000 BTU/h maximum capacity at -20 °C.
This distinction is important for Montréal-Nord homeowners, where winter temperatures can fall well below freezing.
The system can provide a significant portion of seasonal heating, but supplemental heating may still be necessary during the coldest periods. The decision depends on the building’s heating load, insulation, and the exact capacities of the connected indoor units.
Cleanliness and control features
Depending on the indoor units selected, the Hitachi range can include several practical features.
FrostWash
The FrostWash technology uses a freeze-and-thaw process to clean the indoor coil and help remove accumulated contaminants.
Mold Guard
The Mold Guard function circulates air after certain cooling or dehumidification operations to dry the internal components. The cycle can last approximately 60 minutes.
Filtration
Wall-mounted units can use a PM2.5 activated carbon filter, while mini-cassettes can be equipped with the ViroSense S filter.
airCloud Go
An optional Wi-Fi interface allows you to use the airCloud Go app to adjust certain settings and schedule operation remotely.
These features complement maintenance, but they do not replace regular filter cleaning, drain inspections, or professional cleaning when the units become heavily soiled.
Mistakes to avoid in a triple-zone installation
Choose indoor capacities without considering simultaneous demand
Three indoor units can operate together, but they share the outdoor unit's output. Capacities must be selected according to actual needs, not solely according to the maximum capacity listed on each wall-mounted unit.
Mounting the unit to non-structural cladding
The exterior cladding visible on the upper part of the wall must not be used as the sole support point. The supports must be anchored in a structure capable of bearing the weight and vibrations.
Neglecting the plants around the coil
Vegetation that is too close can quickly hinder airflow. The area must remain maintained throughout the heat pump's service life.
Placing objects beneath the unit in winter
The space beneath the unit must remain clear to allow defrost water to drain and limit ice formation near the cabinet.
Confirming a rebate based solely on the commercial name
The brochure states that Hitachi systems may qualify for several provincial incentives. Eligibility nevertheless depends on the certified combination, the current program, the declared capacity, and the building's conditions.
We always verify the outdoor model, the three indoor units, and the recognized reference before presenting a potential price.
A discreet and functional result for this Montréal-Nord home
This installation demonstrates that a triple-zone multi-zone heat pump can be integrated neatly into a landscaped yard without taking up a large amount of ground space.
The result includes:
- a Hitachi airHome Multi unit mounted on the foundation wall;
- reinforced supports;
- anti-vibration pads;
- a height suited to winter conditions;
- clear access in front of the fan;
- an electrical disconnect nearby;
- piping grouped on the technical side;
- three indoor zones supplied by a single outdoor unit.
At AirGreen, we carry out this type of HVAC installation in Montréal-Nord, Anjou, Saint-Léonard, Laval, Longueuil, on the North Shore and the South Shore.
Our work involves more than choosing a heat pump based on its BTU rating. We must integrate the equipment into the building, preserve access, control vibrations, plan the three piping routes, and anticipate future maintenance.
In this project, the wall mounting kept the terrace usable while protecting the unit from debris and ground-level buildup. The triple-zone configuration now provides more precise control in three areas of the home, with a single outdoor unit installed in a structured and accessible manner.