A compact wall-mounted installation designed for three comfort zones and limited outdoor space
In Pierrefonds-Roxboro, in western Montreal, we installed a HITACHI airHome Multi triple-zone multi-zone heat pump to serve three distinct indoor spaces with a single outdoor unit. The project stood out because of its narrow outdoor location, bordered by the house foundation, a small wooden terrace, vegetation, and several existing lines at the base of the wall.
The photo shows an intentionally compact installation. The outdoor unit was mounted on metal wall brackets, slightly above the terrace. On the left, a vertical cover protects the main line-set route. On the right, an electrical disconnect remains accessible. The fan grille is completely unobstructed so air can be discharged toward the open space in front of the unit.
In an installation like this, a few inches can significantly change the result. A heat pump installed too low would have been exposed to leaves, snow, and moisture accumulating near the wood. A unit installed too close to the terrace would have made cleaning beneath the chassis more difficult. A poorly positioned trim piece could have interfered with the vegetation or created a messy route along the exterior siding.
We therefore designed the installation around four specific objectives:
- use a single outdoor unit to supply three zones;
- maintain access to the terrace and existing equipment;
- raise the heat pump to facilitate drainage and maintenance;
- protect the lines while maintaining a clean, understated appearance.
Why a triple-zone heat pump was a good fit for this home
Pierrefonds-Roxboro residences often have interior layouts spread across several floors, with separate bedrooms, a finished basement, and living areas whose heating and cooling needs differ significantly.
A single wall-mounted unit can be effective in an open-concept area, but it has difficulty serving three enclosed rooms or rooms located far from one another. Conversely, installing three single-zone systems would have required three outdoor condensers, more wiring, and much more space along the house.
A triple-zone multi-zone heat pump allows three indoor units to be connected to the same outdoor unit. Each unit can be controlled separately with:
- a setpoint temperature suited to the room;
- an independent fan speed;
- different scheduling;
- the option to remain off when it is not needed;
- a capacity selected according to the zone's load.
In the HITACHI airHome Multi range, the model designed for three indoor connections is the RAM-G24N3HAA. The manufacturer indicates a rated capacity of 24,000 BTU/h in cooling and 24,000 BTU/h in heating. Total capacity is modulated and distributed among the active indoor units.
This point is important: three indoor units do not mean that each one simultaneously receives its full rated capacity. The system distributes its output according to demand, settings, and the limits of the installed combination.
Three zones, but one shared operating mode
Each zone has its own control, but the outdoor system remains shared by the three indoor units.
During summer, the units can operate in:
- cooling;
- dehumidification;
- ventilation.
In winter, they can operate in:
- heating;
- ventilation.
However, one room cannot be heated while another is simultaneously cooled using the same outdoor unit. Temperatures may differ, but the primary mode must remain compatible across all three zones. This is part of the normal operation of a multi-zone heat pump.
During commissioning, we always explain this rationale to the occupants. It prevents control conflicts, particularly during spring or fall days when some rooms may be warmer than others due to sunlight.
Wall installation chosen instead of a ground-level base
The presence of a wooden deck immediately in front of the location made it difficult to use a ground-level pad. A conventional base would have encroached on the walkway while placing the unit near the leaves and moisture accumulated around the boards.
We therefore opted for installation on wall brackets.
Free up space beneath the unit
Wall mounting creates open space beneath the heat pump. This height allows you to:
- to make leaf removal easier;
- to maintain visual access beneath the chassis;
- to limit contact with moisture;
- to reduce the risk of blockage from vegetation;
- to better manage defrost water;
- to keep the unit above part of the accumulated snow.
In the photo, leaves are already visible on the terrace beneath the unit. This clearly illustrates why a ground-level installation would have been less suitable. A heat pump surrounded by wet leaves may have its rear coil become clogged more quickly, especially in the fall.
Anchoring into the foundation
The supports are secured directly into the concrete foundation beneath the exterior cladding. The foundation provides a more suitable structural base than the lightweight siding above it.
The support must be able to withstand:
- the weight of the outdoor unit;
- compressor and fan vibrations;
- forces caused by wind;
- stresses caused by freezing and thawing;
- future servicing work.
The triple-zone RAM-G24N3HAA model has a listed net weight of 121 lb, which requires suitable support and anchoring into a load-bearing material.
Vibration isolators are visible between the unit's feet and the metal supports. Their purpose is to limit mechanical transmission to the building, particularly when the condenser is installed near an occupied room.
A completely unobstructed ventilation face
The front of the heat pump faces the open space above the terrace. No wall, railing, or panel directly blocks the fan.
This arrangement helps the system discharge air without immediately bouncing it back toward the rear coil. Poor airflow can cause recirculation, meaning air the unit has just discharged returns to it.
In cooling mode, the unit discharges warm air. In heating mode, it discharges cooler air. In both cases, the fan must have sufficient clearance.
We also take into account the vegetation visible on the left. Branches, leaves, and plants can grow toward the rear coil and gradually reduce airflow into it. The owner must therefore keep this area clear during the growing season.
A vertical cover suited to the exterior cladding
On the left side of the installation, a white cover runs vertically along the siding. It protects the connections linking the outdoor unit to the three indoor units.
A triple-zone installation requires three separate refrigeration circuits. Each circuit generally includes:
- a liquid line;
- a gas line;
- a power and communication cable;
- a condensate drain, depending on the route selected.
For the RAM-G24N3HAA model, the outdoor connections specified by HITACHI are:
- three liquid lines for 1/4 po;
- three gas lines for 3/8 po.
The molding protects the insulation around the lines from:
- ultraviolet rays;
- accidental impacts;
- birds;
- insects;
- the elements;
- premature deterioration.
Its light color blends with the home’s white siding. The vertical route reduces the number of visible bends and allows the lines to be routed to the indoor units located on different levels.
Routing the lines along the bottom of the foundation
At the bottom of the image, several lines run along the deck and foundation. In an existing environment, it is common to have to work around old cables, pipes, or other technical components already in place.
Before installing a new heat pump, we must distinguish the existing lines from those belonging to the new system. We must also avoid:
- pressing the refrigerant lines against an obstacle;
- creating points where water can accumulate;
- crushing the insulation;
- exposing the cables to mechanical damage;
- placing the drains in an area where they can be torn away.
A clean route is not merely aesthetic. It also facilitates diagnosis during future HVAC maintenance, since each connection remains identifiable and accessible.
An electrical disconnect near the unit
To the right of the heat pump, an electrical disconnect box is installed on the foundation. Its proximity allows a technician to quickly isolate the unit’s power supply during an inspection, cleaning, or repair.
The RAM-G24N3HAA operates on a 208 to 230 volt, single-phase, 60 Hz power supply. The manufacturer specifies the following for this model:
- minimum circuit ampacity of 19 A;
- maximum overcurrent protection of 35 A.
These values are used for electrical sizing, but they must not be interpreted in isolation. The conductor gauge, cable type, route length, and applicable requirements must be verified before installation.
We check, among other things:
- available voltage;
- panel capacity;
- the circuit breaker;
- wiring gauge;
- grounding;
- terminal tightness;
- communication between the outdoor unit and the three indoor units.
Managing defrost water
In heating mode, the outdoor heat exchanger becomes cold. Moisture can freeze on the fins, then melt during the defrost cycle. The water then drains beneath the unit.
On a wooden deck, this water deserves particular attention. If it remains near the boards, it can create:
- an icy area;
- a slippery surface;
- prolonged moisture;
- an accumulation beneath the condenser;
- a risk of long-term wood deterioration.
Wall-mounted installation allows water to fall beneath the unit instead of remaining confined between the chassis and a base. The clearance beneath the heat pump also makes it easier to remove ice manually when winter conditions require it.
Nevertheless, the owner must monitor this area during periods of extreme cold. A heat pump should never become trapped in a mass of ice that reaches its lower grille.
Performance, flexibility, and maintenance of the HITACHI airHome Multi in Pierrefonds-Roxboro
A modulation range suited to varying needs
The three-zone model offers a cooling capacity that can modulate from 7,000 to 28,000 BTU/h in a ductless configuration. In heating mode, the indicated range extends from 9,000 to 26,200 BTU/h.
This modulation allows the Inverter compressor to reduce or increase its operation according to demand from the three zones.
When only a small bedroom needs comfort, the system does not need to operate as if the entire house were experiencing high demand. When two or three zones are calling for heating or cooling, it increases its output within the limits of its available capacity.
This approach helps to:
- maintain more stable temperatures;
- limit on-off cycles;
- adjust consumption according to occupancy;
- improve comfort in closed-off rooms;
- reduce differences between zones.
A TRÉS2 of up to 22.0 for the three-zone model
For the RAM-G24N3HAA connected to ductless units, the technical table indicates:
- a TRÉ2 of 12.5;
- a TRÉS2 of 22.0;
- a CPSC2 of 9.5 in Region 4;
- a CPSC2 of 7.8 in Region 5;
- a COP of 3.5 at 8 °C.
These ratings make it possible to compare the seasonal performance of different heat pumps. However, they do not make it possible to predict a home’s exact consumption.
Actual consumption depends in particular on:
- the level of insulation;
- the building’s airtightness;
- the requested temperatures;
- simultaneous use of the zones;
- sun exposure;
- filter cleanliness;
- the condition of the outdoor coil;
- winter temperatures.
Heating down to -20 °C, with capacity varying according to temperature
The system’s heating operating range extends down to -20 °C. For the three-zone model, HITACHI indicates a maximum heating capacity of 18,500 BTU/h at -15 °C and 13,000 BTU/h at -20 °C.
These values are essential for understanding the heat pump’s behavior during a Montréal winter.
The unit can continue operating in cold weather, but it does not maintain its rated capacity of 24,000 BTU/h at all temperatures. Supplemental heating may therefore still be necessary during the coldest periods, depending on the home's heat loss.
Proper sizing means assessing the actual needs of each zone rather than simply choosing the largest capacity available.
Up to three zone types, without requiring the same indoor format
The airHome Multi platform can accommodate several indoor unit formats:
- airHome 400 wall-mounted units;
- airHome 650 wall-mounted units;
- airHome Floor floor consoles;
- mini-cassettes;
- ducted units.
Available indoor capacities generally range from 7,000 to 24,000 BTU/h, depending on the format.
This flexibility is useful in a three-zone home. A small bedroom may receive a lower-capacity unit, while an open-concept area may require greater airflow. A basement may also require a different location or format from the one selected for the upper floor.
We avoid selecting three identical units simply to standardize the order. Each space should be assessed based on:
- its area;
- its height;
- its windows;
- its insulation level;
- its orientation;
- its use;
- its position in the building.
Outdoor sound level and placement
The outdoor sound level indicated for the RAM-G24N3HAA is 54 dB(A) during high-speed operation.
The actual sound perception also depends on the surface to which the unit is attached and on surrounding obstacles. Walls, fences, and corners can reflect noise. Supports that are too rigid or improperly leveled can transmit vibrations to the structure.
In this project, the front of the unit is unobstructed, and the vibration-dampening mounts separate the unit from its supports. Mounting the unit on the foundation also prevents its weight from resting directly on the deck boards.
FrostWash and Mold Guard
Depending on the selected indoor units, the airHome Multi lineup may include the FrostWash and Mold Guard functions.
FrostWash
FrostWash cools the indoor coil to form frost on it, then uses the melting frost to carry away some of the accumulated contaminants. This function helps maintain airflow and keep the heat exchanger clean.
Mold Guard
Mold Guard circulates air for approximately 60 minutes after certain air-conditioning or dehumidification operations. The purpose is to dry the internal components and reduce the moisture that promotes odors and mold.
These features do not replace complete HVAC maintenance. Filters must be cleaned, drains must be inspected, and indoor fans may require thorough cleaning after several seasons.
Filtration and R32 leak sensor
Depending on the indoor model, the system may use:
- an activated-carbon PM2.5 filter;
- a ViroSense S filter;
- an R32 refrigerant leak sensor;
- a visual or audible alarm;
- a compatible control interface.
The brochure indicates that compatible indoor units may incorporate a sensor designed to alert users in the event of an R32 leak.
R32 refrigerant requires proper installation methods. The quality of the flared connections, leak testing, and evacuation are critical to prevent refrigerant loss and protect the compressor.
Remote control with airCloud Go
An optional Wi-Fi interface allows use of the airCloud Go app. In a three-zone configuration, remote control can be convenient when the indoor units are distributed across multiple floors.
The homeowner can, among other things:
- adjust temperatures;
- turn off an unused zone;
- schedule operating times;
- prepare the home before returning;
- check certain operating parameters.
The ability to control each unit separately improves comfort management, provided the system’s common mode is respected.
Rebates: verify the exact combination before confirming an amount
HITACHI documentation indicates that the airHome Multi range is eligible for most provincial heat pump incentives. Final eligibility nevertheless depends on the program rules, the exact combination of units, and the list in effect at the time of installation.
Before announcing financial assistance, we verify:
- outdoor model;
- the three indoor models;
- certified combination number;
- recognized capacity;
- building type;
- installation date;
- required documents.
The name “airHome Multi” alone is not sufficient to confirm eligibility for a rebate.
Manufacturer’s warranty
The documentation provides a standard warranty of seven years on the compressor and five years on parts. An extended warranty of ten years on the compressor and parts is available for residential installations when the online registration requirements are met. An enhanced option may also include additional protection subject to the applicable terms.
Registration must be completed within the period specified by the manufacturer. We also recommend keeping:
- the invoice;
- serial numbers;
- proof of installation;
- commissioning documents;
- registration confirmations.
Mistakes to avoid in a triple-zone installation near a terrace
This installation in Pierrefonds-Roxboro highlights several common mistakes.
Placing the unit directly on wood
Wood can vibrate, retain moisture, and shift over time. Wall mounting prevents transferring the entire weight to the decking.
Installing the heat pump too low
Leaves, snow, and plants can quickly obstruct the heat exchanger.
Neglecting vegetation
A plant that seems far away during installation can reach the condenser after a growing season.
Blocking the disconnect
The electrical box must remain accessible for service.
Crushing the lines inside trim that is too narrow
A triple-zone installation includes several pipes. They must be organized without reducing the insulation thickness.
Forgetting to clean beneath the unit
The space beneath the condenser must remain clear. Leaves visible on the terrace should be removed regularly.
Sizing the zones based solely on their area
A room with many windows may require more capacity than a larger, well-insulated room.
Assuming that three controls allow three opposite modes
The settings are independent, but the primary mode remains shared.
The final result of our installation in Pierrefonds-Roxboro
This multizone heat pump installation in Montreal can now serve three indoor spaces from a single HITACHI outdoor unit.
The project includes:
- a HITACHI airHome Multi triple-zone heat pump;
- an outdoor unit designed for three connections;
- wall brackets secured to the foundation;
- anti-vibration pads;
- an unobstructed ventilation panel;
- a vertical trim piece matching the siding;
- an accessible electrical disconnect;
- a raised platform protecting the unit from leaves and moisture;
- a configuration designed to facilitate future maintenance.
The result shows that a narrow location near a terrace can accommodate a complete HVAC installation when clearances, structure, drainage, and piping routes are analyzed before work begins.
At AirGreen, we apply this approach throughout Greater Montreal, whether the project is located in Pierrefonds-Roxboro, Laval, Longueuil, on the North Shore, or on the South Shore. The equipment may be similar from one home to another, but the installation method must always suit the property.