An installation on an existing concrete base adapted to the property’s actual constraints
In Auteuil, in northern Laval, we installed a HITACHI airHome Multi dual-zone multi-zone heat pump to cool and heat two distinct areas of the residence using a single outdoor unit. The project clearly illustrates a common reality in residential renovations: the best location is not always an open area where a new prefabricated slab can simply be placed.
On this property, a substantial concrete structure was already located against the side wall of the house. Rather than occupying another part of the yard or unnecessarily creating a second base, we studied the possibility of using this existing surface. Its height, apparent stability, and location near the path of the lines made it an interesting option, provided that the heat pump was installed correctly and the necessary clearances were maintained.
The result visible in the photo is a discreet and functional installation: the HITACHI airHome Multi outdoor unit rests on anti-vibration mounts, the refrigerant lines are directed into a vertical trim piece matching the home’s siding, and the drainage was routed downward in a controlled manner.
This configuration addressed several of the homeowner’s priorities:
- serve two indoor zones without multiplying the number of outdoor units;
- preserve the available lawn space;
- minimize the visual impact of the lines;
- keep the unit above the usual snow level;
- facilitate access to the connections for future HVAC maintenance.
Why a dual-zone heat pump was suitable for this Auteuil home
A home can have very different heating and cooling needs from one floor to another or from one room to another. In Auteuil, as elsewhere in Laval, many residences have a finished basement, a ground floor exposed to the sun, and bedrooms upstairs. A single wall-mounted unit placed in a central area cannot always distribute air evenly throughout all these zones.
A dual-zone multi-zone heat pump allows two indoor units to be connected to the same outdoor unit. Each one can have:
- its own setpoint;
- its own fan speed;
- programming adapted to the room’s use;
- independent control;
- a capacity selected according to the zone’s thermal load.
This makes it possible to maintain a comfortable temperature in a living area while applying a different setting in a bedroom, office, upper floor, or basement.
The HITACHI airHome Multi line is designed to support two to five indoor units, depending on the outdoor model. The two-connection version, RAM-G18N2HAA, offers a rated cooling capacity of 18,000 BTU/h and a rated heating capacity of 22,000 BTU/h. Its actual capacity is distributed among the active indoor units according to their demand and the selected combination.
The practical advantage of a single outdoor unit
Installing two single-zone systems would also have made it possible to control two rooms separately, but this approach would have required two condensers, more wiring, two disconnect devices, and more space around the house.
In this HVAC installation project in Auteuil, the multi-zone system offered several advantages:
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A more orderly exterior appearance
Only one unit is visible along the building. -
Better use of the available space
The existing concrete base could accommodate a single outdoor unit without compromising access or the yard. -
Two distinct comfort zones
Occupants can adjust each indoor unit according to their habits. -
Centralized outdoor maintenance
The compressor and the main outdoor components are housed in a single unit. -
Modulating capacity
Inverter technology adjusts the compressor’s operation to the combined needs of the two zones.
However, it is important to clearly explain how a multi-zone system works: the indoor units can be adjusted separately, but they must 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 the other is simultaneously in cooling mode with the same outdoor unit.
A raised concrete base: a constraint turned into an advantage
The large concrete base visible in the photo occupies a significant portion of the side yard. At first glance, it could have been considered an obstacle. Upon analysis, however, it offered several favourable characteristics.
Valuable protection against snow
In Laval’s climate, a heat pump installed too close to the ground can become surrounded by snow after a storm or after the yard has been cleared. Accumulations can obstruct the rear heat exchanger or reduce the space in front of the fan.
The elevated positioning of this unit helps keep it above:
- ordinary snowbanks;
- snow pushed up against the foundation;
- dead leaves;
- grass and vegetation;
- water that could accumulate at ground level.
This clearance does not eliminate the need for the owner to clear the unit in winter, but it considerably reduces the risk of obstruction at ground level.
A solid and stable surface
A multizone heat pump must rest on a stable base. Any movement, settling, or misalignment can contribute to vibration and place undesirable strain on the connections.
The existing concrete surface provided a rigid support. Nevertheless, we added blocks and anti-vibration supports beneath the unit in order to:
- to limit direct contact with the base;
- to reduce vibration transmission;
- to facilitate drainage beneath the unit;
- to create a small space for inspection;
- to protect the lower part of the cabinet from persistent moisture.
Leveling the unit remains essential. A poorly seated condenser can vibrate, produce more noise, or drain water from the defrost cycles less efficiently.
Visible drainage: a detail that plays an important role
On the side of the concrete base, we can see a transparent line descending toward the ground. In a multizone installation, each indoor unit produces condensation in cooling and dehumidification mode. This water must be drained by gravity or, when the configuration requires it, with a condensate pump.
Poorly designed drainage can lead to:
- indoor leaks;
- water accumulating inside the molding;
- odors;
- the buildup of deposits in the pipe;
- damage to walls or ceilings;
- water returning to the indoor unit.
In this project, the outdoor line was routed downward and secured against the structure to prevent it from remaining loose or being exposed to movement. The slope, outlet point, and stability of the pipe are just as important as its appearance.
It is also important to distinguish water from the indoor units from water produced by defrosting the outdoor unit. During winter heating, a heat pump extracts heat from the outdoor air. Frost may form on the heat exchanger and then melt during the defrost cycle. This water drains beneath the condenser and may freeze on the base.
The available clearance beneath the unit and the absence of an immediate obstruction help reduce the risk of an ice mass reaching the chassis. Nevertheless, the owner must monitor this area during extended periods of freezing temperatures.
A vertical molding selected to protect the connections
One of the most visually discreet elements in this Auteuil installation is the vertical molding that extends to the upper part of the wall. Its light color is close to that of the exterior cladding, reducing the visual impact of the lines.
This trim cover protects several essential components:
- the copper refrigerant lines;
- the insulation surrounding the gas line;
- the communication cables;
- certain drainage components, depending on the route;
- the penetrations and transitions between the exterior and interior.
Without protection, the refrigerant insulation can be damaged by ultraviolet rays, birds, the weather, or maintenance work around the house. Damaged insulation can cause condensation and impair performance.
For the RAM-G18N2HAA dual-zone configuration, the manufacturer specifies two 1/4 in. liquid connections and two 3/8 in. gas connections on the outdoor unit side. The indicated minimum total length is 16 feet, while the maximum total length can reach 165 feet, subject to compliance with the system’s other technical limits.
This data does not mean that all installations should use the maximum permitted length. The more direct and well-planned the route, the easier it is to protect the piping, limit losses, and maintain an accessible installation.
Special attention to the vinyl siding
The exterior wall is covered with vinyl siding. This material must not directly support the weight of the trim cover or technical components. The fasteners must reach a solid structure behind the siding while avoiding crushing the panels.
When carrying out this type of installation, we must consider:
- the expansion and contraction of the vinyl;
- the watertightness of penetration points;
- the location of the studs;
- water management behind the siding;
- the visual alignment of the trim cover;
- the ability to access the lines later.
A trim cover installed at an angle or tightened excessively against the siding may deform with temperature changes. On this project, the vertical routing makes it possible to group the lines without creating a series of horizontal sections visible on the facade.
The day-to-day performance and features of the HITACHI airHome Multi
Efficiency of up to a SEER2 of 23.0
The airHome Multi range covers outdoor capacities from 18,000 to 42,000 BTU/h. Depending on the model and the type of connected indoor units, it can achieve a SEER2 of 23.0 and an EER2-5 of 7.85.
For the RAM-G18N2HAA two-zone ductless configuration, the manufacturer’s table indicates, among other things:
- a rated cooling capacity of 18,000 BTU/h;
- a rated heating capacity of 22,000 BTU/h;
- a TRÉ2 of 12.5;
- a TRÉS2 of 23.0;
- a CPSC2 of 10.0 in Region 4 and 7.85 in Region 5;
- a COP of 3.3 at 8 °C;
- a maximum heating capacity of 14,300 BTU/h at -15 °C;
- a maximum heating capacity of 9,700 BTU/h at -20 °C.
These figures demonstrate why sizing must be carried out carefully. A rated capacity stated at a moderate temperature is not the same as the capacity available during a very cold night in Laval.
We therefore assess the heat loss of each zone, insulation, windows, building orientation, and the presence of a supplementary heating system before confirming the combination of units.
Heating operation down to -20 °C
The manufacturer indicates a heating operating range from -20 °C to 24 °C for the outdoor units in this range. The cooling range extends from -10 °C to 46 °C.
This cold-weather operating capability is relevant for a residence in Auteuil. However, it does not mean that the heat pump will produce its full rated capacity at -20 °C. Performance and capacity gradually decrease as the outdoor temperature drops.
In a well-designed installation, we seek to maximize the efficient use of the heat pump while maintaining appropriate backup heating for periods when demand exceeds its available capacity.
Several indoor unit options
The airHome Multi platform can be combined with different indoor formats:
- airHome 400, a wall-mounted unit focused on essential features;
- airHome 650, a wall-mounted unit with additional smart features;
- airHome Floor, a floor console;
- airHome Mini Cassette, integrated into the ceiling;
- airHome Ducted, concealed in a mechanical space.
Available indoor capacities generally range from 7,000 to 24,000 BTU/h, depending on the selected family. This flexibility makes it possible to adapt each zone to its architecture rather than imposing two identical units in very different rooms.
A sound level suitable for a residential area
The outdoor model with two connections is rated for a high sound level of 52 dB(A). Depending on the model, some wall-mounted indoor units can operate at 27 or 29 dB(A) at low speed, while floor consoles can go as low as 22 dB(A).
However, the outdoor unit’s placement affects acoustic comfort just as much as its specifications. A unit installed in a recess, against several reflective surfaces, or directly beneath a bedroom window may seem noisier.
On this project, the front of the fan faces an open space. The discharged air can therefore disperse without immediately hitting a wall located a few inches in front of the unit.
FrostWash and Mold Guard: useful features that do not replace cleaning
Some compatible indoor units use FrostWash technology. The coil is cooled to form a layer of frost, which then melts and carries away some of the contaminants accumulated on the heat exchanger.
The Mold Guard function continues internal ventilation for approximately 60 minutes after certain cooling or drying operations. It helps dry the internal components and limit conditions that promote odors and mold.
These features can help keep the inside of the appliance clean, but they do not replace:
- periodic filter cleaning;
- inspecting the drain;
- professional cleaning of the tangential fan;
- checking the heat exchanger;
- complete HVAC maintenance when the appliance is dirty.
R32 refrigerant filtration and monitoring
Depending on the indoor model, the range may use a PM2.5 activated carbon filter or a ViroSense S filter. Some units also include an R32 refrigerant leak sensor, accompanied by a visual and audible alarm or an optional receiver kit.
The system uses the refrigerant R32. The installation must therefore be carried out using the appropriate tools, practices, and procedures. The quality of the flared connections, the leak test, evacuation, and commissioning are critical to the system’s reliability.
Smart control with airCloud Go
An optional Wi-Fi interface allows use of the airCloud Go app. The owner can then manage certain settings remotely, create schedules, and monitor the system’s operation.
For a dual-zone installation, this controller can be particularly practical when one unit is on another floor or in a less accessible room. Each zone can be adjusted according to its occupancy while respecting the system’s general mode.
Mistakes to avoid in a multi-zone installation in Laval
This project highlights several common mistakes that we aim to prevent.
Choosing the base simply because it already exists
An existing structure is not automatically suitable. Its stability, level, dimensions, and the clearances around the unit must be checked.
Block access to the connections
The technical side of the heat pump must remain accessible for testing, repairs, and maintenance. A trim piece or obstacle placed too close can unnecessarily complicate servicing.
Underestimating defrost water
An installation elevated on concrete can produce a significant sheet of ice in winter. Space must be maintained beneath the chassis, and buildup must be monitored.
Installing an indoor unit that is too powerful for a small room
An oversized unit can quickly reach the requested temperature without providing good dehumidification. Capacity selection must be based on the needs of each zone.
Assuming that two zones can operate in opposite modes
The controls are independent, but the outdoor unit remains shared. Occupants must understand this feature during commissioning.
Neglecting line protection
Insulation exposed to sunlight deteriorates. The exterior trim is not merely decorative: it protects an essential part of the refrigeration system.
An installation designed to remain accessible
The outdoor unit is positioned high enough to protect it from the ground, while remaining accessible without heavy specialized equipment. The service panels, electrical connections, and lines can be inspected from the base.
This accessibility is important. A highly aesthetic but unserviceable installation often leads to additional costs several years later. At AirGreen, we consider the following from the outset:
- potential replacement of a component;
- heat exchanger cleaning;
- access to the valves;
- wiring inspection;
- drainage control;
- the safe removal of the unit if necessary.
The final result of our installation in Auteuil
This multi-zone heat pump installation in Laval transforms an architectural constraint into a practical solution. The existing concrete base now serves as a stable, elevated support, while the vertical trim protects the lines and blends discreetly with the home’s light-colored siding.
The homeowner now benefits from two separately controlled comfort zones powered by a single HITACHI outdoor unit.
The main elements of the project include:
- a HITACHI airHome Multi dual-zone heat pump;
- an installation raised above the ground;
- anti-vibration supports;
- a protected vertical route for the lines;
- drainage secured along the base;
- a completely unobstructed ventilation facade;
- a configuration adapted to the needs of two spaces;
- an installation designed for Auteuil’s winter conditions.
This project reflects our approach to installations in Montréal, Laval, Longueuil, the North Shore, and the South Shore: observe the building, use the available space intelligently, and build an HVAC solution that remains logical long after our team has left.