Three comfort zones in a Saint-Léonard residence thanks to a discreet, carefully planned wall-mounted installation
In Saint-Léonard, we completed the installation of a HITACHI airHome Multi triple-zone multi-zone heat pump to cool and heat three distinct spaces with a single outdoor unit. The project required precise planning of the indoor locations, since each wall-mounted unit had to provide good air distribution without interfering with circulation, furniture, or the appearance of the rooms.
The photograph shows one of the indoor units installed near the ceiling on a light-colored, unobstructed wall. The wall-mounted air conditioner is operating: its indicator light is on and the air outlet louver is open. This position allows it to project air toward the center of the room while keeping the floor space completely clear.
The visual integration is particularly understated. The white casing of the HITACHI unit blends with the wall and ceiling, while no duct cover is visible in the photographed area. The routing of the lines was therefore planned to limit the visual impact in the room.
In a triple-zone system, this wall-mounted unit represents only part of the work. Behind the installation are three refrigerant lines, three condensate drains, several communication cables, and a shared outdoor unit that must distribute its capacity according to the simultaneous demands of the different rooms.
The client's actual need: correcting temperature differences between rooms
In many Saint-Léonard properties, a single wall-mounted unit installed in the living room is not enough to maintain an even temperature throughout the residence. Doors, corridors, floors, and wall layouts limit the natural circulation of air.
A room exposed to the sun can become much warmer than a north-facing bedroom. A basement may remain cool while the upper floor accumulates heat. A bedroom used at night does not have the same needs as a living space occupied during the day.
The triple-zone configuration addresses these differences by allowing an indoor unit to be placed in each priority area. Occupants can then adjust separately:
- the temperature of each zone;
- the fan speed;
- the airflow direction;
- the usage schedule;
- turning each unit on or off.
This independent control significantly improves comfort, but it must be clearly understood. The three units share the same outdoor unit and must operate in compatible modes. In summer, they can be used for cooling, dehumidification, or ventilation. In winter, they can be used for heating or ventilation.
It is therefore not possible to request heating in one room and cooling in another at the same time. This rule is important during everyday system use.
According to HITACHI documentation, airHome Multi can power up to five indoor units, depending on the outdoor model selected. Each unit can be controlled individually, and several formats are compatible: airHome 400 and airHome 650 wall-mounted units, floor consoles, mini-cassettes, and ducted units.
Why choose a triple-zone installation instead of three separate systems
Installing three single-zone systems would have required three outdoor units, three separate power supplies, and more space on the façade or in the yard.
The multi-zone system reduces this clutter. A single outdoor unit powers three indoor units. This configuration offers several advantages:
- fewer visible outdoor components;
- better use of available space;
- a single main equipment area;
- less outdoor noise than with three separate units;
- centralized management of heating and cooling;
- the ability to adjust capacity according to each room’s needs.
However, the choice between a multi-zone system and several single-zone units should be based on the property. A multi-zone system is particularly suitable when the three rooms are relatively close together and the piping runs can be grouped efficiently.
The outdoor model suitable for three zones
Within the HITACHI airHome Multi range, the outdoor model designed to accommodate up to three indoor units is the RAM-G24N3HAA.
For a ductless combination, the main published data include:
- nominal cooling capacity: 24,000 BTU/h;
- modulating cooling capacity: from 7,000 to 28,000 BTU/h;
- nominal heating capacity: 24,000 BTU/h;
- modulating heating capacity: from 9,000 to 26,200 BTU/h;
- TRÉ2 of 12,5;
- TRÉS2 of up to 22,0;
- CPSC2 for Region 5 of up to 7,8;
- COP of 3.5 at 8 °C;
- heating operation down to -20 °C;
- cooling operation from -10 °C to 46 °C;
- advertised outdoor sound level of 54 dB(A);
- refrigerant R32.
These data concern the equipment family and may vary depending on the exact combination of indoor units. To verify actual efficiency and eligibility for a subsidy, consult the AHRI number corresponding to the precisely installed models.
Capacity distributed according to demand, not divided into three fixed shares
A common mistake is to assume that a 24,000 BTU/h outdoor unit automatically provides 8,000 BTU/h to each of three zones.
Operation is more dynamic. The Inverter compressor adjusts its speed according to overall demand, then distributes capacity among the active zones.
For example:
- if only one unit is operating, it may receive a significant share of the available capacity;
- if two zones are active, output is shared according to their needs;
- if all three zones simultaneously require their full capacity, the outdoor unit distributes its maximum output among them;
- when a zone reaches its setpoint, the system can reduce or redirect its capacity.
This modulation improves comfort, but it makes the choice of indoor units particularly important. Capacities must be selected according to the actual loads of each room and the combinations approved by the manufacturer.
What the photo of the indoor installation shows
A unit installed in an unobstructed part of the wall
The wall-mounted unit is positioned in the upper part of the wall, with no furniture or obstacle in front of it. This position promotes even air distribution throughout the occupied area.
Cold air naturally tends to descend, while warm air rises. In cooling mode, the airflow can be directed more toward the front. In heating mode, the louver can be directed lower to bring warmth toward the occupants.
A good position also helps avoid a direct draft on:
- a bed;
- a sofa;
- a desk;
- a door;
- a television;
- a tall piece of furniture.
Close to the ceiling requires precision
The unit is installed near the ceiling. This position is common, but it must comply with the clearances specified by the manufacturer.
Air intake generally takes place through the upper part of the unit. If the space is insufficient, airflow may be limited. The front panel must also be able to open to allow the filters to be removed.
So we check:
- the distance from the ceiling;
- the alignment of the plate;
- the absence of interference with the trim;
- the ability to open the panel;
- accessibility for cleaning;
- the strength of the fastening.
A clean interior finish with no visible routing
No piping is visible around the unit in the photograph. This indicates that the passage was made directly behind the unit or through a suitable cavity.
This type of result requires good coordination. The hole must be positioned correctly in relation to the mounting plate while ensuring the necessary drain slope.
Appearance should never take precedence over functionality. A concealed drain that is improperly sloped can cause a water leak. A refrigerant line forced through an opening that is too small can be crushed or damaged.
Indoor units compatible with airHome Multi
HITACHI documentation presents several indoor-unit families.
airHome 400
The airHome 400 is a wall-mounted unit focused on essential features. It is available in capacities from 7,000 to 24,000 BTU/h, depending on the model.
The advertised minimum sound level can be as low as 29 dB(A) on certain models. This feature is relevant for a bedroom, office, or any space where quiet is important.
airHome 650
The airHome 650 offers additional features, including a motion sensor on certain models. Its minimum sound level can be as low as 27 dB(A).
It may also be compatible with the optional airCloud Go interface.
Floor console
The airHome Floor console can be installed on a wall or on its stand. It is useful when the upper part of the wall is occupied by a window, beam, or sloped ceiling.
Mini-cassette
The mini-cassette provides four-way air distribution. It can be advantageous in a large open room or commercial space.
Concealed-duct unit
The concealed-duct unit is hidden in a ceiling or mechanical space. It distributes air through grilles when visible wall-mounted units are to be avoided.
Sizing the three zones
We do not select capacities based solely on floor area. Two rooms of the same size can have very different heating and cooling loads.
Our analysis considers, among other factors:
- floor area;
- ceiling height;
- insulation;
- the number of windows;
- solar orientation;
- the type of glazing;
- the number of occupants;
- heat-generating appliances;
- the room’s location within the building;
- the available heating capacity in cold weather.
A well-insulated room may require a small unit, while a south-facing open-concept area may need higher capacity. Therefore, the three heads do not necessarily need to have the same capacity.
The technical elements that determine system reliability
Three refrigerant circuits to identify without error
The RAM-G24N3HAA has three liquid connections of 1/4 po and three gas connections of 3/8 po.
Each indoor unit has its own circuit. The communication wiring and piping must correspond to the same outdoor port.
A mismatch can cause improper operation. For example, if indoor unit A communicates with electrical port A but is connected to refrigerant circuit B, the system may display an error or operate inconsistently.
We therefore identify each circuit before closing the line sets and verify that they correspond during commissioning.
Piping limits to observe
For the triple-zone model, the documentation specifies:
- maximum total length: 200 feet;
- maximum length to an indoor unit: 82 feet;
- maximum total height: 66 feet;
- minimum total length: 16 feet;
- maximum elevation difference between indoor units: 16 feet.
These limits must be calculated before work begins. A distance measured visually between two walls does not represent the actual length. Vertical rises, detours, changes in direction, and passages between floors must be taken into account.
Condensate drainage
Each indoor unit produces water in cooling mode. A triple-zone installation therefore includes three separate drains.
The drain must maintain a continuous slope when drainage relies on gravity. We avoid:
- backfalls;
- sagging sections;
- hard-to-access connections;
- outlets that stain a façade;
- discharges near a door;
- areas where water can freeze.
When gravity drainage is not possible, a condensate pump can be installed. Its location should then be chosen to limit noise and allow for maintenance.
Power supply for the outdoor unit
The RAM-G24N3HAA operates on a 208-230 V, single-phase, 60 Hz power supply. The brochure specifies a minimum circuit ampacity of 19 A and maximum overcurrent protection of 35 A.
The final selection of the circuit breaker, wire, and disconnect switch must always follow the nameplate of the installed equipment and the applicable electrical requirements.
Leak testing and vacuum evacuation
A multi-zone system has more connections than a simple single-zone system. The leak test is therefore essential.
After preparing the flares and tightening them to the appropriate torque, we check for leaks. We then evacuate the system to remove the air and moisture present in the lines.
Residual moisture can damage the compressor oil and reduce the system’s service life. An evacuation that is too short or improperly controlled can therefore compromise an installation that initially appears to be operating normally.
Commissioning the three units
Our procedure includes:
- checking the fasteners;
- validating the electrical circuits;
- identifying the three zones;
- testing each unit individually;
- inspecting each drain;
- measuring discharge-air temperatures;
- checking the louvers;
- testing all three zones simultaneously;
- listening for vibrations;
- explaining the controls to the occupants.
We also confirm that the three units are configured in a compatible mode.
Low-temperature heating performance
The system can operate down to -20 °C, but its capacity decreases as the outdoor temperature drops.
For the RAM-G24N3HAA, the documentation indicates approximately:
- 16,000 BTU/h rated capacity at -8 °C;
- 18,500 BTU/h maximum capacity at -15 °C;
- 13,000 BTU/h maximum capacity at -20 °C.
This distinction is important in Saint-Léonard, where winter temperatures can remain below -15 °C for several hours.
A 24,000 BTU/h unit therefore does not automatically deliver 24,000 BTU/h in the coldest conditions. The load calculation and the presence of supplemental heating must be considered.
FrostWash and Mold Guard
Depending on the indoor unit selected, the airHome Multi lineup offers several maintenance functions.
FrostWash
FrostWash uses a freeze-and-thaw cycle to help remove accumulated contaminants from the indoor coil. This function helps maintain airflow and keep the heat exchanger clean.
It does not replace manual filter cleaning or professional HVAC maintenance when the fan or drain pan is dirty.
Mold Guard
Mold Guard helps dry the inside of the unit after cooling or dehumidification. The system circulates air for approximately 60 minutes to reduce residual moisture that can contribute to odors.
Filtration and control options
Depending on the indoor model, the heat pump may include:
- an activated carbon PM2.5 filter;
- a ViroSense S filter;
- a washable pre-filter;
- an R32 leak sensor;
- a visual or audible alarm;
- an optional airCloud Go interface;
- an optional airPoint Room H700 wall thermostat.
The airCloud Go interface allows you, among other things, to schedule operation and control the system remotely when the compatible accessory is installed.
Mistakes to avoid with a triple-zone installation
Installing all the units based on the shortest outdoor route
The easiest route for the piping is not always the best location for comfort. A unit should be positioned according to airflow distribution, the room’s use, and the occupants’ position.
Oversizing the bedroom units
An oversized unit can cause short cycling, excessive airflow, and less consistent dehumidification.
Forgetting the total capacity limitations
The three indoor units do not necessarily have access to their full rated capacity simultaneously. The outdoor unit distributes its maximum output.
Using opposing modes
One unit in heating mode and another in cooling mode can create a conflict. All three indoor units must remain in compatible seasonal modes.
Neglecting the filters
Three units mean three sets of filters to inspect. A clogged filter increases noise and reduces performance.
Blocking the unit with furniture
A raised piece of furniture or cabinet placed beneath the air conditioner can alter airflow and make maintenance more difficult.
An AirGreen installation designed for Saint-Léonard properties
This HITACHI airHome Multi triple-zone multi-zone heat pump installation in Saint-Léonard meets a common need: maintaining a more uniform temperature in several rooms without installing three separate outdoor units.
The wall-mounted unit visible in the photo is installed in an unobstructed area, near the ceiling, with no exposed piping. The flap is unobstructed, the unit remains accessible, and its color blends into the décor.
Behind this simple finish is a complete technical installation: capacity selection, three refrigerant circuits, three drains, communication wiring, vacuuming, and simultaneous operation testing.
We apply this approach in our heat pump projects in Montréal, as well as in Laval, Longueuil, on the North Shore, and on the South Shore. Each installation is adapted to the building’s structure, the available outdoor space, and the occupants’ actual habits.
In this Saint-Léonard project, the triple-zone configuration makes it possible to directly serve the three priority spaces and adjust comfort according to their use. The result combines individual control, discreet interior integration, and reduced outdoor clutter.