A triple-zone installation integrated into a narrow yard between two residential entrances
This Hitachi airHome Multi triple-zone multi-zone heat pump installation in Mercier–Hochelaga-Maisonneuve shows how decisive outdoor unit placement can be in a dense urban area of Montréal. Here, the available space was bounded by a masonry façade, two doors leading to the yard, a structural column, and a paved surface. Every inch therefore had to be used carefully.
The owner wanted to improve comfort in three distinct areas of the home without cluttering the yard with several outdoor units. We chose a triple-zone configuration, which connects three indoor units to a single outdoor heat pump. This choice reduces the footprint, simplifies the exterior layout, and makes it possible to control the temperature of different rooms separately.
In the photo, the Hitachi airHome Multi unit is installed on a raised metal bracket. It remains high enough to be protected from snow, ice, leaves, and runoff. A white vertical line set cover runs up along the brick wall to protect the refrigerant lines and wiring. The electrical disconnect is located directly behind the unit, while the lines are neatly grouped on its right side.
The result is a compact, accessible HVAC installation adapted to the reality of buildings in Mercier–Hochelaga-Maisonneuve, where yards are often shared, passageways are narrow, and rear façades have several doors, stairs, or structures added over the years.
Why install a triple-zone heat pump in this type of building?
A single-zone heat pump works very well when only one large room needs to be served. However, it becomes less suitable when the home has multiple floors, enclosed bedrooms, or areas that are far apart from one another.
In this Montreal property, three distinct comfort zones had to be served. A three-zone installation can notably serve:
- an open-concept area on the ground floor;
- a bedroom or upper floor;
- an office, basement, or another isolated section of the home.
Each indoor unit can have its own setpoint temperature and fan speed. A little-used room can be turned off while the other two remain operating. This flexibility avoids cooling or heating the entire home to the same level unnecessarily.
The Hitachi airHome Multi range can connect two to five indoor units, depending on the outdoor model. In the technical table on page 4 of the brochure, the three-connection configuration corresponds to model RAM-G24N3HAA, with a nominal capacity of 24,000 BTU/h in cooling and 24,000 BTU/h in heating.
The final sizing does not depend solely on the number of zones, however. We also analyze heat loss, sun exposure, window area, insulation, ceiling height, and how air can circulate between rooms.
An outdoor location subject to several constraints
The unit was placed in a space between a rear door and a second opening on the right. A blue vertical column further reduced the available width. Access therefore had to be preserved while maintaining the necessary clearances around the heat pump.
Poor positioning could have caused several problems:
- obstructing the passage to a door;
- difficulty accessing the technical panels;
- discharging air directly toward an entrance;
- recirculation of discharged air;
- exposing the unit to impacts;
- excessive use of courtyard space.
We positioned the front of the unit toward the open space. This allows the large fan to discharge air without blowing it directly against the brick wall. The unit also remains accessible for inspections, coil cleaning, and future servicing.
This type of decision is particularly important in the central neighborhoods of Montreal, as well as in several areas of Laval, Longueuil, the North Shore, and the South Shore, where a heat pump often has to coexist with a patio, balcony, rear exit, or shared courtyard.
A raised support installed directly on the paving stones
The outdoor unit rests on a metal floor structure. The support has four feet that distribute the weight across the paved surface. Fasteners and vibration-isolating supports are visible between the upper crossbar and the equipment base.
This method offers several advantages.
Protection against snow and ice
A heat pump operating in heating mode produces water during its defrost cycles. If the unit is installed too close to the ground, this water can freeze beneath the chassis and gradually form a mass of ice.
By raising the unit, we create space that facilitates drainage and allows ice or debris to be removed before they reach the condenser base.
Vibration reduction
The Inverter compressor adjusts its speed according to demand. This modulation improves efficiency, but it can generate different vibration frequencies. The pads installed under the heat pump reduce transmission to the support and the paved surface.
This precaution is important when an outdoor unit is located near a door, bedroom, or shared wall.
Simpler maintenance
The clear space beneath the unit facilitates:
- cleaning of the pavers;
- removal of leaves;
- inspection of the base;
- defrost water management;
- access to certain lines.
An installation that remains easy to service is generally more durable than equipment installed in a space that is impossible to clean.
A vertical line set cover suitable for masonry siding
The white line set cover visible behind the heat pump protects the route of the refrigerant lines, communication wiring, and, depending on the configuration, part of the drainage.
In a triple-zone system, three indoor units must be connected to the outdoor unit. This involves several lines that must be organized without creating a tangle on the façade.
For the RAM-G24N3HAA configuration, the documentation indicates:
- three liquid connections of 1/4 po;
- three gas connections of 3/8 po;
- a maximum total piping length of 200 ft;
- a maximum length of 82 ft between an indoor unit and the outdoor unit;
- a maximum total elevation difference of 66 ft.
These limits offer good flexibility in a multistory building. They do not mean that the lines can be installed without planning. We must limit unnecessary detours, protect the insulation, respect bend radii, and provide reasonable access to the fittings.
The raceway also improves the exterior finish. On a light-brick façade like the one at this property, a messy installation would have been immediately noticeable.
An accessible disconnect switch near the unit
The electrical box is installed behind the right side of the unit, in an accessible position. It allows the power supply to be disconnected locally during maintenance or repairs.
For the RAM-G24N3HAA three-zone model, the manufacturer specifies:
- power supply of 208-230 V;
- single-phase current at 60 Hz;
- minimum circuit ampacity of 19 A;
- maximum overcurrent protection of 35 A.
These values must always be confirmed on the nameplate of the unit actually installed. The cable gauge and circuit breaker must never be selected solely according to the number of BTUs.
Performance of the Hitachi airHome Multi three-zone system
The airHome Multi heat pump uses inverter technology to gradually adjust its output capacity. This modulation helps maintain a stable temperature, reduce frequent restarts, and better respond to load variations among the three zones.
For the three-connection ductless configuration, the Hitachi brochure indicates, among other things:
- nominal cooling capacity of 24,000 BTU/h;
- modulating cooling capacity of 7,000 to 28,000 BTU/h;
- nominal heating capacity of 24,000 BTU/h;
- modulating heating capacity of 9,000 to 26,200 BTU/h;
- TRÉ2 of 12.5;
- TRÉS2 of up to 22.0;
- Region 5 CPSC2 of up to 7.8;
- COP of 3.5 at 8 °C.
The available capacity must be distributed among the three indoor units. If all three zones simultaneously require their full capacity, the system modulates and distributes the available power according to the conditions and setpoints.
That is why good design does not consist of arbitrarily choosing three wall-mounted units. A combination that matches the building’s actual needs must be selected.
Heating operation in cold weather
The airHome Multi series is designed to operate in heating mode down to -20 °C. For the three-zone configuration, the documentation indicates a maximum capacity of approximately:
- 18,500 BTU/h at -15 °C;
- 13,000 BTU/h at -20 °C.
These data show that the heat pump continues to produce heat during cold periods, but its capacity decreases as the outdoor temperature drops.
In a Mercier–Hochelaga-Maisonneuve residence, we therefore always assess whether supplemental heating is present. Electric baseboard heaters or another existing system can take over in rooms that are not directly served or during the most severe cold snaps.
The heat pump nevertheless remains a very attractive solution for reducing the use of traditional electric heating during much of the fall, winter, and spring.
Three independent controls, but one shared mode
Each indoor unit can be set independently for temperature and fan speed. One unit can operate while another remains off.
However, the system shares a single main mode. The three units cannot heat and cool simultaneously.
In summer, they can be used for:
- cooling;
- dehumidification;
- ventilation.
In winter, they can operate in:
- heating;
- ventilation.
When two remote controls request opposing modes, one of the units may wait or fail to respond as expected. We explain this feature during commissioning so occupants can use their multizone system correctly.
Several indoor unit formats available
The Hitachi airHome Multi range can be combined with different types of indoor units:
- wall-mounted airHome 400;
- wall-mounted airHome 650;
- airHome Floor console;
- Mini Cassette unit;
- concealed ducted unit.
Depending on the type selected, the available indoor capacities generally range from 7,000 to 24,000 BTU/h.
This flexibility makes it possible, for example, to install a wall-mounted unit in the living room, a more compact unit in a bedroom, and a concealed ducted unit in an area where the interior appearance must be preserved.
The right format depends on the room layout, the available wall space, the direction of the airflow, and how easily the drain can be routed by gravity.
FrostWash, Mold Guard, and indoor filtration
Depending on the selected indoor units, the system may include several maintenance and air-treatment functions.
FrostWash technology
The FrostWash technology uses a freezing and thawing process to help loosen certain contaminants from the indoor coil. The water produced during the cycle then carries some of the residue toward the drain.
This function helps keep the heat exchanger cleaner, but it does not replace professional cleaning when the fan or coil is heavily contaminated.
Mold Guard function
After a period of cooling or dehumidification, the Mold Guard function circulates air to dry the internal components for approximately 60 minutes. The goal is to limit conditions conducive to odors and mold.
Filters according to the selected unit
The brochure notably presents:
- an activated carbon PM2.5 filter on certain wall-mounted units and consoles;
- a ViroSense S filter on the mini-cassettes;
- washable prefilters in the various formats.
Occupants should clean the filters regularly, especially in homes with pets, ongoing work, a lot of dust, or prolonged summer use.
R32 refrigerant and leak tightness testing
The airHome Multi system uses R32 refrigerant R32. Compatible indoor units include a leak sensor that can trigger a visual or audible alert, depending on the equipment and accessories installed.
For a triple-zone installation, the quality of the refrigerant connections is particularly important, since there are more connections than with a single-zone heat pump.
Our procedure notably includes:
- proper preparation of the copper lines;
- making the flares;
- controlled tightening of the connections;
- leak testing;
- completing the evacuation;
- checking vacuum stability;
- opening the valves;
- individual testing of the three indoor units;
- checking the drainage of each zone.
These steps are not visible in the final photo, but they are essential to the reliability of the HVAC installation.
Mistakes to avoid after an installation in a narrow yard
Store objects in front of the fan
The front of the heat pump must remain clear. Bins, bicycles, patio furniture, or seasonal equipment can disrupt air discharge.
Block access to the doors
The installation was positioned to preserve access. Avoid adding objects later that would further reduce airflow around the unit.
Enclose the unit with a decorative screen
A fence or panel can hide the heat pump, but it can also cause air recirculation. Any screen must comply with the required clearances and retain large openings.
Neglecting defrost water
The space beneath the unit must be monitored in winter. Any ice buildup must be removed before it reaches the chassis or creates a slippery surface near the doors.
Allowing the drains to shift
The visible ends of the drainage lines must remain secured and directed toward an appropriate location. They must not discharge water directly onto a frequently used walkway.
Grants and documentation to retain
The brochure indicates that airHome Multi systems may qualify for several provincial incentives. Actual eligibility nevertheless depends on the certified combination of units, the program in effect and the type of building.
For a complete application, it is advisable to keep:
- the detailed invoice;
- the models of the three indoor units;
- the outdoor unit model;
- the serial numbers;
- the applicable AHRI reference;
- warranty documents;
- proof of installation and payment.
A system from the right brand is not automatically eligible. The exact combination must be verified.
An AirGreen installation adapted to the architecture of Mercier–Hochelaga-Maisonneuve
This triple-zone installation shows that a complex outdoor space can accommodate a heat pump in a structured way when the project is properly planned.
We had to take into account the proximity of the doors, the existing column, the brick wall, the pedestrian walkway, the electrical supply and the routing of three sets of lines.
The elevated stand protects the equipment, the line-set cover organizes the refrigerant lines, and the front-facing position keeps the air discharge unobstructed. The unit remains accessible without completely blocking the yard.
At AirGreen, we carry out this type of multi-zone heat pump installation in Montreal, as well as in Laval, Longueuil, on the North Shore and the South Shore. Our approach combines performance, durability, maintenance access and integration with the building.
In this Mercier–Hochelaga-Maisonneuve property, the Hitachi airHome Multi heat pump can now serve three zones with a single outdoor unit. This configuration provides more precise comfort control while preserving a functional yard and a clean outdoor installation.