A High-Mounted Installation Designed for a Brick Wall and Three Comfort Zones
In Rosemont–La Petite-Patrie, we installed a HITACHI airHome Multi triple-zone multi-zone heat pump on the rear brick façade of a residential building. The project required particularly precise planning: a single outdoor unit had to supply three indoor units, while the available ground-level space had to remain clear and the lines had to reach different areas of the building without creating a disorderly assembly on the masonry.
The photo taken during the work shows the HITACHI outdoor unit already mounted high on two metal wall brackets. Several refrigerant connections are visible on its right side, reflecting the logic of a multi-zone system. An electrical disconnect box is mounted nearby, while a brown line-set cover runs vertically downward before continuing horizontally along the brick wall.
The telescopic ladder installed in front of the work site highlights an important reality of this type of HVAC installation in Montreal: when equipment is installed at height, every step becomes more demanding. Securing the supports, lifting the unit, preparing the lines, tightening the connections, installing the disconnect switch, and adjusting the finishing pieces must all be carried out in a rigorous sequence.
The desired result was not simply to install a heat pump out of the way. We had to create a stable, accessible configuration that was consistent with the building’s architecture, while ensuring the proper operation of all three zones.
Why choose a triple-zone heat pump for a building in Rosemont
Buildings in Rosemont–La Petite-Patrie often have interior layouts where a single wall-mounted unit cannot distribute air evenly. The dwellings may be long, divided into several rooms, spread over two levels, or include a more recent rear addition.
In such a property, a triple-zone heat pump can serve three areas separately, for example:
- a main living area;
- a bedroom or an office;
- an upper floor or an addition;
- three bedrooms located in different directions;
- a living room, a kitchen, and an enclosed room;
- two residential areas and a workspace.
Each indoor unit has its own setpoint and fan speed. One zone can be turned off while the other two continue operating. This independence prevents unnecessary conditioning of an unoccupied room and helps correct temperature differences between areas.
The HITACHI brochure nevertheless specifies that the indoor units share the system's general mode. In summer, the zones can operate in cooling, dehumidification, or fan mode. In winter, they can operate in heating or fan mode. An indoor unit therefore cannot actively cool while another requests heating from the same outdoor unit.
We always explain how this works before commissioning. A good understanding of the controls prevents mode conflicts and allows occupants to use their HITACHI multi-zone heat pump more efficiently.
The choice to mount the outdoor unit higher up
For this project, the outdoor unit was attached directly to the masonry using metal supports. This solution preserved ground space and protected the equipment from several common constraints in an urban environment.
A wall-mounted support installation helps keep the equipment away from:
- snow accumulation;
- leaves and debris;
- standing water;
- traffic areas;
- objects stored near the building;
- accidental impacts.
This keeps the bottom of the unit clear, promoting the drainage of water produced during defrost cycles. In heating mode, frost may form on the outdoor coil. The heat pump then temporarily reverses its operation to melt this buildup. The water must be able to fall and flow away from the equipment without immediately becoming trapped beneath its base.
In Montreal, this issue becomes important when temperatures fluctuate around the freezing point. A heat pump installed too close to the ground may become surrounded by ice after several freeze-thaw cycles.
Masonry-appropriate anchors
The presence of a brick wall requires an appropriate fastening method. The outdoor unit of a triple-zone system represents a significant load, compounded by compressor vibrations, fan movement, and forces caused by the wind.
We do not simply attach the supports to any surface. We assess the masonry, the structure behind the cladding, the position of the joints, and the overall condition of the wall. The supports must be installed level and distribute the weight properly.
In the photo, the unit rests on two reinforced metal arms. Vibration-damping elements are visible between the equipment and the support rails. They help reduce the direct transmission of vibrations to the structure.
These components are especially useful when the equipment is located near a bedroom or occupied space. However, their presence does not correct poor fastening. The supports, anchors, unit level, and wall rigidity must work together.
An installation beneath the roof edge
The outdoor unit is positioned beneath the roof overhang but is not enclosed. This position provides some protection from direct precipitation while preserving the space needed for air circulation.
However, we must check several clearances:
- the distance between the top of the unit and the soffit;
- the space in front of the fan;
- the distance from the side walls;
- access to the service panels;
- the ability to remove or replace a component;
- safe ladder access during maintenance.
A heat pump must never be installed like a simple box that one tries to hide. The fan must be able to expel air freely, and the heat exchanger must be able to draw in enough ambient air.
Insufficient clearance can cause recirculation. The air discharged by the unit then returns to the heat exchanger instead of dispersing. This phenomenon can reduce efficiency and increase the strain on the system.
A height that complicates the work but makes the property easier to use
The ladder visible in the photo illustrates the precautions required for a high installation. Our technicians must be able to reach:
- the refrigerant connections;
- the electrical compartment;
- the supports;
- the mounting screws;
- the disconnect switch;
- the line-hide covers.
Lifting the outdoor unit is also an important step. A multi-zone unit must not be lifted or handled by its lines, grille, or thin panels. It must be positioned on the supports without deforming its cabinet.
Once installation is complete, this height frees up the lower part of the wall. It can help preserve a walkway, storage space, or a more functional yard. In central neighborhoods of Montreal, where backyards and passageways can sometimes be very narrow, this advantage can be decisive.
Three refrigerant circuits arranged on the same façade
A triple-zone system has three distinct refrigerant paths between the outdoor unit and the indoor units. Each path normally includes a liquid line, a gas line, a cable, and a condensate drain associated with the indoor unit.
The visible connections on the side of the outdoor unit demonstrate the added complexity of a multi-zone system. An identification error can result in an incorrect match between an indoor unit, its communication cable, and its refrigerant circuit.
We therefore carefully identify each zone before commissioning. The lines must be grouped methodically and routed along a path that limits:
- unnecessary crossings;
- bends that are too tight;
- stress on the copper lines;
- exposed sections of insulation;
- points where water could infiltrate;
- future access difficulties.
The brown line-set cover integrated into the brick wall
Choosing a brown line-set cover reduces the contrast with the brick and the building's tones. In the photo, the vertical section descends directly below the connections, then joins a long horizontal section.
This “L” shape is used to group the lines before they branch off toward the different zones. The line-set cover also protects the insulation from ultraviolet rays, rain, birds, and accidental damage.
A three-zone installation requires a line-set cover of sufficient dimensions. Three sets of lines take up much more space than a single-zone system. The insulation must therefore not be compressed, and the pipes must not be forced into a conduit that is too narrow.
Crushed insulation loses some of its effectiveness and can promote condensation. Finishing components must therefore be selected based on the actual volume of the lines, not solely on their appearance.
The purpose of the outdoor disconnect switch
The gray box visible near the outdoor unit is an electrical disconnect switch. It allows the equipment's power supply to be shut off locally during servicing.
Its placement must follow several principles:
- remain accessible;
- be installed near the unit;
- not be hidden behind the line-set cover;
- be protected against water infiltration;
- avoid areas where water accumulates;
- allow safe work during maintenance.
The wiring must also be secured neatly and protected against movement. A loop or section of cable must not hang freely to the point of rubbing against the masonry or placing strain on the connections.
A three-zone platform designed for three indoor units
The HITACHI airHome Multi range includes outdoor units capable of powering two to five zones, with rated cooling capacities ranging from 18,000 to 42,000 BTU/h. It uses Inverter technology and R32 refrigerant.
For a three-zone configuration, the brochure presents the outdoor model RAM-G24N3HAA, equipped with three indoor connections. The photo does not show the nameplate of the installed unit; the exact model must therefore always be confirmed on-site. Nevertheless, the RAM-G24N3HAA represents the three-zone platform described in the supplied documentation.
According to this specification sheet, it has:
- a nominal cooling capacity of 24,000 BTU/h;
- a nominal heating capacity of 24,000 BTU/h;
- a cooling modulation range of up to 28,000 BTU/h with ductless units;
- a heating range of up to 26,200 BTU/h;
- three connections for indoor units.
This capacity is not automatically divided into three identical portions. Power is distributed according to the zones’ needs and operating conditions.
The performance, sizing, and details that determine the outcome
A three-zone multi-zone heat pump should not be sized simply by adding the figures listed on the three indoor units. The permissible indoor capacities may exceed the outdoor unit’s nominal capacity in certain approved combinations.
When all three zones simultaneously call for full power, the outdoor unit distributes the available capacity. It is therefore essential to determine which zone has the highest load and which rooms are likely to operate at the same time.
At AirGreen, we analyze, among other things:
- the floor area of each room;
- the air volume;
- sun exposure;
- the insulation;
- the type of windows;
- the floor;
- the door layout;
- the kitchen’s proximity;
- the daily use of each zone;
- the heating capacity available at low temperatures.
Energy efficiency of the three-zone configuration
For the RAM-G24N3HAA model with ductless units, HITACHI documentation indicates, among other things:
- 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.
The series can operate in heating mode down to an outdoor temperature of -20 °C. For this three-zone platform, the listed maximum heating capacity is 18,500 BTU/h at -15 °C and 13,000 BTU/h at -20 °C.
This data is particularly important for a Rosemont–La Petite-Patrie homeowner who wants to use their heat pump in winter. A nominal capacity of 24,000 BTU/h does not mean that the unit delivers the same output when the temperature reaches -20 °C.
The existing heating system can therefore continue to serve as backup during the coldest periods, depending on the building’s heat loss and the sizing of the zones.
Inverter Technology and More Stable Comfort
Inverter technology allows the compressor to modulate its speed. Instead of operating only at full capacity and then stopping, the heat pump adjusts its output according to demand.
This modulation can help:
- reduce temperature fluctuations;
- limit repeated starts;
- maintain better dehumidification;
- reduce noise during periods of low demand.
- better distribute capacity among the three zones.
Actual performance always depends on the combination of units, the outdoor temperature, and the number of active zones.
Indoor units compatible with the system
The airHome Multi range allows several types of indoor units to be combined:
- airHome 400 wall-mounted unit;
- airHome 650 wall-mounted unit;
- airHome Floor console unit;
- airHome Mini Cassette;
- airHome Ducted.
Available capacities generally range from 7,000 to 24,000 BTU/h, depending on the format.
This variety is useful in a Montreal building where the three zones do not necessarily have the same layout. A wall-mounted unit can be installed in a bedroom, a cassette in an open area, and a ducted unit in a renovated area with a technical ceiling.
However, the final combination must be compatible with the outdoor unit and validated against HITACHI data.
Permitted piping lengths
For the RAM-G24N3HAA three-zone platform, the documentation lists the following limits:
- Maximum total length: 200 feet;
- Maximum length between the outdoor unit and an indoor unit: 82 feet;
- Minimum length: 16 feet;
- Maximum total height: 66 feet;
- Maximum elevation difference between indoor units: 16 feet.
The three outdoor connections use 1/4 in. liquid lines and 3/8 in. gas lines.
These values directly influence the choice of outdoor unit location. A unit mounted on the rear wall may reduce the routing distance to several rooms, but each run must be measured before installation.
In a multi-story building, the elevation difference becomes just as important as the horizontal distance.
Refrigeration work not visible in the photo
The photo shows an installation in progress. Before commissioning, several steps still need to be completed or verified.
Connection preparation
The ends of the copper lines must be cut cleanly, flared correctly, and free of contamination.
Controlled tightening
The nuts must be tightened according to the applicable requirements. Insufficient tightening may cause a leak; excessive tightening may damage the flare.
Leak test
The circuit must be pressure-tested to confirm that there are no leaks in any of the three zones.
Vacuum evacuation
Vacuuming removes air and moisture from the lines. This step protects the compressor and contributes to long-term reliability.
Circuit matching
Each pair of lines must correspond to the correct wiring and indoor unit.
Drain inspection
All three indoor units produce condensate in cooling mode. Each drain must flow without backflow.
Complete startup
We test all three zones, the controls, communication, and the system’s response to temperature changes.
Electrical data for the triple-zone platform
The RAM-G24N3HAA model operates on a 208-230 V, single-phase, 60 Hz power supply. The brochure indicates a minimum circuit ampacity of 19 A and maximum overcurrent protection of 35 A.
These data concern the model described in the documentation. The nameplate of the equipment actually installed always remains the final reference.
We must also verify:
- the electrical panel capacity;
- the conductor size;
- the circuit breaker;
- the disconnect switch;
- grounding;
- the protection of the outdoor wiring;
- the path to the unit.
Air quality and coil cleaning
Depending on the indoor units selected, the airHome Multi range may offer a PM2.5 activated carbon filter, a ViroSense S filter, the FrostWash function, and Mold Guard mode.
FrostWash technology uses a freeze-and-thaw process to help remove contaminants accumulated on the indoor heat exchanger. The Mold Guard function circulates air for approximately 60 minutes after cooling or dehumidification to dry the internal components.
These functions do not replace HVAC maintenance. Filters must be cleaned regularly, and the fan wheel, condensate pan, and drain must be inspected as needed.
R32 refrigerant leak sensor
Compatible indoor units include a sensor designed to signal a possible R32 leak. Depending on the configuration, the alarm may be transmitted through an indicator light, audible alert, optional receiver, or compatible wall controller.
This monitoring function complements good installation practices but does not replace them. The best prevention remains the quality of the connections, leak testing, and professional commissioning.
Remote control and management of three zones
An optional airCloud Go interface can allow compatible units to be controlled remotely. Occupants can schedule operating periods, adjust settings, and monitor certain information from a connected device.
In a triple-zone installation, this option can be useful when the rooms are not all occupied at the same times. A bedroom, office, and living room can therefore follow different schedules.
However, it is still preferable to avoid extreme differences between zones. A completely cold room can transfer its heat to neighboring areas and increase the building’s overall demand.
Mistakes to avoid when installing a multizone system on a brick wall
Underestimating the unit’s weight
A triple-zone system requires supports and anchors suited to its actual weight.
Securing it only to fragile cladding
The masonry and structure must be assessed before drilling.
Installing the unit too close to the soffit
Insufficient clearance can hinder air intake and service access.
Using a line-set cover that is too small
Three refrigerant circuits require sufficient space to keep the insulation intact.
Crossing the circuits and communication lines
Each indoor unit must be paired with the correct set of pipes and the correct cable.
Forgetting about future maintenance
A unit installed at height must remain accessible with the appropriate equipment.
Failing to plan for defrost water
Water must be able to drain without damaging a passageway, balcony, or structure located below.
Sizing the three zones separately without analyzing the system as a whole
The outdoor unit distributes a shared capacity; simultaneous demands must be taken into account.
A clean installation despite the project’s complexity
This Rosemont–La Petite-Patrie installation stands out for the clarity of its exterior organization. The HITACHI unit is elevated on sturdy supports, the connections are grouped on the side, the disconnect switch remains accessible, and the line-set cover follows a structured path along the wall.
Even during the work, the project’s logic is visible. The technical components are not scattered across the facade, and the pipe route is concentrated in a defined area.
This layout also simplifies future service work. The technician can identify where the circuits enter, access the disconnect switch, and remove the unit’s panels without dismantling a large portion of the finish.
Three comfort zones with a single HITACHI outdoor unit
The HITACHI airHome Multi triple-zone heat pump can cool and heat three areas with a single outdoor unit. For an urban property where available space is limited, this configuration reduces the number of visible pieces of equipment and frees up the yard.
The success of the project nevertheless depends on much more than the choice of brand. It relies on:
- proper sizing of the three zones;
- selection of a compatible combination;
- the sturdiness of the wall mounting;
- clearances around the unit;
- organization of the refrigerant circuits;
- pipe protection;
- electrical compliance;
- leak testing;
- vacuuming;
- complete verification of the controls.
At AirGreen, we apply this method to our multi-zone heat pump, wall-mounted air conditioner, central system, and HVAC installation projects in Rosemont–La Petite-Patrie, Montreal, Laval, Longueuil, the North Shore, and the South Shore.