A multizone installation where the outdoor route had to be as clean as it was effective
At Calixa-Lavallée, we completed this installation of a MIDEA MIDEA 28 dual-zone heat pump on a masonry property where the exterior integration represented an important part of the work. The worksite photo clearly summarizes the challenge: a tall brick wall, several windows spread across different levels, an open but highly visible outdoor space, and above all, a refrigerant route that had to rise a considerable height without looking as though it had been added afterward.
The result is based on a simple principle: a single MIDEA outdoor unit supplying two indoor zones, with independent comfort control. This is precisely the role of a multizone system. Midea's documentation indicates that an outdoor unit can be connected to several indoor units, each of which can be controlled separately according to the desired room temperature.
For this project, however, we did not want to limit our thinking to heating and cooling capacity. The piping had to cross several façade levels, the masonry had to remain visually clean, the compressor had to remain easily accessible, and the outdoor lines had to be protected for the long term.
A detail immediately visible: the black line set cover spanning the entire height of the wall
One of the most distinctive features of this installation in Calixa-Lavallée is the large black vertical route installed on the brick façade.
Rather than leaving the refrigerant lines, wires, and other connections visible, we grouped the route into an outdoor line set cover whose dark color matches the window frames and the building's other architectural elements.
In the photo, the route begins near the outdoor unit, runs horizontally along the lower part of the wall, then rises almost vertically between the windows. This choice offers several advantages:
- the refrigerant lines are better protected from the elements and impacts;
- the façade maintains a much more organized appearance;
- the routing remains clear and accessible for future service;
- direction changes are kept to a minimum;
- the black cover blends naturally with the existing dark frames;
- The vertical rise avoids creating multiple visible passes around the windows.
For a dual-zone heat pump, this type of routing may require much more preparation than a single-zone installation on the ground floor. As soon as the indoor units are located higher up or in remote parts of the building, we must plan the total length of the lines, elevation differences, access points, and fastening method.
An installation on a brick wall requires a different approach
A brick wall must not be treated the same way as a wall covered with vinyl siding.
The holes must be positioned precisely. The line-set cover fasteners must be sturdy, but they must also be suitable for the substrate to avoid unnecessary damage to the masonry. The penetrations must be properly protected against water.
On a project like this, an error of a few centimetres at the beginning of the route can become very noticeable after several metres of vertical ascent.
We therefore plan the entire route before beginning any drilling.
It seems obvious in hindsight, but this is precisely one of the most common mistakes we see in existing installations: an indoor unit is positioned based solely on the room's perspective, and then the exterior route is improvised. The route must then go around a window, return toward a corner of the building, or use multiple finishing fittings.
At AirGreen, we also work the other way around: we check how each decision made indoors will affect the exterior result.
The MIDEA compressor is installed on wall brackets
Another important detail in the photo is the installation of the outdoor unit on metal brackets attached to the building.
The compressor is not placed directly on the ground.
This configuration offers several advantages that are particularly relevant in Quebec. It keeps the unit above the immediate ground level, facilitates airflow beneath the unit, and reduces the risk of the compressor base becoming surrounded by water, leaves, or accumulated snow.
For a heat pump used for heating, winter clearance around the outdoor unit is essential. We must maintain enough space for air to circulate and for the unit to operate properly during defrost cycles.
The large fan grille remains completely unobstructed here. The technical side of the unit also remains accessible, which is important for HVAC maintenance, troubleshooting, and future service work.
Why the MIDEA 28 is well suited to a dual-zone installation
The Midea multi-zone family was designed to allow a wide variety of indoor configurations. The manufacturer's documentation presents wall-mounted units, consoles, cassettes, ducted units, and even air handlers that can be paired with certain multi-zone platforms.
For the platform corresponding to the MIDEA 28 Extreme Heat, the technical documentation identifies the outdoor unit MO4HX-H27B-2A. Midea classifies it as a platform that can support up to four zones, depending on the permitted combinations.
In our Calixa-Lavallée installation, it is used as a dual-zone heat pump. This means that two indoor zones were selected to meet the building's needs, not that the platform is physically limited to only two possible connections.
This distinction is important for homeowners comparing several multi-zone systems. The maximum number of ports alone does not determine the right configuration. What really matters is:
- the heat load of each space;
- the capacity of the selected indoor units;
- the combination permitted by the manufacturer;
- the actual capacity available when multiple zones operate simultaneously;
- the piping lengths;
- the heating performance sought in cold weather.
Nominal 27,000 BTU/h and a SEER2 of 23 in the reference Extreme Heat configuration
In the Midea brochure, the reference Extreme Heat configuration using MO4HX-H27B-2A is listed with a capacity of 27,000 BTU/h in cooling and 27,000 BTU/h in heating.
The manufacturer's table also indicates:
- power supply: 208/230 V, single-phase, 60 Hz;
- SEER2: 23;
- EER2: 12.5;
- indicated seasonal heating rating at 10,5 in the table;
- reference heating capacity of 27,000 BTU/h at 5 °F, or approximately -15 °C;
- maximum outdoor airflow: 2,148 CFM;
- indicated outdoor sound level: 61 dB(A).
For a property in Calixa-Lavallée, this data is much more useful than simply stating “28,000 BTU.”
For Quebec heating, we always look at the system’s performance when the outdoor temperature drops. A heat pump may show excellent rated capacity under moderate conditions, but what actually affects winter comfort is the capacity it can still deliver when the mercury drops.
A multizone heat pump does not automatically share its full output between two rooms
This is an important technical point that is often misunderstood.
If two indoor units are connected to a single outdoor unit, this does not mean that each unit can continuously receive the compressor’s full rated capacity.
Midea specifies in its combination rules that when the total connected capacity of the indoor units exceeds the rated capacity of the outdoor unit, the actual capacity available to each unit may be reduced, particularly in heating mode.
That is why we place so much importance on proper sizing.
Installing two larger indoor units “to be safe” is not necessarily a better solution. A multizone system must be balanced.
A good selection takes into account the floor area, but also many other factors:
- window orientation;
- insulation level;
- ceiling height;
- sun exposure;
- room location by floor;
- air infiltration;
- presence of large glazed areas;
- actual use of the different zones.
Independent control of the two zones genuinely changes comfort
The main advantage of a dual-zone heat pump is the ability to treat two areas of the building differently.
Midea explains that each indoor unit can be controlled individually and that users can choose different temperatures for different spaces.
This is particularly useful in a multilevel home.
During the summer, upper floors often accumulate more heat. A ground-floor zone may be comfortable while a higher room still requires air conditioning.
In winter, the situation may be reversed depending on exposure, windows, and heat loss.
With two zones, the homeowner does not depend on a single distribution point for the entire house.
Inverter technology modulates operation rather than running only in on-off mode
Multizone operation also benefits from inverter technology.
According to Midea, the system can adjust its capacity based on temperature variations by controlling the compressor and fan motors. When all zones do not require full capacity, the equipment can operate at partial load with reduced energy consumption.
This modulation is particularly interesting in a dual-zone system.
One room may reach its setpoint before the other. The system then does not need to operate constantly as if both zones required exactly the same amount of heating or cooling.
For comfort, this can also help reduce sudden temperature fluctuations.
What this Calixa-Lavallée installation shows about the quality of an HVAC project
The exterior finish is part of the installation, not just aesthetics
On this property, it would have been possible to create a technically functional route with much more visible lines.
Instead, we focused on integration.
The long black vertical section follows a clear line along the facade. It does not zigzag between the windows. It is not made up of a series of small pieces oriented in different directions. The horizontal connection then leads directly to the outdoor unit.
For us, this type of finish is important because a heat pump installation remains visible for many years.
A good HVAC installation must therefore meet several criteria at the same time:
performance, accessibility, mechanical protection, drainage, safety and exterior appearance.
Long vertical runs require more preparation
The height of the route visible in the photo also means that the project is not limited to work performed at ground level.
A high-level installation requires specific organization, particularly for:
- work safely;
- keep the route perfectly aligned;
- securely fasten each section;
- make the openings in the right places;
- protect the lines during handling;
- avoid damaging the brick or the frames around the openings.
This part of the work is often underestimated when comparing two quotes.
Two contractors can offer exactly the same MIDEA heat pump, but the final result can vary greatly depending on how the lines are routed and protected.
SynchroConnect adds an extra layer of safety during connections
Multi-zone systems include several refrigerant circuits and multiple wiring assemblies. Correctly identifying the connections is therefore particularly important.
Midea integrates a technology called SynchroConnect. The documentation indicates that the system can check the connection status and synchronize the corresponding wiring and refrigerant lines in certain situations.
This obviously does not relieve the installer of carefully identifying each zone.
At AirGreen, we consider self-diagnostic functions to be a complementary tool. They must be added to a methodical installation that includes checking the connections, pulling a vacuum, electrical verification, operating tests, and commissioning each indoor unit.
The AHRI number must always be associated with the exact combination
The Midea brochure provides the number AHRI 215471460 for the Extreme Heat reference configuration of the MO4HX-H27B-2A paired with a specific set of All Easy Pro indoor units.
This point is essential when a homeowner is seeking to determine their eligibility for a Hydro-Québec LogisVert rebate.
In a multi-zone system, it must not be assumed that an AHRI number associated with the outdoor unit automatically applies to all possible combinations of two indoor units.
The proper approach is to verify the combination actually installed.
For this reason, when we prepare an AirGreen installation in Montréal, Laval, Longueuil, on the North Shore or the South Shore, we verify the precise models of the indoor and outdoor units when a rebate application must be prepared.
Eligibility and the applicable amount must always be confirmed according to the exact AHRI combination and the program rules in effect at the time of installation.
Mistakes to avoid with a dual-zone heat pump
This Calixa-Lavallée project allows us to summarize several mistakes that we systematically seek to avoid.
Choosing the compressor solely according to the total indoor BTUs
Adding together two indoor capacities and mechanically choosing the corresponding outdoor unit is insufficient. The manufacturer’s combination rules and the zones’ simultaneous performance must be verified.
Improvising the routing after the indoor units have been installed
On a multi-story brick wall like this one, this can create a visually disorderly result and unnecessarily lengthen the lines.
Leaving the refrigerant lines exposed
An insulated line left unprotected ages more quickly and detracts from the building’s appearance. The line set cover is an important part of the finish here.
Installing the outdoor unit too close to the ground
For a heat pump intended to operate in winter, snow accumulation and drainage from defrost cycles must be taken into account.
Block access to the service panel
The technician must be able to access the connections and components without dismantling half the installation.
What the owner gets every day
After commissioning, the owner has a system capable of heating and cooling two distinct zones with a single outdoor unit.
The benefit is therefore not simply having fewer pieces of equipment outside.
It is primarily about being able to adapt the home's operation according to the actual use of the rooms.
If one zone requires less cooling, it can be set differently. If another zone needs to maintain a higher temperature in winter, its setting can be adjusted independently.
The Midea brochure specifically highlights the ability to heat or cool occupied spaces rather than treating the entire home identically.
An installation that will remain accessible for maintenance
We also think about what will happen several years after installation.
The compressor remains accessible. The fan is unobstructed. The line-hide cover protects the lines while keeping their path easy to identify.
During HVAC maintenance, these elements matter.
A technician can inspect more easily:
- the electrical connections;
- the condition of the lines;
- the outdoor coil;
- the brackets;
- potential vibrations;
- water drainage;
- the service panels.
A well-planned installation today often simplifies service work tomorrow.
AirGreen in Calixa-Lavallée and throughout Greater Montreal
This MIDEA MIDEA 28 dual-zone heat pump installation in Calixa-Lavallée reflects our approach to a multi-zone project: starting with the building's actual needs, choosing a suitable configuration, and paying as much attention to installation details as to the machine's specifications.
On this project, the long brick wall made the outdoor line path particularly visible. Choosing a black line-hide cover, an aligned vertical rise, mounting the compressor on wall brackets, and maintaining clearance around the outdoor unit resulted in an installation that was much better integrated into the building.
We apply the same approach to our wall-mounted heat pump, dual-zone, multi-zone, and other HVAC projects in Montreal, Laval, Longueuil, the North Shore, and the South Shore.
Every home has its own constraints. The best system is therefore the one whose capacity, indoor units, lines, outdoor placement, and control strategy have been designed as a whole.