In L’Île-Perrot, a rooftop installation that requires as much precision for the support as for the heat pump itself
This installation of a MIDEA MIDEA35 wall-mounted heat pump in L’Île-Perrot presents a very different configuration from a conventional ground-level installation. Here, the outdoor unit was placed directly on a flat roof, in an environment where we had to consider the roof surface, system access, mechanical stability, refrigerant and electrical connections, as well as winter conditions specific to Quebec.
The job-site photograph clearly shows the situation. The Midea outdoor unit is installed on an elevated metal structure, itself supported above the roof. Wooden components and load-distribution surfaces can be seen beneath certain parts of the structure, while the electrical disconnect is installed immediately beside the unit. The refrigerant lines come from the building and connect to the side of the unit along a relatively short route.
This configuration is particularly interesting for a property with L’Île-Perrot, where the available ground-level space, the architectural layout, or the location of the indoor unit may make a rooftop installation preferable.
But a rooftop installation must never be considered a simple adaptation of a ground-level installation. The roof itself becomes part of the HVAC project.
We must consider how the unit will be supported, vibrations, airflow around the coil, snow accumulation, defrost drainage, and the possibility of a technician performing maintenance or a diagnosis later. HVAC maintenance or a diagnosis.
Why elevate the MIDEA35 on a flat roof?
In the photo, the heat pump is not resting directly on the roof gravel. It is placed on a metal support that creates substantial clearance beneath the unit.
This detail is particularly important for a heat pump used for heating.
In winter, the outdoor coil can accumulate frost. The unit must then start a defrost cycle to melt this buildup. The water resulting from defrosting must be able to drain properly from the area beneath the unit.
If a heat pump were installed too close to the roof, several problems could arise:
- ice accumulation beneath the unit;
- reduced clearance beneath the chassis;
- maintenance difficulties;
- prolonged contact with snow;
- gradual obstruction of certain areas around the unit.
The MIDEA35 is specifically designed to operate in heating mode down to -30 °C, according to Midea documentation. This capacity means that the outdoor installation must also be designed for harsh winter conditions.
In L’Île-Perrot, we therefore do not plan an installation only for the hot days of July. We consider what will happen on this roof in January, when there will be snow, ice, and repeated defrost cycles.
A metal structure that keeps the unit accessible
The other obvious advantage of the support is accessibility.
The photograph shows that the unit is positioned at a height that leaves its lower section clear while keeping the service areas accessible. The refrigerant lines, connections, and disconnect switch can be reached without enclosing the heat pump in a recess or placing it directly against an architectural element.
For us, this accessibility is part of the quality of a wall-mounted heat pump installation.
An installation may function perfectly on the day it is commissioned and become very complicated a few years later if the technician can no longer reach the valves, electrical panel, or heat exchanger.
On a flat roof, this issue is even more important: every movement and intervention is already more demanding than at ground level.
The weight must be distributed without treating the roof like a simple slab
In the photograph, we can see that the support does not appear to rest directly on a single point of the roof covering. Load-distribution elements are present beneath the structure.
Without claiming to determine the roof’s exact composition or the building’s structural capacity from a photograph, this project brings an important principle to mind: a flat roof is not an ordinary outdoor surface.
We must avoid unnecessary concentration of loads and protect the surface from movement of the support.
Depending on the MIDEA35’s capacity, the outdoor unit also has a different weight. Midea indicates approximately 99.65 lb for the 9,000 and 12,000 BTU versions and approximately 130.29 lb for the 18,000 BTU version.
The heat pump’s weight is obviously only part of the overall system. The support and the building’s actual conditions must also be considered.
A compact installation that makes smart use of the roof
The MIDEA35 uses an outdoor unit side discharge. Midea describes this architecture as compact and particularly suited to patios, roofs, terraces, and balconies.
This format is particularly practical on a roof.
A large vertical-discharge outdoor unit might require a very different configuration. Here, the rectangular design makes it possible to position the unit in a relatively compact area while keeping the coil exposed.
The photograph also shows that the unit is positioned near a low wall and several rooftop elements, but is not enclosed between four walls.
When a unit is installed on a roof, we pay particular attention to surrounding obstacles. A heat pump must be able to intake and discharge air properly. An installation too close to a wall, chimney, or other equipment can cause air recirculation and reduce performance.
Relatively direct refrigerant lines
The line routing visible in this installation is also noteworthy.
The insulated lines come from the building and connect to the outdoor unit without unnecessarily crossing the entire roof. This approach keeps the installation more orderly and reduces exposed sections.
However, the MIDEA35 series does not use the same line sizes for all its capacities.
Midea documentation specifies:
- 9,000 BTU : 1/4 in. and 3/8 in. liquid/gas lines;
- 12,000 BTU : 1/4 in. and 3/8 in.;
- 18,000 BTU : 3/8 in. and 5/8 in.
We must therefore confirm the exact model before preparing or reusing a refrigerant line.
Different maximum lengths depending on capacity
The series' flexibility becomes especially useful when the outdoor unit is located on a roof.
Midea indicates a maximum line-set length of 82 ft for the 9,000 and 12,000 BTU MIDEA35 units, and 164 ft for the 18,000 BTU version. The published maximum height differences are respectively 49.2 ft, 49.2 ft, and 82 ft.
These possibilities provide greater flexibility when an indoor unit is located on a lower level.
However, this does not mean that we aim to use the maximum length. A short, logical, and well-protected route is generally preferable when compatible with the building's configuration.
Why MIDEA35 meets the needs of a residence in L’Île-Perrot
A range of 9,000, 12,000, and 18,000 BTU
The name MIDEA35 corresponds to a series rather than a single unit.
Midea presents three main combinations:
- MSESU-H09B-2A + MO1SS-H09B-2A: 9,000 BTU, AHRI 215471386;
- MSESU-H12B-2A + MO1SS-H12B-2A: 12,000 BTU, AHRI 215471387;
- MSESU-H18B-2A + MO1SS-H18B-2A: 18,000 BTU, AHRI 215471388.
The installation photo on the roof is not clear enough to read the nameplate and unambiguously confirm which of these capacities was installed in L’Île-Perrot.
We therefore prefer not to assign a capacity to this project based solely on the unit’s apparent dimensions.
This caution is important when a homeowner compares several quotes: two units belonging to the MIDEA35 series may differ considerably in capacity, electrical requirements, line-set diameter, and energy performance.
Up to 33.3 SEER2 depending on the selected model
The MIDEA35 offers high efficiency levels, but they vary according to capacity.
The Midea documentation states:
- 33.3 SEER2 for the 9,000 BTU unit;
- 29.4 SEER2 for the 12,000 BTU unit;
- 25.6 SEER2 for the 18,000 BTU unit.
The published HSPF2 IV values are respectively 22.0, 14.5, and 16.2.
These data are important for properly comparing heat pumps.
The statement “up to 33.3 SEER2” should not be interpreted as the performance of all units bearing the MIDEA35 name.
At AirGreen, we always associate performance with the exact model and AHRI number.
Heating down to -30 °C
For an installation at L’Île-Perrot, winter performance is obviously one of the central criteria.
Midea indicates that the MIDEA35 series can operate in heating mode down to -30 °C.
This feature allows a wall-mounted heat pump to play a much more significant role in heating the residence than an older reversible air conditioner designed primarily for moderate temperatures.
Nevertheless, it remains essential to distinguish between the minimum operating temperature and the available heating capacity.
A heat pump can continue operating at very low temperatures while its capacity changes according to outdoor conditions.
Performance at -15 °C provides much more concrete information
The Midea brochure provides heating values at -15 °C.
At this temperature:
- the 9,000 BTU MIDEA35 is rated at 13,500 BTU/h;
- the 12,000 BTU MIDEA35 at 13,500 BTU/h;
- the 18,000 BTU MIDEA35 at 22,600 BTU/h.
For us, these figures are particularly useful when evaluating a heat pump for a Quebec residence.
They show what the unit can deliver when outdoor temperatures become truly wintry.
Variable-speed technology adapted to changing needs
The MIDEA35 operates with variable-speed technology.
Midea explains that the compressor can continuously adjust its operation as temperature requirements change, helping reduce fluctuations and maintain more consistent indoor comfort.
This modulation is important because a home does not always need the maximum capacity of its heat pump.
An autumn morning, a cold January day, and a hot July afternoon represent three completely different loads.
A variable-capacity heat pump can adapt its operation more effectively to these situations.
Why sizing remains essential
This modulation capacity does not make sizing unnecessary.
We must always choose the right capacity based on the building.
In Île-Perrot, we analyze in particular:
- heated and cooled floor area;
- insulation;
- windows;
- the building's orientation;
- air infiltration;
- ceiling height;
- the distribution of the rooms;
- the planned location of the indoor unit;
- heating needs during cold temperatures.
Systematically choosing the largest available heat pump does not necessarily improve comfort.
A properly sized unit can use its modulation more consistently and provide a better balance between heating, cooling, and dehumidification.
R-454B: the refrigeration technology of this MIDEA35
The series uses R-454B refrigerant, classified as A2L.
Midea documentation also indicates an A2L refrigerant leak detection sensor and suitable dispersion functions on the applicable series.
This new generation of equipment requires appropriate installation and service procedures.
For the owner, this means it is preferable to choose an HVAC company already familiar with modern systems operating with R-454B.
The electrical disconnect switch remains accessible on the roof
In the photograph, we can also see the disconnect switch installed near the outdoor unit.
This proximity is important for service and safety when working on the equipment.
Electrical requirements vary according to the selected MIDEA35.
Midea specifies a power supply of 208/230 V, single-phase, 60 Hz for all three capacities. The minimum allowable ampacities are 16 A for the 9,000 and 12,000 BTU models and 24.9 A for the 18,000 BTU model. The published maximum overcurrent protections are 20 A, 20 A, and 25 A, respectively.
Before installation, we must therefore ensure that the electrical circuit matches the exact model.
The roof also changes how noise and vibrations must be addressed
A heat pump placed directly against an exterior wall and a heat pump installed on a roof do not necessarily transmit vibrations in the same way.
Mechanical support therefore becomes essential.
Midea’s published outdoor sound levels are 57 dB(A) for the 9,000 and 12,000 BTU versions and 61.5 dB(A) for the 18,000 BTU model at high speed.
However, the sound level measured in the documentation and the vibrations felt inside the building are two different things.
A poorly designed structure can transmit vibrations to the roof. We therefore pay particular attention to the stability of the stand and its interaction with the building’s structure.
Snow and defrosting must not be overlooked
The photograph was taken in dry, clear conditions, but we must imagine the exact same roof after a snowstorm.
This is one of the most important aspects of a heat pump installation on a roof in L’Île-Perrot.
The elevation provides more clearance between the unit and the roof surface. It also provides more space for water from defrost cycles.
A heat pump capable of operating down to -30°C must be installed so that it can actually operate during these periods.
It is therefore not enough to consider the compressor’s performance: the outdoor stand must be compatible with the climate for which the equipment was designed.
Indoor features that complement the installation
The MIDEA35 also offers several interesting indoor features.
The manufacturer highlights in particular:
- ECO mode;
- night mode;
- silent mode;
- timer;
- child lock;
- the “Follow Me” function;
- 8°C hold heating;
- horizontal and vertical oscillation;
- automatic cleaning;
- fan control from 1% to 100%;
- several smart control features.
Midea also indicates that the system offers up to 100 air volume settings and control via the SmartHome app and Wi-Fi is available depending on the configuration.
These features make it possible to adjust air distribution much more precisely to the comfort desired in the room.
An indoor design that facilitates cleaning
For long-term maintenance, the series offers another practical advantage.
Midea indicates that the indoor fan wheel can be removed to facilitate deep cleaning and improve access to the inside of the unit.
We consider this feature particularly relevant.
Over the years, the filters are not the only components that accumulate dust. The fan wheel and heat exchanger may also require thorough cleaning.
A unit designed to facilitate this access therefore simplifies a future wall-mounted heat pump maintenance.
Financial assistance must be associated with the exact system
The documentation provided identifies the AHRI numbers for the three MIDEA35 configurations, but does not provide a subsidy amount corresponding to this specific installation in L’Île-Perrot.
We therefore avoid presenting an amount that cannot be confirmed based on the available information.
To determine actual eligibility for financial assistance, the AHRI number, the installed capacity, and the criteria applicable at the time of the application.
This is an important point for homeowners comparing multiple quotes: two units belonging to the same family may not offer exactly the same eligibility conditions.
A residential warranty that also deserves to be documented
The Midea brochure presents a limited residential warranty program of up to 12 years on the compressor, 12 years on parts, and 10 years on labour, according to the applicable terms.
We always recommend keeping the model information, serial numbers, and installation documents.
A good HVAC installation does not end when the team leaves the job site. Documentation and access to after-sales service are also part of the equipment’s long-term value.
What this L’Île-Perrot project shows better than a technical data sheet
This installation of a MIDEA MIDEA35 wall-mounted heat pump in L’Île-Perrot illustrates an important aspect of our work at AirGreen: excellent equipment must be adapted to its actual environment.
The technical data sheet provides the capacities, efficiencies, operating temperatures, and electrical requirements.
The job site itself raises other questions.
Where should the unit be placed? How can it be kept above the snow? How can its weight be distributed properly? How can the roof be protected? How should the lines be arranged? Where should the disconnect switch be installed? How can access be preserved for the next technician?
On this property in L’Île-Perrot, the solution was an elevated outdoor installation on a metal structure, with grouped connections and relatively direct access to the service components.
The MIDEA35, for its part, provides the features required for Quebec’s climate: heating down to -30 °C, R-454B refrigerant, variable-speed technology, and efficiencies of up to 33.3 SEER2 depending on the configuration.
It is the combination of these two elements — the quality of the equipment and the quality of the HVAC installation — which makes it possible to create a solution suited to the building rather than simply placing a heat pump on a roof.