Installation of a MIDEA MIDEA35 wall-mounted heat pump on a flat roof in L’Île-Perrot
In L’Île-Perrot, AirGreen installs a MIDEA MIDEA35 on a flat roof with an elevated metal support, neat connections, heating down to -30 °C, and R-454B technology suited to Quebec winters.
Take a tour of the installation
Each number is a point we check on site. Switch between summer and winter to watch air and heat move.
In summer, the outdoor unit rejects the house's heat outside.
Generic illustration of this type of installation, not a survey of this job site. Tap a number.
Mounted level on a wall plate, high enough for the air to reach the whole room, with enough space around it to slide the filters out easily.
The refrigerant lines, the communication cable and the drain go through the wall in a single opening, sealed against water, cold air and insects.
Two insulated copper pipes connect the two units. Outside, a line cover can protect them from sun, knocks and weather.
A shut-off switch near the outdoor unit isolates it safely for service. It must stay accessible at all times.
The compressor and the fan. In heating mode it captures heat from the outdoor air, even in winter, and moves it inside.
On the ground or on the wall, it keeps the unit above accumulated snow. The unit stays clear and defrost water can drain away.
The fan needs to blow freely. Storage, a fence or a wall too close, and efficiency drops while noise goes up.
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.
The unit on this job, in figures
The range as published on airgreen.ca: pick a size to see its capacity in deep cold.
| Size | Heating at −8 °C | Heating at −15 °C | Coldest certified point | COP at −15 °C | SEER | HSPF | Indicative LogisVert aid |
|---|---|---|---|---|---|---|---|
| Midea Série 35 9 000 | 11,000 | 13,500 | −30 °C: 7,500 | 2.0 | 33.3 | 14.6 | – |
| Midea Série 35 12 000 | 11,000 | 13,500 | −30 °C: 7,500 | 2.0 | 29.4 | 12.7 | $1,320 |
| Midea Série 35 18 000 | 19,300 | 22,600 | −30 °C: 11,900 | 2.34 | 25.6 | 16.2 | $2,316 |
According to NEEP, its certified maximum capacity at −30 °C (−22 °F) is 7,500 BTU/h, 83% of its nominal 9,000 BTU size.
At 8 °C, its certified maximum capacity reaches 17,200 BTU/h, 91% more than its nominal 9,000 BTU size.
According to NEEP, its certified heating capacity at −15 °C (5 °F) is 13,500 BTU/h, 150% of its nominal 9,000 BTU size. Its COP there is 2.00.
According to NEEP, its certified maximum capacity at −30 °C (−22 °F) is 7,500 BTU/h, 62% of its nominal 12,000 BTU size.
At 8 °C, its certified maximum capacity reaches 17,200 BTU/h, 43% more than its nominal 12,000 BTU size.
According to NEEP, its certified heating capacity at −15 °C (5 °F) is 13,500 BTU/h, 112% of its nominal 12,000 BTU size. Its COP there is 2.00.
According to NEEP, its COP at −15 °C is 2.34: the highest of the Série 35 line, which ranges from 2.00 to 2.00 at that temperature.
According to NEEP, its certified maximum capacity at −30 °C (−22 °F) is 11,900 BTU/h, 66% of its nominal 18,000 BTU size.
At 8 °C, its certified maximum capacity reaches 29,700 BTU/h, 65% more than its nominal 18,000 BTU size.
Data read live from the airgreen.ca page of each size (NEEP / AHRI certified performance). When the title names the installed size, it is highlighted; otherwise the whole range is shown. The aid shown is today’s, using Hydro-Québec’s rule ($120 per 1,000 BTU/h at −8 °C); amounts quoted in the article date from its publication. Only Hydro-Québec confirms the assistance granted.A dash in the aid column: amount to be confirmed for this model.
The big day, step by step
The main steps of this kind of job at AirGreen. Every house has its quirks: the estimate brings them out.
We look at the room, the outside wall, the line route and where the outdoor unit will go. That is where the capacity gets chosen.
Model, capacity and price, in writing. We also check whether the model qualifies for assistance programs.
Floors and furniture protected, wall plate position marked level, wall opening located.
A single opening, with the slope the drain needs to flow outside.
Set on a stand raised above the snow, with the clearances the manufacturer requires.
Connected, insulated and protected. The opening is then sealed against water, cold air and insects.
A dedicated circuit and an accessible disconnect near the outdoor unit.
Leak test, vacuum, then start-up and a check of heating and cooling.
Remote, modes, filters: we show you the essentials before we leave.
- The on-site estimateWe look at the room, the outside wall, the line route and where the outdoor unit will go. That is where the capacity gets chosen.
- The quoteModel, capacity and price, in writing. We also check whether the model qualifies for assistance programs.
- Getting readyFloors and furniture protected, wall plate position marked level, wall opening located.
- The wall openingA single opening, with the slope the drain needs to flow outside.
- The outdoor unitSet on a stand raised above the snow, with the clearances the manufacturer requires.
- Lines, cable and drainConnected, insulated and protected. The opening is then sealed against water, cold air and insects.
- The electrical workA dedicated circuit and an accessible disconnect near the outdoor unit.
- Tests and start-upLeak test, vacuum, then start-up and a check of heating and cooling.
- The walkthroughRemote, modes, filters: we show you the essentials before we leave.
What would it look like at your place?
Two quick checks with real numbers: what heat costs, and what your current heaters add up to in BTU/h.
Baseboards and electric furnaces turn 1 kWh of electricity into 1 kWh of heat. A heat pump delivers more: that is its COP. At Hydro-Québec’s rate D (11.142¢/kWh above 40 kWh a day, since 1 April 2026):
Hydro-Québec: a heat pump can be up to three times more efficient than baseboards for heating in the colder months.
Estimate per kWh of heat, at the chosen temperature, using the certified COP from the product page. Taxes, access charge and backup heat not included.
Conversion: 1 W = 3.412 BTU/h. An indication, not a load calculation: baseboards and furnaces are often stronger than the real need, and they can stay as backup. AirGreen confirms the capacity on site.
Four mistakes we do not make
Flip each card to see what we do instead.
Your own project, step by step
What to do, season by season
Three habits per season for this unit. They take a few minutes and prevent many calls.
- Clean the indoor unit's filters.
- Clear leaves and debris left on the outdoor unit by winter.
- Test cooling before the first hot days.
- Clean the filters more often when the unit runs a lot.
- Keep plants away from the outdoor unit.
- Check that no water drips from the indoor unit.
- Rake the leaves around the outdoor unit.
- Test heating before the first cold days.
- Book periodic maintenance before winter.
- Keep snow away from the stand and the front of the unit.
- Let the unit defrost: it is normal.
- Never hit the ice on the fins; call us if the unit stays iced up.
Is your home ready?
Check what applies at your place. A "no" is not a refusal: it is what we sort out during the estimate.
Four statements: true or false?
It all comes down to details you have just seen.
1. In heating mode, the outdoor unit can produce water.
During defrost cycles. That water must drain away without forming ice.
2. You pick the capacity with a simple square-footage rule.
Windows, insulation, orientation and how the room is used all count. Capacity is chosen on site.
3. A multi-zone connects several indoor heads to a single condenser.
One head per room, all on the same condenser. Each room keeps its own temperature.
4. The disconnect can sit behind the patio furniture.
It must stay accessible: it is what shuts the unit off for service.
0 / 4 right answers
What people ask us about this kind of work
Does a wall-mounted heat pump heat in winter?
Wall-mounted or multi-zone: how do I choose?
Where does the outdoor unit go?
Are there grants?
Do I need a permit?
How cold can it heat?
How much can I save?
How is the LogisVert assistance calculated?
Is it noisy?
The outdoor unit is covered in ice: is that normal?
Does AirGreen hold the required licences?
Is the estimate free?
No question matches. Write to us: we answer.
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Text and photo: a real AirGreen Climatisation & Chauffage job. The diagrams are generic illustrations of the type of installation, not a survey of this job site. Sources of the added figures: airgreen.ca product pages (NEEP / AHRI performance), Hydro-Québec (Heat pumps page, LogisVert, read on 13 October 2026), Régie de l’énergie (rate D as of 1 April 2026).