In Coteau-du-Lac, an MIDEA35 heat pump installed on the roof to free up ground space and protect the equipment
Some installations of wall-mounted heat pumps are relatively straightforward: an indoor unit on an exterior wall, an outdoor unit on a support near the foundation, and a short run of lines between the two. This project completed in Coteau-du-Lac required an entirely different approach.
The site photograph shows the outdoor unit MIDEA MIDEA35 installed on a flat roof covered with gravel, among other mechanical equipment. We positioned the heat pump on a raised metal structure resting on wooden elements that serve as its base. The main fan remains completely unobstructed, and the unit is kept well above the roof surface.
This installation choice is not merely aesthetic. On a Quebec roof, we must consider snow, drainage, ice, vibrations, maintenance access, and roof protection.
The Midea series used in this project belongs to the family of MIDEA35 ductless wall-mounted systems, a range specifically presented by the manufacturer among its ductless wall-mounted heat pump solutions.
The MIDEA35 is a low-temperature heat pump using the refrigerant R-454B. Midea states that this series can operate in heating mode down to -30°C, with efficiency reaching 33.3 SEER2 as well as an HSPF2 of up to 22,0, depending on the selected capacity.
Why install the outdoor unit on the roof?
In some properties in Coteau-du-Lac, as is the case in several buildings we serve in Montreal, Laval, Longueuil, the North Shore, and the South Shore, the outdoor space available near the building may be limited or reserved for other uses.
A flat-roof installation can notably:
- keep ground-level areas clear;
- move the unit away from walkways;
- reduce the visual impact from the yard;
- group several mechanical systems in the same area;
- provide a technical routing path better suited to certain buildings;
- install the unit away from areas where snow is pushed or shoveled.
Midea itself highlights the flexibility of its side-discharge outdoor units and indicates that they can be placed on a support, particularly in roof, terrace, or balcony configurations.
But placing a heat pump on a roof does not simply mean lifting the unit up and setting it down on the available surface. This is precisely where our work ofHVAC installation becomes more technical.
A raised structure immediately visible in the photograph
The most interesting detail of this project in Coteau-du-Lac is the structure supporting the unit.
The Midea rests on a rigid metal frame. This keeps the bottom of the unit a significant distance above the roof gravel.
Under the structure, we can also see wooden elements arranged lengthwise. These help create a stable base without placing the metal feet directly in the gravel.
This design offers several advantages.
Keeping the unit above winter accumulations
A heat pump used as a heating system must continue exchanging outdoor air even when snow accumulates on the roof.
A unit installed too close to the surface may gradually become surrounded by snow or ice. This can hinder air intake and complicate the drainage of water produced during defrost cycles.
The support height is therefore an important element in our planning.
Facilitating drainage during defrosting
When a heat pump operates in heating mode during cold weather, frost can form on the outdoor heat exchanger. The unit then periodically performs a defrost cycle.
The ice melts and creates water beneath the unit.
On this site, the considerable space beneath the MIDEA35 allows this water to leave the immediate area around the machine more freely instead of directly forming a mass of ice against its base.
Maintaining access for service
A raised structure also facilitates certain service work.
A technician must be able to access the unit to:
- inspect the connections;
- check the electrical components;
- clean the heat exchanger;
- perform diagnostics;
- measure operating parameters;
- work on the service panels.
The unit’s positioning must therefore remain practical for several years after installation.
The fan benefits from a substantial clearance area
The photograph clearly shows the Midea’s large front grille.
There is no equipment placed at a very short distance in front of it.
This is an important decision, because a heat pump side discharge must expel a considerable volume of air through its fan.
If a unit is positioned directly facing a wall, parapet, or another device that is too close, some of the discharged air may return toward the heat exchanger. This recirculation can impair the machine’s operation.
On a roof containing several units, like the one visible at our site Coteau-du-Lac, so we must study not only the space occupied by the heat pump, but also the space required around it.
Several pieces of equipment on the same roof: improvisation must be avoided
The photo also shows other outdoor units nearby.
This is common in some buildings with several zones or multiple units. Each unit may have its own refrigeration circuit and serve a separate space.
In such a context, the installation must remain organized.
We seek in particular to preserve:
- access corridors between the units;
- clearance around the heat exchangers;
- the ability to identify each system;
- access to the service panels;
- a logical route for the lines;
- a stable base for each unit.
Installing several heat pumps around one another without an overall plan can make a roof extremely difficult to maintain later.
MIDEA35: performance, sizing, and technical details that matter just as much as the roof support
Three main capacities in the MIDEA35 series
Midea’s documentation presents three configurations in the MIDEA35 series:
| Cooling capacity | Indoor unit | Outdoor unit | AHRI reference |
|---|---|---|---|
| 9,000 BTU/h | MSESU-H09B-2A | MO1SS-H09B-2A | 215471386 |
| 12,000 BTU/h | MSESU-H12B-2A | MO1SS-H12B-2A | 215471387 |
| 18,000 BTU/h | MSESU-H18B-2A | MO1SS-H18B-2A | 215471388 |
For heating, Midea indicates nominal capacities of, respectively, 12,000 BTU/h, 12,000 BTU/h, and 20,000 BTU/h.
An EnerGuide label is visible on the unit in our photo, but the nameplate cannot be read clearly enough to determine the exact installed combination with certainty. We therefore do not arbitrarily assign it a capacity.
This is important for a technical article: MIDEA35 refers to a series, not a single BTU capacity.
Up to 33.3 SEER2 for cooling
According to the manufacturer’s technical data:
- the MIDEA35 9,000 BTU unit reaches 33.3 SEER2;
- the 12,000 BTU unit reaches 29.4 SEER2;
- the 18,000 BTU unit reaches 25.6 SEER2.
The corresponding HSPF2 IV ratings are, respectively, 22.0, 14.5, and 16.2.
These differences show why a homeowner should always compare exact model numbers rather than simply two trade names.
The capacity suitable for a project must first meet the building’s heating and cooling needs.
Why a larger heat pump is not necessarily better
Sizing a heat pump is a central part of our work at AirGreen.
We assess in particular:
- the area to be conditioned;
- the ceiling height;
- the quality of the insulation;
- window area;
- solar orientation;
- the layout of the rooms;
- air infiltration;
- heat losses;
- the actual use of each zone.
Choosing more BTUs “to be safe” is not always advantageous.
A properly sized unit can run longer at reduced output and make better use of the modulation capabilities offered by variable-speed technology.
Variable-speed technology to avoid abrupt cycles
Midea’s documentation explains that its variable-speed technology allows the compressor to adjust its operation as temperature needs change, rather than operating exclusively according to an on-off logic.
When the room requires substantial heating or cooling, the system can increase its output.
As the temperature approaches the setpoint, it can gradually reduce its output.
This modulation helps limit large temperature fluctuations and can improve perceived comfort.
Heating down to -30 °C: particularly relevant in Quebec
The MIDEA35 is advertised as having a heating operating range of up to -30°C. In cooling mode, the documentation indicates operation down to 50 °C.
For an installation at Coteau-du-Lac, this cold-weather operating capacity is obviously an important selling point.
But we always emphasize one nuance: the minimum operating temperature does not correspond to a constant capacity.
The amount of heat produced changes as the outdoor temperature drops.
Midea also provides precise data at -15 °C :
- 13,500 BTU/h for the 9,000 BTU model;
- 13,500 BTU/h for the 12,000 BTU model;
- 22,600 BTU/h for the 18,000 BTU model.
When a customer is looking to use their heat pump as the primary heating system, this kind of information is much more significant than the figure “-30 °C” alone.
The roof can lengthen the refrigerant line run
Another distinctive feature of rooftop installations is the potentially greater distance between the indoor and outdoor units.
The piping must therefore be planned before the final positioning.
For the MIDEA35 series, Midea specifies:
- piping 1/4 in and 3/8 in for the 9,000 and 12,000 BTU models;
- piping 3/8 in and 5/8 in for the 18,000 BTU version.
The maximum lengths are also different:
- 82 ft for the 9,000 and 12,000 BTU versions;
- 164 ft for the 18,000 BTU version.
These are values we need to know before definitively choosing the unit’s position on a building.
The height difference between the units matters as well
On a roof, the outdoor unit is naturally higher than the indoor unit.
Midea documentation indicates a maximum height difference of 49.2 ft for the 9,000 and 12,000 BTU models and 82 ft for the 18,000 BTU version.
In a one- or two-story house, this is generally not the first constraint encountered. In some multistory buildings, however, it can become decisive.
Electrical requirements vary by capacity
The MIDEA35 units operate at 208/230 V, single-phase, 60 Hz.
Midea specifies for the outdoor units:
- minimum allowable amperage of 16 A for the 9,000 BTU model;
- 16 A for the 12,000 BTU model;
- 24.9 A for the 18,000 BTU model.
The published maximum protections are respectively 20 A, 20 A, and 25 A.
A heat pump in Coteau-du-Lac must therefore include a check of the available electrical circuit.
We must never assume that an old circuit is automatically compatible with a new appliance simply because the two systems appear to have a similar capacity.
Why the unit’s weight matters on a roof
The support shown in the photo must also be able to bear the equipment’s actual weight.
According to Midea, the MIDEA35 outdoor units weigh approximately:
- 99.65 lb for the 9,000 and 12,000 BTU models;
- 130.29 lb for the 18,000 BTU version.
Added to this are the metal structure, base components, and stresses associated with wind, vibration, and winter conditions.
That is why rooftop installation is not simply a matter of choosing a support that looks large enough.
Vibrations: a greater concern on rooftops
The operation of the compressor and fan naturally produces some vibration.
At ground level, a stable base absorbs a large part of these movements. On a roof, vibration can sometimes be transmitted to the building structure if the support is inadequate.
We therefore pay particular attention to:
- frame stability;
- unit leveling;
- contact points;
- tightening;
- the rigidity of the base;
- near certain structures sensitive to vibration.
A solid installation contributes both to acoustic comfort and to system durability.
Outdoor unit sound level
Midea states a maximum outdoor sound level of 57 dB(A) for the 9,000 and 12,000 BTU versions and 61.5 dB(A) for the 18,000 BTU model.
Rooftop installation can help move the heat pump away from certain occupied areas at ground level, but housing units or rooms located directly beneath the equipment must also be taken into account.
This is another reason why vibration control and management are essential.
MIDEA35 Comfort Features
The MIDEA35 series is not limited to compressor performance.
Midea offers several functions built in or available depending on the configuration:
- ECO mode;
- Turbo;
- night mode;
- timer;
- fan speed adjustment;
- function Follow Me;
- automatic cleaning;
- silent mode;
- 8°C heating;
- horizontal swing;
- vertical swing;
- smart sensor;
- humidity control;
- Wi-Fi control;
- optional wired controller;
- optional 24 V interface.
Fan control allows, among other things, fine adjustment of indoor airflow to achieve operation better suited to the room's needs.
Follow Me: Measuring the Temperature Closer to the Occupant
The Follow Me uses the sensor built into the remote control to measure the temperature near where it is located.
This feature can be useful when the indoor unit is located some distance from the area actually occupied.
A temperature measured near the ceiling or an exterior wall may differ slightly from the temperature felt in the center of a room.
Easier Interior Maintenance Through the Series Design
Midea also indicates that the blower wheel in the MIDEA35, MIDEA28, and MIDEA25 series can be removed to allow for more thorough cleaning.
This design is particularly valuable in the long term.
During wall-mounted heat pump maintenance, we sometimes need to go beyond simply cleaning the filters.
Over the years, dust can accumulate on the heat exchanger, blower wheel, and internal areas that remain invisible during routine maintenance.
Subsidies: Verify the Exact AHRI Combination
The three MIDEA35 models listed in the brochure have the following AHRI reference numbers:
- 215471386;
- 215471387;
- 215471388.
They are also identified Cold Climate V6.1 in the documentation.
For any subsidy or financial assistance application, however, we recommend verifying the exact combination installed and the program criteria in effect when the work is carried out.
The MIDEA35 trade name alone is not sufficient to determine a financial incentive amount.
Residential Warranty Presented by Midea
For the residential sector, the Midea brochure indicates a 12-year limited warranty on the compressor, 12 years on parts, and 10 years on labor, according to the conditions applicable to its program.
The registration conditions and precise terms must always be verified for the actual equipment installed.
Errors We Avoid When Installing on a Roof
A photograph like this one from the Coteau-du-Lac project highlights several important practices.
Installing the unit too close to the roof
A unit installed too low is more likely to be exposed to snow, water, and ice.
Neglecting weight distribution
The support must distribute the load appropriately without creating an unnecessary pressure point on the roof.
Placing equipment right next to one another
Each heat exchanger must have sufficient space to draw in and discharge air.
Forgetting future maintenance
A technician must be able to move between the units and access the necessary panels.
Ignoring vibrations
A poor base can turn a small mechanical vibration into a disturbance felt throughout the building.
Choose the model before calculating the refrigerant line route
The distance and difference in height between the indoor and outdoor units must remain within the manufacturer’s limits.
This Coteau-du-Lac project is a good representation of how we work at AirGreen
This MIDEA MIDEA35 wall-mounted heat pump installation in Coteau-du-Lac is interesting because the most important part of the project is not necessarily the part the owner uses every day.
Inside, the occupant simply enjoys heating and air conditioning.
On the roof, however, we had to consider the support, the unit’s height, airflow, the roofing, other equipment, vibrations, and future maintenance.
The final photograph shows an outdoor unit properly installed on an elevated metal supportprojects, with substantial clearance beneath the unit and in front of its fan. The presence of other nearby equipment further underscores the importance of methodical roof organization.
This is the same attention we apply to our wall-mounted heat pump, air conditioning, heating, and HVAC installation to Montreal, Laval, Longueuil, the North Shore, and the South Shore.
The MIDEA35 offers a particularly interesting technical foundation: heating operation down to -30°C, refrigerant R-454B, variable-speed technology, Cold Climate certification, and efficiency reaching 33.3 SEER2.
Our role is then to ensure that these features can be utilized in an installation genuinely suited to the building.
To Coteau-du-Lac, this meant one very concrete thing: not simply placing the heat pump on the roof, but building it a stable, accessible location suited to the realities of Quebec’s climate.