Installation of a MIDEA MIDEA35 wall-mounted heat pump on a rooftop in Les Coteaux

A rooftop installation that requires much more than simply having available space

This installation of a MIDEA MIDEA35 wall-mounted heat pump in Coteaux features a very different configuration from a typical residential ground-level installation. Here, the outdoor unit was installed directly on a flat roof covered with gravel, among several existing mechanical systems, roof outlets, and other air-conditioning units.

The photo taken after our work clearly shows the approach chosen by our team: the Midea heat pump is not placed directly on the roof. It is installed on an elevated metal support, itself positioned on two long pieces of wood used to distribute the load across the roof surface.

This configuration addresses several technical concerns specific to rooftop HVAC installations: stability, drainage, snow accumulation, vibration, clearance around the unit, service access, and roof protection.

In a project like this in the Coteaux, the choice of heat pump obviously matters, but the way we install its outdoor unit is just as important.

Why raise a heat pump installed on a roof?

A heat pump used in Quebec must be able to operate when it snows, when it freezes, and during defrost cycles.

On a flat roof, we especially do not want the unit resting at the level of the gravel or in an area where water, ice, and snow can accumulate around its base.

The support visible in this installation keeps the MIDEA35 at a more suitable height.

This elevation helps to:

• keep the unit’s base away from the roof surface;
• leave more space beneath the unit for defrost water;
• limit the impact of snow buildup around the heat pump;
• facilitate certain service proceduresHVAC maintenance;
• keep the unit stable;
• provide greater protection for the lower components of the equipment;
• allow better airflow around the unit.

On site, these details become particularly important in January and February, when an outdoor installation must continue operating in conditions very different from those of a summer day.

A roof already occupied by several HVAC systems

The photo also shows several outdoor units already present on the adjacent buildings and around the installation area.

For us, this is an important constraint.

A mechanical rooftop cannot be organized solely according to the visible free space at the time of the work. We must take each unit’s airflow into account.

The MIDEA35 uses an outdoor unit with side discharge. Midea also highlights the compact design of its units and their ability to be installed in various types of locations, including roofs, terraces, and balconies.

We must therefore maintain an appropriate area in front of the fan and around the heat exchanger to prevent another appliance, parapet, or piece of mechanical equipment from unnecessarily disrupting airflow.

Airflow is critical on a rooftop

The large circular grille visible on the front of the outdoor unit corresponds to the fan that moves air through the heat exchanger.

If this air immediately encounters an obstacle or flows directly back toward the unit, the heat pump may experience recirculation.

This can reduce system performance, particularly when several pieces of equipment are grouped on the same roof.

Our analysis therefore does not focus solely on the distance between two units. We also consider:

• the discharge direction;
• the height of neighboring equipment;
• the parapets;
• the ventilation outlets;
• the ducts present on the roof;
• the position of the other condensers;
• the technicians’ future traffic areas.

A HVAC installation on a rooftop in Les Coteaux must remain functional even as the roof becomes more cluttered over the years.

The metal support: stability and access

In the photo, the Midea rests on a relatively high metal frame. The unit is fastened to the upper rails, while the support rests on the wooden elements installed on the gravel.

This type of arrangement notably creates a more stable structure than a unit simply placed on improvised blocks.

However, we must always verify the support method, the support’s strength, the unit’s fastening, and the roof protection.

An outdoor heat pump is subject to:

• compressor vibrations;
• fan rotation;
• wind;
• rain;
• freezing;
• snow;
• repeated heating and cooling cycles.

The mechanical installation must therefore remain stable throughout the equipment’s service life.

Protecting the roof is part of HVAC work

On a flat roof, the membrane is a building component that must be protected.

An equipment support should not create unnecessary pressure points or damage the surface over time.

Using longer support elements allows the load to be distributed over a larger surface. In this installation, the two crossbars visible beneath the support contribute to this distribution.

This also makes it easier to create a level, stable base in an area where the gravel layer does not necessarily provide a perfectly uniform surface.

Special attention to vibrations

A rooftop heat pump can transmit certain vibrations to the building structure if its mechanical installation is inadequate.

We therefore pay attention to several elements:

• the stability of the base;
• leveling the unit;
• the contact points;
• the rigidity of the support;
• the refrigerant line routing;
• areas where the pipes may touch or vibrate against a structure.

The goal is not simply for the unit to be quiet when we are standing next to it. We also want to prevent mechanical vibration from becoming perceptible noise inside the building.

The refrigerant line route is different on a roof

Another important aspect of this installation is the connection between the outdoor unit and the indoor wall-mounted heat pump.

Midea ductless systems offer considerable positioning flexibility. The brochure specifies that the indoor unit is connected to the outdoor unit through a relatively compact passage and that certain configurations allow for substantial line lengths.

However, for a rooftop installation, we must analyze:

• the total horizontal distance;
• the height difference;
• the copper line routing;
• line insulation;
• weather protection;
• the mounting points;
• the passage through the roof or walls;
• the possible amount of additional refrigerant required.

These details must be determined according to the heat pump's exact capacity.

The MIDEA35: a high-efficiency heat pump suited to Quebec winters

A series designed for heating down to -30°C

The MIDEA35 is presented by Midea as its premium wall-mounted series and as an extreme heat pump.

It uses the refrigerant R-454B and is designated Cold Climate V6.1.

According to the manufacturer's specifications, the heating operating range goes down to -30 °C for all three capacities in this series. The cooling range can reach 50°C.

This low-temperature operating capability is particularly relevant in an installation such as that of the Coteauxwhere the outdoor unit is fully exposed to winter conditions on a rooftop.

It is not enough for a heat pump to be able to start in cold weather. We must also examine what it can produce when temperatures become truly demanding.

Three different capacities in the MIDEA35 series

The documented range includes three cooling capacities:

• 9,000 BTU/h;
• 12,000 BTU/h;
• 18,000 BTU/h.

The corresponding indoor models are MSESU-H09B-2A, MSESU-H12B-2A and MSESU-H18B-2Aassociated with the outdoor units MO1SS-H09B-2A, MO1SS-H12B-2A and MO1SS-H18B-2A.

The AHRI numbers are respectively:

• 215471386;
• 215471387;
• 215471388.

Since the rating plate is not legible in the project photo, we do not claim to identify the unit’s precise capacity based solely on its appearance.

This is an important distinction: outdoor units with different capacities can look very similar.

Up to 33.3 SEER2

The performance figures advertised by Midea vary according to the selected capacity.

For the MIDEA35:

• the 9,000 BTU model reaches 33.3 SEER2;
• the 12,000 BTU unit reaches 29.4 SEER2;
• the 18,000 BTU unit reaches 25.6 SEER2.

The listed HSPF2 IV values are respectively 22.0, 14.5 and 16.2.

We always consider these figures for the exact combination rather than automatically attributing the maximum 33.3 SEER2 performance to all MIDEA35 units.

Capacity at -15 °C: important data for Les Coteaux

When selecting a heat pump for Quebec, we pay particular attention to low-temperature heating data.

At -15 °C, Midea indicates:

MIDEA35 9,000 BTU

Nominal heating capacity: 13,500 BTU/h
COP: 3.60

MIDEA35 12,000 BTU

Nominal heating capacity: 13,500 BTU/h
COP: 3.60

MIDEA35 18,000 BTU

Nominal heating capacity: 22,600 BTU/h
COP: 4.40.

These data provide a more useful picture of the system’s winter performance than a simple nominal capacity calculated under much milder conditions.

Why a rooftop unit deserves even more attention in winter

On the photographed roof, the heat pump is directly exposed to wind and precipitation.

Snow can shift and form localized accumulations that differ considerably from those observed at ground level.

The elevated support therefore becomes particularly important.

It is also important to prevent snow from being pushed or accumulated around the heat pump when clearing the roof.

We recommend maintaining:

• the back of the unit clear;
• the fan face unobstructed;
• enough space beneath the unit;
• safe access for technicians;
• an area that allows defrost water to drain away.

Snow should never be piled against the outdoor heat exchanger.

Dimensions vary considerably depending on capacity

The 9,000 and 12,000 BTU MIDEA35 versions use an outdoor unit measuring approximately 35.04 in wide × 13.46 in deep × 26.50 in high.

The 18,000 BTU version measures approximately 37.24 in × 16.14 in × 31.89 in.

The weight also changes: approximately 99.65 lb for the 9,000 and 12,000 BTU versions, compared with 130.29 lb for the 18,000 BTU unit.

On a roof, these differences must be considered when choosing the support and positioning.

The copper diameters are not the same

For the MIDEA35 units of 9,000 and 12,000 BTU, Midea specifies lines of 1/4 in and 3/8 in version.

For the 18,000 BTU, the dimensions increase to 3/8 in and 5/8 in.

The stated maximum lengths are also different: 82 ft for the two smaller capacities and 164 ft for the 18,000 BTU model.

On a roof, the actual line length can quickly increase because of the routing required between the wall-mounted unit and the mechanical area.

An accurate measurement of the route is therefore essential before installation.

R-454B and new installation practices

The MIDEA35 uses R-454B, an A2L refrigerant.

The series documentation also mentions an A2L refrigerant leak detection sensor, as well as temperature and humidity control.

For us, this means that installation and commissioning procedures must be adapted to the generation of equipment being installed.

We pay particular attention to refrigeration work: line preparation, connections, evacuation, checks, and commissioning.

The electrical specifications must match the exact model

The MIDEA35 units operate at 208/230 V, single-phase, 60 Hz.

The documentation states:

• 9,000 BTU: minimum ampacity 16 A, maximum fuse 20 A;
• 12,000 BTU: minimum ampacity 16 A, maximum fuse 20 A;
• 18,000 BTU: minimum ampacity 24.9 A, maximum fuse 25 A.

Even on a roof where several electrical devices are already present, we never assume that an existing circuit is automatically compatible.

Outdoor noise and vibrations on a roof

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.

On a roof, the distance from living spaces can help reduce the direct perception of noise. However, mechanical transmission through the structure becomes equally important.

This is another reason why we pay close attention to the unit’s supports and contact points.

A very quiet heat pump indoors

Indoors, the MIDEA35 can operate at very low noise levels.

The 9,000 and 12,000 BTU units are rated at up to 19 dB(A) in quiet mode, while the 18,000 BTU version can go as low as 16 dB(A).

Midea also offers up to 100 airflow control levels, allowing finer adjustment of indoor airflow.

The series also includes several useful functions:

• ECO mode;
• sleep mode;
• timer;
• quiet mode;
• “Follow Me” function;
• horizontal swing;
• vertical swing;
• 8°C heating;
• automatic cleaning;
• humidity control.

The AHRI number is essential for verifying a rebate

The AHRI references associated with the three MIDEA35 combinations are 215471386, 215471387 and 215471388.

To determine whether the installation carried out at Coteaux is eligible for financial assistance and to determine the applicable amount, the exact installed combination and the current program criteria must be verified.

The brochure provided alone does not allow us to confirm the rebate amount for this specific project. We therefore prefer to verify AHRI and the applicable conditions rather than announce an amount that might not correspond to the installation.

A substantial residential warranty

Midea states in its brochure that the limited residential warranty is 12 years on the compressor, 12 years on parts, and 10 years on labor, subject to the applicable registration conditions and terms.

It is therefore important to retain the model numbers, serial numbers, and installation documents.

The mistakes we want to avoid when installing a rooftop heat pump

Installing the unit directly on gravel

The heat pump must rest on an adequate, stable base.

Underestimating snow

A flat roof can experience significant and uneven snow accumulation.

Placing the unit too close to another piece of equipment

Insufficient clearance can disrupt airflow and complicate servicing.

Neglecting vibrations

A unit installed at height can transmit vibrations if its support is poorly designed or unstable.

Overlooking maintenance access

A technician must be able to reach the unit, remove its panels, and perform the necessary diagnostics.

Choose the capacity before measuring the refrigerant line route

The lengths, elevation changes, and diameters of the lines are directly related to the installed model.

This project in Coteaux is a good example of our approach to complex HVAC installations

This photo shows an environment where several elements must work together: flat roof, gravel, nearby mechanical equipment, supports, lines, roof outlets, and Midea outdoor unit.

Our goal was not simply to find an empty space in which to install the heat pump.

We had to create an installation capable of remaining stable, accessible, and functional throughout all four seasons.

The MIDEA MIDEA35 offers particularly interesting features for this type of project: heating operation down to -30 °C, efficiency of up to 33.3 SEER2, R-454B refrigerant, variable-speed technology, and several available capacities.

But an excellent technical data sheet can never replace an excellent installation.

At AirGreen, we apply this same logic to our wall-mounted heat pumps and HVAC installation to Coteaux, as well as Montréal, Laval, Longueuil, on the North Shore and the South Shore : first analyze the building and the equipment’s actual environment, then adapt the system to those constraints.

On this Coteaux rooftop, the most visible part of our work is the MIDEA35 installed on its support.

The most important part remains everything that was designed so it could operate properly year after year.