Installation of a MIDEA EVOX G3 electric furnace in Brossard, on Montreal’s South Shore: horizontal configuration in the attic

In Brossard, a central installation that had to adapt to the attic rather than a conventional mechanical room

This installation carried out by AirGreen in Brossard, on Montreal’s South Shore, illustrates a scenario very different from replacing a furnace in a basement. Here, the MIDEA EVOX G3 electric furnace was installed horizontally in the attic, amid the framing, blown-in insulation, and existing ducts.

The project photo immediately makes the main constraint clear. The unit is not installed upright against a wall. It rests on a structure built between the framing members and must operate in a space where working room, installation access, and connection options are much more limited than on the ground floor or in the basement.

This is precisely the type of application for which the modular design of the MIDEA EVOX G3 becomes particularly interesting. The documentation provided by MIDEA presents this range as a central ducted Inverter system intended in particular to facilitate the modernization of existing heating systems.

For this project in Brossard, so our work did not consist solely of installing a new unit. We had to plan its orientation, support, clearances, refrigerant line routing, connection to the air ducts, and above all the possibility of carrying out future HVAC maintenance without turning every service call into a major operation.

A horizontal installation: the defining feature of this project

The most obvious difference compared with a conventional central installation is the orientation of the unit.

The MIDEA EVOX G3 is lying horizontally in the attic. The photo clearly shows the front of the unit turned sideways, with the body of the appliance passing through several spaces between the framing members.

MIDEA specifically provides different installation orientations for this range. The documentation notably mentions:

• upflow;
• downflow;
• horizontal right;
• horizontal left;
• configurations adapted to spaces with limited height.

The manufacturer also emphasizes that the modular design makes it easier to move the unit through difficult areas such as attics and crawl spaces.

In a project like this, this flexibility is not merely a brochure feature. It directly affects the feasibility of the installation.

Why a furnace installed in an attic requires more preparation

A traditional mechanical room generally offers a solid floor, relatively direct access, and sufficient space around the equipment.

In an attic, almost everything changes.

For this Brossard installation, we had to work around:

• the existing wooden framing;
• blown-in insulation covering the attic floor;
• limited working height;
• the existing ducts;
• the routing of the refrigerant lines;
• the need to properly support the appliance;
• access that must remain possible for servicing;
• much greater temperature variations than in a living space.

The goal is never simply to manage to get the unit into the attic. It must be able to operate properly there for several years while remaining accessible.

The support structure visible beneath the appliance is important

The photograph shows that the EVOX G3 does not rest directly in the insulation.

The appliance is positioned on structural elements that keep its weight above the insulated surface. In an attic, it is particularly important to consider how the equipment’s weight will be transferred to the existing structure.

A central unit contains, among other things, a fan, a heat exchanger, a metal cabinet, and various electrical components. Its installation must therefore be stable and sufficiently rigid to limit unwanted movement.

An improperly built support can contribute to:

• vibration;
• noise transmitted to the structure;
• misaligned connections;
• deformation around the duct connections;
• service difficulties.

We therefore pay just as much attention to the support as to the machine’s connections themselves.

A modular design particularly well suited to passing through an attic access opening

One of the EVOX G3’s interesting features is its sectional design.

MIDEA describes a modular locking system that makes the unit easier to handle and reconfigure. The manufacturer specifically highlights the benefit of an appliance that is easier to carry up stairs, into basements, and into attics, as well as the ability to change its orientation with fewer steps than a conventional appliance.

This detail can determine whether an attic installation is realistic or not.

In many homes in Brossard, Saint-Lambert, Longueuil, La Prairie, and the South Shore, the attic access opening is much smaller than the final dimensions of the installed equipment. Each project must therefore be assessed on site before promising that a given unit can be transported and positioned properly.

Electric furnace or air handler?

In Quebec residential terminology, we often use electric furnace to refer to the indoor unit of a central system.

In the case of the MIDEA EVOX G3 paired with a heat pump, the unit nevertheless serves several functions.

It is used to:

• circulate air throughout the house;
• receive the energy transferred by the heat pump;
• distribute heating through the ducts;
• distribute cooling in the summer;
• accommodate, when the configuration allows, auxiliary electric heating.

Electric heating therefore does not necessarily have to produce all the heat during the winter. The central heat pump can provide much of the heating, while the electric elements provide supplemental heat when demand requires it.

MIDEA offers multi-stage auxiliary heating kits capable of reaching 25 kW, depending on the equipment configuration.

However, the appropriate capacity must be selected based on the building and the electrical installation; the maximum available in a product range is not automatically the right choice for a given home.

The attic makes condensate management particularly important

A furnace or air handler paired with a heat pump produces condensate when operating in cooling mode.

Moisture in the air condenses on the cold coil. This water must then be drained properly.

When the unit is installed in the basement near a drain, condensate management can be relatively straightforward. In an attic, the consequences of a drainage problem can be much more serious, since uncontrolled water can reach the insulation, ceiling, or finishing materials beneath the unit.

That is why we pay particular attention to:

• the proper orientation of the system;
• condensate drainage;
• the slope of the drainage pipes;
• access for inspecting and cleaning the drainage;
• the complete commissioning in cooling mode.

The photo does not show the entire drainage network for this installation; therefore, we do not attribute components that are not visible or confirmed to this project.

Routing refrigerant lines through the middle of the framing

In the lower part of the photograph, we can see an insulated pipe that follows the attic floor before reaching the equipment.

This routing must be planned carefully.

A refrigerant line must not be left in a position where it could be crushed during future work in the attic, damaged by other work, or become impossible to access.

In a project like the one in Brossard, we must find a compromise between:

• a sufficiently direct route;
• mechanical protection;
• insulation;
• the structural framing constraints;
• access to the unit;
• future work that may be carried out in the attic.

This is an excellent example of a detail invisible from the living areas but that greatly influences the quality of a central HVAC installation.

R-454B and the new EVOX G3 generation

The label visible on the unit also displays the A2L designation.

MIDEA documentation confirms the use of R-454B refrigerant for the central EVOX range concerned. The manufacturer assigns it a global warming potential, or GWP, of 466.

R-454B belongs to the A2L category.

For us, this means following the procedures intended for this generation of refrigerants when connecting, evacuating the circuit, commissioning, and carrying out any future work on the refrigeration system.

The refrigerant is therefore not merely information printed on the nameplate. It is one of the technical parameters to consider from the very beginning of the project design.

Winter performance, airflow, and maintenance: what matters after successfully installing the unit in the attic

Up to -30 °C of operation announced for the range

For a house located in Brossard, the winter performance of a central heat pump is naturally a major consideration.

MIDEA states that the EVOX G3 heat pump can operate continuously down to approximately -30 °C. The documentation also presents, for certain conditions and tested systems, significant heating capacity at -25 °C, with a COP of approximately 1.9. MIDEA specifies that some data are based on a three-ton system.

However, these figures must be used correctly.

The range includes several models. We therefore cannot automatically attribute all the maximum values published in the brochure to every EVOX G3.

The performance of a specific installation depends on exact match between the indoor and outdoor units.

A range covering multiple capacities

The technical table provided by MIDEA includes several central configurations, including:

• 18,000 BTU/h;
• 24,000 BTU/h;
• 30,000 BTU/h;
• 36,000 BTU/h;
• 48,000 BTU/h;
• 54,000 BTU/h.

Efficiency ratings also vary depending on the system.

In the Brossard photograph, the data label is visible, but it is not clear enough for us to confirm with certainty the model number and exact capacity.

We therefore prefer not to make up a value.

For a homeowner comparing multiple quotes for a central heat pump, which is a simple but important rule: the name “EVOX G3” alone is not enough to compare performance. You need to know the indoor model, outdoor model, and their exact match.

Up to 19 SEER2 depending on the selected system

MIDEA's documentation presents the following maximum efficiency ratings for the range:

• 19 SEER2;
• 12.5 EER2;
• 10.8 HSPF2;
• COP of 2.14 at 5 °F, or approximately -15 °C.

Again, these are the maximum values for the range. The detailed data shows performance variations among the different capacities.

Our approach at AirGreen is therefore to focus on the performance of the system as actually installed rather than on the best value printed in large type in a brochure.

Airflow becomes even more important in a configuration with existing ducts

Installing a new furnace in the attic does not guarantee that the duct network will automatically distribute the correct volume of air to each room.

The resistance of the duct network, duct dimensions, filters, and various branches must be taken into account.

The MIDEA EVOX G3 features a technology called Computational Constant Airflow 2.0. The documentation indicates that the system can adjust the output and fan speed based on the resistance encountered in the duct network. MIDEA presents conditions of up to 1.2 in. of external static pressure.

The adjustment range can include up to 60 airflow levels, offering more options when configuring the system.

This technology helps fine-tune the settings, but it does not replace a properly sized duct network.

A higher-performance filter is only useful if the system can still breathe

MIDEA also indicates that certain configurations in the range can use filters of 1, 2, or 4 inches, particularly with an MERV 13 filtration level.

In an attic installation, the choice of filter must also take accessibility into account.

An excellent filter that requires excessive contortions to replace may simply not be changed often enough.

We therefore consider filtration while taking all of the following into account simultaneously:

• the desired level of filtration;
• static pressure;
• the filter area;
• the required airflow;
• the available space;
• ease of access for the owner or technician.

Future access is an essential part of the installation

The Brossard photograph shows how much the space around the equipment is structured by the studs and framing elements.

We must think today about the operations that may be required in five, ten, or fifteen years.

A technician may need access to:

• to the blower motor;
• to the coil;
• to electrical components;
• to controls;
• to refrigerant lines;
• to drainage;
• to the filtration system.

An installation that works perfectly today but requires cutting through part of the framing or dismantling several ducts to perform a simple repair has not been properly designed.

The EVOX G3 controls offer several modernization options

MIDEA documentation provides for operation with different control strategies.

The EVOX G3 can use communication 485 in some configurations, but MIDEA also provides options using conventional thermostats 24 V, including certain combinations with third-party components.

This flexibility can be particularly useful in renovations, since it is not always easy to add new cables between the attic and the thermostat installed in a finished room.

However, exact compatibility must be validated based on the selected components.

Mistakes to avoid when a furnace must be installed in an attic

This project has Brossard highlights several points that we systematically check before this type of installation.

Underestimate the access dimensions

You must check not only the space where the equipment will operate, but also the route needed to bring it there.

Install the unit directly on or in the insulation

The equipment support must be designed separately from the building insulation.

Neglect drainage

In an attic, a condensate leak can affect the ceilings and materials below.

Route refrigerant lines through traffic areas

Someone returning to work in the attic must not be able to accidentally step on an essential line.

Forgetting the service panels

The space in front of the equipment access points must remain usable.

Choosing the capacity solely according to the building’s square footage

The tonnage must match the building’s loads as well as the duct system’s capacities.

Confusing the best rating in the range with the installation’s rating

The SEER2, HSPF2, and low-temperature performance vary depending on the exact pairing.

What about rebates for this MIDEA EVOX G3?

The MIDEA documentation provided with this project mainly presents the technical characteristics of the range and does not, by itself, confirm this Brossard installation’s eligibility for Quebec financial assistance.

The range includes several combinations of indoor and outdoor units.

You must therefore verify the exact pairing, its applicable performance reference, and the criteria of the current program before announcing a subsidy amount.

For a homeowner, this is an important precaution: financial assistance should never be considered guaranteed simply because a brand or series name appears on a quote.

An installation that highlights another aspect of the work performed by our AirGreen technicians

This project in Brossard is especially representative of projects where the difficulty lies not in the machine, but in its environment.

The MIDEA EVOX G3 offers several features that are particularly useful in this context: modular construction, horizontal configurations, adjustable blower, operation with a cold-climate heat pump, and several control options.

But none of these advantages replaces site preparation.

Here, we had to work around joists, studs, insulation, ducts, and service pathways while leaving a logical installation for years to come.

This is the approach we apply at AirGreen in our installations of electric furnaces and central heat pumps in Brossard, Longueuil, Montreal, Laval, on the South Shore and the North Shore : understand the house first, then adapt the equipment to the building rather than forcing a standard configuration into a space that is not suited to it.

This horizontal installation of the MIDEA EVOX G3 in an attic in Brossard is a concrete example: barely visible once the access panel is closed, yet technically demanding in every detail.