Installation of a MIDEA EVOX G3 electric furnace in Westmount, on the Island of Montreal

In Westmount, an MIDEA EVOX G3 furnace integrated into an existing system with a custom-made return-air assembly and sheet metalwork

In this HVAC installation in Westmount, the main difficulty is immediately visible in the worksite photo: the new MIDEA EVOX G3 electric furnace had to be installed in a very narrow mechanical area, between a wood structure on the right and a large network of galvanized sheet-metal ducts on the left. There was practically no room to correct a sizing error after installation.

Our work therefore began well before the unit was started. We had to organize the airflow path, adapt the existing ductwork, plan for filtration, maintain access to the service components, and position the new unit so that it could operate properly during both winter heating and summer cooling.

One photographed detail particularly summarizes this project: on the new return-air cabinet, we can read “20 × 20 FILTER”. This simple marking reveals part of the work that often remains invisible to the owner once the panels are closed. A modern central furnace cannot be evaluated solely by its brand, efficiency, or appearance. The return air, filter size, sheet-metal transitions, and static pressure are integral to the system’s performance.

A vertical installation designed around the space actually available

We installed the MIDEA EVOX G3 in a vertical configuration.

In the photo taken during the work, the front panels are still removed, making it possible to see the unit’s internal components, including the control electronics and the blower section. The electrical supply and certain connections are also still accessible: this is therefore clearly a stage of connection and commissioning, rather than the final presentation of the installation.

Above the furnace, a new sheet-metal transition connects to the upper ductwork. On the left, we worked around a substantial return-air duct already connected to several ducts, including some flexible sections visible in the upper part of the photo.

This is exactly the kind of configuration in which choosing the EVOX G3 becomes particularly interesting.

MIDEA designed this unit with a modular architecture called Block N Lock and offers up to six installation orientations: upward, downward, left-horizontal, and right-horizontal airflow, as well as configurations adapted to height restrictions. The manufacturer also points out that the modules can be separated to make it easier to move them through basements, attics, or other hard-to-access spaces.

In Westmount, this flexibility makes it possible to work with the existing architecture rather than having to rebuild the entire mechanical room around the new unit.

The detail that changes everything: a 20 × 20 filter return-air grille

The large galvanized cabinet located immediately to the left of the furnace deserves particular attention.

The lower section was fitted with a designated space “20 × 20 FILTER”. In a central system, the filter does more than just trap dust. It becomes a resistance in the airflow path and directly affects:

• airflow through the coil;
• system static pressure;
• sound level;
• blower motor operation;
• air distribution in the rooms;
• the actual heating and cooling capacity.

Choosing excellent equipment while neglecting its return air is one of the mistakes we systematically strive to avoid at AirGreen.

Why filter surface area matters so much

A filter that is too small for the requested airflow can create a significant pressure drop. When the filter then begins to load with dust, this restriction increases further.

In an inverter system such as the EVOX G3, the blower motor can compensate for part of this variation, but that does not mean a poorly designed duct system suddenly becomes acceptable.

MIDEA also describes its technology for the EVOX G3 as Computational Constant Airflow 2.0, designed to automatically adjust the fan power as system resistance changes. The documentation indicates management of up to 1.2 in. of water column of external static pressure under the specified conditions, along with airflow adjustment that can reach up to 60 levels.

This capability is particularly relevant in an existing home in Westmount, where we often have to preserve a large part of the existing ductwork.

But our philosophy remains the same: we prefer to correct restrictions rather than ask the motor to fight them constantly.

Transitions manufactured to guide the air, not simply to fill a space

The project shows several new sheet metal sections.

This work may seem secondary when comparing two quotes for an electric furnace or central heat pump in Montreal, but it has a considerable influence on the outcome.

When a new furnace does not have exactly the same dimensions as the old one, transitions must be created.

A good transition should allow the airflow to change dimensions or direction gradually. A reduction that is too abrupt can increase turbulence and cause:

• more noise;
• pressure losses;
• uneven air distribution;
• excessive velocities in certain sections;
• reduced comfort at the ends of the system.

On this Westmount installation, the sheet metal was built around the building’s reality: a left-side return, a vertical unit on the right, existing upper ducts, and limited mechanical space.

It is a true integration project.

Why the EVOX G3 is well suited for furnace replacements

MIDEA's documentation places strong emphasis on renovation projects.

Depending on the capacity, EVOX G3 units use cabinets with widths ranging from approximately 14.5 to 21.5 inches, meaning dimensions designed to fit several common sizes of existing furnaces. The manufacturer also provides an adaptable indoor power supply for 115 V or 208/230 V for the configurations listed.

This characteristic is particularly valuable when every inch counts.

In Westmount, a much wider cabinet could have required:

• significant duct relocation;
• modification of the adjacent structure;
• reduced service access;
• more finishing work;
• a more extensive return-air reconstruction.

A proper HVAC renovation therefore seeks to combine mechanical performance and physical compatibility with the existing building.

MIDEA electric furnace or air handler: a useful distinction

In Quebec residential terminology, we commonly use the expression electric furnace to refer to the indoor equipment of a forced-air central system.

Technically, the EVOX G3 is an air handler designed to work with an inverter central heat pump. It can also accommodate an auxiliary electric heating kit.

MIDEA offers multi-stage auxiliary heating options rated up to 25 kW depending on the configuration. The manufacturer indicates that these stages can be adjusted to temperature variations to achieve more precise control of heating and electricity consumption.

This does not mean that a 25 kW electric element is suitable for every home.

At AirGreen, we must consider:

• the available electrical capacity;
• the home's heating load;
• the heat pump capacity as the temperature drops;
• the system airflow;
• the staging sequence;
• the thermostat settings.

An oversized auxiliary heating element can unnecessarily increase electrical demand if it is not properly controlled.

A range from 18,000 to 54,000 BTU/h

The EVOX G3 documentation presents several capacity combinations.

On page 11 of the technical data sheet provided, MIDEA specifically lists systems corresponding to approximately 18,000, 24,000, 30,000, 36,000, 48,000, and 54,000 BTU/h, depending on the selected indoor and outdoor unit. The same table shows, depending on the combinations, efficiencies for systems rated up to 19 SEER2, 12.5 EER2 and 10.8 HSPF2.

However, the rating plate visible in the photo from the job site is not sufficiently legible to identify the exact capacity of this Westmount installation with certainty.

We therefore prefer not to state a tonnage based solely on the physical size of the equipment.

To properly identify a central system, you must use:

1. the indoor model number;
2. the outdoor model number;
3. the AHRI combination;
4. the nominal capacity;
5. above all, the heating capacity available at low temperatures.

Heating down to -30 °C: an important factor for Montréal

For an installation in Québec, cold-weather performance matters more than a simple SEER2 figure.

MIDEA indicates for its EVOX G3 Extreme Heat platform a continuous heating operation down to -30 °C. In the tests cited by the manufacturer for a three-ton MIDEA system, the documentation also reports capacity reaching 100% at around -25 °C, with a COP reaching approximately 1.9 under the stated test conditions.

However, these data must be interpreted correctly.

The exact performance varies according to the indoor/outdoor combination. A two-and-a-half-ton system does not necessarily have the same capacity curve as a four-ton model.

For a home in Westmount, Montréal, Laval, Longueuil, on the North Shore or the South Shore, so we look at the certified capacity of the selected system at different temperatures rather than settling for a statement such as “operates at -30 °C.”

The EVOX G3 uses the new R-454B refrigerant

The EVOX G3 central system lineup uses R-454B, an A2L-category refrigerant.

MIDEA assigns it a global warming potential, or GWP, of 466.

For the homeowner, the heat pump’s day-to-day operation remains familiar. On the installation side, however, switching to A2L refrigerants requires using the appropriate methods and equipment.

Our technicians must take into account, among other things:

• refrigerant handling procedures;
• leak detection;
• evacuation;
• connection practices;
• specific requirements for A2L equipment.

This technological change makes choosing a contractor who regularly works with the new generation of systems even more important HVAC with R-454B.

From airflow checks at LogisVert: what we verify before handing an EVOX G3 over to the owner

An inverter system requires precise fan adjustment

Commissioning a central furnace does not simply involve pressing the thermostat and checking whether warm air comes out of the vents.

We must confirm that the airflow matches the equipment’s capacity and operating mode.

MIDEA’s constant-airflow technology can respond to pressure variations caused, among other things, by the ductwork or filtration. The manufacturer explains that the control adjusts the fan power and speed to maintain the desired airflow.

At the Westmount job site, the presence of a new return-air cabinet and a 20 × 20 filter makes this check particularly relevant.

Our commissioning checks

Before considering a MIDEA EVOX G3 electric furnace installation as complete, several checks may be necessary depending on the configuration:

• system static pressure;
• airflow;
• supply air temperature;
• heat pump operation;
• auxiliary electric heating sequence;
• thermostat settings;
• condensate drainage;
• refrigerant connections;
• ECM motor operation;
• filter condition and ease of access;
• noise and vibrations;
• return-air and register behavior.

An installation can be perfectly straight and visually very clean while still being improperly adjusted. The true result is measured when the equipment is operating.

Several thermostat and communication options

MIDEA has also provided different control architectures.

The documentation indicates that the EVOX G3 can operate using communication 485 or in certain configurations with a traditional thermostat 24 V. MIDEA also describes Sub-1 GHz wireless communication between certain EVOX devices, which can simplify renovations when it is difficult to add new conductors inside the walls.

This flexibility is useful in existing buildings, but the configuration must be set up correctly.

The thermostat influences, among other things:

• when auxiliary heating comes on;
• system modulation;
• the available stages;
• the changes between heating and cooling;
• certain comfort settings.

Filtration: MERV 13 is possible, but not under every condition

The EVOX G3 documentation also indicates compatibility with 1, 2, or 4 inches, including 1-, 2-, or 4-inch filters MERV 13 in suitable configurations. MIDEA points out that better filtration can capture more dust, pollen, particles, and pet hair.

However, the MERV rating should never be selected in isolation.

The more restrictive a filter is, the more it can affect airflow. That is why the 20 × 20 cabinet visible in our Westmount installation must be considered together with the desired airflow and available static pressure.

LogisVert: eligibility depends on the complete heat pump, not the furnace alone

The question of rebates comes up regularly during a central heat pump installation in Montréal.

In 2026, Hydro-Québec indicates that the Heat Pump measure of the program LogisVert offers, when all conditions are met, $50 per 1,000 BTU/h at -8°C for an ENERGY STAR-certified heat pump and $120 per 1,000 BTU/h at -8°C when it is ENERGY STAR certified for cold climates. The amount depends on the eligible capacity at -8°C and the installation date.

One point is particularly important for a system like the EVOX G3: replacing only one indoor unit, one outdoor unit, or one coil is not eligible for this measure. Hydro-Québec therefore evaluates the heat pump as a complete system.

We therefore need to verify:

1. the exact furnace or air handler model;
2. the exact outdoor unit model;
3. the ENERGY STAR combination;
4. the AHRI number;
5. the rated capacity at -8°C;
6. the LogisVert conditions applicable on the installation date.

The MIDEA brochure confirms that the EVOX G3 line includes several combinations and capacities, but it is not sufficient on its own to confirm the Quebec financial assistance for a specific installation.

Errors this project helps avoid

An installation like the one in Westmount highlights several common errors made when replacing a central system.

Automatically copying the old equipment’s tonnage

An old furnace or air conditioner may have been oversized. We prefer to verify the residence’s current needs.

Neglecting the air return

A new system cannot move its airflow properly if the return remains too restrictive.

Installing the filter as a secondary accessory

The filter is part of the airflow design. Its surface area and restriction are important.

Building transitions that are too abrupt

A poorly designed transition can unnecessarily add turbulence and noise.

Choosing the maximum available electric heating capacity

The auxiliary capacity must match the building and the available electrical capacity.

Failing to plan for future maintenance

In the photo, the service panels are accessible from the front despite the very tight space. This accessibility must be planned before the mechanical room is closed.

Confusing an eligible brand with an eligible combination

A product line may include several models. For LogisVert, the exact combination number remains crucial.

What this Westmount installation really demonstrates

The technical result of this project relies on much more than the presence of a new MIDEA EVOX G3.

We had to integrate the following into a single space:

• a vertical central unit;
• an existing duct network;
• new custom-fitted sheet metal;
• an air return sized around a 20 × 20 filter;
• the refrigerant connections;
• the electrical supply;
• the controls;
• the access required for future servicing.

That is precisely how we approach an HVAC installation in Westmount.

At AirGreen, we do not merely want a furnace to fit into the available space. We want the air to circulate properly, the equipment to modulate as intended, the filter to be accessible, the heat pump to heat efficiently during cold periods, and the next technician to be able to access the components without having to dismantle half the mechanical room.

This same level of rigor applies to our electric furnaces, central heat pumps, and HVAC systems everywhere for Montreal, Laval, Longueuil, on the North Shore and the South Shore.

In the case of this MIDEA EVOX G3 in Westmount, the most revealing detail may be the one that seems the least spectacular: this custom-fabricated cabinet, marked “20 × 20 FILTER”. It points out that a high-performance central system always begins with a fundamental mechanical question: how to move the right amount of air, to the right place, with as little resistance as possible.