Installation of a MIDEA EVOX G3 electric furnace in a narrow mechanical room in Ange-Gardien, Montérégie

In Ange-Gardien, a few inches of clearance determined our entire installation strategy

This MIDEA EVOX G3 electric furnace installation in Ange-Gardien, in Montérégie, perfectly represents a challenge that technical specifications rarely show: how to integrate a modern central system into a mechanical space where the available width is barely greater than that of the equipment.

The photograph taken at our worksite is particularly telling. The new indoor unit, the MIDEA EVOX G3, is positioned between two closely spaced partitions, installed vertically on a lower galvanized-steel cabinet, and connected at the top to an existing ductwork system by means of a custom metal transition. On the left, copper piping runs along the wall; at the back of the room, several existing cables and pieces of equipment further occupy the available space.

In this configuration, the challenge was not simply to determine whether the EVOX G3 could physically fit in the room. Above all, we had to ensure that once installed, it could breathe properly, be connected without unnecessary restrictions, and remain accessible for future maintenance.

This is exactly the kind of situation where a few inches can make the difference between an installation that is merely possible and a truly well-designed HVAC installation.

A narrow mechanical room where nothing could be positioned at random

When a furnace is installed in the center of a large basement, we generally have some flexibility to position the lines, filter, drainage, and service access points.

At Ange-Gardien, this flexibility was much more limited.

The photograph shows that the cabinet occupies practically the entire width of its space. We therefore had to plan carefully:

• the furnace’s exact position;
• its connection to the lower plenum;
• the transition to the upper duct;
• the routing of the various lines;
• access to the panels;
• the clearance required for service work.

It is never enough to say, “the unit fits.”

We need to ask ourselves what will happen in five, ten, or fifteen years when a technician needs to access the fan, an electronic board, the coil, or the auxiliary heater.

The vertical configuration made it possible to use the entire available height

For this project, we worked with a vertical configuration.

Since the main ductwork was above the unit, this orientation allowed for logical integration with the existing duct system without unnecessarily adding several changes in direction.

The EVOX G3 is specifically designed for different installation configurations. Midea provides upflow and downflow orientations, right- and left-horizontal arrangements, as well as low-height configurations for particular applications. The design is also intended to facilitate use of the unit in challenging spaces.

This flexibility is particularly valuable in renovation, because an existing home does not change to fit the equipment. The installation must intelligently adapt to the building.

The lower plenum: an essential return-air component

Under the MIDEA cabinet, a metal plenum fabricated to provide the transition to the lower ductwork is clearly visible.

This type of component deserves much more attention than it generally receives.

The furnace fan must be able to draw in enough air before redistributing it throughout the system. If the return-air opening is too small or if a transition creates excessive restriction, the new unit may be limited by its surroundings.

Poor return airflow can notably lead to:

• more noise;
• an increase in static pressure;
• insufficient airflow;
• poor heat exchange;
• increased fan consumption;
• less even distribution throughout the house.

On an installation such as the one in Ange-Gardien, where physical space is already very limited, it is especially important to not sacrifice air cross-section simply to gain a few inches.

The upper transition had to connect a new unit to an existing geometry

The upper part of the photograph shows another element that is highly representative of replacement work: the outlet of the new furnace does not exactly match the shape of the existing duct.

We therefore need to fabricate a transition.

This transition is sealed to limit air loss, but its geometry is also important. We seek to avoid unnecessarily aggressive changes in cross-section and internal obstacles that would increase resistance to airflow.

When replacing an electric furnace in Ange-Gardien, Longueuil, Montréal, Laval, on the South Shore or the North Shore, this sheet-metal work is often a decisive part of the final result.

The new machine may have excellent rated efficiency; if the transitions were poorly designed, the owner will never fully benefit from its capabilities.

Why the dimensions of the EVOX G3 facilitate certain replacements

Midea paid particular attention to the dimensions of the EVOX G3 cabinet.

According to the manufacturer's documentation, the indoor units in the range use approximate widths from 14.5 to 21.5 inches, depending on their capacity. Midea presents this design as a way to facilitate the replacement of certain existing furnaces. The platform also provides for adaptation to different power supplies depending on the application.

In a space as narrow as the one photographed in Ange-Gardien, this feature immediately becomes relevant.

A difference of a few inches in cabinet width can determine:

• if the panels remain accessible;
• if the ducts can be routed properly;
• if a reasonable transition can be fabricated;
• if the new unit can be positioned without rebuilding the entire room.

A modular construction that helps when access is difficult

The EVOX G3 also uses a modular design called Block N Lock.

Midea explains that the unit can be separated or reconfigured more easily to facilitate handling, particularly in areas such as basements and attics.

In a renovation project, this feature is much more important than it may appear in a brochure.

We sometimes have to transport a unit through:

• a narrow staircase;
• a small door;
• a corridor;
• a low ceiling;
• a mechanical room already filled with other equipment.

A system designed with these realities in mind offers more possibilities during installation.

Airflow, heating, R454B, and efficiency: what we need to check after successfully fitting the EVOX G3 into the space

The physical space is only half the job

Once the furnace is positioned, we still need to make sure it operates properly with the building.

This is where the checks concerning the following begin:

• airflow;
• static pressure;
• fan settings;
• auxiliary electric heating;
• communication with the thermostat;
• the outdoor heat pump;
• the filtration;
• the condensate.

In other words, successfully installing the cabinet between two walls is never the final objective.

Computational Constant Airflow 2.0: particularly interesting in a renovation

One of the most relevant EVOX G3 technologies for existing homes is Computational Constant Airflow 2.0.

Midea states that the system can adjust the output and fan speed when ductwork resistance changes. In the applications illustrated by the manufacturer, the platform can operate with a total static pressure of up to 1.2 in. of water column.

The manufacturer also provides up to 60 airflow adjustment levels, allowing operation to be fine-tuned according to the actual ductwork.

In a replacement such as the one in Ange-Gardien, this capability is particularly relevant because we are not necessarily starting with new ducts designed specifically for the new equipment.

Constant-airflow technology does not, however, correct poor ductwork.

This point must be made very clear.

Even a sophisticated fan cannot eliminate the consequences of a severely undersized duct, an overly restrictive filter, or a poorly fabricated transition.

The motor can increase its effort to maintain airflow up to certain limits, but this does not mean that every restriction becomes acceptable.

That is why our approach at AirGreen is first to make the ductwork as coherent as possible, then take advantage of the equipment's adjustment capabilities.

The M-Coil and the symmetrical fan

Midea documentation also describes an internal architecture combining an M-Coil with a symmetrical fan.

The stated objective is to achieve a more even distribution of air across the coil's surface and limit airflow differences between different sections of the heat exchanger.

This technical detail is important because a heat exchanger is truly effective only when air flows properly across its surface.

In a central system, efficiency therefore depends as much on the equipment as on how air enters and leaves it.

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

The expression MIDEA EVOX G3 refers to a complete family of systems, not a single capacity.

Midea documentation covers configurations ranging from 18,000 to 54,000 BTU/h, with efficiencies reaching up to 19 SEER2, 12.5 EER2, 10.8 HSPF2, and a maximum stated COP of 2.14 under the indicated test condition, depending on the selected combination.

The manufacturer's technical table includes configurations of 18,000, 24,000, 30,000, 36,000, 48,000, and 54,000 BTU/h.

The photograph of our Ange-Gardien installation does not allow us to reliably read the full model number. We therefore do not arbitrarily assign it a specific capacity.

Why we do not automatically copy the tonnage of the old furnace

Replacing an old three-ton unit with a new three-ton unit may seem logical.

Yet this is not always the right approach.

The old unit could have been:

• oversized;
• undersized;
• installed with a system unable to carry its airflow;
• selected at a time when the home's insulation was different.

We consider the heat load, building envelope, windows, ducts, air returns, and actual heating and cooling needs.

A platform designed for heating in cold climates

When paired with the corresponding EVOX outdoor heat pump, Midea presents the platform as capable of heating operation down to -30 °C. The manufacturer also provides low-temperature results for a three-ton system used during its testing.

This capacity is particularly important in Quebec.

Summer performance is not enough to assess a heat pump intended for a home in Ange-Gardien or Montérégie. Its performance must also be examined when temperatures drop to -15 °C, -20 °C, and below.

Auxiliary heating: up to 25 kW, but not necessarily 25 kW for this house

The EVOX G3 platform can accommodate a multistage auxiliary heating kit.

Midea lists options of 10 kW, 15 kW, and up to 25 kW, with a strategy for adjusting heating use according to conditions.

This maximum value is never a universal recommendation.

Auxiliary heating must be determined according to:

• the heat pump's capacity;
• the property's heat loss;
• the capacity of the electrical panel;
• wiring;
• electrical protection;
• the control strategy.

Adding electrical capacity unnecessarily can increase peak demand without providing any real benefit to the homeowner.

The ducts visible on the left side must also comply with the service clearance

In the photograph, various sections of copper piping run along the left wall.

In such a narrow room, the routing of the ducts must be planned before considering the installation complete.

We seek to prevent a duct from being positioned in a way that would later prevent:

• the removal of a panel;
• the replacement of a component;
• access to a connection;
• the relocation of a filter.

A piping route can look very clean and still cause problems if it blocks the only path that allows access for servicing the unit.

Filtration must also be designed with airflow in mind

The EVOX G3 documentation provides for modules that can accommodate 1-, 2-, or 4-inch filters, including MERV 13 options depending on the configuration. Midea indicates that this filtration can capture more dust, pollen, particles, and pet hair.

However, filtration must always be coordinated with airflow.

A very small or heavily loaded high-efficiency filter can impose significant resistance.

We therefore prefer to consider these together:

filter surface area + MERV rating + required airflow + static pressure.

Conventional thermostat or Midea communication

The EVOX G3 platform offers several control options.

The documentation specifically provides for Midea 485 communication and certain configurations compatible with a conventional 24 V thermostat.

With the appropriate communicating components, Midea also provides for schedule programming, monitoring of certain comfort and consumption parameters, and diagnostic functions through the SmartHome app.

This flexibility can be particularly useful in a renovation when the thermostat wiring is already concealed in the walls.

R454B and A2L classification

The EVOX generation presented in the documentation uses R454B.

Midea states that this refrigerant has a global warming potential, or GWP of 466, and specifies that it was chosen for its new product line.

R454B is an A2L-classified refrigerant. Its installation and servicing must therefore follow procedures adapted to this new generation of equipment.

This is an important difference compared with several older R410A systems still found in Quebec homes.

LogisVert: the complete combination must be verified, not just the indoor furnace

For heat pumps installed since November 26, 2025, Hydro-Québec currently requires ENERGY STAR certification for the LogisVert Heat Pump measure. When all conditions are met, the grant is $50 per 1,000 BTU/h at -8°C for an ENERGY STAR heat pump and $120 per 1,000 BTU/h at -8°C when it is certified ENERGY STAR – Cold Climate.

However, it is essential not to consider the EVOX G3 indoor furnace alone as proof of eligibility.

Eligibility depends in particular on the complete heat pump combination, the outdoor model, the indoor model, certification, and compliance with the program’s other conditions. Hydro-Québec also specifies that replacing only one indoor or outdoor unit is not eligible for this measure.

For this Ange-Gardien project, the photograph does not allow us to identify the exact outdoor combination; we are therefore not presenting any specific amount for this installation.

The particularly costly mistakes in such a narrow mechanical room

Choosing the unit before measuring the actual access

Cabinet dimensions are not enough. The clearances required for servicing must also be considered.

Positioning the furnace against a wall without considering the panels

A few inches gained during installation can make a future service call extremely difficult.

Building a transition that is too restrictive to gain height

The air-distribution network’s section must remain compatible with the desired airflow.

Neglecting the return air

A central system cannot blow air properly if it cannot draw in enough air.

Running the pipes in front of the only service access

The shortest route is not always the best.

Assuming that 19 SEER2 applies to all EVOX G3 units

Performance varies depending on the combination and capacity. The Midea table clearly shows different values from one model to another.

This Ange-Gardien project illustrates exactly why we inspect the space before choosing the final configuration

This installation appears relatively simple once the machine is in place: a vertical unit, a lower plenum, and an upper duct.

The photograph nevertheless shows just how limited the room for maneuver was.

The MIDEA EVOX G3 had to be integrated between two walls, connected to an existing ductwork layout, and positioned so as not to block access to components that will need servicing later.

This is the reality we regularly encounter during our electric furnace and central heat pump installations in Ange-Gardien, Montérégie, Longueuil, the South Shore, Montreal, Laval, and the North Shore.

At AirGreen, we do not consider an installation successful simply because the new unit occupies the former unit’s location.

We want the system to move the right airflow, operate with the planned heat pump and auxiliary heating, remain accessible, and fit cleanly within the building’s actual constraints.

In this Ange-Gardien installation, the challenge was not finding an empty spot for a new furnace. It was using a space intelligently when there was almost no room to spare.