Installation of a MIDEA EVOX G3 electric furnace in Saint-Léonard, Montreal: integration with existing ductwork and refrigerant connection

In Saint-Léonard, this installation shows what really happens between the delivery of a furnace and its commissioning

A new central electric furnace never arrives at a home simply to take the place of the old one. Between the dimensions of the ductwork, the unit’s orientation, the refrigerant connections, drainage, electrical supply, and the access required for maintenance, each installation becomes a project adapted to the building.

This installation carried out by AirGreen in Saint-Léonard, Montreal, is an excellent example. The photo was taken during the work, while our technicians were still in the process of connecting the new MIDEA EVOX G3. It shows details that are usually hidden once the project is complete: the indoor unit’s modules, the existing metal plenum, the copper refrigerant connections, the pipe insulation, and the relatively limited workspace around the appliance.

We have here a MIDEA EVOX G3 electric furnace, which is part of Midea’s Inverter ducted central systems platform. The manufacturer specifically presents the EVOX G3 series as a solution designed to facilitate the modernization of existing residential heating systems.

The Saint-Léonard project helps explain why this design is relevant in Greater Montreal: in an existing home, we rarely work with a completely empty mechanical space. Instead, we must integrate recent technology with what is already there.

A job-site photo revealing much more than a new furnace

Several components are visible in this installation.

The new Midea unit is placed directly beneath an existing metal plenum. The upper transition was adjusted and then sealed to integrate the new appliance into the air distribution system. On the side of the appliance, we can see the refrigerant connections linking the indoor unit to the heat pump located outside.

The pipes are insulated and protected during the work. Their routing must be organized without creating kinks, overly tight bends, or mechanical stress on the connections.

The characteristic black fasteners between the different cabinet sections are also visible. This detail is not merely aesthetic: it is part of one of the most interesting design features of theEVOX G3.

Finally, the environment around the unit confirms that we are in a true residential basement in Montreal: existing ducts, neighboring mechanical equipment, construction tools, an already-built structure, and limited clearance. The installation must therefore be adapted to the home, not the other way around.

The “Block N Lock” modular design changes how the unit is installed

Midea documentation describes the EVOX G3 as a modular design with a locking system, intended in particular to facilitate transporting and reconfiguring the unit.

The manufacturer provides up to six installation configurations :

• upward vertical supply;
• downflow configuration;
• right horizontal;
• left horizontal;
• compact “low-boy” configuration;
• other orientations suited to the return and supply air depending on the configuration.

The modules can be separated and reassembled, which particularly facilitates moving them through stairways, basements, or difficult-to-access spaces. Midea specifically promotes this modularity for basement installations and locations where handling a conventional indoor unit can be complicated.

In the photo of our installation in Saint-Léonard, the large mechanical fasteners between the equipment sections make this architecture particularly visible.

For our technicians, this feature means that a project that might have required much more dismantling around the mechanical room can sometimes be completed more efficiently.

Electric furnace or air handler: why both terms may apply

We are referring here to electric furnace, since the unit can accommodate the electrical elements that provide the home's auxiliary heat. Technically, however, the EVOX G3 is also anair handler of the central heat pump system.

It therefore performs several functions at once.

When the heat pump heats the home, the indoor unit recovers the energy transferred by the refrigerant circuit, and the fan distributes that heat through the ducts.

In cooling mode, the same indoor assembly cools and dehumidifies the air.

When the system calls for auxiliary heat, the furnace’s electrical elements can take over or supplement the heat pump, depending on the selected sizing and programming.

For the EVOX G3 platform, Midea offers auxiliary assemblies capable of reaching 25 kW, with controls that can operate in multiple stages to better match the electrical power to the heating demand.

The power of the electrical element actually selected for a home must nevertheless be determined based on the heating load and the electrical installation. Never simply choose the maximum number of available kilowatts.

An important detail: we do not invent the BTU capacity based on a photo

The MIDEA EVOX G3 series is available in several capacities. The technical documentation presents systems ranging from 18,000 to 54,000 BTU/h depending on the selected combination.

In this particular photo, the unit’s full model number is not legible enough to confirm with certainty whether the installed equipment is a 24,000, 30,000, 36,000, 48,000, or 54,000 BTU/h configuration.

We therefore prefer not to assign a fictitious capacity to the project.

This distinction is important because central heat pump sizing should never be determined simply by looking at the furnace’s physical size or the capacity of the old equipment.

In an AirGreen project, we consider, among other factors:

• the heated area;
• heat losses;
• the insulation;
• the windows;
• the number of stages;
• the duct configuration;
• the available airflow;
• the heating capacity required in very cold weather.

A properly sized central system generally provides more stable operation and better temperature control than a unit selected solely according to the “bigger is better” rule.

Performance of up to 19 SEER2 depending on the combination

The EVOX G3 range includes several configurations. In its technical table, Midea indicates efficiencies of up to 19 SEER2, 12.5 EER2 and 10.8 HSPF2, with a COP of up to 2.14 at 5°F, or approximately -15°C, depending on the equipment pairing.

For example, the documentation notably presents the following configurations:

• 18,000 BTU: up to 19 SEER2;
• 24,000 BTU: up to 18.6 SEER2;
• 30,000 BTU: up to 17.2 SEER2;
• 36,000 BTU: up to 17.7 SEER2;
• 48,000 BTU: up to 17.5 SEER2;
• 54,000 BTU: up to 17.5 SEER2.

These data must be used correctly. They correspond to specific combinations of indoor and outdoor units and do not constitute a universal rating that automatically applies to every EVOX G3.

To confirm an installation’s efficiency, we always check both model numbers and the certification for the complete combination.

The refrigerant connection visible in the photo requires genuine field precision.

The most interesting part of this photo is probably the routing of the refrigerant lines in front of and alongside the unit.

The large line is covered with insulation to limit heat transfer and condensation. The lines are kept together and protected as they are routed toward the indoor coil connections.

A refrigeration circuit must not be installed like a simple flexible cable.

We must maintain an appropriate bend radius and avoid:

• of crushing the copper;
• of creating a restriction;
• of putting strain on the coil connections;
• of damaging the insulation;
• of allowing the pipes to rub against a metal edge;
• of obstructing the panels that will need to be removed for future HVAC maintenance.

The photo was taken during installation, so some components and tools are still visible around the unit. This is precisely the stage at which we can adjust the routing before completing the finishing work.

Why proper brazing and proper pipe preparation are essential

In a system operating with R454B, the quality of the refrigeration circuit is fundamental.

The connections must be prepared properly, and the system must then undergo the appropriate technical steps before being commissioned. A professional installation is not simply a matter of connecting two pipes and opening the outdoor unit’s valves.

In particular, we must ensure the circuit is clean and leak-free, and that the vacuum performed before releasing the refrigerant meets the equipment’s applicable procedures.

Internal contamination, moisture, or a tiny leak can eventually affect compressor operation and system reliability.

R454B A2L: a new reality for central systems

Midea says it selected R454B refrigerant for this generation of products. The manufacturer indicates a global warming potential, or GWP, of 466, and identifies this refrigerant as being in the A2L category.

This transition is important for the HVAC industry HVAC in Montreal.

R454B has different characteristics from the older refrigerants commonly found in residential systems. The A2L classification refers specifically to a mildly flammable refrigerant, which requires appropriate procedures, equipment, and precautions during installation or service work.

For the homeowner, this mainly means that a new R454B heat pump must be serviced by technicians who understand the requirements applicable to this new generation of equipment.

The existing plenum had to work with the new furnace, not simply connect to it.

The top of the MIDEA EVOX G3 shown in the photograph is connected to an existing galvanized sheet metal duct system.

For us, a metal transition is not only intended to close the gap between two different dimensions. It directly contributes to airflow.

A poorly designed transition can create:

• turbulence;
• noise;
• an increase in static pressure;
• uneven airflow;
• vibrations;
• an unnecessary restriction.

We therefore aim to obtain a properly sized and sufficiently airtight transition.

On this installation in Saint-Léonard, we also notice the sealing work around the upper junction. Air leaks around the plenum represent energy lost in the mechanical room rather than distributed throughout the rooms of the house.

A constant-airflow technology that is particularly useful in an existing duct system

One of the most interesting technologies in the MIDEA EVOX G3 is Computational Constant Airflow 2.0.

Midea indicates that the fan can automatically adjust its output and speed to the conditions of the duct system. The documentation describes operation reaching approximately 1.2 in. of external static pressure and up to 60 airflow settings.

This technology is particularly relevant in Saint-Léonard, where many homes already have central ductwork installed several decades ago.

However, it does not replace our verification work.

If the return air opening is much too small, if a duct is blocked, or if a transition is extremely restrictive, we must correct the cause of the problem. Asking the fan motor to constantly compensate for a poor duct system is not a professional solution.

What we check before considering an EVOX G3 installation truly complete

Low-temperature heating: the heat pump must remain the primary efficient source

The Extreme Heat versions of the EVOX G3 platform are designed for cold climates. Midea indicates continuous operation down to -30 °C in the configurations concerned and describes a compressor technology designed to maintain heating capacity as the outdoor temperature drops.

For a home located in Saint-Léonard, this capacity is particularly valuable.

The electric furnace therefore does not necessarily need to operate at full capacity every time it is cold. Proper programming allows the heat pump to efficiently provide much of the heating and call on the auxiliary elements when conditions require it.

This strategy can considerably reduce the amount of heating produced solely by electric resistance.

A 10, 15, or 25 kW element completely changes the electrical load

The choice of auxiliary heating directly influences the electrical installation.

A heating element 25 kW represents a very different demand from a 10 kW element. We therefore check the panel capacity, conductors, and electrical protection devices before determining what can be installed.

One of the most costly mistakes would be to order a configuration based solely on heating needs without verifying whether the existing electrical service can properly support it.

In some projects, an electrical upgrade may be necessary. In others, a different auxiliary-heating capacity is the more logical solution.

MERV 13 filtration: worthwhile, but it must be factored into the static-pressure calculation

The EVOX G3 platform can be configured with filters measuring 1, 2, or 4 inches, and Midea mentions compatibility with MERV 13.

An MERV 13 filter can capture fine dust, pollen, and certain particles more effectively than a low-efficiency filter.

However, we must maintain sufficient airflow.

That is why we look at the filter, return air, and static pressure simultaneously. Adding a more restrictive filter without checking these parameters can reduce the airflow of an otherwise high-performing installation.

24 V control, 485 communication, and smart integration capability

The MIDEA EVOX G3 also offers several control options.

The manufacturer indicates that the system can operate with 485 communication or with different thermostat configurations 24 V, depending on the installed components. Some configurations also provide wireless communication between the indoor unit, heat pump, and controls.

With the compatible communicating thermostat, the platform can also provide functions related to scheduling, comfort monitoring, electricity consumption, and diagnostics through the SmartHome app.

For a renovation, this flexibility allows us to select a control method suited to the wiring actually present in the home.

LogisVert in 2026: the EVOX G3 must be verified as a complete system

For homeowners in Montreal, Laval, Longueuil, the North Shore, and the South Shore, Hydro-Québec financial assistance often represents an important factor in choosing a heat pump.

In 2026, Hydro-Québec specifies that heat pumps installed since must be ENERGY STAR certified as of November 26, 2025 to qualify for the LogisVert heat pump measure. When all conditions are met, the financial assistance is currently $50 per 1,000 BTU/h at -8 °C for an ENERGY STAR heat pump or $120 per 1,000 BTU/h at -8 °C when it is recognized as a cold-climate heat pump.

The essential point is that MIDEA EVOX G3 alone is not proof of eligibility.

Hydro-Québec requires the complete system to meet the applicable conditions. We must therefore know the exact number of the outdoor unit and that of the indoor unit, then verify the combination in the list in effect on the installation date. Hydro-Québec also specifies that eligible models and amounts may change over time.

That is why we never promise a rebate based solely on the Midea logo or the advertised BTU capacity.

Practical mistakes we aim to avoid in a central installation

This Saint-Léonard project summarizes several best practices we apply when replacing a electric furnace and central heat pump :

1. Measure the system and available space before selecting the unit.
2. Size the heat pump according to the building's needs, not solely based on the old equipment.
3. Verify the electrical capacity before choosing auxiliary components.
4. Protect refrigerant lines and respect their bend radii.
5. Build duct transitions that limit restrictions and leaks.
6. Measure and adjust the airflow after installation.
7. Keep access to the panels and components available for future maintenance.
8. Verify the ENERGY STAR combination and LogisVert eligibility rather than assuming that an entire product line qualifies for the same amount.

A successful installation is also evident in what disappears after the work is done

When the work is complete, the homeowner can no longer see most of the work shown in this photo.

The tools disappear. The lines are finalized. The connections are complete. The system is commissioned and the panels are closed.

What remains is an MIDEA EVOX G3 electric furnace integrated into the home's central system.

For us, however, the quality of the result depends precisely on all the steps that become invisible: sizing, sheet-metal transition, sealing, refrigerant lines, airflow, drainage, electrical adjustments, and commissioning.

This installation in Saint-Léonard This illustrates our approach at AirGreen. We do not view a furnace as an isolated appliance. We look at the entire HVAC system and how it needs to operate in the actual building where it is installed.

It is this attention to the complete project that allows us to carry out central heat pumps and electric furnaces in Montreal, but also Laval, Longueuil, on the North Shore and the South Shore, with a consistent priority: to create a system suited to the home, accessible for maintenance, and properly adjusted for Quebec winters.