Installation of a MIDEA EVOX G3 electric furnace in Saint-Nazaire-d’Acton with complete adaptation of the existing ductwork

In Saint-Nazaire-d’Acton, an EVOX G3 integrated into an existing basement where the sheet metal had to be fabricated around the house

This MIDEA EVOX G3 electric furnace installation in Saint-Nazaire-d’Acton perfectly illustrates the adaptation work involved in replacing an old central system. The new unit was not installed in a new mechanical room with ducts designed specifically for it. We were working in an existing basement, between a concrete foundation wall, the home’s wooden structure, a laundry area, and an existing duct network.

The project photograph immediately shows what makes this installation interesting. The MIDEA EVOX G3 is positioned vertically on a metal base fabricated to integrate it into the network. Above the unit, we created a substantial sheet-metal transition that gradually reduces the cross-section before connecting to the existing main duct. The joints are carefully sealed with aluminum tape to limit air leakage.

To the right of the unit, the copper refrigerant lines rise vertically toward their route through the building. A washing machine is installed nearby, confirming that we had to preserve the room’s functional space while maintaining reasonable clearance around the HVAC system.

This type of project summarizes our approach at AirGreen well: we do not simply replace a machine; we integrate a new generation of equipment into the existing building.

A vertical installation chosen to use the available space efficiently

The MIDEA EVOX G3 photographed in Saint-Nazaire-d’Acton is installed in a vertical position. In this basement, this orientation keeps the floor footprint relatively compact and naturally connects to the distribution duct located above.

This flexibility is part of the EVOX G3’s design itself. Midea’s documentation presents six installation possibilities, including upflow, downflow, left horizontal, right horizontal, and low-profile configurations intended for limited spaces. The modular design is particularly suited to renovations and locations where handling a single-piece unit would be difficult.

In our case, the vertical position was the most logical. The important point, however, is not to systematically favor this orientation: we choose the configuration that allows the airflow, ductwork, and service access to function properly together.

The visible metal transition above the unit is an essential part of the installation

One of the most interesting elements in this photo is not a Midea component. It is the sheet-metal piece fabricated between the new furnace and the existing duct.

The top of the EVOX G3 has a geometry that does not directly match the cross-section of the existing vertical duct. A transition therefore had to be created.

A good transition should allow the air to change cross-section gradually. If it is unnecessarily abrupt or restrictive, it can contribute to:

• increase static pressure;
• create turbulence;
• generate more noise;
• reduce the airflow available at the registers;
• force the fan to work harder.

In the photograph, we see a transition with sloped sides and sealed joints. This part of the installation never appears on a heat pump’s SEER2 rating sheet, but it directly affects how the system will operate once connected to the home’s actual ductwork.

Sealing the ducts is not a cosmetic finishing touch

The visible strips of metal tape around the transitions are used to seal the sheet-metal assemblies.

In a forced-air system, a leak at the plenum means that some of the heated or cooled air does not reach the intended rooms. In an unfinished basement, these losses can go unnoticed for a long time because the air does not necessarily leak in a location visible from the living spaces.

We therefore place as much importance on sealing the connections as we do on adjusting the equipment.

A high-efficiency central heat pump connected to a leaky ductwork system does not deliver the full benefit expected from its rated efficiency.

A design intended to make replacing old furnaces easier

Midea specifically presents the EVOX G3 as a solution that facilitates the modernization of existing systems. Depending on capacity, the cabinets in this generation use widths suited to the common dimensions of central furnaces, and the indoor unit can accept different power supplies depending on the configuration.

This feature is particularly useful for an installation such as Saint-Nazaire-d’Acton, since any significant increase in the unit’s width would have affected the sheet metal, clearances, and use of the laundry area.

Even when a unit is designed to facilitate replacements, we still need to measure before ordering:

• the available width;
• the height between the floor and the ducts;
• the service depth;
• the return air position;
• the supply air position;
• the refrigerant line routing;
• the available access to the panels.

An electric furnace that works with a heat pump rather than solely with resistance heaters

The term electric furnace is commonly used in Quebec and accurately describes this unit’s residential application. However, the EVOX G3 is more precisely a central air handler designed to operate with an inverter heat pump and, when required, auxiliary electric heating.

This distinction is important for understanding how it operates in winter.

When conditions permit, the heat pump handles a large portion of the heating by transferring thermal energy from outdoors into the home. The electric elements can then provide additional heat depending on the outdoor temperature, thermal load, and system settings.

Midea’s documentation provides for auxiliary modules of up to 25 kW, including 10, 15, and 25 kW configurations with multi-stage control.

However, we never select auxiliary heating simply by choosing the highest available kilowatt rating.

Proper sizing must take the heat pump, the residence’s heat loss, and the available electrical capacity into account.

R454B: The A2L label reflects the new generation of central equipment

The EVOX G3 range presented by Midea uses R454B refrigerant, classified as A2L. The manufacturer states that this refrigerant has a global warming potential of 466.

This represents a significant change from many central systems being replaced today, which operated with R410A or, for much older equipment, other refrigerants.

For the homeowner, the day-to-day controls remain familiar. For our technicians, R454B requires installation and servicing to be performed using procedures, tools, and practices appropriate for A2L refrigerants.

The photograph from Saint-Nazaire-d’Acton also shows the copper refrigerant lines routed vertically along the side of the installation. Their route must be planned to avoid unnecessary mechanical stress while maintaining sufficient clearance around the equipment.

Heating in extreme cold: an important feature for this region of Quebec

Low-temperature performance is a major criterion when a heat pump becomes a primary heating source.

Midea states that this platform can operate continuously down to -30 °C. The documentation also presents significant heating performance around -25 °C for the 3-ton system used in the cited tests.

It is important not to turn these platform data into an identical promise for every EVOX G3 combination. Exact performance varies according to the indoor and outdoor models.

For a residence in Saint-Nazaire-d’Acton, we are particularly interested in the available capacity when temperatures drop significantly, because proper sizing should minimize unnecessary reliance on electric resistance heating while maintaining comfort.

EVOX G3 capacities meet a range of residential needs

The product line documentation presents various combinations of 18,000, 24,000, 30,000, 36,000, 48,000 and 54,000 BTU/h.

In the photograph provided for this project, the full model number is not visible clearly enough for us to state with certainty which of these capacities was installed.

We never infer tonnage solely from the cabinet width.

The sizing of a central system should instead take the building load and air distribution network into account. Important factors include:

• heated area;
• insulation level;
• window quality;
• air infiltration;
• home orientation;
• duct dimensions;
• return air capacity;
• heat losses at design temperatures.

Up to 19 SEER2, but only for certain combinations

The EVOX G3 lineup reaches, depending on the combination shown in the documentation, up to 19 SEER2, 12.5 EER2, 10.8 HSPF2, and a COP at 5 °F of up to 2.14.

The detailed table also shows why we should not automatically attribute these maximum values to all units. Performance differs notably among the 18,000, 24,000, 30,000, 36,000, 48,000, and 54,000 BTU/h capacities.

When a homeowner compares two quotes for central heat pumps, it is therefore much more useful to compare the exact combinations and their certified references than to compare only the series name.

From airflow to rebates: the checks that turn a good machine into a good installation

Computational Constant Airflow 2.0: useful when retaining existing ductwork

An important characteristic of this installation is that we are working with an existing ductwork system.

The EVOX G3 fan uses the technology Midea calls Computational Constant Airflow 2.0. It is designed to adjust the fan’s output and speed when system resistance changes. The documentation indicates operating capability of up to 1.2 in. of water column static pressure under the stated conditions.

The manufacturer also provides up to 60 airflow adjustment levels.

This flexibility is especially useful in renovations where the existing ductwork does not perfectly match the conditions of a new system.

However, it does not replace good ductwork design. An undersized return-air duct or highly restrictive ductwork remains a mechanical issue that should be corrected.

The existing ductwork must be able to accommodate the selected capacity

A common mistake when replacing a furnace is selecting a higher capacity without checking the ductwork.

More BTUs generally mean greater airflow.

If the system has to move 1,400 or 1,600 CFM through a network historically designed for much less, we may end up with:

• more noise at the grilles;
• high static pressure;
• imbalances between the components;
• increased fan demand.

That is why the visible transition on this installation in Saint-Nazaire-d’Acton is only part of the equation. We must also take into account what comes after it.

MERV 13 filtration: air quality must remain compatible with airflow

The platform can be paired with modules compatible with 1-, 2-, or 4-inch MERV 13 filters, depending on the configuration. Midea indicates that they can capture more dust, pollen, particles, and pet dander or hair.

A more efficient filter nevertheless creates resistance to airflow.

We therefore prefer a properly sized and maintained filter to an extremely restrictive filter added without checking the static pressure.

A platform compatible with different types of control

The EVOX G3 documentation also provides several control strategies. It specifically mentions 485 communication, as well as configurations that can operate with a third-party 24 V thermostat.

For a replacement in an existing home, this flexibility can avoid unnecessarily rewiring all the control wiring.

Compatibility must nevertheless be confirmed based on the actual equipment pairing and the thermostat selected.

LogisVert: an EVOX G3 may be eligible, but the product line name is not enough

For a heat pump installed in Québec on or after November 26, 2025, Hydro-Québec requires the equipment to be ENERGY STAR certified to qualify for the LogisVert financial incentive. Hydro-Québec also specifies that the applicable lists and amounts are those in effect on the installation date.

In 2026, the basic incentive announced by Hydro-Québec is $50 per 1,000 BTU/h at -8°C for an eligible ENERGY STAR heat pump, or $120 per 1,000 BTU/h at -8°C when it is ENERGY STAR – Cold Climate certified.

The amount is therefore not calculated from the number of BTUs simply included in the product name. We need to know the heating capacity recognized at -8°C for the eligible combination.

For this specific installation in Saint-Nazaire-d’Acton, we are not publishing an arbitrary amount because the photograph does not make it possible to identify the complete indoor model with certainty, and the outdoor model is not shown.

The proper method is to verify:

1. the exact model of the indoor unit;
2. the exact model of the outdoor heat pump;
3. the certified combination;
4. the Hydro-Québec list applicable on the installation date.

What we want to avoid in a replacement like this

Reusing the ducts without inspecting them

“The ducts were already there” is not a technical validation. They must be capable of carrying the new system’s airflow.

Fabricating a transition that changes size too abruptly

A sudden reduction or increase in duct size can hinder airflow. The shape of the sheet-metal fitting therefore deserves as much attention as its airtightness.

Blocking access with laundry appliances

The washing machine visible near the system is a reminder that basements evolve. We must preserve areas that allow access to the panels, filter, and components requiring maintenance.

Choosing the auxiliary electric heating solely according to the maximum available

A 25 kW module is not automatically better than a 10 or 15 kW module. The home’s heating load and the electrical panel’s capacity should guide the choice.

Confusing the series’ maximum performance with that of the installed model

A rating of “up to 19 SEER2” describes a product line. Actual efficiency belongs to a specific combination.

A project that demonstrates the value of genuine HVAC adaptation

This Saint-Nazaire-d’Acton installation is a good example of the type of project where the most important work is not necessarily the most spectacular.

The MIDEA EVOX G3 is at the center of the installation, but the result also depends on:

• the base on which it rests;
• the sheet-metal transition fabricated above it;
• the tightness of every joint;
• the refrigerant line routing;
• the fan setting;
• the system’s actual capacity;
• the auxiliary heating;
• the thermostat;
• access for the next service visit.

At AirGreen, we apply the same approach to our electric furnace and central heat pump projects in Montreal, Laval, Longueuil, the North Shore, and the South Shore: a high-efficiency machine deserves an installation capable of maintaining that efficiency once connected to the building’s reality.

In Saint-Nazaire-d’Acton, the project’s success rests precisely on integrating a new-generation MIDEA EVOX G3 with a home whose ductwork, structure, and mechanical room existed long before it.