Installation of a MIDEA EVOX G3 electric furnace in Sainte-Marie-Madeleine, Montérégie

A central installation carried out in an already very crowded basement, with direct access to the components during commissioning

In Sainte-Marie-Madeleine, in Montérégie, we installed an MIDEA EVOX G3 electric furnace in a basement where the building’s mechanical systems share space with existing ducts, electrical equipment, storage, and several HVAC components already in place. The photograph taken during our work is particularly interesting because it shows the system in the middle of the installation phase: a panel from the MIDEA EVOX G3 has been removed and placed in front of the unit, while an adjacent unit is also open to provide access to the electronic boards, wiring, and blower.

This is therefore not a photo taken only after the finishing work. It shows an essential stage of the trade: access to the components before the cabinets are permanently closed, when we check the connections, mechanical integration, controls, and airflow.

The EVOX G3 is part of the MIDEA line of Inverter central ducted systems. In Quebec, the indoor unit is often called an electric furnace, although it also serves as an air handler when paired with a central heat pump.

On this project, the real work was not simply a matter of positioning a new unit. We had to integrate the MIDEA into the existing duct network, organize the refrigerant lines, maintain convenient access to the panels, plan the drainage, and configure the system correctly so it could operate efficiently in the home.

An installation where the available space had to be shared intelligently

The first visible feature in the photo is the density of the mechanical space.

The MIDEA EVOX G3 is positioned at the center of the installation. Above it, a galvanized sheet-metal plenum connects to the ducts that distribute air throughout the property. On the left, another piece of equipment is open, exposing its entire control section. To the right and behind the MIDEA, the space is also used for storage and various building components.

This imposes a very simple rule: we cannot sacrifice accessibility simply to make the new machine fit.

During planning, we must preserve enough space to work later on:

• the blower;
• the indoor coil;
• the auxiliary electric heating;
• the controls;
• the circuit boards;
• the drainage;
• the refrigeration lines;
• the filtration system.

The photo clearly shows why this issue is important. The MIDEA's front panel is accessible enough to be removed and placed on the floor during the service visit. This may seem obvious, but in a cramped mechanical room, a few poorly used inches can make a future repair much more complicated.

Removing the panel gives us access to the internal sections without dismantling the ductwork

A good central system installation must be designed to operate today, but also to be serviced in five, ten, or fifteen years.

In this Sainte-Marie-Madeleine installation, removing the panel provides direct access to the internal components without having to dismantle the plenum above or move the refrigeration lines.

That is precisely what we are looking for.

A common mistake in HVAC installation is to place a duct, pipe, or cable directly in front of a service door. The installation may look neat on the day of the work, but the first technician who needs to access the equipment will discover the problem.

We therefore seek to arrange the lines and connections in a way that keeps access clear.

The EVOX G3's modular design plays a practical role in this type of project

The MIDEA EVOX G3 uses a modular design that allows for multiple installation orientations. The manufacturer's documentation specifically provides for upflow, downflow, right-horizontal, left-horizontal, and certain low-clearance configurations. MIDEA also highlights the ability to handle the unit sections more easily when work must be carried out in a basement or another difficult-to-access location.

This design is particularly relevant in existing homes.

On a new construction site, we can sometimes build the ductwork around an appliance that has already been selected. In a renovation in Sainte-Marie-Madeleine, we often have to do the opposite: select and configure the appliance based on the existing ductwork and available space.

The manufacturer also indicates different cabinet widths, approximately 14.5 to 21.5 inches depending on capacity, as well as certain multivoltage options for the indoor unit, including 115 V and 208/230 V depending on the configuration.

In a crowded technical space, this variety of formats can considerably reduce the extent of the modifications required.

Sheet-metal transitions are just as important as the new furnace

Above the MIDEA, we see a set of metal ducts that provides the transition between the unit and the building's ductwork.

For a homeowner, this part may seem secondary compared with the heat pump or the furnace itself.

Technically, it is fundamental.

Air must leave the unit without encountering an unnecessary restriction. A transition that is too small, an abrupt change in direction, or a poorly sealed connection can create:

• noise;
• turbulence;
• an increase in static pressure;
• insufficient airflow;
• uneven distribution between rooms;
• an increase in the work required from the blower.

When adapting a MIDEA EVOX G3 electric furnace to an existing system, we must therefore consider the duct geometry as much as the equipment's characteristics.

The refrigerant lines visible in the center of the photo also require careful planning

An insulated black pipe runs vertically near the MIDEA. It is an important part of the circuit connecting the indoor unit to the outdoor heat pump.

This line must be:

• properly sized for pairing;
• insulated when required;
• supported;
• protected against damage;
• positioned so as not to block the service panels.

In a crowded mechanical room, the temptation may be strong to run the piping “wherever there is room.” We specifically avoid this approach.

The line routing must be part of the installation plan from the outset.

R-454B: a new generation of central system

MIDEA documentation indicates that the EVOX central system in question uses R-454B, an A2L-classified refrigerant, with an announced global warming potential of 466.

For an HVAC company, this has a direct consequence: the work methods used on the refrigeration circuit must be adapted to this generation of equipment.

This notably includes:

• connections;
• leak tests;
• evacuation;
• commissioning;
• the tools used;
• future work on the circuit.

For the homeowner, the important point is that R-454B is not simply a new designation on a technical data sheet. It also entails specific installation and service practices.

An electric furnace that works with the heat pump

The term electric furnace may give the impression that heating is produced solely by resistance elements.

In an EVOX G3 system paired with a central heat pump, the logic is different.

The heat pump provides much of the heating by transferring energy from the outdoor air indoors. The MIDEA unit then distributes this heat through the ductwork. Auxiliary electric heating may operate when the outdoor temperature, heating demand, or system settings warrant it.

MIDEA offers multi-stage auxiliary heating kits rated up to 25 kW, depending on the configuration and model.

This does not mean that the maximum available capacity should always be installed.

At AirGreen, the supplemental heating capacity must be consistent with:

1. the building’s heat loss;
2. the heat pump’s actual capacity;
3. the electrical panel;
4. conductors;
5. electrical protection;
6. the selected heating strategy.

The Montérégie climate demands genuine winter performance

In Sainte-Marie-Madeleine, a central heat pump must be evaluated based on its performance when temperatures become decidedly winter-like.

MIDEA presents the EVOX G3 as a platform that can continue operating down to approximately -30 °C. The documentation also indicates, for certain tested configurations, high heating capacity at approximately -25 °C, with a COP that can reach approximately 1.9. The manufacturer specifies that some of these values come from tests conducted on a three-ton system.

This clarification is important.

We never automatically transfer the best published value in the brochure to all EVOX G3 systems. Actual performance depends on the exact match between the indoor and outdoor units.

What capacity was installed on this project?

The photo shows the nameplate on the removed panel, but the text is not clear enough to confirm the model’s complete reference without risking an error.

We therefore prefer not to arbitrarily assign a tonnage to this installation.

MIDEA documentation presents several capacities, including 18,000, 24,000, 30,000, 36,000, 48,000, and 54,000 BTU/h.

The corresponding models also vary according to capacity, with different indoor and outdoor unit references.

To properly compare two central heat pump quotes, we therefore need to look at the complete references, rather than simply the wording “MIDEA EVOX G3.”

Properly adjusting airflow, filtration, and controls: the less visible part that determines comfort

The blower must work with the existing ductwork

The large sheet-metal section above the furnace clearly shows that the new unit must integrate with an already-built ductwork system.

The EVOX G3 uses Computational Constant Airflow 2.0 technology, designed to adjust blower operation to the different resistances encountered in the ductwork. The documentation describes conditions of up to 1.2 in. of external static pressure.

MIDEA also mentions up to 60 airflow settings.

This is particularly useful for a renovation.

This allows us to fine-tune system operation when the existing ductwork differs from a perfectly standardized new installation.

However, the blower cannot correct everything.

An undersized return, a highly restrictive filter, or inadequate ductwork must be considered separately.

Why we do not simply set the blower to maximum

More airflow does not automatically mean greater comfort.

An airflow rate that is too high can cause:

• more noise;
• unpleasant drafts;
• less effective dehumidification in summer;
• an imbalance between certain rooms.

An airflow rate that is too low can impair heat transfer and efficiency.

Commissioning therefore involves finding a setting consistent with the heat pump tonnage, static pressure, and ductwork.

This is one of the reasons the panels are open in our photograph: this adjustment and verification step is genuinely part of the installation.

High-performance filtration must remain compatible with the system

MIDEA documentation provides filtration options of 1, 2, and 4 inches, including solutions that can accommodate MERV 13 media.

A more efficient filter can capture more dust and particles, but it also creates resistance to airflow.

We therefore need to consider several elements together:

• the filter size;
• its depth;
• its surface area;
• its MERV rating;
• the required airflow;
• the system's static pressure.

Automatically installing the most restrictive filter is not always an improvement.

Several thermostat strategies are possible

The EVOX G3 also offers different control modes.

MIDEA documentation indicates compatibility with 485 communication as well as with certain configurations using 24 V thermostats. It also describes various scenarios in which MIDEA or third-party components can be used.

This flexibility is useful for renovations, as the existing thermostat wiring can often be retained depending on the configuration.

However, we must precisely verify the desired functions:

• number of stages;
• auxiliary heating;
• heat pump control;
• communication;
• accessories;
• programming.

Up to 19 SEER2 depending on the exact match

The EVOX G3 lineup offers performance 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 combination.

However, the detailed values vary according to capacity. The MIDEA table indicates, among other things:

• 18,000 BTU/h: up to 19 SEER2;
• 24,000 BTU/h: 18.6 SEER2;
• 30,000 BTU/h: 17.2 SEER2 and 10.8 HSPF2;
• 36,000 BTU/h: 17.7 SEER2;
• 48,000 and 54,000 BTU/h: 17.5 SEER2 in the combinations presented.

We therefore always emphasize the word match when discussing performance.

Grant: the name EVOX G3 is not enough

The same equipment family includes several indoor and outdoor model numbers. MIDEA documentation confirms this diversity of models.

It would therefore be incorrect to claim that a system automatically qualifies for financial assistance simply because it bears the name EVOX G3.

Eligibility must be verified based on:

• the exact indoor model;
• the exact outdoor model;
• the corresponding AHRI certificate;
• the program criteria applicable on the installation date.

The potential amount of financial assistance must also be associated with the system actually installed, not simply with its nominal capacity indicated in a brochure.

What this Sainte-Marie-Madeleine installation particularly illustrates

This photo allows us to show a stage that homeowners rarely see: the furnace is in place, but the technical work is still ongoing.

A panel on the EVOX G3 has been removed. The adjacent equipment is open. The tools are on the floor. The controls and blower are accessible.

This is precisely when several important decisions are verified.

We do not simply check whether the unit fits in the space. We must ensure that:

• the connections are correct;
• the panels can be put back in place without obstruction;
• the airflow system is consistent;
• the refrigerant lines are properly positioned;
• the controls work;
• the drainage is ready;
• the blower can be configured correctly.

The mistakes we seek to avoid with this type of replacement

Choosing the furnace solely based on the old unit’s dimensions

An old unit may have been oversized or undersized. The replacement must be checked against the current building.

Building the sheet metal without considering airflow

A transition can be sturdy and airtight while still creating a significant restriction.

Placing the refrigerant lines in front of the panels

The installation must remain serviceable.

Adjusting the blower without measuring or assessing the ductwork

The settings must match the actual pressure and airflow conditions.

Automatically installing the largest auxiliary-heating kit

The electrical capacity must be properly sized.

Promising performance or a rebate based on the series name

The exact matching of components remains essential.

Our AirGreen approach to a complete central-system upgrade

This MIDEA EVOX G3 installation in Sainte-Marie-Madeleine clearly represents our approach to central systems.

We start with the building’s reality: available space, ductwork, electrical supply, access, refrigerant lines, and heating needs. We then determine how the new furnace and heat pump can fit into this setup.

This work is particularly important when replacing an existing system, because every home has its own mechanical history.

At AirGreen, we carry out HVAC, central heat pump, and electric furnace installations in Greater Montreal and the areas we serve in Montérégie, including Montreal, Laval, Longueuil, the North Shore, and the South Shore.

Our goal is not simply for a new unit to start up on the day of installation. We want the system to be properly connected, adjusted, accessible, and compatible with the building so that it can provide heating and cooling for many seasons.