Installation of a MIDEA EVOX G3 electric furnace in Longueuil, Montreal’s South Shore

In Longueuil, integrating an EVOX G3 beside a second central system required precise adaptation of the existing ductwork

This MIDEA EVOX G3 electric furnace installation in Longueuil features a particularly interesting configuration: the new MIDEA unit had to be installed in a mechanical room that was already heavily occupied, directly beside another central unit and beneath an existing sheet-metal duct network.

The photo taken during our work immediately shows the reality of the job site. On the left, the MIDEA EVOX G3 is recognizable by its dark gray cabinet, the Midea logo, and our AirGreen identification. To the right is another central unit, with its own refrigerant connections. Above both pieces of equipment, the plenums and sheet-metal transitions occupy practically the entire available width. Beneath the units, a large metal cabinet provides the transition to the existing ductwork, while a PVC condensate drainage system runs along the front of the installation.

For us, this project was therefore not simply a matter of removing an old furnace and sliding the new one into the same spot. We had to integrate theEVOX G3 within an existing infrastructure, preserving the operation of the adjacent equipment and fabricating transitions capable of meeting the new system’s airflow requirements.

It is precisely in this type of renovation that good HVAC installation in Longueuil makes the difference between an appliance that is simply functional and a truly well-integrated central system.

Two appliances side by side: a constraint that changes the entire planning process

When two central units are positioned so close together, the available space must be used methodically.

We must plan for all of the following simultaneously:

• the physical dimensions of the new furnace;
• sheet-metal transitions;
• access to service panels;
• filter position;
• refrigerant connections;
• drainage;
• electrical connections;
• the possibility of working on either unit later.

An installation could be very compact on the day it is commissioned, but become extremely difficult to repair if a pipe, cable, or piece of sheet metal blocks an essential panel.

At our job site Longueuilso we paid particular attention to the vertical placement of the MIDEA and its connection to the network located immediately above it.

Sheet-metal transitions fabricated for the building, not just for the machine

The photograph clearly shows the modifications to the metal ductwork above the EVOX G3.

The new furnace cabinet does not necessarily have the same dimensions as the old equipment. We must therefore fabricate a custom sheet-metal transition to connect to the existing ductwork.

A well-designed transition does more than simply close the gap between two openings. It directly affects airflow.

A reduction that is too abrupt can cause:

• an increase in static pressure;
• more noise in the ducts;
• less uniform air distribution;
• an increase in the effort required of the blower;
• insufficient airflow in certain rooms.

On this project, the vertical space available between the unit and the main ductwork required a relatively compact transition. Our task was therefore to use the available height without creating an unnecessary restriction.

Why the EVOX G3 width is advantageous for replacement

Midea designed this generation of central units with dimensions suited to replacements.

The documentation for theEVOX G3 indicates cabinet widths of approximately 14.5 to 21.5 inches, depending on capacity, to better match the dimensions found in existing furnaces. The indoor platform also provides multi-voltage power options depending on the configuration, including 115 V and 208/230 V.

In an installation like the one in Longueuil, every inch counts. The neighboring system limits the lateral space, and the ducts above impose their own dimensions.

Even when a unit offers a suitable width for replacement, we must still check the depth, height, return-air position, and clearances required for servicing.

A multiposition design useful in renovations

The EVOX G3 range can also be installed in different orientations.

Midea provides configurations including:

• vertical, with upward airflow;
• with downward airflow;
• horizontal, right or left;
• of the “low-boy” type for certain height constraints.

The modular design Block N Lock also aims to facilitate handling and reconfiguration of the unit in difficult spaces such as basements or attics.

In the photographed case in Longueuil, the vertical installation was consistent with the existing system and made it possible to retain the main air distribution located above the mechanical room.

The A2L marking visible directly on the unit

On the nameplate of the installed MIDEA unit, we can distinguish the symbol A2L.

The EVOX range presented in the documentation uses R454B refrigerant. Midea states that this refrigerant has a global warming potential, or GWP, of 466.

This is an important aspect of this new generation of central systems.

R454B belongs to the A2L category, which entails specific installation and service procedures. Technicians must work with methods and equipment compatible with the refrigerant used by the system.

For a homeowner in Longueuil or the South Shore, this also means that, during future HVAC service, it will be important to clearly communicate the model and refrigerant type before any work is performed.

The exact capacity must be confirmed from the model, not guessed from the cabinet

The nameplate of our unit is visible in the photo, but the full model number is not legible enough to confirm its exact capacity with certainty.

We therefore deliberately do not assign it a tonnage that cannot be verified.

The MIDEA EVOX G3 series presented in the documentation covers several capacities, ranging from approximately 18,000 to 54,000 BTU/h. Depending on the exact combination of the indoor and outdoor units, the stated performance can reach 19 SEER2, 12.5 EER2, 10.8 HSPF2 and a COP of up to 2.14 under the stated test condition.

The series’ technical table includes configurations of 18,000, 24,000, 30,000, 36,000, 48,000, and 54,000 BTU/h, each with its own airflow and efficiency ratings.

This is an important point when two homeowners compare quotes that both mention “MIDEA EVOX G3.” The series name alone does not reveal the capacity or efficiency of the proposed system.

Airflow, auxiliary heating, and drainage: the technical details behind this Longueuil installation

A system capable of working with different duct systems

Existing ductwork is often one of the main limiting factors when replacing an old furnace.

The MIDEA EVOX G3 uses Computational Constant Airflow 2.0, which is intended to adjust fan operation according to the resistance encountered in the duct system.

In its documentation, Midea presents applications of up to 1.2 in. of static pressure.

The manufacturer also specifies up to 60 airflow adjustment levels, allowing more precise airflow adjustment according to the installation’s needs.

This feature is particularly relevant here, since the photo shows a complex existing duct system with several metal transitions around two central units.

Fan technology does not replace a good duct system

We never consider these electronic capabilities a license to ignore a ductwork problem.

If the return airflow is insufficient or a transition creates a significant restriction, the problem must be corrected.

Excessively high static pressure can cause, among other things:

• more noise;
• reduced airflow;
• higher motor consumption;
• inadequate supply-air temperatures;
• uneven distribution between rooms.

For this reason, when replacing an electric furnace in Longueuil, we always consider the equipment and the ductwork as a single system.

An indoor architecture designed to distribute air through the coil

Midea also describes the use of an M-Coil with a symmetrical fan design to improve air distribution across the heat exchanger surface.

In the data presented by the manufacturer, this architecture is intended to achieve a much smaller airflow difference between the coil sections than with certain conventional designs.

Uniform airflow over the coil helps the system properly use its heat-exchange surface.

This becomes particularly important when a central heat pump is used both for summer cooling and winter heating.

Up to 25 kW of auxiliary electric heating depending on the configuration

An EVOX G3 electric furnace can also receive an auxiliary heating kit.

Midea’s documentation presents options for 10 kW, 15 kW, and up to 25 kW, with logic that can distribute the heating across multiple stages.

However, the maximum available capacity must never be interpreted as the capacity required for every home.

We determine the auxiliary heating while taking into account, among other factors:

• of the building’s heat loss;
• of the heat pump’s heating capacity;
• of the electrical panel capacity;
• of the existing conductors;
• of the available circuit breakers;
• of the control strategy.

A home equipped with an excellent cold-climate heat pump may have very different auxiliary heating needs from a building with significant heat loss.

A heat pump platform designed for very low temperatures

When the EVOX G3 indoor unit is paired with the corresponding outdoor heat pump, Midea states that the platform can operate down to -30 °C.

For the three-ton system used in the tests described by the manufacturer, the documentation also shows sustained performance at very low temperatures.

It is essential to distinguish this performance from that of electric heating.

The heat pump transfers heat and can produce more heat than the electricity it consumes when its COP is above 1. The electric elements, on the other hand, provide supplemental resistance heating.

The optimal strategy is therefore generally to operate the heat pump according to the planned capabilities of the installed combination, then use auxiliary components when the home’s needs require them.

The drainage visible at the bottom of the system

Another particularly interesting detail in the photo is the PVC drainage system installed in front of the large lower cabinet.

We can see a section forming a trap, as well as a vertical rise that provides access to the drain.

This component may appear much simpler than the MIDEA unit itself, but it is essential for cooling operation.

When the indoor coil cools the air, moisture condenses on its surface. This water must be collected and drained properly.

We pay attention to:

• the drain slope;
• the positioning of the trap when required;
• accessibility for cleaning;
• the risk of blockages;
• the strength of the connections;
• the entire route to the discharge point.

A high-performance central installation can still cause damage if drainage is neglected.

The neighboring system’s refrigerant lines show the importance of access

On the right side of the photo, we can see an insulated refrigerant line and a small copper line connected to the adjacent equipment.

This proximity demonstrates why we need to considerfuture maintenance before fabricating the final transitions.

If we place a plenum, duct, wire, or piping in front of a component that may one day need to be repaired, a relatively simple service call can turn into major disassembly.

We therefore plan the new installation with access to both units in mind, not just the one we are installing that day.

MERV 13 filtration: possible, but always to be coordinated with the airflow

Midea also offers a filtration module compatible with filters of 1, 2, or 4 inches, including configurations MERV 13. The manufacturer indicates that this filtration can help capture more dust, pollen, particles, and pet hair while keeping the indoor coil cleaner.

However, we avoid choosing a filter solely based on the highest MERV rating.

The filter’s surface area, thickness, and resistance must remain compatible with the system’s airflow.

In an installation that already includes several transitions, like the one in Longueuil, this verification is particularly important.

Communicating thermostat or conventional 24 V control

The EVOX platform offers several control strategies.

According to Midea, it can operate in communicating mode 485 or with certain configurations using a conventional thermostat 24 V.

With the corresponding communicating components, the Midea ecosystem also provides features such as schedule programming, monitoring of certain comfort and energy-consumption parameters, and diagnostic functions through the SmartHome app.

In a renovation, this flexibility can be useful when thermostat wiring already exists and would be difficult to replace without opening the walls.

Eligibility for a subsidy must be verified for the exact combination

The Midea brochure attached to this project provides extensive performance data, but it alone cannot confirm eligibility for a LogisVert subsidy in Quebec.

The financial assistance mentioned in this document mainly concerns U.S. programs.

For an installation in Longueuil, we must verify the exact combination of the indoor and outdoor units, the applicable certification, its reference number when required, and the criteria of the Quebec program in effect at the time of the application.

Since the outdoor model and the system's exact capacity cannot be reliably identified from this photo, we are not presenting a specific subsidy amount for this project.

What this Longueuil installation really shows about a central replacement

This photo is particularly representative of renovation work in HVAC on the South Shore.

We are not working in an empty room with new ductwork designed specifically for the new equipment. We must work with existing infrastructure:

• two central units installed side by side;
• very little space between the equipment;
• existing plenums above;
• sheet-metal transitions to be adapted;
• a lower metal cabinet;
• an existing drainage system;
• refrigerant lines;
• service access to be maintained.

The MIDEA EVOX G3 is of interest in this context because its design allows relatively flexible adaptation for replacements, but the equipment cannot do the work by itself.

Final performance depends on the quality of the connections, airflow, sizing, auxiliary capacity, drainage, and commissioning.

At AirGreen, this is the approach we apply when carrying out our installations of electric furnaces and central heat pumps in Longueuil, but also Montreal, Laval, the North Shore, and throughout the South Shore.

We are not simply trying to fit a new appliance into the space occupied by the old one. We want the new installation to integrate properly with the building, the ductwork, and the other systems already in place, while remaining accessible for years of future maintenance.