In Saint-Marcel-de-Richelieu, a central integration designed around air return, drainage, and service access
This MIDEA EVOX G3 electric furnace installation in Saint-Marcel-de-Richelieu clearly shows why replacing a central system should never be treated as a simple equipment swap. On this AirGreen project, the new unit had to be installed in an existing mechanical room, between the building structure, the duct network, the refrigeration lines, and a water heater already installed nearby.
The photograph highlights several technical aspects that are often invisible in a quote: the MIDEA cabinet rests on a sheet-metal base fabricated for the installation, the upper connection to the duct network is carefully adapted, the refrigerant lines run up along the right side, and the condensate drainage remains fully accessible from the front of the unit.
To the right, the Giant water heater remains unobstructed. To the left, the framing and part of the existing masonry remind us that this is indeed an existing building, with dimensions and constraints that must be respected rather than unnecessarily modified.
This is precisely the type of project where our experience in HVAC, ventilation, ductwork, refrigeration, and commissioning becomes just as important as the choice of the equipment itself.
A vertical installation adapted to the existing network
The MIDEA EVOX G3 is installed here in a vertical configuration. The cabinet consists of stacked modules connected by the characteristic side fasteners of this generation.
This modular architecture is not merely a manufacturing detail. MIDEA provides six installation configurations, including upflow, downflow, left horizontal, right horizontal, and various compact configurations. The manufacturer also emphasizes that the modules are designed to facilitate handling in basements, attics, and difficult mechanical spaces.
In this Saint-Marcel-de-Richelieu residence, the vertical configuration made it possible to maintain a logical layout: air return at the base, air treatment through the unit, and connection to the distribution network at the top.
The choice of orientation should never be made solely because “the old furnace was like that.” Instead, we consider:
- the position of the existing ducts;
- the direction of flow;
- the available height;
- the location of the refrigerant lines;
- drainage;
- electrical access;
- the proximity of other equipment;
- and especially the ability to open the panels several years from now.
A return-air base fabricated for the unit
The lower part of the photo is particularly interesting.
The furnace sits on a sheet-metal cabinet that integrates it with the return-air ductwork. A handwritten dimension of approximately 21 1/4 × 20 in. even appears on this piece, which aptly illustrates the reality of our trade: connections and transitions are often measured and fabricated to fit the actual building.
The return air is one of the most underestimated elements when replacing a central system.
A new central heat pump may deliver excellent performance on paper, but it cannot distribute heating and cooling properly if the fan does not get enough air at the inlet.
An undersized return can contribute to:
- excessively high static pressure;
- reduced airflow;
- more noise;
- extended operation;
- less favorable heat exchange;
- and increased wear on the ventilation system.
That is why we always examine the return-air dimensions and the geometry of the plenum before finalizing the installation.
The upper connection: an airtight continuity of airflow
In the upper part of the photograph, the MIDEA connects to the existing ductwork through a sheet-metal section fitted to the cabinet. The joints are sealed with metal tape.
This step may seem simple once completed, but it directly affects system performance.
A poorly designed upper transition can create an overly abrupt contraction, excessive turbulence, or an air leak before the air even reaches the rooms in the home.
We therefore seek a connection that meets all of the following:
- the required airflow;
- the available cross-sectional area;
- sealing;
- the clearances around the cabinet;
- and the constraints of the existing duct.
This approach is particularly important in homes where we retain a significant portion of the original ductwork.
Computational Constant Airflow 2.0: useful, but not magic
One of the technical advantages of the EVOX G3 is its Computational Constant Airflow 2.0 technology.
According to MIDEA, the system can adjust fan operation when ductwork or filtration conditions change. The documentation presents examples of maintaining airflow up to 1.2 in. of external static pressure under the conditions specified by the manufacturer.
The platform also allows up to 60 levels of airflow adjustment, giving the technician a particularly useful adjustment range during a renovation.
That said, we never present this technology as an excuse to neglect the ductwork.
If a return is much too small or a section of the system imposes a major restriction, the electronics cannot eliminate the physical limitation.
The right approach is to combine a properly sized system and precise fan adjustment.
The visible details on this job that will make a difference over the coming years
A condensate drainage system designed for easy cleaning
At the front of the equipment, we can clearly see the PVC drainage system as well as a transparent trap with a red top access port. A small maintenance brush is also attached nearby.
This is one of the most practical details of this installation.
When the heat pump operates in cooling mode, the indoor coil condenses the moisture in the air. This water must then be continuously drained away.
Over time, a condensate line can accumulate deposits. If the system is difficult to access, a very simple cleaning operation can become unnecessarily complicated.
Here, the arrangement makes it possible to:
- see the trap;
- access the drain;
- perform cleaning;
- check the drainage;
- carry out work without dismantling the cabinet.
In a slab-on-grade basement like the one in this Saint-Marcel-de-Richelieu residence, this also makes it possible to quickly spot an anomaly before it becomes a more serious problem.
The refrigeration lines remain grouped along the side of the equipment
The refrigeration connection is clearly visible to the right of the cabinet.
The larger-diameter line is covered with black insulation. The smaller copper line runs almost vertically alongside it before joining the indoor unit.
This arrangement keeps the front of the system relatively clear.
This is an important consideration for future HVAC maintenance. We want to avoid forcing a technician to move pipes simply to access a service panel.
With a central system, we therefore consider two moments at the same time:
the day we install the equipment and the day someone may eventually need to repair it.
An additional, readily accessible refrigeration component
We can also see a blue cylindrical component integrated into one of the refrigeration lines in the upper-right section.
The photograph shows its location, but not its markings clearly enough to confirm its exact model. What we can nevertheless observe is that the component remains visible and accessible rather than being enclosed behind the structure or ductwork.
This accessibility principle is important in any refrigeration installation.
The adjacent water heater had to remain fully usable
The Giant water heater installed to the right of the furnace is another concrete site constraint.
It would have been very easy to gain a few inches by moving the EVOX G3 closer or routing certain lines in front of the water heater. However, that would have made maintenance and any future replacement of either unit more difficult.
We therefore aim to preserve the service areas for all mechanical equipment, not just the equipment we install.
A mechanical room must remain functional as a whole.
The modular design makes it easier to manage difficult access
MIDEA's documentation presents the EVOX G3 construction as a Block N Lock architecture that makes it easier to separate and reassemble certain sections. The manufacturer particularly highlights ease of movement through stairways, basements, and difficult spaces.
This type of feature has real value in the field.
A complete central unit can be heavy and bulky. In some homes, the route between the front door and the mechanical room includes:
- a narrow staircase;
- a 90-degree turn;
- a narrow doorway;
- a low beam;
- or several pieces of equipment already installed.
Being able to work with modules reduces difficult handling and provides more options for final placement.
An EVOX G3 range with several capacities
MIDEA offers this platform in several capacities.
The documentation provided specifically presents systems rated at 18,000, 24,000, 30,000, 36,000, 48,000, and 54,000 BTU/h.
Depending on the indoor-outdoor combination, the manufacturer publishes performance figures of up to:
- 19 SEER2;
- 12.5 EER2;
- 10.8 HSPF2;
- and a COP of up to 2.14 at 5 °F (-15 °C).
The unit's nameplate is visible in the photograph from Saint-Marcel-de-Richelieu, but the characters are too small to reliably confirm the complete model number.
We therefore do not want to make up a precise capacity.
To state the exact performance of an installation, we always use the complete indoor unit + outdoor unit combination, not just the EVOX G3 series.
A platform designed to operate at very low temperatures
MIDEA's documentation presents the EVOX G3 as a cold-climate heat pump platform and indicates continuous operation down to -30 °C. The manufacturer also publishes test data at approximately -25 °C for a three-ton system.
These figures are particularly relevant for an installation in Montérégie.
A Quebec central heat pump must not only perform well in cooling mode. It is important to consider what it can deliver when the outdoor temperature actually drops.
So we look at:
- low-temperature heating capacity;
- the COP;
- the home's heating and cooling load;
- the point at which electric backup becomes necessary;
- and how the thermostat or controller manages the different heat sources.
Auxiliary electric heating: up to 25 kW does not mean 25 kW for everyone
The EVOX G3 can accommodate different auxiliary electric heating kits.
The MIDEA documentation mentions options of 10, 15, and up to 25 kW, with control that can operate in multiple stages depending on the configuration.
The capacity selection must nevertheless be based on the building.
We must specifically check:
- the home’s heat loss;
- the heat pump’s actual capacity in winter;
- the electrical panel capacity;
- the conductor gauge;
- the required circuit breaker;
- the other electrical loads;
- the type of backup strategy.
The largest available unit is therefore not automatically the best.
R-454B and A2L classification
The central EVOX range presented in the documentation uses R-454B refrigerant. MIDEA states that it has a global warming potential, or GWP of 466, and identifies it as an A2L refrigerant.
The A2L classification means that the refrigerant is mildly flammable.
For occupants, this does not change the system’s normal operation. However, it affects the installation and service procedures that technicians must follow.
In particular, we must use the appropriate methods and equipment for work on A2L systems.
Filtration: MERV 13 is possible, but airflow must always be assessed
The EVOX G3 documentation provides for the integration of 1-, 2-, or 4-inch filters, with MERV 13 options.
A higher level of filtration can be beneficial, particularly for capturing more particles, but a filter should not be selected solely according to its MERV rating.
The filter pressure drop is part of the system.
If we install a highly restrictive media filter in an already marginal return, the blower will have to work harder.
We are therefore seeking a balance between:
- filtration;
- airflow;
- static pressure;
- sound level;
- and the homeowner’s actual needs.
Several control methods depending on the configuration
MIDEA also provides different control strategies.
The documentation mentions compatibility with 485 communication, certain 24 V architectures, and wireless communication options between certain compatible EVOX components.
This flexibility can be particularly useful during a replacement.
In an existing home, the cable connecting the thermostat to the basement may not have enough conductors for all the functions of a modern system. Being able to adapt the control method can avoid invasive work in finished walls.
The rebate must be verified based on the exact combination
The documentation provided confirms the general performance of the EVOX G3 range, but it is not sufficient to confirm eligibility or the amount of a Quebec rebate for this specific installation.
For a central heat pump financial assistance application, we must verify separately:
- the exact indoor unit model;
- the exact outdoor unit model;
- their certified combination;
- the heating capacity used by the program;
- and the criteria applicable on the date of the work.
This is an important distinction.
Two installations both bearing the name MIDEA EVOX G3 may use different capacities and combinations. It would therefore be incorrect to promise an amount based solely on the series name.
Mistakes to avoid when replacing a central system in Saint-Marcel-de-Richelieu
This installation highlights several common pitfalls:
- choose the new equipment solely based on the tonnage of the old furnace;
- overlook the size of the return-air system;
- install the furnace without considering the neighboring water heater;
- block the panels with the refrigerant lines;
- use a filter that is too restrictive;
- make the condensate drain difficult to clean;
- automatically choose the largest electrical component;
- improperly seal the connection to the upper duct system;
- forget to check the static pressure;
- announce a rebate without knowing the exact combination;
- overlook the specific requirements of R-454B A2L.
An installation that clearly reflects the way we work at AirGreen
This project in Saint-Marcel-de-Richelieu is not noteworthy simply because the equipment is new.
It is noteworthy because every part had to be organized around practical constraints.
We have a vertical MIDEA EVOX G3, a return-air base built for the installation, an upper duct system that has been connected and sealed, a transparent drain that is easy to maintain, refrigerant lines positioned on the side, and an adjacent water heater whose access had to remain unobstructed.
These are the details that turn equipment replacement into a true HVAC installation.
At AirGreen, we apply the same approach to our projects in Montreal, Laval, Longueuil, the North Shore, and the South Shore: looking at the building as a whole before deciding how the equipment should be installed.
The EVOX G3 model offers considerable flexibility thanks to its modular design, adjustable fan, and numerous possible configurations. However, these features reach their full potential only when the ductwork, air return, drainage, refrigerant lines, electrical connections, and service access are also properly planned.