Installation of a MIDEA EVOX G3 electric furnace in a horizontal configuration in the attic in Roxton Falls

A central furnace installation in an attic where every access point, connection, and adjustment matters

This installation carried out by AirGreen in Roxton Falls shows a rarely visible aspect of a central electric furnace project: the moment when the unit is already in place in the attic, but our technicians are still working directly inside the cabinet to complete the necessary connections, adjustments, and checks before the panels are fully closed.

The photo is particularly revealing. The MIDEA EVOX G3 is installed horizontally beneath a wooden roof, surrounded by framing elements and insulated ductwork. Its service panel is open, making it possible to see the circuit board, connectors, internal wiring, and some of the components that are normally invisible after commissioning. Several tools have been temporarily placed on the cabinet during the work, while a heavily insulated rectangular duct is connected to one end of the unit.

This is therefore not a photo of a carefully cleared mechanical room after the work is complete. It is a real construction-site image, in a space where HVAC installation logistics are almost as important as the machine’s technology.

The MIDEA EVOX G3 series is part of Midea’s family of Inverter ducted central systems, developed with a clear focus on modernizing residential heating systems. In an attic like the one at this property in Roxton Falls, this design flexibility becomes a tangible feature rather than just a brochure claim.

A furnace installed horizontally because the space dictates its own logic

The first distinctive feature of the project is obvious: the unit is not installed upright.

Because the headroom under the roof is limited, the MIDEA EVOX G3 is installed horizontally between the structural members. This configuration makes it possible to use the available length rather than looking for nonexistent vertical clearance.

Midea specifically provides several installation orientations for the EVOX G3, including:

• upflow;
• downflow;
• horizontal;
• configurations adapted to height constraints;
• variants that allow the return and supply to be adjusted according to the job site.

The documentation also highlights a modular construction and an assembly system that facilitates handling the unit in attics, crawl spaces, basements, and other hard-to-access locations.

At the Roxton Falls job site, this capability is essential. A large packaged unit can be very difficult to move through a hatch or between roof trusses. Here, the equipment must not only reach its location but also be oriented so that technicians can still access its panels.

The open panel reveals the system's true brain

The photo provides a direct view of one of the EVOX G3's most important components: its control board.

The circuit board, relays, terminal blocks, and multiple cable harnesses connecting the different sections of the unit are clearly visible. A small diagnostic display is also visible on the board.

This electronics system manages much more than a simple on-off contact.

In a modern central system, the unit must coordinate, among other things:

• the indoor fan;
• the heating request;
• air conditioning;
• any auxiliary electric heating stages;
• communication with the outdoor unit;
• requests from the thermostat;
• different airflow settings;
• safety features and diagnostic codes.

This complexity explains why commissioning a modern electric furnace cannot be limited to checking whether the fan starts.

We must confirm that the controls are configured correctly for the actual installation.

485 communication, 24 V control, and renovation flexibility

Midea provides several control architectures for the EVOX G3.

The documentation indicates compatibility with 485 communication as well as traditional 24 V systems. Some configurations also allow the use of a third-party thermostat, while others can operate with wireless communication between certain compatible components.

This versatility is particularly useful in a renovation project.

In an existing home, the wiring connecting the thermostat to the attic may be old or limited in the number of conductors. It is not always practical to open several walls just to add communication wires.

Depending on the configuration selected, the EVOX G3 can therefore adapt the controls to the existing infrastructure instead of unnecessarily rebuilding part of the house.

Why the front access visible in this photo must be preserved

The photo also shows something we consider during installation: the space required in front of the service components.

The technician must be able to remove the panel and reach the circuit board. This seems obvious when the unit is new and open as shown in the photo. However, poor placement can quickly make this operation difficult if a duct, beam, platform, or other equipment is installed too close to the cabinet.

In an attic, access is already more demanding than in a basement.

We must therefore consider what will happen several years later if a technician has to:

• read an error code;
• check a connection;
• replace a relay;
• inspect the motor;
• work on the coil;
• perform HVAC maintenance;
• clean or check a drain.

A compact installation must remain serviceable.

The tools on top of the cabinet also tell the story of the job site

Several screwdrivers and tools are placed on the unit at the time of the photo.

This detail reminds us that installing a central furnace in an attic often requires several trades and successive operations: securing the cabinet, adapting the sheet metal, wiring, installing ducts, making connections, insulating, and sealing the joints.

We have to work in a much less comfortable position than in a large mechanical room.

In Roxton Falls, the framing elements are close to the unit, and the insulated ducts occupy a significant portion of the available space. The choice of the unit’s orientation therefore directly affects how easily all the connections can be properly completed.

An insulated transition to prevent heat loss in the attic

To the right of the unit, the photo shows a rectangular section connected to the furnace and wrapped in reflective insulation.

This insulation is particularly important when the ducts pass through a space that is not necessarily kept at the same temperature as the inside of the house.

In air conditioning, a duct carrying cold air can create condensation if it is poorly insulated. In heating, heat loss in the attic reduces the energy actually delivered to the rooms.

We therefore pay attention not only to the unit, but also to:

• for airtight joint seals;
• the continuity of the insulation;
• the absence of crushed sections;
• the transitions between ducts;
• the mechanical support for the ducts.

A system that is efficient on paper can lose a significant part of its advantage if heated or conditioned air passes through a poorly insulated network.

Airflow becomes critical with ducts installed in an attic

A duct network located beneath a roof often includes changes in direction and constraints imposed by the structure.

Static pressure therefore becomes an element that must be monitored closely.

Midea equips the EVOX G3 with its Computational Constant Airflow 2.0 technology. According to the manufacturer, the unit can adjust its fan operation according to the network’s resistance and maintain airflow under conditions of up to approximately 1.2 in. of external static pressure. The system also offers up to 60 airflow adjustment levels.

This is particularly useful when replacing equipment on an existing duct network.

But we insist on one point: the fan’s ability to compensate for resistance does not mean that an improperly sized duct can be ignored.

If a section is crushed, if the return air is insufficient, or if a transition creates excessive restriction, we must correct the problem.

Electric furnace and central heat pump: one system, multiple heat sources

The EVOX G3 indoor unit can accommodate an auxiliary electric heating kit.

Midea provides configurations of 10, 15, and up to 25 kW, with staging that can operate in multiple steps to further modulate the amount of electric heat used.

In a central heat pump installation, the electrical resistance heaters should not be considered independently of the outdoor unit.

The overall strategy is generally to use the heat pump for as long as its operation remains appropriate, then supplement it with the electrical elements when the building’s demand warrants it.

Proper sizing depends in particular on:

• the property’s heat loss;
• the heat pump’s low-temperature capacity;
• the electrical panel;
• the available wiring;
• the thermostat’s logic;
• the desired level of comfort.

The photo does not allow us to determine with certainty the capacity of the electrical element installed in this specific unit. We therefore do not arbitrarily assign a kilowatt rating to this project.

The performance of the EVOX G3 lineup varies depending on the installed combination

Midea documentation presents several EVOX G3 capacities ranging approximately from 18,000 to 54,000 BTU/h.

Depending on the indoor-outdoor pairing, the lineup can reach up to 19 SEER2, 12.5 EER2, 10.8 HSPF2, and a COP of up to 2.14 at 5 °F, or approximately -15 °C.

The manufacturer's table covers configurations including:

• 18,000 BTU;
• 24,000 BTU;
• 30,000 BTU;
• 36,000 BTU;
• 48,000 BTU;
• 54,000 BTU.

In our photo from Roxton Falls, the full model number is not sufficiently legible to confirm the exact tonnage unambiguously.

We never consider the physical size of the cabinet a reliable method for determining its capacity.

The difference between “installing in an attic” and designing an HVAC installation truly suited to the attic

A platform designed for heating in cold climates

Certain EVOX G3 Extreme Heat configurations are documented to continue operating down to -30 °C.

Midea also explains that its compressor technology is designed to maintain substantial heating capacity at low temperatures.

In the Roxton Falls area, this winter performance is obviously essential.

A central heat pump should not be selected solely based on its summer cooling performance. We must examine how it performs when the temperature drops well below freezing.

Central heating then becomes a combination of several elements: heat pump capacity, airflow, ductwork, building heat loss, and auxiliary heating.

R454B: a new generation of refrigerant

Midea uses R454B for the EVOX G3 lineup and indicates a global warming potential, or GWP, of 466. The documentation identifies R454B as a category refrigerant A2L.

This classification requires appropriate service practices.

For us, this notably concerns the methods used when making connections, checking for leaks, recovering the refrigerant, and carrying out future work on the system.

Homeowners do not need to master these procedures, but they should know that maintenance of an R454B system must be entrusted to technicians equipped and trained for this new generation of equipment.

In an attic, condensate drainage requires extra attention.

In cooling mode, the indoor coil produces condensation.

In an installation located above occupied spaces, any drainage failure can become much more problematic than simply having a little water on a concrete basement floor.

We must therefore carefully plan:

• the condensate pan;
• the main drain;
• the slope of the pipe;
• access for cleaning;
• the additional protections required by the configuration.

The photo from Roxton Falls focuses mainly on the control compartment and ductwork; it does not show enough of the drainage system for us to describe its exact configuration.

We prefer to clarify this rather than invent a detail that is not visible.

Filtration must also be sized according to airflow

For the EVOX G3 platform, Midea provides filtration options of 1, 2, and 4 inches, as well as compatibility with MERV 13 filters in the intended applications.

A high MERV rating can capture more particles, but it is only part of the equation.

We also check the filter surface area and its impact on static pressure. A highly restrictive filter installed on an undersized return can reduce airflow and increase the fan’s workload.

The filtration must therefore be selected based on the complete system.

Smart features come after mechanical commissioning

For compatible configurations, Midea also offers a communicating thermostat and features through its SmartHome app, including scheduling, comfort monitoring, and certain diagnostics.

These options may be appealing to the homeowner, but they never replace fundamental commissioning.

Before handing the system over to the customer, we must first ensure that:

1. the fan is operating properly;
2. the airflow settings match the ductwork;
3. the thermostat communicates properly with the system;
4. the auxiliary heating stages are configured correctly;
5. the electrical connections are secure;
6. the ducts are airtight and insulated;
7. the service panels can be closed and removed without difficulty.

A rebate cannot be determined solely from the name EVOX G3

When a homeowner compares a central heat pump, it is natural to take an interest in the financial assistance available.

However, the Midea documentation provided for this project describes a complete product range, not a single certified combination.

To confirm eligibility or the amount of financial assistance, it is necessary to know:

• the exact indoor unit model;
• the exact outdoor unit model;
• the certified combination;
• the recognized performance of this combination;
• the program conditions applicable on the installation date.

Therefore, we never calculate a rebate based solely on the words MIDEA EVOX G3.

Mistakes to avoid when installing an electric furnace in an attic

This Roxton Falls project particularly highlights several practical points:

• Do not select the equipment before verifying physical access to the attic.
• Do not place the service side against a roof truss or an inaccessible wall.
• Do not crush insulated ducts to gain a few inches.
• Do not leave leaky duct joints in an unconditioned space.
• Do not underestimate condensate drainage.
• Do not determine the auxiliary electrical capacity without checking the available power supply.
• Do not confuse the maximum performance of the product line with that of the installed combination.
• Do not forget that a technician must be able to open exactly the panel we see in the photo several years later.

A project highlighting the invisible side of AirGreen quality

This MIDEA EVOX G3 electric furnace installation in Roxton Falls is not interesting solely because the unit is lying horizontally in an attic.

What makes it representative of our work is everything the photo reveals behind the final result: technicians working in a very confined space, an open electronic panel, an insulated duct network, connections adapted to the structure, and service access designed around the framing.

Once the project is complete, the tools will be gone, the panel will be closed, and the homeowner will no longer see the circuit board or cable harnesses.

However, he will feel the effects of these details every day: consistent airflow, heating, cooling, and coordinated operation of the entire system.

At AirGreen, we apply this same approach to our HVAC installations in Montreal, Laval, Longueuil, on the North Shore and on the South Shore: the equipment must be adapted to the actual building, not simply installed because it physically fits in the space.

In Roxton Falls, the attic space imposed significant constraints. The horizontal, modular configuration of the MIDEA EVOX G3 allowed us to work with those constraints rather than against them, while preserving the access needed for commissioning and future service.