Installation of a MIDEA EVOX G3 electric furnace in a horizontal position in an attic in Senneville

In Senneville, a MIDEA EVOX G3 installed horizontally where a traditional vertical furnace simply could not fit

This installation carried out by AirGreen in Senneville, in the western part of the Island of Montreal, perfectly illustrates why choosing a central electric furnace cannot be limited to comparing BTU capacities or efficiency ratings. Here, the main challenge was architectural: the indoor system had to be installed directly in a low-clearance attic, beneath a steeply sloped roof, amid existing wood framing and a network of insulated flexible ducts.

The job-site photograph clearly shows the reality encountered by our team. The rafters impose decreasing headroom, several structural elements cross the mechanical area, and the existing ducts already occupy a significant portion of the space. In this configuration, a conventional vertical installation would have been extremely difficult, if not impossible without major modifications.

We therefore integrated the MIDEA EVOX G3 in a horizontal position, on a support structure adapted to the attic. This orientation makes intelligent use of the available length beneath the roof slope while maintaining a logical airflow path and facilitating connection to the existing ductwork.

This is exactly the kind of job where the modular design of the EVOX G3 becomes much more than a feature on a technical data sheet.

A horizontal configuration that directly addresses the constraints of the home

In a conventional basement, a central unit is often installed upright. In this Senneville attic, that solution would have used up valuable headroom and placed certain parts of the equipment directly in the roof slope.

Midea’s documentation specifically provides for several orientations for the EVOX G3: upflow, downflow, right horizontal, left horizontal, as well as low “low-boy” configurations. The manufacturer presents six installation options and specifically emphasizes the value of the modular design for difficult-to-access areas such as attics and basements.

At our Senneville job site, the unit is positioned on its side, parallel to the structural framing. This arrangement preserves as much usable space around the unit as possible.

In the photo, we can also see several indications of the installation work in progress:

• the the MIDEA EVOX G3 electric furnace rests on a wooden support structure;
• the unit is installed horizontally beneath the rafters;
• a level is placed on the cabinet during the work;
• the existing insulated flexible ducts run around the equipment;
• a sheet-metal transition is prepared at one end;
• the service panels remain oriented toward an area where they can be accessed;
• the coil connections remain accessible despite the limited space.

In an attic installation, these details have a direct impact on future reliability.

Why leveling becomes particularly important in an attic

The visible level on the unit in the job-site photo is not an insignificant detail.

When the heat pump operates in cooling mode, warm, humid air from the home passes over a cold coil. Water naturally forms on this coil and must be collected by the condensate pan before being drained away.

A horizontal unit must therefore be positioned in accordance with the manufacturer's requirements and the planned drainage system.

In a basement, a drainage problem may sometimes be noticed quickly. In an attic, a water leak can remain hidden for some time and affect:

• the insulation;
• the ceiling below;
• the wood components;
• the interior finishes;
• the materials around the unit.

For this reason, during an HVAC installation in a Montreal attic, we pay particular attention to mechanical support, unit stability, and drainage.

A modern electric furnace integrated with a central heat pump

The term electric furnace is perfectly understood by Quebec homeowners, but the EVOX G3 is more specifically a central indoor air handler that can be combined with a heat pump.

In a complete configuration, the indoor unit provides, among other things:

• air circulation through the ductwork;
• heat exchange with the indoor coil;
• filtration;
• the distribution of heating and cooling;
• the integration of auxiliary electric heating when required.

The outdoor heat pump normally provides much of the heating. The furnace's electric heating elements can then supplement the demand when conditions require it.

For the EVOX G3 platform, Midea offers auxiliary heating modules in various capacities, including configurations of 10 kW, 15 kW, and up to 25 kW, with management that can be handled in several stages depending on the application.

At AirGreen, we do not automatically choose the largest available electrical component. The appropriate power depends in particular on the home’s heating load, the heat pump’s capacity, the electrical panel, and the desired operating strategy.

What is the exact capacity of this EVOX G3 in Senneville?

The rating plate is visible on the side of the photographed unit, but its angle and the image resolution do not allow us to confirm the complete indoor unit number with certainty.

We therefore prefer not to arbitrarily assign a capacity in BTU/h to this installation.

The range MIDEA EVOX G3 presented in the technical documentation covers several capacities. The listed combinations include units of 18,000, 24,000, 30,000, 36,000, 48,000 and 54,000 BTU/h.

This range of capacities is particularly important for central installations. A home in Senneville with large glazed areas, high ceilings, or an older building envelope does not necessarily have the same needs as a home of similar size built to more recent standards.

Sizing must therefore be based on the building and not solely on the capacity of the old unit.

Performance of up to 19 SEER2 depending on the selected combination

The technical specifications for the third-generation EVOX G3 indicate performance of up to 19 SEER2 for certain combinations. The published range also includes values of up to 12.5 EER2, 10.8 HSPF2 and a COP at 5 °F, or approximately -15 °C, that can reach 2,14, depending on the pair of units used.

It is important to clarify that these maximum values cannot automatically be attributed to all EVOX G3 units.

To determine the exact performance of an installation, we need to know:

1. the indoor unit model;
2. the outdoor heat pump model;
3. the corresponding certified combination.

It is this complete combination that determines the system’s official performance.

Heating down to -30 °C: a relevant feature for Senneville

In Greater Montreal, a central heat pump must be selected based on its winter performance and not solely on its summer efficiency.

Midea announces for the EVOX G3 platform a continuous operation down to -30 °C. The documentation also indicates, for the test conditions specified by the manufacturer, a heating capacity that can reach 100% around -25 °C, with a COP that can reach approximately 1,9 under these conditions.

This ability to continue producing heat at low temperatures is particularly interesting for a residence in Senneville, Montréal, Laval, Longueuil, on the North Shore or South Shore, where periods of extreme cold are part of normal operating conditions.

However, this does not mean that the heat pump must operate alone in every situation. Electric backup remains an essential component of many central Québec installations.

The goal is instead to have the heat pump operate efficiently before asking the electrical elements to provide a larger share of the heat.

This Senneville project shows why an HVAC installation in an attic requires much more than simply replacing a unit

Getting the equipment inside is already a challenge

Even before connecting a furnace in an attic, it must be possible to transport it there.

Access openings are often narrow, stairs may be absent, and the space between framing members can make moving a single-piece unit extremely difficult.

The EVOX G3 uses modular interlocking construction, designed to facilitate handling and assembly in confined spaces. Midea’s documentation specifically refers to transporting the unit through attics and to the difficulties encountered with larger traditional appliances.

For our teams, this type of design makes it possible to approach homes differently when access is one of the project’s main obstacles.

We must work with the framing, not against it

The Senneville photo shows a roof whose wooden members run directly through the area where the unit is installed.

In this kind of environment, we must choose the equipment’s location and orientation while taking the existing structure into account.

An HVAC installation obviously does not justify arbitrarily cutting a rafter or structural element simply to gain a few centimetres.

We are instead looking for a configuration that allows the unit to pass between and beneath the existing constraints, while maintaining the clearances required for servicing.

This is one of the reasons why a horizontal unit like the one installed here is particularly appropriate.

Insulated flexible ducts should remain as straight as possible

Several insulated black flexible ducts are clearly visible in the photograph.

These ducts distribute air throughout the different areas of the home, but their performance depends greatly on how they are installed.

A flexible duct that is excessively compressed, sharply bent, or sagging increases resistance to airflow. An installation can therefore have a perfectly sized unit but insufficient airflow at the grilles.

During our work, we therefore pay particular attention:

• to duct diameter;
• to bend radii;
• to their support;
• to their length;
• to connection tightness;
• to insulation;
• to network balancing.

The network must be considered an integral part of the system.

The EVOX G3 can adapt to different static pressures

The fan design is particularly interesting in a renovation context.

The technology Computational Constant Airflow 2.0 Midea’s system is designed to adjust fan power to maintain the desired airflow when network resistance varies. The manufacturer indicates control of up to 1.2 in. of water column static pressure in certain configurations.

The platform also offers up to 60 airflow adjustment levels, allowing the system’s operation to be fine-tuned according to the network and comfort requirements.

This possibility is particularly interesting when replacing an old furnace because much of the duct network often remains in place.

However, it does not replace good design.

If a duct is much too small or if return air is insufficient, we must identify the restriction rather than asking the motor to compensate indefinitely.

MERV 13 filtration available with several filter thicknesses

The EVOX G3 platform also includes a filtration module compatible with 1-, 2-, or 4-inch MERV 13, depending on the configuration selected. Midea indicates that this filtration helps capture more dust, pollen, and particles, as well as pet hair and dander.

In a home with a central system, filtration must nevertheless be selected carefully.

A more restrictive filter can increase static pressure. We must therefore look at the system as a whole: filter, return air, ductwork, fan, and required airflow.

R454B and the new generation of MIDEA central systems

The EVOX G3 presented in Midea documentation uses R454B refrigerant, classified as A2L. The manufacturer indicates a global warming potential for this refrigerant of 466.

The use of A2L refrigerants changes certain installation and service practices. Our technicians must work with the tools, methods, and procedures appropriate for the refrigerant specified by the manufacturer.

This is an increasingly important consideration when replacing older central systems in Greater Montreal.

Future accessibility is part of the installation

A furnace installed in an attic can operate for years. At some point, however, it will need to be inspected, maintained, or repaired.

On this Senneville project, we therefore had to think not only about how to install the new MIDEA EVOX G3, but also to how a technician will be able to service it later.

We particularly aim to maintain reasonable access:

• to the service panels;
• to the blower motor;
• to the coil;
• to the electric heating;
• to the filter;
• to the refrigerant connections;
• to the drainage system;
• to the electrical controls.

An extremely compact installation that blocks access to the equipment can create significant costs during future HVAC maintenance.

The controls offer several options during a renovation

Another advantage of the EVOX G3 is its control architecture.

Midea documentation indicates compatibility with communications 485 as well as with certain conventional thermostat configurations 24 V. The platform also provides various communication options between the heat pump, indoor unit, and controls.

This flexibility can be particularly useful in an existing home where running new cables between the attic, thermostat, and outdoor unit would be complex.

The final choice must, however, always be made according to the equipment actually installed and the requirements of its wiring diagram.

Mistakes to avoid when installing an electric furnace in an attic

Our experience with projects in Montréal, Laval, Longueuil, North Shore, and South Shore shows us that certain mistakes occur frequently in central-system installations in tight spaces.

Choose the capacity solely based on the old furnace

An old furnace may itself have been oversized. Copying its BTU rating is therefore not a true load calculation.

Neglect mechanical support

A horizontal unit must rest on a stable, suitable structure. Vibration, equipment weight, and service access must be considered from the outset of the installation.

Reduce the ducts excessively to facilitate connections

An overly restrictive transition can increase static pressure and reduce airflow.

Forget about future maintenance

An installation that works but has no panels that can be properly removed is poor planning.

Underestimate drainage

In an attic, condensate management is particularly critical because a leak can directly affect the ceilings of finished rooms.

Oversize the auxiliary electric heating

The EVOX G3 can receive up to 25 kW of auxiliary heating depending on the configuration, but the maximum available is not automatically the best choice.

The electrical panel and the home's actual needs must be verified before selecting the components.

Subsidies: verify the exact combination before announcing an amount

For a central heat pump, eligibility for financial assistance should never be determined solely from the commercial name “EVOX G3.”

The range includes several indoor and outdoor units. Midea's technical table also lists different model pairings and different capacities.

For a Quebec project, we must verify the exact number of the outdoor unit and the indoor unit, then compare this combination with the criteria and applicable lists for the program in effect at the time of installation.

Since the complete nameplate number cannot be read with certainty in the photograph from Senneville, we are not providing a precise subsidy amount for this project.

This is an important precaution to avoid confusing two different capacities within the same product family.

An installation where the best solution was horizontal, modular and adapted to the existing structure

This project in Senneville clearly shows what distinguishes a standard central installation from an installation requiring genuine adaptation to the building.

We were faced with an attic with:

• a sloped roof;
• a dense wooden frame;
• limited height;
• an existing duct network;
• restricted-access areas;
• a need to keep the equipment accessible for years to come.

The MIDEA EVOX G3 electric furnace allowed us to work with these constraints precisely because of its modular architecture and horizontal installation options.

The photo summarizes the project better than a view of a unit installed in a large, empty mechanical room: here, every orientation, clearance and connection must be carefully considered.

At AirGreen, this is the part of the work that particularly interests us. A professional HVAC installation is not about forcing a house to adapt to a machine. Instead, we seek to select and configure the equipment so that it works properly with the reality of the home.

To Senneville, as in our installations in central heat pumps and electric furnaces in Montreal, Laval, Longueuil, on the North Shore and on the South Shore, the result depends just as much on this mechanical integration as on the performance figures listed on the technical data sheet.