Installation of a MIDEA EVOX G3 electric furnace in Henryville, Montérégie: central replacement in a tight mechanical space

An installation in which accessibility, refrigeration piping, and connection to the ductwork were just as important as the furnace itself

In Henryville, in the Montérégie, we installed a MIDEA EVOX G3 electric furnace in an especially compact mechanical space. The photograph taken after our work clearly shows the reality of the job site: the unit occupies almost the entire width available between the wall and the adjacent mechanical system, while a large insulated refrigeration pipe descends directly in front of the unit.

This configuration might seem relatively simple because the furnace is installed vertically. In practice, it requires several very precise decisions. The system must be connected to the existing ductwork, the refrigeration lines must be routed without compromising their bend radius, the panels must remain accessible, the necessary service clearances must be respected, and a compact installation must not be turned into a maintenance problem in the years ahead.

The MIDEA EVOX G3 belongs to the family of ducted inverter central systems developed by MIDEA. In an existing home such as the one in Henryville, the value of this platform lies as much in its performance as in its ability to adapt to an already-built HVAC infrastructure.

What the photograph reveals about this installation in Henryville

Several details are immediately visible.

The unit is installed vertically, directly beneath its connection to the duct network. On the left, the wall leaves very little space. On the right, other mechanical components also limit access. On the front, we can see:

• the manufacturer’s nameplate;
• the R-454B / A2L marking;
• the electrical diagrams attached to the panel;
• the AirGreen label;
• the separation between the unit’s modular sections;
• a large insulated pipe descending in front of the furnace.

The latter is particularly interesting. In a narrow mechanical room, the refrigeration piping route must be designed so as not to block the panels that we may eventually need to remove for diagnosis or repair.

An installation can be very compact while remaining functional. It simply must not be compact at the expense of HVAC maintenance.

R-454B and A2L classification directly visible on the equipment

The photographed nameplate shows the marking associated with R-454B as well as the A2L classification.

MIDEA documentation confirms that R-454B was selected for this lineup and indicates a global warming potential, or GWP, of 466.

This detail is important for several reasons.

Refrigerant is not merely a data point used to compare equipment generations. It also influences the methods used during:

• refrigerant connections;
• leak testing;
• system evacuation;
• commissioning;
• future diagnostics;
• any work requiring the circuit to be opened.

At AirGreen, we must therefore consider the refrigerant generation from the outset of project planning.

Substantial refrigerant piping in a very limited passage

The large black pipe visible in the foreground is protected by insulation. In a central heat pump system, insulating a refrigerant line is essential to limit unwanted heat exchange and, depending on the operating mode, condensation forming on its surface.

But insulation alone is not enough.

Its routing must also follow service logic.

On this installation, the available space required us to bring the line closer to the front of the system. Our job was therefore to find a route that maintained:

• sufficient mechanical support;
• protected piping;
• a reasonable bend radius;
• access to the components;
• a layout that a technician will be able to understand easily several years from now.

This is exactly the type of detail that distinguishes a planned central heat pump installation from one where the lines were simply placed in the first available space.

Why the MIDEA EVOX G3’s format makes replacements easier

The photographed space in Henryville clearly shows why the furnace’s physical dimensions must be reviewed before ordering the equipment.

MIDEA offers different cabinet widths depending on the capacities in the lineup, approximately from 14.5 to 21.5 inches. The documentation also describes a multivoltage architecture for the indoor unit, allowing certain applications at 115 V or 208/230 V.

In a large new mechanical room, a few inches of difference sometimes matter little.

In a space like this, they can determine everything.

A unit that is slightly too wide may require:

• modifying a wall;
• rebuilding the return-air system;
• a new large transition;
• moving other equipment;
• insufficient service access.

That is why we measure the available space and ductwork before considering a capacity or brand definitively selected.

The EVOX G3's modularity is not only useful for attics

MIDEA documentation presents a modular design with several installation options: upflow, downflow, right horizontal, left horizontal, and certain low-boy configurations. The manufacturer also emphasizes how easy the unit is to handle when it must be moved into difficult-to-access spaces.

Even in a vertical configuration like Henryville's, this architecture is useful.

A furnace often has to pass through:

• a basement door;
• a staircase;
• a narrow hallway;
• existing ductwork;
• pipes that cannot be moved.

Being able to work with a unit designed around modules facilitates certain renovation projects where a large conventional cabinet would be much more difficult to transport.

The existing ductwork must be considered a component of the new system

When installing a new furnace, it is tempting to take the existing system for granted: it worked with the old unit, so it should work with the new one.

This reasoning is incomplete.

Older equipment may have used:

• a different airflow;
• a different blower;
• a different capacity;
• a different filter;
• different supply-air temperatures.

The new central heat pump must therefore be configured according to the system to which it is actually connected.

Excessive restriction can notably cause:

• low airflow;
• more noise;
• temperature differences between rooms;
• increased motor workload;
• less stable coil performance.

Computational Constant Airflow 2.0: a useful tool during a modernization

The MIDEA EVOX G3 incorporates Computational Constant Airflow 2.0 technology.

According to the documentation provided, this function allows the blower to adjust its power and speed when the system resistance varies. MIDEA specifies conditions of up to 1.2 in. of external static pressure.

The system also offers up to 60 airflow volume adjustment levels.

This adjustment range gives us more flexibility during commissioning.

However, it does not replace a properly sized duct network. If the return air is genuinely insufficient or a section of ductwork presents a significant restriction, the right solution remains to identify and correct that constraint when necessary.

Why “more CFM” does not automatically mean more comfort

When a new central system is installed, some homeowners think it is enough to set the blower to maximum.

In reality, excessive airflow can also cause problems:

• more noise at the registers;
• a draft-like sensation;
• less comfortable air distribution;
• less effective dehumidification in cooling mode.

Conversely, airflow that is too low can affect heat transfer and coil operation.

We therefore seek a setting that matches the installed combination, ductwork, and actual static pressure.

Electric furnace does not mean that resistive heating operates continuously

The term electric furnace can be confusing when referring to a central system with a heat pump.

The indoor MIDEA EVOX G3 contributes to several functions:

• air circulation;
• heating provided by the heat pump;
• air conditioning;
• indoor heat exchange;
• auxiliary electric heating when necessary.

For much of the winter, the heat pump can therefore provide the primary heating. The electric elements are not necessarily the first heat source every time the thermostat calls for heat.

MIDEA documentation provides multi-stage auxiliary heating kits, with configurations of up to 25 kW depending on the model and application.

Why we do not automatically choose 25 kW

The maximum available option is not necessarily the right choice.

Before selecting the auxiliary electric heater, we must verify:

1. the building’s heat loss;
2. the heat pump’s heating capacity;
3. the electrical panel capacity;
4. the available conductors;
5. the required circuit breakers;
6. the desired system behavior during cold-weather peaks.

A properly sized auxiliary heater makes more sense than an oversized heating element that unnecessarily strains the electrical system.

Winter performance, efficiency, and maintenance: the details that matter once the system is installed

A platform designed to operate down to -30 °C

The climate of Henryville and the Montérégie region makes it important to consider winter performance, not just cooling data.

MIDEA states that the EVOX G3 heat pump operates continuously down to approximately -30 °C. The manufacturer also claims up to 100% heating capacity at -25 °C under certain conditions, with a COP of approximately 1.9.

The brochure also specifies that some climate-performance data were obtained from tests of a three-ton system.

This distinction is essential: the best performance in a range should not automatically be attributed to all capacities.

Several capacities are hidden behind the EVOX G3 name.

The documentation provided includes several systems:

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

The indoor and outdoor unit references also vary by capacity.

In the photo of this installation in Henryville, the nameplate is visible, but the full model number is not legible enough to confirm the exact tonnage unambiguously.

We therefore prefer not to assign a capacity simply by estimating the cabinet dimensions.

This is also practical advice for a homeowner comparing two quotes: “MIDEA EVOX G3” is not a complete specification.

You need to obtain the indoor and outdoor model numbers.

Different efficiencies depending on the matched system

Depending on the configuration, the range reaches 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 table on page 11 of the brochure nevertheless clearly shows that performance varies by capacity. It includes, among other things:

• 18,000 BTU/h: 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 BTU/h: 17.5 SEER2;
• 54,000 BTU/h: 17.5 SEER2.

The right way to compare central heat pumps is therefore to compare the actual matched systems, not the maximum values advertised for an entire series.

The electrical diagrams visible on the front panel are not there by accident.

The photo shows several electrical diagrams mounted directly on the front panel of the unit.

They are an important resource for technicians.

During troubleshooting, we must be able to quickly identify:

• the terminals;
• the control logic;
• the inputs and outputs;
• the auxiliary heating;
• the safety protections;
• the unit configuration.

Leaving this information intact and accessible makes future service calls easier.

This is also part of our philosophy: an installation should remain understandable after the team that carried it out has left.

485 control or 24 V thermostat depending on the application

The EVOX G3 offers several control options.

MIDEA indicates compatibility with 485 communication, as well as with certain 24 V thermostat configurations, including various scenarios combining EVOX or third-party components.

For a replacement in an existing home, this flexibility can be very useful.

Thermostat wiring may run through finished walls that have been in place for several decades. Being able to work with an appropriate 24 V architecture can sometimes avoid additional work.

Compatibility must nevertheless be validated based on the specific thermostat and the required functions.

The filter must remain replaceable despite the tight space

The EVOX G3 range can be configured with different filtration solutions. MIDEA mentions 1-, 2-, and 4-inch filters, including certain MERV 13 configurations.

In a compact installation like the one in Henryville, we must consider two constraints simultaneously:

air resistance, because a more restrictive filter increases static pressure;

accessibility, because a filter media must be removable regularly.

A high-performance filter installed in a location that is nearly impossible to reach may simply not be replaced often enough.

The easiest mistake to make in a space like this: forgetting the next technician

The photograph shows equipment positioned extremely close to its mechanical surroundings.

In this context, we must always ask ourselves how a future service call will be carried out.

The technician may need access to:

• the blower;
• electronic boards;
• the coil;
• heating elements;
• the drain;
• refrigerant connections.

A few centimeters gained today by placing a conduit in front of a panel can lead to much more work later.

This consideration is part of the installation from day one.

Errors We Aim to Avoid During a Central System Replacement in Henryville

Estimating capacity solely based on the old furnace

The old equipment was not necessarily properly sized. A modernization is an opportunity to reassess the system.

Ordering the furnace before measuring all clearances

Cabinet width is only one of several dimensions: depth, piping, and panels must also be taken into account.

Treating refrigerant lines as a finishing detail

Their route must be planned before the unit is permanently positioned.

Confusing the product line’s maximum performance with that of the installed system

The figures vary according to tonnage.

Installing an auxiliary heater that is too large “just in case”

Electrical and thermal sizing must determine the capacity.

Increasing filtration without checking static pressure

A more restrictive filter must be compatible with the system.

Rebates: why the AHRI number remains decisive

The MIDEA brochure establishes the characteristics of the product line, but it cannot by itself confirm whether the installation shown in the photographs qualifies for a Quebec financial incentive.

Several EVOX G3 pairings are possible.

To properly verify an incentive such as LogisVert, we must work with the exact indoor-unit and outdoor-heat-pump numbers, along with the corresponding AHRI certificate and the criteria applicable at the time of the project.

In other words, a series name or a nominal BTU rating is not enough to promise a rebate.

A compact installation that aptly sums up our approach at AirGreen

This MIDEA EVOX G3 electric furnace installation in Henryville shows that a successful modernization does not require a huge mechanical room. Rather, it requires a proper understanding of the limitations of the available space.

Here, the new unit had to be integrated into the existing system while managing a refrigerant line very close to the façade, limited clearances, and the need to keep the equipment accessible.

We therefore treated the furnace, ductwork, piping, controls, and service access as a single project.

This is the same approach we apply in our work on electric furnaces, central heat pumps, and HVAC installations throughout Greater Montreal and the areas we serve in Montérégie, including Montreal, Laval, Longueuil, the North Shore, and the South Shore.

A central installation is not limited to the day the equipment starts up. It must also remain properly adjusted, accessible, and serviceable throughout all the seasons that follow.