In Saint-Anicet, an EVOX G3 installed on the roof: a project where the support, snow, vibrations, and service access matter just as much as the BTUs
This MIDEA EVOX G3 central heat pump installation in Saint-Anicet immediately stands out because of its location. The outdoor unit is neither placed on the ground near the foundation nor mounted on wall brackets: it is installed directly on a flat roof, on a raised metal structure resting on two long bases that distribute the load across the roof.
For us at AirGreen, this type of project requires a different approach from a conventional residential installation. On a roof, we must consider the load, membrane protection, vibrations, air movement, snow accumulation, defrost water drainage, refrigerant line routing, and future access for HVAC maintenance simultaneously.
The jobsite photo shows this reality precisely. The Midea heat pump is held well above the roof surface by a four-legged support. These rest on two longitudinal bases that prevent the equipment's entire weight from being concentrated on four small points. To the right of the unit, we can also see the route of the refrigerant and electrical connections, guided toward the building along a support structure.
It is therefore not just a MIDEA EVOX G3 placed on a roof. It is a system whose outdoor environment has been designed for the actual conditions of a Quebec roof.
Why elevate a central heat pump on a flat roof
On a flat roof in Saint-Anicet, one of the most important challenges is snow.
An outdoor unit operating almost at membrane level could quickly find itself surrounded by significant accumulation after a few storms. On a roof, wind also creates snow movement and drifting patterns that differ from those observed at ground level.
By elevating the heat pump, we aim to preserve more space around the coil and beneath the unit.
This height also facilitates the management of water from defrost cycles. A central heat pump in heating mode must occasionally defrost its outdoor coil. The resulting water must be able to drain away without immediately creating a mass of ice directly beneath the condenser base.
The support visible in the photo therefore contributes to several objectives:
- keep the unit above the immediate roof level;
- reduce the risk of partial burial by snow;
- leave more space for defrost water;
- make access beneath and around the unit easier;
- maintain good clearance for airflow;
- make service work more practical.
The ideal height always depends on the exact roof configuration and the manufacturer's requirements. We therefore do not treat all rooftop installations identically.
A base designed to protect the roof and distribute loads more effectively
Perhaps the most interesting detail in the photo is found beneath the support's four feet.
Rather than placing each foot directly on the membrane, the installation uses two long bases beneath the metal structure. On a flat roof, this allows us to distribute the loads more effectively and avoid unnecessarily concentrating the weight in a few small areas.
This is particularly important when working with an existing roofing membrane. Supports, fasteners, protective materials, and service penetrations must be installed in a way that does not create damage that could later become a source of water infiltration.
The structure must also remain stable while the condenser is operating. The compressor and fan generate normal vibrations, and an improperly designed support could transmit more noise to the building structure.
In a rooftop project, our objective is therefore twofold: properly support the equipment while respecting the building envelope.
The EVOX G3's front air discharge is particularly important on a rooftop
The large round grille at the front of the condenser corresponds to the horizontal fan.
Midea uses a horizontal discharge design on the EVOX G3, combined with a vertical heat exchanger. According to the manufacturer's documentation, this architecture is intended to provide more uniform airflow across the heat exchanger and better efficiency as the outdoor temperature decreases.
In the photo, the front of the unit is largely unobstructed. This is exactly what we want to look for with this type of equipment.
A heat pump that discharges air horizontally should not be placed directly facing a nearby obstruction. On a rooftop, we must therefore consider the position of parapets, other mechanical equipment, and taller walls that could promote air recirculation.
Here, the selected location provides particularly open space in front of the fan.
The refrigerant line route is part of the work, even on a roof
To the right of the unit, we can see the path of the lines connecting the condenser to the indoor system.
On a roof, it is not enough to connect the lines and leave them resting freely on the membrane. They must be protected, supported, and organized in a way that limits movement, wear, and unnecessary contact points.
A good route also facilitates future service calls. If a technician has to return for a heat pump diagnosis, an inspection, or a repair, they must be able to easily follow the circuit without having to move improvised elements.
We therefore seek to maintain a clear path between the outdoor MIDEA unit and the point where it enters the building.
The roof environment also affects maintenance work
A heat pump located on a roof is generally less accessible than equipment installed next to a house.
This means that service access must be planned from the outset.
A technician must be able to:
- approach the equipment safely;
- open the service panels;
- access the refrigerant connections;
- take electrical measurements;
- inspect the heat exchanger;
- clean the unit when necessary;
- work without having to move the condenser.
That is precisely why we avoid positioning a unit in a corner that is too tight solely to gain a few more feet of available roof space.
The MIDEA EVOX G3 is designed for heating at very low temperatures
A rooftop installation like this would be much less appealing if the heat pump were intended only for air conditioning.
The MIDEA EVOX G3 is an Inverter central heat pump designed to operate year-round. Midea documentation states continuous operation down to -30 °C for Extreme Heat configurations. For the three-ton system used by Midea as a reference for the cited tests, the manufacturer also indicates up to 100% heating capacity at -25 °C, with a COP that can reach approximately 1.9 under these conditions.
Midea explains that its compressor technology uses an intermediate-temperature vapor injection during extreme cold conditions to increase the amount of compressed refrigerant and support heat production.
This feature is especially relevant in Saint-Anicet, where a heat pump must be able to operate during winter periods that are much more demanding than those in a temperate climate.
Several capacities are available in the EVOX G3 range
The name EVOX G3 does not refer to a single capacity.
The documentation presents a range of central systems covering approximately 18,000 to 54,000 BTU/h of nominal cooling capacity, with several combinations of indoor and outdoor units.
Among the combinations published by Midea, we find in particular:
- 18,000 BTU/h;
- 24,000 BTU/h;
- 30,000 BTU/h;
- 36,000 BTU/h;
- 48,000 BTU/h;
- 54,000 BTU/h.
Depending on the configuration, the range reaches up to 19 SEER2, 12.5 EER2, and 10.8 HSPF2.
However, the photograph from Saint-Anicet does not allow us to read the model number clearly enough to honestly assert the exact tonnage of this installation. We therefore prefer to present the range's performance and explain how it varies rather than arbitrarily assigning a capacity to the visible condenser.
An interesting example: the 30,000 BTU central configuration
To understand the importance of the exact combination, let's look at the 30,000 BTU configuration presented in the technical documentation.
Midea indicates a nominal capacity of 30,000 BTU/h in cooling, a nominal heating capacity of 33,000 BTU/h, an SEER2 of 17.2, an EER2 of 12.0, and an HSPF2 of 10.8 for this combination. At -15 °C, the technical data sheet still indicates approximately 33,200 BTU/h of heating with a COP of 1.97.
This detail is particularly interesting for homeowners who compare two systems based solely on the number of tons.
The nominal rating does not tell the whole story.
We must also consider the available capacity in cold weather, seasonal efficiency, duct system capacity, and the building's thermal profile.
A three-ton heat pump is not automatically the right solution just because the old one was
For a central replacement, one of the most common mistakes is to blindly copy the tonnage of the old system.
A property may have changed since the old equipment was installed:
- new windows;
- added insulation;
- finished basement;
- addition;
- new ducts;
- sealed-off duct sections;
- major changes in occupancy habits.
We therefore prefer to size the system according to current needs.
Oversizing does not automatically provide greater comfort. It can cause shorter cooling cycles and limit the time needed for proper dehumidification. Conversely, an undersized unit may lack capacity during the most demanding periods.
The indoor duct system remains crucial
Even if the photo of this project mainly shows the exterior, a central heat pump always operates as a system.
The quality of the indoor duct system has a direct impact on comfort.
A high-performance outdoor unit cannot fully compensate for:
- an undersized return air duct;
- undersized ducts;
- a highly restrictive duct system;
- poorly balanced dampers;
- an overly restrictive filter;
- poorly insulated ducts in certain areas.
This is precisely the part of the system where the EVOX G3 platform offers an interesting feature.
Beyond the rooftop outdoor unit: the EVOX G3 indoor unit and the real quality of the central system
The MIDEA EVOX G3 was designed as a modernization platform for a complete central system. The outdoor unit visible in Saint-Anicet is therefore only one element of an installation that also includes the air handler, duct system, filtration, controls and, potentially, auxiliary electric heating.
Computational Constant Airflow 2.0: adapting the fan to the duct system
Midea integrates a technology called Computational Constant Airflow 2.0 into the EVOX G3.
The documentation states that the system can adjust fan capacity to adapt to different duct and filtration conditions, with static pressure management of up to 1.2 in. of water column under the conditions presented by the manufacturer.
The airflow can also be customized across up to 60 levels, providing greater latitude during commissioning.
For us, this flexibility is useful when replacing an old central system.
But it should not become an excuse to ignore a poorly designed duct system. Advanced fan technology does not turn a severely undersized duct into a good duct.
A modular indoor unit for challenging mechanical rooms
The EVOX G3 system also uses a modular design called Block N Lock.
The documentation presents six installation configurations, including upflow, downflow, right horizontal, left horizontal and low-boy configurations.
This can help us in buildings where interior space is limited.
The mechanical rooms in Montréal, Laval, Longueuil, the North Shore and the South Shore present very different realities: old basements, low ceilings, existing ducts that are difficult to relocate, or spaces arranged around the mechanical equipment.
The modularity of the indoor unit can therefore limit certain modifications.
A width suited to several furnace replacements
Midea also presents the EVOX G3 as a solution designed to facilitate certain furnace replacements.
The announced indoor units have approximate widths of 14.5 to 21.5 inches, similar in size to several common central furnace formats.
This can make it possible to preserve part of the existing plenum geometry when the dimensions are compatible.
We must of course assess each project individually, because ducts, height, return air and metal transitions are never identical from one house to another.
Auxiliary heating up to 25 kW
A Quebec central heat pump is often paired with auxiliary electric heating.
For the EVOX G3, Midea provides three-stage auxiliary kits reaching 25 kW, with activation and adjustment based on temperature changes.
However, this component must be carefully sized.
We must check the electrical panel capacity, the property's heating needs and the system's control strategy. Automatically adding the largest available component is not a good design method.
485 communication, 24 V and retrofit possibilities
The EVOX G3 is compatible with several control strategies.
The documentation indicates compatibility with 485 communication as well as 24 V control systems, including third-party thermostats. Midea also specifies that the equipment can automatically identify the control mode being used.
Sub-1 GHz communication modules can also, in some configurations, reduce the need for a new communication wire between the indoor unit, heat pump and thermostat.
This flexibility can be particularly useful when replacing equipment in an already finished property, where running new cables would require opening up several surfaces.
R-454B: the next generation of refrigerant
The EVOX central system lineup in question uses R-454B refrigerant, classified as A2L.
Midea indicates a GWP of 466 for this refrigerant and states that it has adopted it for its new central system lineup.
For us, installers, this means that work methods, tools and commissioning procedures must be adapted to the refrigerant actually being used.
The refrigerant change is therefore not merely a line in a technical brochure.
MERV 13 filtration up to four inches
Midea also provides a filtration module compatible with 1-, 2- or 4-inch MERV 13 filters. The documentation indicates that this filtration is intended to capture more dust, pollen, particles, as well as some pet hair and dander, while helping keep the indoor coil cleaner.
However, we must always consider the filter's pressure drop.
Better filtration must be integrated into the system, not simply added without measuring its impact on airflow.
The mistakes this rooftop installation helps us avoid
This Saint-Anicet project is an excellent opportunity to highlight some common mistakes with central heat pumps installed on a roof:
- place the unit too close to the membrane and snow;
- concentrate all the weight on small support points;
- leave the refrigerant lines loose on the roof;
- point the fan toward an obstacle that is too close;
- neglect defrost water;
- place the condenser where no technician can easily service it;
- size the unit solely according to the old tonnage;
- forget that system performance also depends on the indoor unit and the ducts;
- announce the maximum values for the range as if they applied to all capacities.
A good HVAC installation consists precisely in anticipating these details before they become problems.
A central heat pump that must be considered as a complete system
In the photo, the most striking element remains the EVOX G3 condenser installed in the middle of this roof surrounded by trees.
But the actual performance of this installation depends on much more than this outdoor unit.
They depend on sizing, the duct network, airflow, the thermostat, filtration, the auxiliary heating element, the refrigerant line routing and the quality of commissioning.
In Saint-Anicet, the elevated mounting shown in the photo already addresses several constraints specific to the roof: snow, defrosting, accessibility and surface protection. MIDEA EVOX G3 technology complements this approach with a central Inverter platform designed to operate in very cold winter conditions.
At AirGreen, we apply this same logic to central heat pump projects in Montreal, Laval, Longueuil, the North Shore and the South Shore: we are not simply looking to install a machine. We aim to create an HVAC system that is consistent with the building, its duct network and Quebec's actual conditions.