A rooftop installation in Montreal where the structure, clearance, and membrane protection become just as important as the heat pump
This MIDEA EVOX G3 central heat pump installation carried out by AirGreen in the Mercier–Hochelaga-Maisonneuve, Montreal borough presents a very different challenge from a conventional ground-level installation. Here, the outdoor unit is installed on a flat roof, in front of a masonry wall, with a configuration specifically designed to keep the unit elevated while distributing its weight and protecting the roof surface.
The project photo clearly shows several interesting elements. The MIDEA condenser is placed on a metal structure, which is itself supported by long pieces of wood resting on white protective pads. This keeps the unit well above the roof surface. Nearby, we can still see the commissioning tools, refrigerant hoses, and a cylinder used during the technical work. We are therefore looking at a photograph taken in the middle of the project, before the work area was finally tidied up.
This configuration says a lot about our work. When a central heat pump has to be installed on a rooftop in Montreal, it is not enough to find an empty space and place the condenser there. We must consider the weight, wind, snow accumulation, roof drainage, membrane, vibrations, service access, refrigerant line lengths, and fan clearance simultaneously.
The MIDEA EVOX G3 is particularly well suited to this context thanks to its horizontal discharge design and Inverter technology. The range covers capacities from 18,000 to 54,000 BTU/h and reaches, depending on the match, up to 19 SEER2, 12.5 EER2, and 10.8 HSPF2.
However, the exact capacity of the unit installed on this project cannot be confirmed from the photograph alone. At AirGreen, we avoid arbitrarily assigning a capacity based solely on the cabinet size. The correct information always comes from the nameplate and the match between the outdoor unit and the indoor equipment.
Why install a central rooftop heat pump in Mercier–Hochelaga-Maisonneuve
In many Montreal properties, particularly in urban neighbourhoods such as Mercier–Hochelaga-Maisonneuve, ground-level space is valuable.
Yards can be narrow. Side passages must remain clear. Facades may be close to a property line. A balcony, alley, or circulation area may prevent the installation of a large condenser in a conventional location.
The roof then becomes an interesting solution, but one that is technically more demanding.
A heat pump installed on a roof must be positioned so that it:
- remain sufficiently elevated above the snow;
- allow air to circulate freely;
- provide access to service panels;
- distribute its weight properly;
- avoid damaging the roof membrane;
- maintain space for drainage;
- limit vibration transmission;
- withstand stresses related to wind;
- maintain a refrigerant line route that complies with the manufacturer's limits.
In this installation, the height of the support is particularly noticeable. This is not a small support measuring a few inches: the condenser is installed on a substantial structure that keeps it far from the roof surface.
The long bases beneath the support are not merely an aesthetic detail.
In the photo, the metal structure does not rest directly on the roof. It is supported by two long wooden pieces, themselves separated from the surface by protective elements.
This approach helps, in particular, to distribute the load over a larger surface area rather than concentrating the system's entire weight on a few small points.
On a flat roof, this issue is important.
A support that is too narrow can create concentrated loads on the roofing. It can also complicate water drainage or sink into certain materials over time.
The exact choice of support always depends on the building's structure and site conditions. A successful outdoor installation must meet both the heat pump's requirements and those of the roof.
The elevation helps prepare the heat pump for Montreal's winter.
The MIDEA EVOX G3 is designed to operate in heating mode at very low temperatures.
The manufacturer's documentation indicates continuous operation down to -30 °C. It also reports performance reaching 100% of heating capacity at -25 °C, with a COP of up to 1.9 under the stated test conditions.
Installing a heat pump capable of operating down to -30 °C very close to a roof where snow can accumulate would be contradictory.
An efficient machine in a cold climate needs an environment that allows it to continue breathing.
In Montreal, a snowstorm accompanied by wind can create significant accumulation near a wall or around an obstacle. The height of the support provides more clearance before the snow approaches the air intake and the lower part of the condenser.
The defrost water must also be able to drain away
In heating mode, the outdoor heat exchanger may accumulate frost. The heat pump must periodically perform a defrost cycle.
This means that a certain amount of water may be released around and beneath the unit.
On a roof, this water must be able to drain away properly without forming a mass of ice directly beneath the condenser or blocking a roof drain.
We must therefore consider the installation's geometry even before the machine starts up.
A good HVAC installation in Montreal takes into account what the unit will do in January, not just what it looks like on a sunny autumn day.
A completely unobstructed fan face
The MIDEA EVOX G3 shown in the photo has a front-mounted fan with horizontal airflow.
In this configuration, the area in front of the fan remains completely open. No nearby parapet, panel, grille, or equipment directly blocks the air discharge.
This configuration is important to prevent unnecessary recirculation.
If the air discharged by the heat pump immediately hits an obstacle and returns toward the heat exchanger, the system may operate under less favorable conditions. In cooling mode, it may draw in warmer air again; in heating mode, colder air.
The condenser's placement must therefore always be assessed with its clearances, not solely its physical dimensions.
The tools visible in the photo tell the story of the commissioning phase
This photo is particularly interesting because it shows not only the final result, but also part of the technical work.
To the right of the installation, several hoses, a cylinder, and construction equipment can be seen. This corresponds to a phase in which our technicians carry out the connections, checks, and necessary operations before declaring the system ready to operate.
A central heat pump should never be considered complete as soon as it has simply been mounted on its support.
Commissioning includes, among other things, verifying the refrigerant connections, checking for leaks, preparing the circuit according to the applicable procedures, making the electrical connections, adjusting the system, and conducting operational tests.
With a generation operating on R-454B, the rigor of these procedures is particularly important.
MIDEA EVOX G3: an Inverter central system designed for replacements, cold climates, and existing duct networks
R-454B: the new generation of refrigerant used by EVOX G3
MIDEA states that this range uses R-454B, an A2L-category refrigerant whose global warming potential, as stated in the documentation, is 466.
For the homeowner, this change is relatively inconspicuous: the system continues to heat and cool the house through the central ductwork.
For the installer, however, it requires methods and equipment suited to the type of refrigerant used.
This includes handling the refrigeration circuit, leak checks, compatible service tools, and following the procedures intended for this generation of equipment.
A range of performance ratings, not a single SEER2 figure
When a customer asks us, “What SEER2 rating does the EVOX G3 have?”, the correct answer depends on the model.
MIDEA's technical table shows several combinations:
- 18,000 BTU/h: 19 SEER2, 12.5 EER2 and 10.1 HSPF2;
- 24,000 BTU/h: 18.6 SEER2, 12 EER2 and 10 HSPF2;
- 30,000 BTU/h in cooling / 33,000 BTU/h in heating: 17.2 SEER2, 12 EER2 and 10.8 HSPF2;
- 36,000 BTU/h: 17.7 SEER2, 12 EER2 and 10 HSPF2;
- 48,000 BTU/h: 17.5 SEER2, 12 EER2 and 9.5 HSPF2;
- 54,000 BTU/h in cooling / 55,000 BTU/h in heating: 17.5 SEER2, 12 EER2 and 9.5 HSPF2.
This data corresponds to the combinations listed by MIDEA in its performance table.
That is why we never choose a central heat pump simply based on the maximum efficiency advertised in a promotion.
Actual sizing remains the priority.
Performance at -15 °C provides a better understanding of winter operation
The same table also indicates heating capacities and COPs at approximately -15 °C for several models.
For example, some combinations still provide tens of thousands of BTU/h under these conditions, with COPs close to or above 2 depending on capacity.
This data is much more useful for a Mercier–Hochelaga-Maisonneuve property than a nominal capacity figure used without context.
Choosing a central heat pump must take the building's actual heating load at low temperatures into account.
The EVOX G3 air handler is designed for renovations
The indoor part of the system, which does not appear in this exterior photograph, is another interesting feature of the range.
MIDEA designed the EVOX G3 to make replacing existing central systems easier. The indoor unit can recognize different voltages, and the range includes widths comparable to those of many residential furnaces, generally between 14.5 and 21.5 inches depending on capacity.
In Montreal properties, this kind of detail can make a big difference.
Basement mechanical rooms are not always spacious. A new unit may need to fit between existing ductwork, a water heater, pipes, and a ceiling structure.
A modular design for fitting into difficult spaces
The EVOX G3 also uses a modular design called Block N Lock.
MIDEA offers up to six installation orientations for the indoor unit: vertical, horizontal, and low-height configurations. The modules can be separated to simplify transport through stairs, basements, and other constrained spaces.
This type of modularity is particularly useful in Montreal, where some homes have basement access points that are much narrower than the mechanical space itself.
The duct system must be able to deliver the required airflow
A central heat pump never operates independently of its ductwork.
Even an excellent unit can deliver disappointing results if the duct system is too restrictive, return air is insufficient, or the filter creates excessive resistance.
MIDEA integrates Computational Constant Airflow 2.0 technology into this platform. It is designed to maintain airflow by adjusting fan speed and power according to the pressure encountered in the system.
The documentation indicates operating capacity of up to approximately 1.2 in. of water column static pressure under certain conditions and airflow adjustment across up to 60 levels.
This function does not make a poor duct system acceptable, but it allows for much finer system adjustment.
MERV 13 filtration: yes, but with airflow verification
The EVOX G3 offers a filtration option compatible with 1-, 2-, or 4-inch MERV 13 filters. The documentation specifically mentions improved capture of dust, pollen, particles, and pet hair.
Nevertheless, we must choose filtration with static pressure in mind.
A highly effective filter that is too restrictive for a given installation can reduce airflow. That is why we always assess the behavior of the system as a whole.
Auxiliary heating up to 25 kW
For extreme cold conditions or certain heating scenarios, MIDEA offers multi-stage auxiliary heating kits capable of reaching 25 kW. Their activation can be adjusted according to requirements and temperature fluctuations.
In a properly configured installation, the auxiliary heat supplements the heat pump rather than unnecessarily replacing it.
The strategy depends on the sizing, the property's electrical capacity, the thermostat, and the home's heating and cooling needs.
Advanced communication and 24 V compatibility
The EVOX G3 also uses communication that can operate on Sub-1 GHz between certain components, which can in some cases eliminate the need for a new full communication cable.
The range is also compatible with 485 or 24 V modes and with certain configurations using a third-party thermostat.
For a replacement in an existing property, this flexibility can simplify installation when access between the indoor and outdoor units is difficult.
SmartHome control and diagnostics
With the MIDEA communicating thermostat and the SmartHome app, the system can offer, among other things:
- schedule programming;
- comfort adjustment;
- energy consumption monitoring;
- diagnostic functions;
- remote software updates;
- temperature, airflow, and humidity adjustments according to the configuration.
These capabilities are described in the EVOX G3 documentation.
For an Inverter system, control quality is important because the goal is to modulate the equipment rather than cause unnecessary starts and stops.
Why the roof completely changes the way maintenance must be considered
A ground-mounted heat pump is relatively easy to access. A rooftop installation requires more planning for the future.
We must think about the technicians who will need to return to:
- clean the heat exchanger;
- measure the electrical parameters;
- check the refrigeration circuit;
- access the panels;
- perform diagnostics;
- work on the fan or components;
- inspect the supports.
The support visible in this installation keeps the unit elevated and accessible from its sides. The front panel and side panels can therefore be reached without enclosing the unit in a structure.
A mistake to avoid: placing the condenser directly on the roof
Placing an outdoor unit directly on a membrane is rarely a desirable solution.
This can complicate drainage, transmit more vibration, facilitate debris buildup around the unit, and create pressure points on the roofing membrane.
The photograph of this project, on the other hand, shows an installation where we created a true elevated, structured base.
The heat pump is physically separated from the roof, and the long bases distribute the loads more evenly.
Grants and eligibility: the exact model remains decisive
The MIDEA brochure presents this range as exceeding certain ENERGY STAR Most Efficient requirements.
For Quebec, however, this alone is not enough to automatically determine the applicable financial assistance.
Eligibility for a program such as LogisVert must be verified based on the actual combination of indoor and outdoor models, the AHRI reference or the reference recognized by the program, as well as the rules in effect on the installation date.
We therefore avoid associating a specific amount with the expression “EVOX G3” alone.
For a client comparing several quotes, we recommend asking for:
- the exact outdoor unit model;
- the exact indoor unit model;
- the certified capacity;
- the AHRI reference when applicable;
- the rebate amount calculated for this specific combination.
This Mercier–Hochelaga-Maisonneuve project shows another side of HVAC work
On this installation, the main challenge was not simply connecting a central heat pump.
We needed to install a MIDEA EVOX G3 on a Montreal flat roof, maintain sufficient clearance above the surface, protect the roofing, distribute the load, preserve a large clear area in front of the fan and allow technicians to access the machine in the future.
The photograph also shows something clients rarely see: the work phase, with service equipment still present around the unit. This is when the installation becomes a true functioning HVAC system rather than simply a condenser placed on a support.
At AirGreen, we carry out central heat pump installations in Montreal, Laval, Longueuil, on the North Shore and the South Shore, but each building has its own constraints.
In Mercier–Hochelaga-Maisonneuve, urban density, existing architecture and flat roofs are regularly part of the equation. A solution that suits a suburban home with a large lot cannot always be copied directly onto a Montreal building.
It is precisely on these projects that planning becomes essential.
The MIDEA EVOX G3 offers a very interesting platform thanks to its operation down to -30 °C, Inverter technology, efficiency ratings of up to 19 SEER2, R-454B refrigerant, modular indoor design and advanced airflow management. But the machine represents only part of the result.
The final quality also depends on what is underneath it, around it and behind it.
On this Mercier–Hochelaga-Maisonneuve project, this notably meant a robust elevated support, an installation compatible with the roof and clear access for commissioning work and future maintenance.
It is this combination of equipment, structure, refrigeration, electrical systems, ductwork and actual building conditions that transforms a central heat pump that performs well on paper into an installation suited to a Montreal home.