A rooftop installation in La Présentation where the support, clearances, and technical access mattered just as much as the heat pump
At La Présentation, we installed a Fujitsu AIRSTAGE Orion XLTH wall-mounted heat pump in a particularly interesting configuration: the outdoor unit was installed on a flat roof already occupied by several mechanical systems. This type of project requires more than simply choosing a location. We must consider the stability of the support, the clearances around the heat exchanger, water drainage during defrost cycles, the presence of other equipment, and how our technicians will be able to access the system several years after installation.
The photo taken on site shows this reality precisely. The Fujitsu unit is elevated on a metal structure, which is positioned above long pieces of wood used to create a distributed base across the roof. Nearby, several other outdoor units and various ventilation components are already present. For us, this configuration immediately turns a wall-mounted heat pump project into genuine HVAC coordination work.
The Fujitsu AIRSTAGE Orion XLTH lineup used for this type of project belongs to Fujitsu’s single-zone H series. The manufacturer offers several capacities in this family, with nominal cooling capacities of 9,000, 12,000, 14,500, 18,000, and 22,000 BTU/h, corresponding to different heating capacities. The series is designed to operate in heating mode down to -26 °C, a particularly relevant criterion for Quebec.
Why install a wall-mounted heat pump on a roof?
In some properties, a ground-level installation is the simplest solution. In others, it is simply not the best option.
A rooftop can be chosen when the exterior walls offer little space, when the unit must be protected from passersby, when a building already has a mechanical area intended for equipment, or when the refrigerant line routing is more logical from the roof.
At La Présentation, the photo clearly shows that the building already has a mechanical area on the roof. Several outdoor units are grouped in this area, allowing the technical equipment to remain in one place rather than having the units spread around the property.
For the owner, this can also provide a more discreet result at ground level.
However, a rooftop installation imposes additional constraints. An outdoor unit placed there is more exposed to wind, sunlight, snow, and water. It must therefore be installed on a properly designed and sufficiently stable base.
An intentionally elevated outdoor unit
One of the most visible details of our installation is the elevated metal support.
We avoid placing a heat pump directly on a membrane or on a roof covering. An installation that is too low can create several problems: snow accumulation, ice around the lower pan, partial obstruction of the heat exchanger, and difficult access for maintenance.
In heating mode, an outdoor heat pump naturally accumulates frost on its heat exchanger. The system periodically runs a defrost cycle to melt this frost. The resulting water must be able to drain freely.
Fujitsu’s documentation specifically states that the Orion XLTH has a base pan heater designed for extremely cold climate regions.
This component helps the system operate in difficult winter conditions, but it never replaces a proper installation. Even with a unit designed for cold climates, sufficient space must be left beneath the unit so that water and ice can be managed properly.
The long wooden bases visible on the roof serve a very specific purpose
In the photo, long pieces of wood can be seen beneath the metal structure.
This detail is interesting because it shows part of the work that often goes unnoticed once the project is complete. On a roof, we seek to avoid overly concentrated points of support.
An elongated base helps distribute loads more evenly and creates a stable platform for the mechanical support.
Nevertheless, the type of roof, its structure, the materials present, and local conditions must be taken into account. We do not automatically use the same method for every building.
An installation on a membrane roof, a built-up roof, or a rigid surface is not handled in exactly the same way.
Clearances are even more important when there are several outdoor units.
The photo shows that this Fujitsu heat pump is not alone on the roof.
Several other units are located nearby. In this context, we must pay close attention to airflow.
An outdoor unit draws air through its heat exchanger and discharges it using its fan. If two units are installed too close to each other, or if a wall, parapet, or duct blocks the airflow, the unit may recirculate some of its own air.
This can reduce efficiency, particularly when several units are operating simultaneously.
For this type of project, we therefore consider:
- the distances between the various units;
- the direction of the air discharge;
- the height of the parapets;
- the ventilation outlets;
- the areas where snow may accumulate;
- the access corridors required for maintenance;
- the routing of the refrigerant and electrical lines.
A proper rooftop heat pump installation must work correctly today while remaining accessible five or ten years from now.
Fujitsu Orion XLTH: designed to provide heating in cold weather
The main reason to choose an XLTH heat pump in Quebec remains its heating capacity as the temperature drops.
Fujitsu announces an operating range for heating down to -26 °C for the Orion XLTH series. The documentation also shows very high heating capacities at low temperatures, depending on the model.
For example, the technical specifications indicate that the 12K model can provide up to 124% of its rated capacity at -21 °C and approximately 102% at -26 °C, under the reference conditions used by the manufacturer.
For us, these figures are much more relevant than the simple number of BTUs displayed on a label.
A homeowner in Montréal, Laval, Longueuil, on the North Shore, the South Shore, or in La Présentation is not buying a heat pump only for days when the temperature is +10 °C. If they plan to use the unit as a significant heating source, they need to look at how the system performs at -15 °C, -20 °C, and even lower.
A range available in several capacities
The Orion XLTH series includes several capacities to suit different spaces.
According to the Fujitsu specification sheet, the rated cooling capacities are:
- 9,000 BTU/h;
- 12,000 BTU/h;
- 14,500 BTU/h;
- 18,000 BTU/h;
- 22,000 BTU/h.
For heating, the corresponding nominal capacities range from 12,000 to 25,200 BTU/h, depending on the model.
The exact capacity installed for a project must always be determined based on the building. We avoid choosing a heat pump solely from a quick square-footage estimate.
Why an oversized unit is not necessarily better
A larger unit may seem reassuring, but heat pump sizing must remain balanced.
An excessively large unit may reach the requested temperature very quickly, reduce its operation, or cycle more frequently depending on conditions. This can impair dehumidification in summer and comfort stability.
Conversely, an undersized unit may run continuously without reaching the desired temperature during very cold periods.
We assess factors including insulation, windows, the building’s exposure, ceiling height, air distribution, and heat loss.
This sizing process allows the Fujitsu Orion XLTH to be used within the range where its Inverter technology offers the greatest benefits.
Inverter technology: adapting output to actual demand
The Orion XLTH series uses an Inverter compressor.
Instead of operating only at 100% and then stopping, the system can modulate its capacity according to demand.
The technical data sheet clearly illustrates this modulation. The 12K model, for example, has a cooling range of approximately 3,100 to 16,000 BTU/h and a heating range of approximately 3,500 to 23,600 BTU/h.
This modulation capability becomes particularly useful during the shoulder seasons.
An October morning may require relatively little heating. In January, the same building may need several times more energy. The heat pump can adjust its operation instead of constantly producing its maximum capacity.
R-32: the refrigerant used by this new generation of Fujitsu systems
The Fujitsu AIRSTAGE Orion XLTH series operates with R-32.
In its documentation, Fujitsu compares the global warming potential of R-32 with that of R-410A. The manufacturer indicates a GWP of 675 for R-32 versus 2,088 in the comparison presented for R-410A, representing an announced reduction of approximately 68 %.
For the installer, this evolution also requires adapting work methods and equipment.
The tools, commissioning procedures, refrigerant handling, and inspections must be compatible with the installed system.
We never consider this part a minor detail. A high-quality heat pump can have performance issues if the refrigerant piping, vacuum, or connections have not been completed properly.
Pipe sizes vary by capacity
The Fujitsu technical data sheet shows a significant difference between the models.
The specified pipe sizes include:
- 9K and 12K: 1/4 in. liquid and 3/8 in. gas;
- 15K : 1/4 in. liquid and 1/2 in. gas;
- 18K and 24K: 3/8 in. liquid and 5/8 in. gas.
This information becomes crucial when a customer replaces an older heat pump.
It is not enough for the two units to have similar capacities for the existing lines to be retained automatically.
We must check the diameter, condition of the copper, length, elevation difference, and the manufacturer's specifications.
Long piping distances can make a rooftop project easier
A rooftop installation often involves a longer piping route than a back-to-back installation on an exterior wall.
The Orion XLTH lineup offers considerable flexibility in this regard.
The 9K and 12K models allow up to approximately 25 meters or 82 feet of piping. The 15K model can reach approximately 30 meters, while the 18K and 24K models can accommodate up to approximately 50 meters or 164 feet, subject to the manufacturer's requirements.
These limits make certain projects easier when the indoor unit is installed several floors below the outdoor unit.
However, the maximum vertical elevation difference, which varies by capacity, must also be considered.
A compact unit that is useful on an already occupied roof
The roof visible in the photo has several pieces of equipment.
In this context, the outdoor unit’s footprint is far from insignificant.
Fujitsu presents the Orion XLTH as a compact outdoor unit. The various models use a relatively narrow chassis, making them easier to install in mechanical areas where every square foot counts.
That does not mean we need to place the units as close together as possible.
On the contrary, we use the compact format to provide better clearances and make it easier for technicians to move around the equipment.
This project in La Présentation illustrates why a good HVAC installation is never limited to the heat pump brand.
Future maintenance must be planned from day one
A heat pump must be serviceable.
On a roof, this aspect becomes even more important because access is already more complex than at ground level.
A technician must be able to:
- access the service panels;
- check the electrical connections;
- inspect the piping;
- clean the heat exchanger;
- clear away debris buildup;
- take pressure and temperature measurements;
- work without dismantling neighboring equipment.
The photo of this project specifically shows that circulation space has been preserved around the unit.
For us, this is an installation-quality factor, just like leveling the equipment or keeping the connections clean.
Do not overlook vibrations on a roof
Vibrations can sometimes be more noticeable when a unit is installed on a roof.
A heat pump can be very quiet in itself but transmit vibrations to the building structure if its mounting system is poorly designed.
Fujitsu specifies outdoor sound levels for this range of approximately 46 to 50 dB(A), depending on capacity. Indoor units can reach as low as 23 dB(A) on certain models in quiet mode.
The mounting system therefore plays an important role in preserving this acoustic advantage.
We must limit mechanical transmission to the building as much as possible.
High efficiency that varies by capacity
Fujitsu documentation indicates HSPF2 ratings ranging from 33.1 for the 9K model to 24.0 for the 24K model, including 30.5 for the 12K and 25.5 for the 18K.
These values reveal another important reality: not all capacities in the same product family have exactly the same efficiency.
When comparing several heat pumps for a customer, we therefore look at the exact combination of units rather than just the commercial name.
Energy Star and rebates: verify the exact system
The Fujitsu specification sheet lists Energy Star ratings, including the categories identified by the manufacturer for cold-climate systems.
However, eligibility for a heat pump rebate in Quebec must always be verified using the exact model and the program criteria in effect at the time of purchase and installation.
We avoid promising a price solely because a heat pump belongs to a particular product line.
The same product name may encompass several capacities, multiple model numbers, and sometimes different approved combinations.
Mistakes We Avoid on Rooftop Installations
For a heat pump like this Fujitsu Orion XLTH installed in La Présentation, several mistakes can reduce the quality of the project.
Placing the equipment directly on the roof. This can affect drainage, stability, and maintenance.
Installing the unit too low. A buildup of snow or ice can become problematic in winter.
Forgetting the clearance from other units. In an already occupied mechanical area, airflow must be carefully assessed.
Creating a support structure that is too narrow or unstable. The heat pump must remain perfectly stable despite wind and vibrations.
Blocking service access. A compact installation must not become inaccessible.
Choosing the BTU capacity based solely on floor area. The building’s actual heat load must be taken into account.
Automatically reusing the existing piping. The diameters vary depending on the Orion XLTH model.
An AirGreen approach adapted to real-world projects
Our installations in Montreal, Laval, Longueuil, on the North Shore, the South Shore, and in municipalities such as La Présentation regularly place us in front of very different configurations.
A heat pump can be installed on a brick wall, on a balcony, on a foundation, in a narrow yard, or, as in this case, in a rooftop mechanical area.
Our responsibility remains the same: understand the building before deciding how to install the equipment.
This Fujitsu AIRSTAGE Orion XLTH in La Présentation installation is a good example of a project where the support structure, clearances, and planning for future servicing play a role just as important as the heat pump’s technical performance.
The owner thus gets a system designed to provide heating and cooling, with Inverter technology, R-32 refrigerant, and performance intended for Quebec’s winter temperatures—but above all, an installation adapted to the building’s actual environment.