At Saint-Robert, a rooftop installation where stability, clearance, and future maintenance made all the difference
At Saint-Robert, we installed a FUJITSU AIRSTAGE ORION XLTH wall-mounted heat pump in a configuration that requires much more rigorous planning than a conventional ground-level installation. As shown in the project photo, the outdoor unit is installed on a flat gravel roof above the building, in an environment where several technical elements are already present: ventilation outlets, ducts, existing equipment, and rooftop structures.
For this type of project, our work at AirGreen does not simply involve finding an open space and placing the condenser there. On a roof, every decision must take into account support stability, membrane protection, drainage, airflow around the unit, snow accumulation, vibrations, and access for HVAC maintenance.
The photo shows a particularly important detail: the FUJITSU outdoor unit is installed on a raised metal support, itself positioned on load-distribution elements. This approach keeps the unit above the gravel level and reduces the risks associated with water, snow, or accumulation around the condenser.
This is exactly the kind of detail that distinguishes an installation designed to operate properly for many years from one that was simply completed quickly.
Why Install a Wall-Mounted Heat Pump on a Flat Roof
In some buildings, particularly urban, commercial, or semi-commercial properties, the roof becomes the most logical location for the outdoor unit.
There can be many reasons:
- lack of available ground space;
- need to keep the façades clear;
- architectural constraints;
- proximity to neighbours;
- presence of balconies or walkways;
- desire to keep the equipment out of sight;
- more practical refrigerant line route to the indoor unit.
At Saint-Robert, the building’s layout made rooftop installation particularly appropriate.
The roof provided enough space to position the condenser at a safe distance from immediate obstacles, but its location still had to be carefully analyzed in relation to vents, parapet walls, and other existing equipment.
The FUJITSU ORION XLTH: a series designed for heating in cold climates
The FUJITSU AIRSTAGE ORION XLTH series presented in the technical documentation is a single-zone range intended for wall-mounted installations. It includes 9,000, 12,000, 15,000, 18,000, and 24,000 BTU/h versions in nominal cooling capacity.
One of the most relevant features for Québec is its heating operating range.
Fujitsu indicates that this series can operate down to -26 °C, making it particularly well suited to residential and commercial needs in areas such as Saint-Robert, Montréal, Laval, Longueuil, the North Shore, and the South Shore.
The series also uses R-32 refrigerant, an Inverter compressor, a base pan heater for cold climates, and built-in Wi-Fi connectivity.
An installation on an elevated support: an essential choice for a rooftop
In the photo, the outdoor unit is not placed directly on the membrane or directly on the gravel.
It is mounted on an elevated metal structure.
This decision addresses several requirements.
First, it is important to prevent a heat pump from resting directly on a surface that can retain moisture, accumulate ice, or shift slightly as the seasons change.
Next, the clearance beneath the unit provides:
- better airflow;
- better drainage of the water produced during defrosting;
- better protection against snow accumulation;
- more convenient access to the connections;
- a reduced risk of direct contact with roofing materials.
On a flat roof, the support is therefore an integral part of the HVAC system.
Load distribution on the roof must not be improvised
A condenser may seem compact, but its weight remains significant.
Depending on the capacity of the ORION XLTH series, the technical data sheet indicates an outdoor unit weight of approximately 39 kg (86 lb) for the 9,000, 12,000, and 15,000 BTU models, and approximately 53 kg (117 lb) for the 18,000 and 24,000 BTU models.
In addition to this:
the metal support, dynamic vibrations, snow, and stresses related to wind.
That is why we avoid unnecessarily concentrating the load on a small area of the roof.
In the photo, longitudinal elements can be seen beneath the support, helping distribute the load over a larger surface area.
For a rooftop heat pump installation, this approach is particularly important to avoid excessive pressure points on the roof.
The height of the unit becomes even more important in winter
On a flat roof, snow accumulation can be much greater than at ground level in certain areas.
Wind can create irregular snowdrifts around parapets, chimneys, or other equipment.
An outdoor unit installed too low can therefore become partially obstructed.
The FUJITSU ORION XLTH is designed to operate in heating mode down to -26 °C, but this capability never eliminates the need for a physical installation properly adapted to the climate.
The heat pump must be able to breathe.
Even the best equipment will lose efficiency if its coils or air intake areas are surrounded by snow or ice.
The base pan heater is particularly relevant for this type of project
Fujitsu documentation specifies that the ORION XLTH series has a base pan heater designed for extremely cold climate regions.
This feature is particularly valuable for a rooftop installation.
When the heat pump operates in heating mode, frost naturally forms on the outdoor heat exchanger. The unit periodically performs a defrost cycle to melt this buildup.
The water produced must then be able to drain away.
On a roof, poor management of this water can lead to:
- ice sheets;
- accumulation beneath the unit;
- progressive obstruction;
- reduced clearance;
- maintenance difficulties.
By raising the unit, we create more space for this drainage.
What this Saint-Robert project reveals about a well-designed rooftop HVAC installation
Positioning in relation to existing vents
The photo shows several ventilation outlets and pieces of equipment on the roof.
This detail is important.
When an outdoor heat pump unit is installed near air outlets, it must not directly draw in undesirable exhaust air or interfere with the operation of existing systems.
We must therefore examine:
the direction of vent discharge, the distance between equipment, natural airflow, and required clearances.
The location shown in the photo allows the condenser to retain a relatively open space in front of its coil.
The orientation of the condenser affects airflow
An outdoor heat pump moves a significant amount of air.
On a roof, natural wind can be stronger than at ground level. Depending on the building configuration, it can also create areas of turbulence.
We therefore seek to position the unit so that:
- avoid direct obstructions in front of the coil;
- minimize recirculation;
- keep an adequate distance from parapets;
- maintain access to service panels;
- limit exposure to unfavorable air currents.
The FUJITSU ORION XLTH also offers a low-noise outdoor mode, according to the manufacturer’s documentation.
Performance that varies according to the model’s exact capacity
The ORION XLTH series covers several sizes.
According to the technical specification sheet, the nominal cooling capacity is:
9,000, 12,000, 14,500, 18,000, and 22,000 BTU/h, depending on the model.
The nominal heating capacities are, respectively:
12,000, 16,000, 18,000, 21,600, and 25,200 BTU/h.
These differences must be taken into account during sizing.
We do not choose a heat pump simply based on the exterior size available on the roof. The building’s heating requirements remain the priority.
The energy efficiency of the ORION XLTH range
The Fujitsu specification sheet indicates HSPF2 values of:
- 33,1 for the 9,000 BTU capacity;
- 30,5 for the 12,000 BTU capacity;
- 27,5 for the 15,000 BTU capacity;
- 25,5 for the 18,000 BTU capacity;
- 24,0 for the 24,000 BTU capacity.
The models in the range shown in the documentation are also identified with their corresponding ENERGY STAR ratings.
For homeowners who want to reduce their energy consumption, this data is relevant, but it tells only part of the story.
Actual performance also depends on:
sizing, insulation, set temperatures, maintenance, building airtightness, and especially installation quality.
Particularly impressive heating performance at low temperatures
Fujitsu documentation also provides maximum heating percentages at different outdoor temperatures.
At -26 °C, the indicated values are:
- 127% for the 9,000 BTU model;
- 102% for the 12,000 BTU model;
- 109% for the 15,000 BTU model;
- 106% for the 18,000 BTU model;
- 80% for the 24,000 BTU model.
This data is important for a customer who wants to use their wall-mounted heat pump as the primary heating source for much of the winter.
They also help explain why two models bearing the same brand can behave differently at very low temperatures.
Inverter technology contributes to comfort
The FUJITSU range uses Inverter technology.
Unlike a system that operates only in full-capacity on-off mode, the Inverter modulates power to adapt operation to actual demand.
This can help to:
- stabilize the indoor temperature;
- reduce abrupt fluctuations;
- improve comfort;
- limit short cycles;
- optimize consumption according to conditions.
In a well-insulated building, this modulation becomes particularly beneficial during periods when heating or cooling demand is moderate.
R-32: an important feature of this series
The FUJITSU ORION XLTH uses R-32.
In its documentation, Fujitsu indicates a global warming potential of 675 for R-32, compared with 2,088 for R-410A, representing an announced reduction of 68% in GWP.
For our installations, this also means using procedures suited to this refrigerant.
The choice of refrigerant is therefore not merely a detail listed on a technical data sheet; it has practical consequences for the tools, handling, and installation methods.
Piping dimensions vary by model
Another essential detail concerns the refrigerant piping.
The technical data sheet specifies:
- 9,000 BTU: 1/4 in. liquid and 3/8 in. gas;
- 12,000 BTU: 1/4 in. liquid and 3/8 in. gas;
- 15,000 BTU: 1/4 in. liquid and 1/2 in. gas;
- 18,000 BTU: 3/8 in. liquid and 5/8 in. gas;
- 24,000 BTU: 3/8 in. liquid and 5/8 in. gas.
This information is crucial when a heat pump is installed on a roof, because the route between the indoor and outdoor units may be longer than in a conventional wall-to-wall installation.
Piping length suited to complex configurations
The series offers some flexibility in this regard.
According to Fujitsu:
- the 9,000 and 12,000 BTU models accept up to 25 m (82 ft);
- the 15,000 BTU model up to 30 m (98 ft);
- the 18,000 and 24,000 BTU models up to 50 m (164 ft).
On some projects in Montreal, Laval, or Longueuil, this flexibility can make the difference between a clean installation and a configuration in which the outdoor unit would have to be placed in a much less desirable location.
The electrical supply must also match the model
The series models operate at 208 to 230 V, 60 Hz, single-phase.
The technical data sheet specifies a 15 A circuit breaker for the 9,000 and 12,000 BTU models, and a 20 A circuit breaker for the 15,000, 18,000, and 24,000 BTU capacities.
This detail is important during a replacement.
An old electrical supply is not automatically compatible with the new appliance.
Before installation, we must therefore check the circuit, conductor gauge, protection, and requirements specific to the selected model.
Errors to avoid when installing on a roof
A project like Saint-Robert highlights several common errors we seek to prevent:
- Placing the unit directly on the membrane or gravel.
- Undersizing the condenser support.
- Installing the machine too low in relation to snow accumulation.
- Placing the unit too close to a parapet or vent.
- Creating an area where discharged air can be recirculated.
- Forgetting about the drainage of defrost water.
- Concentrating the entire load on a small area of the roof.
- Positioning service panels against an obstruction.
- Neglecting the future maintenance route.
- Reusing existing piping without checking its diameter and condition.
These mistakes may seem minor at the time of installation, but they can cause significant problems after several seasons.
Access for future maintenance was incorporated from the design stage
On a flat roof, HVAC maintenance must be planned from the outset.
A technician may eventually need access to the outdoor coil, connections, electrical panels, and control components.
The photo shows that the unit is installed in an open area, with enough clearance to work around the appliance.
That is an important advantage.
An extremely high-performance system becomes much less appealing if part of the installation must be dismantled simply to perform routine maintenance.
This Saint-Robert project clearly summarizes our approach at AirGreen
This FUJITSU AIRSTAGE ORION XLTH wall-mounted heat pump installation in Saint-Robert is a good example of a project where success depended as much on the support and location as on the heat pump itself.
The roof already contained several pieces of equipment and ventilation components. We therefore had to find a sufficiently clear area, distribute the load properly, and raise the condenser to account for water, snow, and future maintenance.
At AirGreen, we apply this same logic to our installations in Montreal, Laval, Longueuil, the North Shore, and the South Shore.
We never treat the outdoor unit as a simple appliance to place somewhere.
We analyze its entire environment: airflow, structure, snow levels, drainage, accessibility, piping, electrical supply, and system behavior during severe cold.
The FUJITSU ORION XLTH offers features particularly well suited to our climate: heating operation down to -26 °C, Inverter technology, R-32 refrigerant, a base pan heater, high energy efficiency, and piping options that simplify more complex installations.
But as always in HVAC, the advertised performance of an excellent machine only reaches its full potential when supported by a rigorous installation.
In Saint-Robert, that is precisely what we sought to accomplish: a properly sized FUJITSU wall-mounted heat pump installed on a stable, accessible rooftop support suited to the realities of Quebec’s climate.