Installation of a Fujitsu AIRSTAGE Altair 500 wall-mounted heat pump on a flat roof in Sainte-Anne-de-Sabrevois

A rooftop installation where the quality of the support, the routing of the lines, and technical access become just as important as the heat pump itself

In Sainte-Anne-de-Sabrevois, we completed an installation of a Fujitsu AIRSTAGE Altair 500 wall-mounted heat pump in a configuration that requires a very different approach from a conventional outdoor installation at ground level. Here, the outdoor unit was positioned directly on a flat roof covered with gravel, on a raised support designed to keep the machine stable, accessible, and clear of the roof surface.

The photo of this installation immediately highlights several important elements. The Fujitsu outdoor unit is installed on a raised metal structure, which is itself supported by crossbars that distribute the load across the roof. The insulated refrigerant lines leave the unit toward the back, following a clear route that allows them to connect to the rest of the system without obstructing the condenser’s front. The area in front of the large outdoor fan remains completely clear, which is essential for ensuring adequate airflow.

For a project like this, it is not enough to place a heat pump on the roof and connect two pipes. You need to consider the structure, vibrations, drainage, natural snow removal, clearances, the routing of the lines, and future access for HVAC service.

This is precisely what makes this Fujitsu Altair 500 installation in Sainte-Anne-de-Sabrevois particularly interesting.

Why install a heat pump’s outdoor unit on a flat roof?

In some properties, the available ground space is limited, poorly located, or unsuitable for a clean installation.

A heat pump placed near an entrance, patio, narrow passage, or property line can become obtrusive. Installing it on the roof makes it possible to move the equipment to a less visible area while maintaining good airflow.

In the photographed case, the elevated location provides several practical advantages:

• the condenser's face remains largely unobstructed;
• the machine is kept away from everyday pathways;
• the risk of accidental impacts against the unit is reduced;
• the piping can be routed from the roof to the building;
• outdoor noise is kept away from the immediate area used by occupants;
• the installation remains accessible to a technician with the appropriate access equipment.

However, this approach requires more preparation than an installation on a concrete pad at ground level.

An elevated support to avoid placing the machine directly on the roof

One of the most important details visible in this project is the elevated metal support.

We avoid placing an outdoor unit directly on a membrane or gravel surface without a suitable base. A heat pump produces vibrations, is affected by wind, and must remain perfectly stable throughout the seasons.

The support keeps the outdoor unit above the roof surface. Beneath it, crossbars distribute the load over a wider area. This arrangement also facilitates water drainage and preserves space beneath the unit.

On a Quebec roof, this additional height becomes particularly useful in winter. Even if a roof is cleared of snow or relatively exposed to wind, localized accumulations can form. An unit installed too low could then become partially surrounded by snow.

For a heat pump used for heating, clearance around the outdoor heat exchanger remains essential.

The weight must be distributed without compromising the roof

A rooftop heat pump installation should never be improvised.

An outdoor unit can weigh several dozen kilograms. Depending on the capacity of the Altair 500, Fujitsu lists outdoor unit weights ranging from approximately 23 kg to 53 kg, or roughly 51 to 117 lb. The dimensions and weight vary considerably among the models in the range.

This is precisely why we must consider how this load is transferred to the roof.

In the Sainte-Anne-de-Sabrevois project, the unit is not simply placed on four small feet directly on the gravel. The structure forms a wider base and creates a stable supporting surface.

This precaution also helps reduce equipment movement and unwanted vibration transmission.

An accessible piping route

The refrigerant lines visible at the back of the unit are protected by black insulation and directed toward the rest of the building along a sufficiently flexible route.

In a rooftop installation, we pay particular attention to ensuring that the lines are not crushed, unnecessarily tensioned, or left directly in a position that could create a wear point.

The routing must also comply with the maximum length permitted by the manufacturer.

For the Fujitsu Altair 500 series, these limits depend on capacity. The 9,000 and 12,000 BTU models allow up to 20 m, or 66 ft, the 18,000 and 24,000 BTU models up to 30 m, or 98 ft, while the 30,000 and 36,000 BTU versions can reach 50 m, or 164 ft.

This flexibility is an obvious advantage when an outdoor unit must be installed on a roof, since the distance to the indoor unit may be greater than in a back-to-back installation on an exterior wall.

The piping dimensions must match the installed capacity exactly.

The Altair 500 is available in several capacities, and the line diameters are not the same throughout the series.

According to the Fujitsu technical data sheet:

9,000 and 12,000 BTU: 1/4 in. liquid line and 3/8 in. gas line.

18,000 and 24,000 BTU: 1/4 in. liquid line and 1/2 in. gas line.

30,000 and 36,000 BTU: 3/8 in. liquid line and 5/8 in. gas line.

This distinction is essential when a homeowner replaces an old heat pump.

We cannot conclude that existing piping is compatible simply because it already reaches the roof. Its diameter, condition, insulation, and routing must be verified.

This is one of the most common mistakes in replacement projects: trying to adapt the new equipment to the old lines instead of checking the manufacturer’s actual requirements.

Fujitsu AIRSTAGE Altair 500: an R-32 wall-mounted heat pump designed to combine modulation, efficiency, and installation flexibility

A range from 9,000 to 36,000 BTU

The Fujitsu AIRSTAGE Altair 500 belongs to Fujitsu’s single-zone H series.

The lineup includes the 09KPAS1, 12KPAS1, 18KPAS1, 24KPAS1, 30KPAS1, and 36KPAS1 models.

The nominal cooling capacities listed by Fujitsu are respectively 9,000, 12,000, 18,000, 22,000, 30,000, and 33,000 BTU/h. In heating, the nominal values increase to 10,000, 14,000, 18,000, 24,000, 30,000, and 34,000 BTU/h.

Because the exact capacity of the photographed unit is not sufficiently legible on its nameplate, we will not invent it. This is important: in a real installation, the precise model number must always be confirmed on the unit's label or in the technical documentation before communicating data specific to a given capacity.

This rigor helps prevent confusion between the electrical requirements, piping dimensions, and performance of two models that nevertheless look visually similar.

Inverter technology: capacity that adjusts rather than operating only at full power

The Altair 500 series uses an Inverter compressor.

This technology allows the system to modulate its output according to demand instead of operating solely in an on-off cycle at full capacity.

In a home, this can provide several benefits: more stable temperatures, less abrupt starts, and better power adjustment when demand is low.

The modulation range varies by capacity. For example, Fujitsu specifies a cooling range of 3,100 to 13,600 BTU/h and a heating range of 2,700 to 17,000 BTU/h for the 12,000 BTU model. The 18,000 BTU model, meanwhile, modulates from 4,000 to 20,000 BTU/h in cooling and from 4,150 to 24,000 BTU/h in heating.

This modulation explains why proper sizing remains so important. A correctly selected unit can take full advantage of its operating range.

High efficiency ratings depending on capacity

The Fujitsu technical data sheet lists TRÈS2 values ranging from 21.0 to 26.0 depending on the model.

The 9,000 BTU model reaches 26.0, the 12,000 BTU model 24.0, the 18,000 BTU model 22.0, the 24,000 BTU model 21.5, the 30,000 BTU model 22.0, and the 36,000 BTU model 21.0.

The CPSC2 Region V values, which are important for evaluating seasonal heating efficiency in a cold climate, range from 7.7 to 8.3 depending on capacity.

For homeowners comparing several wall-mounted heat pumps in Sainte-Anne-de-Sabrevois, Montréal, Laval, Longueuil, on the North Shore, or on the South Shore, these figures are useful indicators, but they should never be considered separately from the building’s context.

A heat pump that is highly efficient on paper but improperly sized or installed will not necessarily deliver the expected results.

R-32: a refrigerant with a lower GWP than R-410A

The Altair 500 series operates with R-32 refrigerant.

Fujitsu indicates a global warming potential of 675 for R-32 compared with 2088 for R-410A, representing an announced 68% reduction in GWP. The manufacturer also states that R-32 systems use less refrigerant while maintaining the desired heating performance.

In the photo of our installation, the marking R32 is also clearly visible on the front of the outdoor unit.

For a new installation, this refrigerant change also affects our technicians’ work methods, the tools they use, and commissioning best practices.

Heating down to -15 °C according to the official operating range

Fujitsu indicates an operating range for heating from -15 °C to 24 °C for the entire Altair 500 lineup.

This information must be interpreted correctly.

A wall-mounted heat pump can provide a significant portion of the heating during the winter, but homeowners should understand their unit’s limitations and the building’s heating strategy when the outdoor temperature falls below the stated operating range.

In Sainte-Anne-de-Sabrevois, winter temperatures can occasionally drop below -15 °C. When selecting a system, we therefore consider the role of the heat pump in the home’s overall heating system rather than looking only at its cooling performance.

Up to 19 dB(A) indoors for certain capacities

Noise is also an important consideration when a heat pump is installed in a bedroom, living room, or office.

The 9,000 and 12,000 BTU Altair 500 models can operate as quietly as 19 dB(A) in quiet mode indoors. The 18,000 BTU model is rated at 26 dB(A), while the higher-capacity models naturally require greater airflow.

The indoor unit has six fan speeds plus automatic mode, allowing the airflow to be adjusted to comfort needs.

Indoor components designed to better withstand corrosion

Fujitsu documentation mentions ProCore copper coils on the indoor unit, along with a Hydro Fin heat exchanger designed to improve corrosion resistance.

The manufacturer also offers a backlit wireless remote control and various control options, including Wi-Fi interfaces, wired controllers, and certain BACnet or Modbus integrations.

For a simple residential installation, none of these options is necessary. Their presence nevertheless demonstrates the flexibility of the AIRSTAGE platform.

The electrical installation varies according to the heat pump’s capacity

As with the refrigerant lines, the electrical requirements are not uniform across the entire range.

The 9,000, 12,000, and 18,000 BTU models are specified with a 15 A circuit breaker. The 24,000 BTU model requires 20 A, while the 30,000 and 36,000 BTU versions are specified at 30 A.

The power supply for the entire series is 208 to 230 V, 60 Hz, single-phase.

Before installation, we therefore check the electrical panel, the designated circuit, and the exact model to be installed.

The particular challenge of an exposed outdoor unit on a roof

A heat pump installed on the ground often benefits from some natural protection provided by the building. On a roof, it may be more exposed to wind, sunlight, and precipitation.

We must therefore place even greater importance on its stability.

The photo of this installation in Sainte-Anne-de-Sabrevois shows ample clearance around the heat pump. This is exactly what we are looking for: no immediate obstruction in front of the fan and enough space around the outdoor unit to prevent its heat exchange from being restricted.

Clearance also serves the technician. A unit placed in an inaccessible corner can become very difficult to service a few years later.

Protect the membrane and plan for the next service

On a flat roof, a successful installation must be planned with two different time horizons in mind.

The first is immediate: installing the unit correctly.

The second is long-term: being able to service the heat pump and the roof without creating problems.

The base must allow access underneath and around the equipment. The lines must remain identifiable and accessible. The technician should not have to move the entire installation to reach a service panel.

Likewise, a roofer should be able to quickly understand how the equipment is supported when work on the roof becomes necessary.

This coordination between HVAC and the building is especially important on flat roofs.

What we avoid when installing a rooftop heat pump

We pay particular attention to mistakes that can turn a good machine into a problematic installation.

In particular, we avoid placing the condenser directly in the gravel, using a support that is too low, allowing the lines to rest abrasively on a rough surface, blocking the fan face, creating an unnecessarily long route, or installing the unit somewhere inaccessible for service.

We also verify that the pipes comply with the selected model’s vertical elevation limits. Fujitsu allows up to 15 m on the 9,000 and 12,000 BTU models, 25 m on the 18,000 and 24,000 BTU models, and 30 m on the 30,000 and 36,000 BTU models.

On a rooftop project, this factor takes on particular importance.

An installation that shows the difference between selling a machine and creating an HVAC system

This Fujitsu Altair 500 wall-mounted heat pump installation in Sainte-Anne-de-Sabrevois clearly shows why the choice of installer matters just as much as the choice of brand.

The machine provides its technology: R-32, an inverter compressor, high efficiency, quiet operation, and several available capacities.

Our job is then to create the conditions that allow this technology to operate properly: a well-chosen location, stable support, unrestricted airflow, properly routed lines, compliance with maximum lengths, suitable electrical power, and future access for maintenance.

We apply the same method when installing heat pumps in Montreal, Laval, Longueuil, on the North Shore, and on the South Shore.

Every building presents us with a different configuration. Some projects require a wall-mounted support. Others require a ground slab. Still others, like this one, call for a flat-roof installation with particular attention to stability and building protection.

For us, a successful HVAC installation is not simply one that starts when we press the remote control at the end of the day. It is one that remains accessible, stable, efficient, and logical several years later.