In Coteau-du-Lac, a rooftop installation that requires much more than simply finding a place for the outdoor unit
This installation carried out in Coteau-du-Lac highlights an HVAC configuration that differs greatly from a heat pump installed at ground level. In the job-site photo, we can see two Fujitsu AIRSTAGE outdoor units installed on a flat roof, each on an elevated metal structure. Around the units are the roof parapet, a roof vent, refrigerant lines, wiring, and an outdoor electrical device.
This configuration requires a precise approach. On a roof, we must consider the stability of the supports, membrane protection, airflow around the condensers, drainage during defrosting, vibrations, wind, and the access required for future HVAC maintenance work—all at the same time.
For this project, the selected series is the Fujitsu AIRSTAGE Altair 700, a line of single-zone wall-mounted heat pumps operating with R-32 refrigerant. Fujitsu documentation covers the 09KMAS1 and 12KMAS1 models, corresponding respectively to nominal cooling capacities of 9,000 and 12,000 BTU/h.
However, the photo reveals an aspect that the technical specifications cannot show: how these units must actually be integrated into a building.
Two outdoor units on a roof: airflow becomes a priority
The presence of two outdoor units in the same area requires special attention.
A heat pump continuously exchanges heat with the outdoor air. It is therefore important to prevent one unit from directly taking in the air discharged by the other or to avoid enclosing the units between obstacles.
At this Coteau-du-Lac installation, the two units are positioned on separate structures, with their heat exchangers and fans accessible. We can also see that they are elevated above the roof surface.
For this type of project, we analyze in particular:
- the orientation of the units;
- the space available between the units;
- the distance from the parapet;
- the position of the heat exchangers;
- access to the service panels;
- the routing of the pipes;
- the presence of other equipment on the roof;
- the direction in which the warm or cool air will be discharged.
This planning becomes especially important when several wall-mounted heat pumps share the same roof.
Why elevate units on a flat roof?
In the photo, the Fujitsu units are not placed directly on the roof. They rest on metal supports that create substantial clearance beneath the units.
For us, this elevation serves several purposes.
First, it facilitates water management. In heating mode, a heat pump may perform defrost cycles and produce a significant amount of water. On a flat roof, this water must be able to drain away without the underside of the unit becoming a constantly saturated area.
The additional height also helps keep the equipment away from:
- snow accumulation;
- leaves and debris;
- water present on the roof;
- small accumulations of ice;
- dirt that could gradually clog the heat exchanger.
In Coteau-du-Lac, as elsewhere in Greater Montreal and Montérégie, an outdoor installation must always be planned with winter in mind, not just the conditions on the day the work is carried out.
The roofing membrane must be part of the planning
A flat roof is, above all, a watertight envelope.
When adding HVAC equipment, we must therefore avoid treating the roof as a simple concrete slab. The support points, the weight of the units, technician movement, and the routing of the lines must be planned to limit risks to the roof.
In this installation, the units are mounted on independent structures that distribute their position above the roof rather than allowing them to rest directly on the surface.
Fujitsu documentation indicates that the outdoor unit of the Altair 700 weighs approximately 32 kg (71 lb).
Added to this are the weight of the supports, stresses caused by wind, and forces generated by the operation of the compressor and fan.
The support for a flat-roof heat pump must therefore be considered a mechanical component in its own right.
Wind is a much more important factor on a roof
At ground level, a heat pump may be partially protected by the building, a fence, or the landscaping.
On a roof, exposure to wind can be very different.
The roof visible in the photo is surrounded by a relatively low parapet, and the area above the neighboring buildings is unobstructed. The units must therefore be secured and positioned with this exposure in mind.
Fujitsu also includes a wind baffle among the series' optional accessories, along with a snow hood and hail protection for certain applications.
This does not mean that every installation automatically requires these accessories. The need depends on the building, exposure, and the actual roof configuration.
A service access area that remains usable
Another advantage of the layout shown in this installation is that the units' panels remain accessible.
We never think only about the day of installation.
A Fujitsu heat pump will eventually need to be:
- inspected;
- cleaned;
- tested;
- diagnosed;
- repaired;
- or simply checked during maintenance.
An appliance wedged against a parapet, placed too close to another machine, or inaccessible without disassembly becomes much more difficult to service.
On a rooftop, this question is even more important because site access is already more complex than at ground level.
The presence of a roof vent also had to be taken into consideration
To the left of the units, the photo clearly shows a mechanical outlet or vent installed on the roof.
We must leave enough space around this type of equipment so as not to interfere with its operation and to avoid creating an unnecessary concentration of equipment in a confined area.
The work of an HVAC installer therefore does not consist solely of finding a place where the heat pump can physically fit. The installer must understand the complete environment in which it will be installed.
This applies to this Coteau-du-Lac rooftop, as well as to our projects in Montreal, Laval, Longueuil, the North Shore and the South Shore, where residential and multi-unit flat roofs often present similar constraints.
Fujitsu AIRSTAGE Altair 700: 9,000 or 12,000 BTU/h
The Altair 700 series documented by Fujitsu includes two configurations.
Altair 700 – 09KMAS1
The configuration includes:
- indoor unit ASUH09KMAS;
- outdoor unit AOUH09KMAS1;
- rated air conditioning capacity of 9,000 BTU/h;
- modulated air conditioning capacity from 3,100 to 12,100 BTU/h;
- rated heating capacity of 12,000 BTU/h;
- heating capacity from 2,800 to 14,500 BTU/h;
- VERY2 of 30,0;
- CPSC2 region V of 9,9.
Altair 700 – 12KMAS1
The second configuration uses:
- indoor unit ASUH12KMAS;
- outdoor unit AOUH12KMAS1;
- rated air conditioning capacity of 12,000 BTU/h;
- air conditioning modulation from 3,100 to 13,800 BTU/h;
- rated heating capacity of 14,000 BTU/h;
- heating capacity of 2,800 to 15,000 BTU/h;
- VERY2 of 27,5;
- CPSC2 region V of 8,5.
The photo does not make it possible to read the equipment nameplates clearly enough to identify without reservation whether the photographed units are 9,000 or 12,000 BTU. We therefore retain both possibilities covered by the series documentation.
From R-32 to roof supports: the technical details that determine the final quality of an HVAC installation
Heating down to -15 °C according to Fujitsu specifications
Both Altair 700 configurations are designed to operate in heating mode down to -15 °C, while cooling can operate from -10 °C to 50 °C according to the Fujitsu technical data sheet.
This feature is particularly important on a roof, since the outdoor unit is directly exposed to weather conditions.
However, a common confusion must be avoided: minimum operating temperature and heating capacity required for the building are two different things.
The required capacity depends in particular on:
- the area served;
- insulation;
- fenestration;
- the building’s airtightness;
- heat losses;
- the use of the different rooms.
We therefore determine the sizing before deciding which capacity to install.
Inverter technology adapted to load variations
The Altair 700 series uses an Inverter compressor.
This allows it to adjust its capacity rather than operate constantly at full power.
In a room requiring only a small amount of heating or cooling, the system can reduce its output. When greater demand arises, its capacity can increase.
Fujitsu documentation even indicates that the outdoor unit can provide up to 33% more heat than its labeled rated capacity, depending on operating conditions.
This modulation helps provide more consistent comfort and is one of the major advantages of a properly sized Inverter wall-mounted heat pump.
R-32: the refrigerant used by the new Altair 700
The units in the series operate with R-32.
Fujitsu states in its documentation a global warming potential of 675 for R-32, compared with 2,088 for R-410A, representing an announced 68% reduction in GWP.
For an HVAC company, this change is not limited to a label on the equipment panel.
It affects refrigerant-handling procedures, evacuation, leak checks, and commissioning practices. We must use methods and equipment suited to the system actually installed.
1/4 in. and 3/8 in. piping
The two documented Altair 700 units use:
- 1/4 in. for the liquid line;
- 3/8 in. for the gas line.
Fujitsu specifies a minimum length of 10 ft and a maximum length of up to 66 ft. The maximum vertical difference is 49 ft, and the factory charge covers a stated length of up to 49 ft.
On a rooftop installation, this flexibility can be very useful.
The indoor unit may be several meters lower or located elsewhere in the building, requiring a more elaborate piping route than a simple penetration directly behind a wall-mounted unit.
In the photograph, we can see the insulated pipes descending from the units and joining the roof’s technical area.
The pipes must be supported and protected
On a roof, a refrigerant line left free to move in the wind or rub against a surface can become a source of problems.
We therefore pay attention to:
- pipe insulation;
- their fastening;
- absence of strain on the connections;
- protection against rubbing;
- changes in direction;
- passage near metal structures;
- the resistance of the outdoor finish to weather conditions.
Installation quality is never limited to the two connections at the condenser inlet.
An accessible electrical device near the units
In the photograph, we can also see an outdoor electrical box installed between the equipment.
The positioning of the electrical components is part of project planning. They must be accessible for service and installed according to applicable requirements.
The Fujitsu specifications sheet indicates a 208 to 230 V, 60 Hz, single-phase power supply and a 15 A circuit breaker for both Altair 700 units.
The maximum currents indicated are:
- 09KMAS1 : 6.4 A in cooling mode and 9.4 A in heating mode;
- 12KMAS1 : 6.9 A in cooling mode and 9.4 A in heating mode.
During installation, we always refer to the exact requirements on the nameplate of the actual unit delivered.
Relatively compact outdoor units
The Fujitsu specifications sheet gives the following dimensions for the outdoor units in both capacities:
- width: 31 7/16 in.;
- height: 21 5/16 in.;
- depth: 11 7/16 in.;
- weight: approximately 71 lb.
This relatively shallow depth helps make the series suitable for spaces where available room is limited.
On a roof like the one photographed in Coteau-du-Lac, a few inches can make a real difference when technical clearances must be maintained and other equipment avoided.
The rain visible in the photo highlights a reality of outdoor installations
The water droplets visible on the units are a reminder that outdoor equipment is constantly exposed to Quebec’s actual conditions.
Rain, snow, freeze-thaw cycles, wind, summer heat, and dust are all part of a heat pump’s normal environment.
That is also why we place so much importance on the quality of the support, cable routing, line insulation, and the finish of the connections.
An outdoor installation must be designed to withstand years of exposure, not just to look good in a photo taken on the day it is commissioned.
Indoor operation as quiet as 19 dB(A)
Although this photo focuses on the roof, the comfort is obviously felt indoors.
Altair 700 indoor units can operate at sound levels as low as 19 dB(A) in cooling and 21 dB(A) in heating in quiet mode.
The specification sheet indicates four fan speeds, plus automatic operation.
The indoor unit measures approximately:
- 32 13/16 in. wide;
- 10 5/8 in. high;
- 8 3/4 in. deep.
It weighs only about 22 lb.
This format makes it easy to integrate the unit into several rooms without using a central duct network.
Integrated Wi-Fi for managing different zones
The Altair 700 series also features integrated Wi-Fi connectivity, which can be used with the AIRSTAGE mobile app.
The presence of two outdoor units on this project highlights one of the advantages of single-zone systems: different areas of the building can be equipped with their own system.
Each space can then be controlled independently according to the installed configuration.
This approach may be relevant for certain homes, additions, or buildings where installing central ductwork would be complex.
ENERGY STAR and eligibility for financial assistance
The 09KMAS1 and 12KMAS1 models appear in Fujitsu documentation with the ENERGY STAR designations, including the classification associated with the cold climate presented on the specification sheet.
This feature may be relevant when analyzing subsidy programs available in Quebec.
However, we never determine financial assistance solely from the trade name “Altair 700.”
To confirm a subsidy, it is necessary to verify, among other things:
- the exact combination of indoor and outdoor models;
- the required certification references;
- the requirements of the program in effect;
- the type of building;
- the conditions specific to the applicant.
Technical certification and eligibility for financial assistance should not be considered automatically equivalent.
Errors to avoid when installing a heat pump on a flat roof
This Coteau-du-Lac project helps illustrate several critical points.
Among the errors we seek to avoid:
- Placing the unit directly on the roofing membrane without an appropriate support.
- Installing two condensers too close to each other.
- Obstructing the air discharge or intake with a parapet or another piece of equipment.
- Neglecting snow accumulation around the unit.
- Forgetting about water drainage during defrosting.
- Creating an unsupported pipe route or one exposed to friction.
- Making the electrical disconnect difficult to access.
- Placing the unit where it cannot be properly serviced.
- Underestimating wind exposure on the roof.
- Choosing the capacity solely according to floor area without considering the actual heat load.
These principles apply equally to a small residential installation and to a project involving multiple units.
Why the photo of this project is particularly representative of our work at AirGreen
When people think of a wall-mounted heat pump installation, they often imagine a white indoor unit and an outdoor condenser installed beside the house.
This Coteau-du-Lac installation illustrates a more complex reality.
Several pieces of equipment had to be integrated on an existing roof, access around the units had to be maintained, work had to be carried out near a vent, the piping and electrical supply had to be organized, the machines had to be raised, and enough space had to be preserved so that each unit could operate normally.
The heat pump is only one part of the project.
Our job is to ensure that all components — the unit, support, piping, power supply, clearances, and building — work together.
This is the approach we apply at AirGreen for our Fujitsu wall-mounted heat pump installations in Coteau-du-Lac, Montreal, Laval, Longueuil, the North Shore, the South Shore, and wherever the building’s characteristics call for an adapted HVAC solution rather than a standard installation copied from one job to the next.
For this project, the Fujitsu AIRSTAGE Altair 700 benefits not only from its technical features — R-32, Inverter technology, high efficiency, integrated Wi-Fi, and heating operation down to -15 °C — but above all from a rooftop installation designed for the practical realities of Quebec buildings and climate.