An elevated outdoor installation designed for stability, defrosting, and Quebec’s winter conditions
At Saint-Mathieu, our AirGreen team installed a Fujitsu AIRSTAGE Aquila XLTH dual-zone heat pump to serve two distinct zones of the property with a single outdoor unit.
The photograph taken during the work clearly shows one of the important technical elements of this installation: the Fujitsu AIRSTAGE outdoor unit, identified as R32, was installed on an elevated metal support, itself placed on an elongated base designed to distribute the load and keep the unit at a suitable distance from the ground or supporting surface.
This choice is not merely an aesthetic consideration. In Quebec, a heat pump used for heating must be able to handle snow, ice, and the water produced during defrost cycles. A unit positioned too low can quickly become surrounded by frozen accumulations, especially after several heating cycles followed by defrosting.
For this project in Saint-Mathieu, the installation was therefore designed to maintain adequate clearance beneath the unit, ensure its stability, and preserve access to the components for future servicing.
What the visible outdoor installation in the photo shows
The Fujitsu unit rests on a rectangular metal frame. Beneath the machine’s feet, intermediate elements can also be seen, intended to limit direct contact between the cabinet and the support.
The structure itself is positioned on two long parallel bases, with wooden pieces serving as an interface and distributing the load.
This configuration accomplishes several things at once:
- keep the heat pump elevated;
- stabilize the equipment;
- distribute the weight over a larger surface;
- improve the space available beneath the unit;
- reduce risks related to water and ice;
- keep the connections accessible;
- facilitate future servicing.
The unit is installed in an open area, with no obstacle directly in front of the large front fan. This detail is essential, as the air discharge must remain unobstructed to prevent the expelled air from being drawn back in by the heat exchanger.
Why Raise a Heat Pump in Saint-Mathieu?
A heat pump operating in heating mode works differently from a simple air conditioner. In winter, the outdoor heat exchanger becomes cold, and frost can form on its fins. The system then periodically initiates a defrost cycle.
During this cycle, the frost melts and produces water.
If the unit is installed too close to the ground, this water can:
- freeze directly beneath the machine;
- gradually form a block of ice;
- restrict drainage;
- make it difficult to reach the underside of the unit;
- block certain openings;
- impair ventilation;
- complicate maintenance.
The raised stand visible in the photo provides substantial clearance beneath the cabinet. This height is particularly relevant in a region where snow accumulation can be significant.
A dual-zone heat pump for two different areas
The installed system is a dual-zone heat pump. This means that a single outdoor unit supplies two indoor units.
This configuration makes it possible to tailor comfort to two areas that do not necessarily have the same heating and cooling needs.
For example, a dual-zone system can be used for:
- a ground floor and an upper floor;
- an open-plan area and a bedroom;
- a front section and a rear section of the house;
- a very sunny area and a more shaded area;
- a main living area and a basement;
- two rooms occupied at different times.
Each indoor unit can be controlled separately. Fujitsu documentation specifies that H-Series AIRSTAGE multi-zone systems allow individual control of the indoor units. However, the system provides heating or cooling in the same overall mode and cannot heat one zone while another simultaneously requests cooling.
Independent control: what it really means
In a dual-zone installation, occupants can set different temperature targets.
For example, it is possible to:
- heat one zone to 20°C and the other to 22°C;
- cool one room to 22°C and the other to 24°C;
- operate only one indoor unit;
- use different fan speeds;
- adjust the louver direction separately;
- temporarily turn off one zone.
However, the two indoor units share the same outdoor unit.
Therefore, the system cannot simultaneously provide heating and cooling in two different zones.
This characteristic is normal for this type of multi-zone system and must be taken into account during the shoulder seasons.
Fujitsu AIRSTAGE Aquila XLTH: A Flexible Multi-Zone Design
Fujitsu documentation for H-series Aquila systems presents several outdoor units, including 18,000, 24,000, 36,000, and 45,000 BTU/h. Depending on the model, a single outdoor unit can power up to five indoor units.
Compatible indoor unit types include:
- wall-mounted units;
- Slim Duct;
- compact cassettes;
- Mid Static Duct.
This flexibility makes it possible to adapt the solution to the home's architecture.
In a dual-zone project, the two indoor units do not necessarily have the same capacity. A living area may require a larger unit than a bedroom or office.
Possible combinations for a dual-zone configuration
For the AOUH18KWAS2 and AOUH18KWAH2 outdoor units, Fujitsu presents several combinations of two indoor units.
The permitted nominal combinations include:
- 7,000 + 7,000 BTU/h;
- 7,000 + 9,000 BTU/h;
- 7,000 + 12,000 BTU/h;
- 7,000 + 15,000 BTU/h;
- 9,000 + 9,000 BTU/h;
- 9,000 + 12,000 BTU/h;
- 9,000 + 15,000 BTU/h;
- 12,000 + 12,000 BTU/h.
These tables can be used to verify whether a combination is approved by the manufacturer. However, they do not replace system sizing.
Fujitsu clearly states that these tables are not intended to select the final capacity and recommends using its Design Simulator software for H-series AIRSTAGE equipment.
Why we do not size systems based solely on floor area
An estimate based solely on square footage does not account for many essential factors.
For each zone, we must consider in particular:
- actual floor area;
- ceiling height;
- insulation;
- the building's airtightness;
- the amount of glazing;
- solar orientation;
- wind exposure;
- the number of occupants;
- heat-generating appliances;
- the presence of an upper floor;
- the door layout;
- winter heat losses.
Two rooms of the same size may require different capacities.
A south-facing room with large windows may have a much higher cooling load than a north-facing bedroom.
Conversely, a zone located above a garage or near a less-insulated part of the building may have higher winter heat losses.
A connected capacity that can exceed 100%
Fujitsu documentation specifies that certain multi-zone units accept a connected capacity of up to 130%.
This means that the nominal sum of the indoor capacities can sometimes exceed the nominal capacity of the outdoor unit.
This option is useful when the zones do not require their maximum capacity simultaneously.
However, it is important to understand one key nuance: Fujitsu also indicates that exceeding 100% does not increase the outdoor unit's actual production capacity.
If both zones require their full capacity at the same time, the available power must be divided between them.
Sizing must therefore account for the actual use of the spaces, not simply the sum of the nominal capacities.
A range designed for cold-climate heating
Fujitsu documentation presents the Aquila CTEB units as capable of operating in heating mode down to -26 °C and in cooling mode up to 50 °C.
This low-temperature operating capability is particularly relevant in the Quebec context.
The system uses an inverter-driven compressor. Unlike a compressor that operates only at full power or is switched off, an inverter system can modulate its speed according to demand.
This modulation helps to:
- reduce temperature fluctuations;
- maintain more consistent comfort;
- adjust capacity when only one zone is operating;
- reduce some on-off cycles;
- better meet the building's actual needs.
In a dual-zone system, this modulation is important because demand constantly changes between the two areas.
The R32 refrigerant visible on the unit
Identification R32 is clearly visible on the outdoor unit cabinet.
Refrigerant is an integral part of the system design. Handling it requires a rigorous installation method.
The important steps include:
- proper line preparation;
- connection quality;
- flare fittings;
- evacuation;
- leak testing;
- following commissioning procedures.
A refrigeration installation is not complete simply because the units are secured in place.
The quality of the vacuum and connections directly affects system reliability.
Clearance in front of the fan
One of the positive features visible in the photo is the open space in front of the front fan.
The fan must be able to discharge a large volume of air without obstruction.
A heat pump placed too close to a wall, fence, or structure can cause air recirculation.
This situation can lead to:
- reduced capacity;
- increased operating temperatures;
- reduced efficiency;
- noisier operation;
- greater compressor strain.
We therefore always check the front clearance, as well as the space behind the coil and on the sides of the cabinet.
Support stability is just as important as height
An elevated support must be sufficiently rigid to prevent movement.
A heat pump contains mechanical components that generate slight vibrations. If the support is poorly leveled or unstable, these vibrations can be amplified.
In this project, the unit rests on a metal frame supported by long parallel bases.
This configuration helps to:
- distribute the load;
- keep the unit upright;
- limit movement;
- facilitate leveling;
- keep the space beneath the unit clear.
We also check that the lines do not transmit vibrations to the structure.
A line that is too taut or firmly pressed against a rigid surface can produce an audible hum indoors.
Line routing
The refrigerant lines generally leave the side of the outdoor unit and connect to the two indoor units.
In a dual-zone system, each indoor unit has its own refrigerant connection.
The route must be organized in such a way as to:
- avoid mechanical stress;
- protect the insulation;
- maintain the appropriate bend radii;
- prevent rubbing;
- facilitate access to the fittings;
- maintain a clean finish.
When the lines run outdoors, they must also be protected against UV rays, the elements, and mechanical damage.
Outdoor unit drainage in winter
Winter drainage deserves special attention.
Unlike a conventional air conditioner, a heat pump can produce a great deal of water beneath its outdoor unit during heating.
This water must be able to drain away without flowing back toward the foundations or creating a hazardous area.
We must therefore take into account:
- the slope of the ground;
- the position of the support;
- the distance from pedestrian walkways;
- possible ice formation;
- snow accumulation;
- the location of the drains.
Proper elevation reduces several of these risks.
Commissioning checks
Once the physical installation is complete, we perform several checks.
Support check
The frame must be stable, level, and sufficiently rigid.
Clearance check
Air must be able to circulate around the unit without obstruction.
Line inspection
The refrigerant lines must be insulated and properly protected.
Vacuum evacuation
The circuit must be free of air and moisture.
Leak test
The connections must be checked before commissioning.
Electrical verification
The connections and protective devices must comply with requirements.
Testing both zones
Each indoor unit is tested individually, then both are observed together.
Noise check
We check the operation of the compressor, fan, and support.
Control verification
Each indoor unit must respond properly to the temperature and ventilation settings.
Mistakes to avoid with a dual-zone heat pump
Several problems can be avoided with proper planning.
-
Installing the outdoor unit too low
Snow and ice can quickly reduce the clearance. -
Using an unstable support
Vibrations and movement compromise comfort and durability. -
Placing an obstacle in front of the fan
The air discharge must remain completely unobstructed. -
Neglecting defrost water
It can create significant ice buildup. -
Choosing indoor units based solely on square footage
Actual heating and cooling loads are more complex. -
Installing an unauthorized combination
The models must be verified according to Fujitsu’s tables. -
Assuming that 130% connected means 130% output
The outdoor unit’s capacity remains limited. -
Setting one zone to heating and the other to cooling
Both units share the same general operating mode. -
Neglecting future access
The connections and panels must remain accessible. -
Neglecting outdoor maintenance
The coil must remain clean and unobstructed.
An HVAC installation in Saint-Mathieu designed for two zones and Quebec winters
This Fujitsu AIRSTAGE Aquila XLTH dual-zone heat pump installation in Saint-Mathieu illustrates the importance of adapting the outdoor support to the site’s actual conditions.
The unit was raised on a rigid metal structure resting on a widened base, with enough space beneath the machine to manage snow and defrost water more effectively.
At AirGreen, we install wall-mounted heat pumps, dual-zone systems, and multi-zone systems in Montreal, Laval, Longueuil, on the North Shore, and on the South Shore.
We assess not only the equipment’s capacity, but also the location, clearances, drainage, stability, vibrations, line routing, and future maintenance.
In this project in Saint-Mathieu, the Fujitsu Aquila XLTH dual-zone now provides a heating and cooling solution distributed across two areas, with an outdoor unit installed to remain accessible and better prepared for Quebec’s winter conditions.