Three comfort zones, one outdoor unit: a Fujitsu installation designed down to the interior details
At Saint-Marcel-de-Richelieu, we completed an installation of a Fujitsu AIRSTAGE Aquila XLTH triple-zone heat pump designed to provide heating and cooling for several spaces in the residence from a single outdoor system. In this project, one detail of the indoor installation particularly highlights the difference between a quick installation and a truly well-planned HVAC installation: one of the wall-mounted units had to be positioned above an existing opening, in an area where the available space between the door frame and the ceiling was limited.
The photo shows a Fujitsu AIRSTAGE wall-mounted unit precisely integrated above this opening. The clearance above it, the unit’s alignment, the proximity of the trim, and the piping route all had to be considered before drilling the wall. This type of placement may seem natural when looking at the completed room, but it actually requires careful preparation.
For this project, we did not simply want to place three evaporators in three rooms. Our goal was to create a cohesive multi-zone system, in which each indoor unit meets the needs of its space while operating with the same Fujitsu outdoor unit.
Why a triple-zone heat pump was particularly well suited to this residence
A triple-zone heat pump can serve three distinct spaces without installing three compressors around the property.
The principle is simple: a single outdoor unit powers several indoor units, each of which can have its own setpoint temperature. Fujitsu explains that, for its AIRSTAGE H series, each indoor unit can be controlled independently using a remote control. The manufacturer also offers different indoor unit configurations, including wall-mounted units, Slim Duct, compact cassettes, and Mid Static Duct.
In a residence, this flexibility makes it possible to address spaces according to their actual use.
A bedroom does not necessarily need the same temperature as a kitchen or living room. A space with many windows may also have a higher cooling load than a room located on the shaded side of the building.
With a multi-zone heat pump, we can therefore distribute comfort where it is truly needed.
The wall-mounted unit above the door: a location that requires precision
In the photo of this job site in Saint-Marcel-de-Richelieu, the Fujitsu indoor unit is installed just above an opening surrounded by mouldings.
Several factors had to be checked before selecting this location.
Clearance from the ceiling
A wall-mounted unit must be able to properly draw in air from the room. Air generally enters through the upper part of the unit before being filtered and redistributed through the lower outlet.
Placing the evaporator too close to the ceiling can hinder this airflow and make it difficult to open the front panel during HVAC maintenance.
We must therefore comply with the manufacturer’s requirements while making intelligent use of the available space.
The space above the frame
Here, the clearance between the door’s upper moulding and the ceiling required a relatively precise position. A difference of a few centimetres could have placed the unit too close to the ceiling or too close to the frame.
The unit also had to remain visually straight in relation to the existing architectural lines.
When walls have mouldings, tiles, cabinets, or openings, alignment becomes particularly noticeable. A slightly tilted unit is immediately apparent.
Routing the lines
The white line-set cover on the left side of the unit also neatly conceals the technical routing.
This type of channel normally houses the components required to connect the unit: refrigerant lines, electrical communication wiring, and drainage, depending on the selected configuration.
With a triple-zone heat pump, this step becomes much more important than with a single-zone system, since several circuits must ultimately connect to the outdoor unit.
A Fujitsu system designed around several possible combinations
The technical documentation for the H Aquila series shows several outdoor unit configurations.
The systems presented by Fujitsu include units of:
- 18,000 BTU/h, up to two indoor units;
- 24,000 BTU/h, up to three indoor units;
- 36,000 BTU/h, up to four indoor units;
- 45,000 BTU/h, up to five indoor units.
For a three-zone installation like this one, the mere presence of three indoor units is therefore not enough to determine which outdoor capacity to use.
The sizing of each zone and the complete combination determine the appropriate configuration.
Fujitsu tables: useful for compatibility, but not a substitute for a load calculation
The Fujitsu document provides detailed tables of approved combinations. For three-zone systems, various combinations of 7,000, 9,000, 12,000, 15,000, and 18,000 BTU/h indoor capacities are listed, depending on the outdoor unit used.
However, Fujitsu adds an essential clarification: these tables are not intended to determine the system’s required capacity. The manufacturer recommends its Design Simulator software for selecting AIRSTAGE H Series equipment.
In other words, a combination may be mechanically and technically permitted without necessarily being the best combination for a given home.
At AirGreen, we consider, among other factors:
- the actual area of each zone;
- insulation;
- the amount of fenestration;
- orientation;
- floors;
- heat loss;
- solar gains;
- the natural movement of air between rooms;
- the actual use of each space.
Why simply adding up the BTUs of the three heads can be misleading
Multizone systems have an important characteristic: the combined nominal capacity of the indoor units can sometimes exceed the outdoor unit’s nominal capacity.
Fujitsu mentions a connection capacity of up to 130% in certain configurations. However, the manufacturer explicitly states that exceeding 100% of the connected capacity does not increase the maximum capacity produced by the outdoor unit.
This is an important consideration for homeowners comparing multiple quotes.
For example, seeing three indoor units whose combined capacities exceed that of the outdoor compressor does not automatically mean that the system is undersized or poorly designed. In several residences, the three zones do not require their maximum capacity simultaneously.
However, this flexibility should never be used as an excuse to install random combinations.
The building’s actual behavior must be taken into account.
Each zone is independent, but the system shares a common mode
Fujitsu documentation specifies that the indoor units can be controlled independently. Each room can therefore have a distinct setpoint temperature.
However, this architecture has one inherent limitation: the system provides either heating or cooling, but not both simultaneously.
This means that one bedroom can request 20 °C and another 22 °C in heating mode, but one zone cannot be in cooling mode while another simultaneously uses heating on the same outdoor unit.
We always explain this feature when selling a three-zone heat pump, because it is part of the normal operation of a shared multizone system.
A discreet indoor installation that relies on extensive invisible work
The evaporator’s positioning directly affects comfort
The location of a wall-mounted unit should not be chosen solely according to where it “fits.”
We analyze the direction of the airflow, obstacles, furniture, openings, and how the air will be able to circulate in the room.
On this installation in Saint-Marcel-de-Richelieu, the unit positioned above the door benefits from a high location that allows air to be projected into the room rather than blown directly at an occupant seated immediately in front of the unit.
A high position is generally advantageous for cooling since cold air naturally descends, but the discharge angle must also be adjusted correctly for heating.
Why we avoid placing a unit simply where the piping route is shortest
A location may make the technician’s work much easier but be poor for the client’s comfort.
At AirGreen, we instead seek a compromise between:
- performance;
- airflow;
- aesthetics;
- accessibility;
- piping length;
- drainage;
- building structure.
The shortest route is not always the best location for the indoor unit.
Drainage deserves as much attention as the refrigerant piping
When a wall-mounted unit operates in cooling mode, moisture condenses on its heat exchanger.
This water must be drained properly.
Insufficient slope, a crushed pipe, or an incorrect configuration can cause drainage problems several months after installation.
That is why we plan the drainage when choosing the location, rather than after the unit has already been mounted on the wall.
Inverter technology and its benefits in a three-zone system
Fujitsu indicates that the multizone AIRSTAGE systems in this family use an inverter-driven compressor, meaning Inverter technology that modulates its operation according to demand.
This modulation is particularly relevant when a system serves multiple rooms.
A single zone may operate at low capacity for part of the day. A few hours later, two or three units may demand more heating or cooling.
The outdoor unit must therefore continuously adjust its output.
This modulation helps reduce excessive temperature fluctuations while adapting output to actual demand.
Heating down to -26 °C for the CTEB variants documented by Fujitsu
The Fujitsu document provided with this project presents the Aquila and Aquila CTEB variants. Fujitsu indicates that CTEB units are designed to operate in heating mode down to -26 °C and in cooling mode up to 50 °C.
In a region like Saint-Marcel-de-Richelieu, this information is particularly relevant.
A heat pump installed in Quebec should not be evaluated solely according to its summer performance. The available capacity in cold weather and the operating range are essential criteria when selecting a system.
However, we avoid automatically assigning a low-temperature rating to any unit bearing the Aquila name: the exact outdoor unit model must always be verified.
An indoor unit that is easily accessible for maintenance
One advantage of the visible position shown in the photo is that the evaporator remains accessible for routine maintenance.
The filters on a wall-mounted unit must be cleaned periodically. Over the longer term, a deep cleaning of the wall-mounted air conditioner may also become necessary to remove buildup from the heat exchanger, blower wheel, and drain pan.
A unit placed in an extremely difficult-to-access location unnecessarily complicates these operations.
The quality of an HVAC installation is therefore also measured several years later, when it is time to maintain the equipment.
Mistakes we seek to avoid with a triple-zone heat pump
The first mistake is selecting the three indoor units solely according to a rough square-footage rule.
The second is oversizing each room “to have more power.”
The third is overlooking the collective behavior of the outdoor system.
The fourth is choosing indoor locations based on how easy they are to drill through rather than on air circulation.
Finally, on an installation like the one in Saint-Marcel-de-Richelieu, it would also be easy to position the unit too high or too low above the door while overlooking the required clearances.
We prefer to measure several times before drilling just once.
A particularly appealing solution when you want to limit the number of outdoor units
Homes with three areas to condition can be equipped with three separate single-zone systems or a multi-zone solution.
Three single-zone systems offer complete independence for each compressor. A Fujitsu triple-zone heat pump, on the other hand, can significantly reduce the number of visible units around the building.
The best choice therefore depends on the building, budget, required capacities, and the owner’s priorities.
For this project, the Fujitsu multi-zone solution made it possible to combine individualized control of the spaces with a more compact outdoor installation.
Subsidies: verify the exact combination before announcing an amount
The subsidy programs applicable to heat pumps in Quebec generally rely on the certification of specific combinations of indoor and outdoor units.
The Fujitsu document provided for this project presents the series, approved combinations, and general specifications, but it alone does not make it possible to identify a specific AHRI number or a subsidy amount applicable to the photographed installation.
We therefore always recommend checking the system’s complete reference before confirming financial assistance.
This approach avoids estimates based solely on the brand, nominal capacity, or commercial name.
Our AirGreen approach in Saint-Marcel-de-Richelieu
This project clearly shows that a triple-zone heat pump is not simply a matter of choosing a compressor and three evaporators.
The installation must form a coherent whole.
In Saint-Marcel-de-Richelieu, we notably had to integrate an indoor unit into a precise space above an opening, maintain the required clearances, organize the line-set route neatly, and account for the collective operation of the three zones.
It is the same approach we apply in our heat pump installations in Montreal, Laval, Longueuil, the North Shore, and the South Shore.
We place as much importance on visible details as on those hidden behind line-set covers: sizing, connections, insulation, drainage, vacuuming, communication checks, and commissioning.
A successful installation should look simple once it is complete. But this visual simplicity is generally the result of many technical decisions made before the Fujitsu unit is even mounted on the wall.