A raised wall-mounted installation between a window and a terrace, designed to preserve outdoor space
In Candiac, on the South Shore of Montreal, we installed a Fujitsu Aquila XLTH dual-zone heat pump to provide heating and cooling for two distinct areas of the property from a single outdoor unit. The project presented a very concrete exterior constraint: the available space was limited by a large window, a brick wall, the building’s foundation, and a wooden terrace immediately to the right of the unit.
The photograph shows the Fujitsu AIRSTAGE unit using R32 refrigerant, mounted on a metal wall bracket. It is raised above the ground, installed beneath the window, and precisely positioned between the masonry and the terrace structure. This configuration preserves floor space, protects the unit from accumulating water and snow, and maintains reasonable access for future service work.
An installation in such a compact space cannot be improvised. A few poorly calculated centimetres could have hindered airflow, blocked access to the refrigeration panel, placed the unit too close to the terrace, or created an installation that would be difficult to maintain.
Our job was therefore to find the right balance between four essential requirements:
- comply with operating clearances;
- keep the unit at a height suited to Quebec’s climate;
- protect the masonry and existing structure;
- efficiently power two indoor units with a single outdoor unit.
Why was a dual-zone heat pump the right choice for this Candiac property?
A dual-zone heat pump allows two indoor units to be connected to a single outdoor unit. This configuration is particularly useful when a property includes two areas with different heating and cooling needs.
A single wall-mounted head can hardly distribute air through walls, closed doors, or a stairwell. Even when installed in an open area, its effectiveness quickly decreases in more distant rooms.
In a Candiac home, a dual-zone configuration can be used to treat separately:
- the ground floor and the upper floor;
- an open-plan area and a primary bedroom;
- the main floor and the basement;
- a very sunny front section and a cooler rear section;
- a home office and the family area;
- an extension with insulation that differs from the main building.
Each indoor unit has its own controller. Occupants can therefore adjust the temperature according to the actual use of the rooms rather than maintaining a single setpoint throughout the house.
Two separately controlled zones, but one shared mode
Fujitsu zoning allows each indoor unit to be turned on, turned off, and adjusted independently. One zone can therefore operate while the other remains inactive.
There is, however, an important rule: the two units connected to the same compressor cannot request opposite modes at the same time. The system can heat or cool, but it cannot heat one room while cooling another.
Fujitsu documentation specifies that AIRSTAGE multi-zone systems provide heating and cooling, but not simultaneously. It also indicates that each indoor unit can be controlled independently and that certain outdoor units can power up to five indoor units, depending on the model selected.
In a residence, this constraint is generally easy to manage. In winter, both zones normally require heating. In summer, they require cooling. Nevertheless, we explain this to the homeowner during commissioning to avoid conflicting commands.
Fujitsu Aquila XLTH: a solution designed for cold conditions
The Fujitsu Aquila XLTH range is suited to projects where winter performance is an important criterion. The documentation provided for the Aquila and Aquila CTEB H-series multi-zone systems mentions heating operation down to -26 °C for models designed for cold climates.
In Candiac, this characteristic is particularly relevant. Temperatures can drop well below freezing, and a heat pump used as a significant source of heating must be selected based on its actual winter performance, not just its stated nominal capacity under milder conditions.
We assess, in particular:
- the area of each zone;
- the quality of the insulation;
- the number and type of windows;
- exposure to wind;
- solar orientation;
- ceiling height;
- air infiltration;
- the presence of auxiliary heating;
- the simultaneous demand of both indoor units.
The minimum operating temperature does not mean that the heat pump maintains exactly the same output at all temperatures. Available capacity varies with outdoor conditions and must be compared with the building’s heat loss.
Multi-zone systems available in several capacities
Fujitsu documentation presents outdoor units rated at 18,000, 24,000, 36,000, and 45,000 BTU/h. Depending on the model, they can power two to five indoor units.
For a dual-zone installation, several capacity combinations are permitted. The manufacturer’s tables show, for example, different combinations of 7,000, 9,000, 12,000, or 15,000 BTU/h indoor units for certain outdoor units designed for two zones.
However, a common error must be avoided: adding the capacities listed on the two wall-mounted heads and treating the sum as the capacity automatically provided by the outdoor unit.
Some permitted combinations exceed 100% of the outdoor unit’s rated capacity. Fujitsu specifies that this excess does not increase the system’s output capacity.
A combination of two indoor units with a total capacity greater than the outdoor unit’s capacity may be acceptable when the two zones do not require their maximum output simultaneously. When both heads place a heavy demand on the compressor at the same time, the available capacity is distributed.
The manufacturer also recommends using its Design Simulator software to select H-series AIRSTAGE equipment. Combination tables are used to verify that an association is permitted, but they do not replace a load calculation.
The technical choices visible in this outdoor installation in Candiac
A wall bracket to keep the ground clear
The outdoor unit is installed on two metal arms secured to the wall. This method keeps the ground clear and avoids placing the heat pump directly beside the foundation.
The wall bracket offers several advantages in this location:
- the unit remains above normal water accumulation;
- ground cleaning remains possible;
- leaves and debris are less likely to reach the base;
- the snow must rise higher before blocking the unit;
- the bottom of the unit remains accessible;
- the neighboring terrace does not need to be modified to create a base.
Wall mounting nevertheless requires a sufficiently strong structure. The weight of the unit and normal vibrations must be borne by anchors suitable for the wall.
We also check that the support is level before placing the unit on it. A tilted heat pump can cause mechanical stresses and complicate water drainage during defrost cycles.
Anti-vibration blocks visible beneath the unit
The photograph shows blue elements placed between the unit’s feet and the support rails. These blocks help reduce the transmission of mechanical vibrations to the wall.
This precaution is particularly important when the unit is mounted near a window or an occupied room. Even a quiet heat pump can transmit a noticeable vibration if it is bolted directly to a rigid structure without adequate isolation.
However, anti-vibration supports cannot compensate for weak fastening or an improperly balanced unit. They are part of an assembly comprising:
- a sturdy support;
- appropriate anchors;
- a level unit;
- properly supported lines;
- the absence of unnecessary rigid contact with the building.
A unit installed beneath a window
The unit is positioned beneath a window. This choice makes it possible to use a section of wall that would otherwise have been difficult to utilize.
Before proceeding, we must verify that the heat pump does not obstruct the opening, maintenance, or possible replacement of the window. We must also ensure that air expelled by the fan does not cause discomfort when a window is open.
In this installation, the window remains above and set back from the unit. The outdoor unit does not appear to interfere with its normal operation.
We must also take vibrations into account. Improperly executed fastening near a window frame can cause resonance in the masonry or finishing elements.
A significant proximity to the deck
The wooden structure visible to the right of the unit represents one of the project’s main constraints. The unit had to be far enough away to allow for:
- air circulation;
- opening the service panel;
- a technician’s access;
- cleaning the heat exchanger;
- the absence of contact between the casing and the deck;
- the normal expansion of materials.
A heat pump must not be installed in a cavity that is too enclosed. If the air expelled by the fan immediately encounters a structure, it may return toward the heat exchanger and reduce performance.
The deck must not later be modified in a way that encloses the unit. Adding a decorative panel or storage near it could turn a functional location into an inadequately ventilated space.
Preserved front clearance
The fan side faces an unobstructed area. This detail is essential because the fan must discharge a large volume of air without encountering an immediate obstacle.
When airflow is blocked, several problems can arise:
- reduced capacity;
- increased operating time;
- increased system pressure;
- air recirculation;
- possible increase in noise;
- less effective defrosting in winter.
We therefore recommend that the homeowner never store patio furniture, bins, or materials in front of the unit.
The side heat exchanger to protect
The left side of the unit reveals the finned heat exchanger, recognizable by its bluish color. Fujitsu documentation mentions a blue-fin cooling heat exchanger designed to provide greater corrosion resistance and a longer coil life.
These fins are nevertheless fragile. They can bend as a result of an impact, a tool, or overly aggressive cleaning.
Avoid:
- to lean an object against the coil;
- to use a pressure washer;
- to brush the fins with a hard tool;
- to let plants grow against the unit;
- to allow mulch or leaves to accumulate around the heat exchanger.
R32 refrigerant and the A2L marking
The wording R32 is clearly visible on the appliance. The lower plate also features a symbol related to the category A2L.
This classification indicates that the refrigerant has low flammability and must be handled using appropriate procedures. For the homeowner, daily system operation remains normal. However, any work on the refrigeration circuit must be entrusted to a qualified technician.
The lines must never be cut, moved, or punctured during deck, masonry, or renovation work.
An EnerGuide label visible on the unit
The photograph also shows an EnerGuide label affixed to the front panel. It displays comparative efficiency ranges for cooling and heating.
The image cannot confirm the exact rating of this particular combination with certainty. A comparison label does not replace the technical data sheet or the performance reference for the complete system.
For the exact data, consult:
- the complete outdoor unit model number;
- the models of both indoor units;
- the approved combination;
- the applicable performance rating;
- the system’s certification documents.
Defrost water must be able to drain away
In winter, a heat pump accumulates frost on its outdoor heat exchanger. The system then initiates a defrost cycle, producing water beneath the unit.
The elevation visible in the photo helps maintain clearance beneath the heat pump. However, the water must be able to flow away from the foundation and must not form a block of ice that gradually reaches the base.
The owner must monitor:
- ice accumulation beneath the unit;
- blocked access around the bracket;
- the formation of a slippery surface;
- water directed toward the building;
- snow obstruction.
Do not strike the base or coil with a metal tool. Any abnormal buildup should be assessed by a professional.
Two refrigerant circuits that must be identified correctly
A dual-zone heat pump has two sets of lines connecting the outdoor unit to the indoor units.
Each assembly generally includes:
- a liquid line;
- a gas line;
- insulation;
- a power or communication cable;
- a separate indoor-side drain.
It is essential that the Zone A circuit correspond to the correct wiring and indoor unit. A mix-up can cause communication errors or inconsistent operation.
During commissioning, we test the zones individually and then together:
- startup of the first indoor unit;
- verification of its communication;
- confirmation of the corresponding circuit;
- testing of the second zone;
- operation of both heads;
- supply-air temperature check;
- drain inspection.
Leak test and vacuum procedure
The refrigerant connections must be perfectly leak-tight. A slow leak can reduce performance and damage the compressor over time.
After assembly, we perform the necessary checks, followed by a complete vacuum procedure. This step removes the air and moisture present in the lines before commissioning.
The quality of this work is not visible in the final photograph, but it directly affects the reliability of the installation.
Mistakes to avoid near a patio
This project in Candiac highlights several common mistakes:
- installing the unit too close to a railing;
- blocking the fan with furniture;
- securing the bracket without vibration isolation;
- neglecting the wall’s load-bearing capacity;
- placing the heat pump too low;
- forgetting the defrost water;
- block access to the service panel;
- build around the unit later;
- choose the capacity by simply adding the indoor units;
- assume that all Fujitsu combinations are equivalent.
A proper installation takes the terrace’s future use into account. The free space available on the day of the work must remain free after adding furniture, storage, or decorative elements.
Recommended maintenance
To keep this Fujitsu heat pump in good condition, we recommend a few simple steps.
Outdoors:
- keep the area in front of the fan clear;
- remove leaves and debris;
- check the anti-vibration blocks;
- monitor the stability of the support;
- clear away snow;
- inspect the condition of the coil;
- do not lean objects against the unit.
Indoors:
- clean the filters of both units;
- monitor the drains;
- check for unusual noises and odors;
- note the error codes;
- have HVAC maintenance performed when thorough cleaning is required.
Eligibility for financial assistance
Some cold-climate heat pumps may be eligible for financial assistance. However, eligibility depends on the exact combination installed.
The following must be confirmed:
- the complete outdoor unit number;
- the models of both indoor units;
- the recognized combination;
- the performance reference;
- the purchase date;
- the installation date;
- the applicable program rules.
The presence of an EnerGuide label and the Fujitsu Aquila XLTH designation alone is not enough to advertise a specific amount.
The result achieved in Candiac
This Fujitsu Aquila XLTH dual-zone heat pump installation in Candiac now makes it possible to heat and cool two zones using a single outdoor unit, while meeting the constraints of a space located between a window and a terrace.
The project stands out for:
- an elevated wall bracket;
- anti-vibration components;
- an unobstructed ventilation facade;
- an R32 unit;
- precise integration near the terrace;
- continued access for servicing;
- two separately controlled indoor zones;
- a solution designed for heating in cold climates.
At AirGreen, we install wall-mounted and multi-zone heat pumps in Candiac, on the South Shore, as well as in Montreal, Laval, Longueuil, and on the North Shore.
Every project requires an analysis of the building and its exterior surroundings. A high-performing unit must also be properly positioned, well supported, correctly connected, and accessible throughout its service life.