An elevated HVAC installation among several mechanical systems
This installation of a Hitachi airHome 600 wall-mounted heat pump in Delson presents a reality quite different from a conventional installation beside a single-family home. The outdoor unit was installed on a flat gravel-covered roof, at the heart of a mechanical area that already contained several condensers, ventilation ducts, roof outlets, and air-handling equipment.
In this context, the main challenge was not simply finding an open space. It was necessary to select a location that would allow the Hitachi heat pump to operate without drawing in the hot or cold air discharged by nearby units, while maintaining safe access for maintenance and future technical work.
The project photo shows the airHome outdoor unit positioned on sturdy crossbars, with anti-vibration pads visible beneath its feet. It is therefore not placed directly on the gravel or roofing membrane. This method helps stabilize the unit, distribute its weight, and limit the transmission of vibrations to the building structure.
The installation was also planned to preserve an air corridor in front of the fan. On a roof where several units operate simultaneously, improper positioning can cause discharged air to recirculate, increase operating pressure, and reduce actual performance.
Why install a wall-mounted heat pump on a roof?
A rooftop installation may be considered when a building does not have a suitable outdoor location at ground level. In a commercial building, apartment building, or property with architectural constraints, façades may be reserved for entrances, windows, traffic routes, or aesthetic requirements.
The roof can therefore be used to group mechanical equipment in a less visible area. It offers several advantages:
- reduced ground-level footprint;
- protection against certain accidental damage;
- greater distance from areas frequented by occupants;
- integration with the building’s other HVAC equipment;
- the possibility of locating the outdoor unit closer to certain indoor areas;
- reduced visual impact on the main façade.
However, this solution introduces additional constraints. A heat pump installed on a roof is more exposed to wind, sunlight, snow, and rapid temperature changes. The installation must therefore be designed to maintain its stability and accessibility throughout the year.
An installation among existing equipment
The image of this installation in Delson shows several outdoor units installed close to one another. Some belong to other systems, while large ventilation and air-handling equipment occupies the background.
In such a dense environment, we must analyze:
- the discharge direction of each unit;
- the space available in front of the fans;
- the necessary distances behind the heat exchangers;
- access to the service panels;
- the position of the refrigerant connections;
- technicians’ travel paths;
- the risk of snow accumulation;
- the proximity of the building’s air intakes and outlets.
A heat pump must not draw in the warm air discharged by another air conditioner during the summer. This recirculation would raise the temperature of the air entering the outdoor heat exchanger and could reduce cooling capacity.
In winter, the same principle applies differently. Air cooled by a unit operating in heating mode must not be immediately drawn in by another heat pump. The spacing and orientation of the units therefore directly contribute to their performance.
Supports that protect the roof
The Hitachi airHome 600 rests on two crossbars positioned beneath the unit. The metal feet are separated from these supports by vibration-damping pads.
On a flat roof, it is important to avoid direct contact between the equipment and the membrane. Concentrated pressure or repeated movement could damage certain surfaces. A properly prepared base helps distribute the load and keep the unit level.
Leveling is essential for several reasons:
- mechanical stability of the compressor;
- proper drainage of defrost water;
- reduction of vibrations;
- prevention of gradual movement of the unit;
- maintenance of the specified clearances;
- protection of the refrigerant connections.
Roof gravel alone does not provide a stable base. It can shift under the weight of the unit or during service work. The supports provide a more predictable footing while preventing the unit from being placed directly on the roofing membrane.
The importance of vibration-damping pads
The blue pads visible beneath the heat pump’s feet play a discreet but important role. Even a well-balanced Inverter compressor produces mechanical vibrations during operation.
On a roof, these vibrations can be transmitted to the structure and then perceived in the rooms below. The noise felt indoors does not always come from the outdoor fan. It may be caused by a frequency transmitted through the supports, lines, or framework.
To reduce this risk, we pay attention to several elements:
- choice of pads;
- position of the supports;
- uniform tightening of the fasteners;
- absence of excessive tension in the piping;
- separation between the lines and rigid surfaces;
- crossbar stability;
- final leveling of the unit.
A refrigerant line resting directly against a metal wall can also transmit a humming sound. Vibration management must therefore cover the entire installation, not just the heat pump's feet.
Preserving access to the service panels
The right side of the outdoor unit contains the connections, cables, and panels that provide access to several components. The chosen position leaves this space accessible.
This accessibility is essential for:
- check the pressures and temperatures;
- inspect the refrigerant connections;
- check the electrical connections;
- measure voltage and current;
- access the circuit boards;
- perform a leak search;
- replace a component;
- clean the heat exchanger.
On a roof crowded with equipment, a unit can easily be installed too close to another appliance or duct. The installation may seem acceptable on the day of the work, but become problematic as soon as a technician needs to open the service panel.
At AirGreen, we consider future maintenance from the project-planning stage. A good location must suit the heat pump's daily operation, but also the service work that will be required throughout its lifespan.
The route of the lines on a roof
The refrigerant and electrical connections for this installation exit from the side of the unit before following the planned route to the building. On a roof, the lines must be protected from ultraviolet rays, the elements, and mechanical damage.
The piping must also maintain gradual bends. A copper line bent too sharply can be crushed or partially constricted, limiting refrigerant flow.
Depending on the capacity of the airHome 600, the refrigerant connections vary. The liquid line is 1/4 in., while the gas line may be 3/8 in., 1/2 in., or 5/8 in. The maximum total line length can range from 82 to 98 feet depending on the combination selected.
These limitations must be verified before installation begins. A significant height difference between the indoor unit and the outdoor unit must also comply with the manufacturer's specifications.
An installation exposed to sun and wind
The Delson roof is fully exposed. No tree or neighboring building consistently shields the unit from the sun. In summer, the roof surface temperature can be significantly higher than the temperature measured in the shade.
The Hitachi airHome 600 is designed to operate in cooling mode when the outdoor temperature reaches up to 46 °C, according to the technical data sheet. However, this capability does not eliminate the need for a well-ventilated installation.
The fan must be able to discharge heat without encountering an obstruction. Hot air must not remain trapped between the units or beneath a structure.
Wind is another consideration. On a roof, gusts can be stronger than at ground level. The unit must therefore be stable, properly positioned, and protected against shifting. The support method must be suited to the building, the unit, and the requirements applicable to the project.
Managing snow and defrost water
When a heat pump operates in heating mode, frost may form on the outdoor heat exchanger. The system then initiates a defrost cycle to melt this buildup.
The water produced must be able to drain beneath the unit without forming a mass of ice that reaches the bottom of the cabinet. The elevated positioning of the unit in Delson leaves space beneath the heat pump and helps facilitate this drainage.
The airHome 600 includes a heating element in the condensate pan. This feature helps maintain water drainage during cold periods.
However, winter maintenance on a roof must remain rigorous. Wind-driven snow can accumulate around the units and form localized drifts. Building managers must avoid shoveling or blowing snow directly against the heat pump.
The features of the Hitachi airHome 600 installed in Delson
A range suited to different heating and cooling needs
The Hitachi airHome 600 is available in several capacities. The models listed in the manufacturer's documentation have nominal cooling capacities of 9,000, 12,000, 15,000, 18,000, and 22,000 BTU/h.
The exact capacity of the unit visible on the roof cannot be confirmed from the photo alone. Exterior dimensions vary by model, but precise identification must always be based on the nameplate and the combination of the indoor and outdoor units.
Depending on the selected model, the nominal heating capacity ranges from 11,000 to 25,200 BTU/h. The maximum capacity available at low temperatures also varies according to the unit size.
For an installation in a building in Delson, the selection must take several parameters into account:
- heat loss from the served area;
- ceiling area and height;
- insulation level;
- glazed surface area;
- room occupancy;
- heat-generating equipment;
- ventilation and infiltration;
- design temperature;
- the role of the heat pump as the primary or supplementary heating system.
A unit installed on a rooftop should never be sized solely according to the available outdoor space.
Continuous heating down to -25 °C
The airHome 600 series can maintain heating operation down to -25 °C. The manufacturer also indicates a capacity of up to 100% at -15 °C, depending on the combination.
This data is particularly relevant for a rooftop installation, where the unit is directly exposed to winter conditions. Actual performance, however, depends on the model, the building load, coil maintenance, and airflow around the unit.
Hitachi’s documentation also indicates seasonal efficiency ratings of up to 23.0 SEER2 for cooling and up to 9.2 HSPF2 in Region 5 for heating. The listed models are ENERGY STAR certified and use R32 refrigerant.
Why Inverter technology is useful in a commercial building
Inverter technology allows the compressor to modulate its speed according to demand. In a commercial or variably occupied building, requirements can change quickly.
The system may need to compensate for:
- frequent door opening;
- heat generated by occupants;
- lighting;
- electrical appliances;
- solar radiation;
- unoccupied periods;
- ventilation variations.
Rather than operating only at full capacity, the heat pump can reduce its capacity as the temperature approaches the setpoint. This modulation promotes a more stable temperature and limits repeated start-up cycles.
An outdoor unit designed to withstand the elements
The airHome 600 uses a metal cabinet designed to withstand outdoor conditions. Hitachi also indicates that the condenser has an anti-corrosion coating.
On a rooftop, this protection is relevant because the unit is continuously exposed to the effects of sun, rain, snow, and humidity. It may also be exposed to particles from other building equipment.
However, the cabinet’s durability does not replace HVAC maintenance. The coil must remain clean and free of obstructions. Dirt accumulated between the fins reduces heat transfer and can lead to longer operating times.
FrostWash and DuraSpin on the outdoor unit
The Hitachi airHome 600 features FrostWash on the outdoor unit. The system uses a freezing and thawing process to help remove some of the dust and impurities present on the coil.
The DuraSpin function temporarily reverses the fan rotation to expel larger particles.
These features are useful in a rooftop environment, where the units may be exposed to:
- dust;
- pollen;
- light debris;
- particles from ventilation ducts;
- residue carried by the wind;
- lint expelled by certain systems.
They do not replace manual or professional cleaning when the heat exchanger is clogged. A maintenance program remains essential, especially in a mechanical area containing several units.
A sound level to consider in a rooftop installation
Depending on capacity, the outdoor sound level at high speed varies approximately from 51 to 54 dB(A) according to the manufacturer's technical data.
A rooftop installation can reduce the noise perceived outside at ground level. However, it can create structural vibrations in rooms located directly below if the supports are inadequate.
The anti-vibration pads visible in this installation help limit this phenomenon. The choice of location in relation to bedrooms, offices, or quiet areas of the building should also be considered.
Wi-Fi control with airCloud Go
The Wi-Fi adapter is included with the airHome 600 combinations presented in the Canadian documentation. The airCloud Go app allows you to:
- adjusting the temperature remotely;
- changing the operating mode;
- scheduling time periods;
- tracking estimated energy use;
- controlling multiple settings without accessing the unit;
- adapting operation to occupancy periods.
In a commercial or multi-unit building, this function can simplify the management of a hard-to-access room. It also helps avoid unnecessary trips to the wall-mounted remote control.
The Smart Eco function can detect when a room is unoccupied and automatically reduce consumption after a set period. When occupancy is detected again, the system resumes its initial operation.
Mistakes to avoid when installing a rooftop heat pump
Placing the units too close to one another
Insufficient clearance can cause discharged air to recirculate and reduce efficiency.
Placing the unit directly on the membrane
Weight and vibrations can cause damage or localized wear.
Blocking the service panel
An installation that is too cramped makes maintenance more difficult and increases the time required for repairs.
Neglecting winter drainage
Defrost water must be able to drain away without forming a mass of ice beneath the unit.
Leaving the lines unprotected
UV rays and the elements can damage the insulation and expose the piping.
Forgetting about vibration transmission
The supports, pads and routing of the lines must be planned as a whole.
Choosing capacity based solely on nominal BTUs
Capacity at -8 °C, -15 °C, -20 °C and -25 °C must be compared with the building's actual needs.
Recommended maintenance for this installation in Delson
A heat pump installed on a roof should be inspected periodically. Since access is less immediate than for a ground-level unit, it is preferable to schedule maintenance rather than wait for a loss of performance.
An inspection should include, in particular:
- cleaning of the outdoor heat exchanger;
- verification of the supports;
- inspection of the vibration-dampening pads;
- checking the electrical connections;
- inspection of the refrigerant lines;
- checking for signs of oil or leaks;
- clearance around the fan;
- inspection of the water drainage;
- verification of operation in heating and cooling mode;
- inspection of the filters and indoor unit.
After roofing work, it is also important to check that no material, tool or debris has been left near the unit.
Financial assistance and eligibility
Hitachi documentation presents the airHome 600 series as eligible for several provincial heat pump incentives. Actual eligibility must nevertheless be confirmed based on the exact combination, building type and program in effect.
For a project in Delson, we must verify:
- the indoor and outdoor models;
- the corresponding certification number;
- the recognized heating capacity;
- the type of building use;
- the residential or commercial status;
- the billing requirements;
- the requested photos;
- the purchase and installation date.
A heat pump installed in a commercial building or common area is not necessarily handled the same way as a unit installed in a single-family home.
An AirGreen project adapted to a complex mechanical environment
This Hitachi airHome 600 wall-mounted heat pump installation in Delson demonstrates that installing a system on a roof requires a much broader analysis than simply connecting two units.
We had to take into account the presence of several condensers, ventilation equipment, the roofing, access to service panels and air circulation pathways.
The unit was installed on stable supports, with vibration-dampening pads and sufficient clearance for operation. Its position preserves access to the connections while limiting the risk of recirculation with nearby equipment.
We carry out this type of HVAC installation in Delson as well as in Montreal, Laval, Longueuil, the North Shore and the South Shore. Every roof, building and mechanical environment requires a solution adapted to its actual constraints.