Installation of two Hitachi airHome 800 wall-mounted heat pumps in Auteuil, Laval, beneath an outdoor metal staircase

An HVAC installation adapted to a complex façade without compromising access to the units

This installation of Hitachi airHome 800 wall-mounted heat pumps in Auteuil, in northern Laval, clearly illustrates a common reality in Montreal and Laval buildings: the available space for outdoor units is rarely completely unobstructed. On this building, the rear façade was occupied by a large exterior steel staircase, several vertical posts, a small window, vegetation, and various utility pathways.

We had to integrate two outdoor units in a clean and functional manner while taking several essential factors into account: airflow, snow accumulation, defrost water drainage, access for HVAC maintenance, the routing of the refrigerant lines, and the presence of an aging metal structure above the units.

The result is an orderly installation comprising two Hitachi airHome outdoor units, each installed on its own elevated support and concrete base. The lines were grouped inside rigid line covers secured to the façade to preserve the building’s appearance and protect the refrigerant lines.

Why install two systems instead of a single, larger unit?

The presence of two outdoor units indicates a configuration that allows different areas of the building to be treated separately. This approach can offer several advantages in a duplex, a multi-level dwelling, or a building with areas having distinct heating and cooling needs.

With two wall-mounted heat pumps, each zone can generally be controlled independently. This means part of the building can be heated or cooled without imposing exactly the same setting on all occupants.

This configuration notably allows:

• to adapt the temperature to the needs of each floor or dwelling;
• to reduce temperature differences between sun-exposed areas and those with more shade;
• to avoid oversizing a single indoor unit;
• to maintain greater autonomy when spaces are occupied on different schedules;
• to improve heating distribution in a compartmentalized building.

However, the final capacity selection should never be based solely on the total floor area or the machine’s external dimensions. At AirGreen, we also assess the insulation, windows, solar exposure, room layout, ceiling height, and heat losses specific to each zone.

Units installed above ground level

The two outdoor units visible in this installation in Auteuil, Laval do not rest directly on the ground. They are mounted on metal supports secured to individual concrete slabs.

This method addresses several practical needs specific to Quebec’s climate.

Reducing snow-related risks

An outdoor unit placed too close to the ground can be obstructed by accumulated snow, particularly after clearing a driveway or following several closely spaced snowfalls. The supports create space beneath the appliances and keep their air intakes at a safer height.

Clearance must nevertheless be monitored during the winter. A heat pump must be able to draw in and discharge air freely. A snowdrift forming in front of the fan can reduce performance, increase the frequency of defrost cycles, and place unnecessary strain on the equipment.

Defrost water management

In heating mode, a heat pump extracts heat from the outdoor air. Frost may then form on the coil, periodically triggering a defrost cycle. The water produced must be able to drain beneath the appliance without accumulating in the chassis.

The separate bases and elevated supports facilitate this drainage. They also limit the appliance’s prolonged contact with ground moisture, leaves, and organic debris.

Mechanical stabilization

A ground surface made up of soil and vegetation can shift with freeze-thaw cycles. A stable base helps keep the unit level and protect the refrigerant lines from repeated movement.

In this installation, each unit has its own slab. This arrangement also makes it possible to service one appliance without moving or destabilizing the other.

An installation designed around the outdoor staircase

The main visible constraint at the site was the metal staircase installed directly in front of and above the available area. Its structure includes several vertical posts, inclined steps, and an upper platform highly exposed to the elements.

Such an environment requires more precise planning than an installation on a completely unobstructed façade.

In particular, we need to verify:

• that the front of the units is not blocked by a post;
• that the service panel can be opened;
• that the fan has sufficient clearance;
• that the lines are not exposed to movement or vibrations from the stairs;
• so that water from the platform does not continuously flow into the units;
• so that technicians can access the connections during servicing or repairs.

The two units were positioned in the open spaces between the studs. Their fans remain directed toward an open area, while the service sides remain accessible.

This decision is important. An outdoor unit should not simply “fit” into the available space. It must also be serviceable throughout its entire service life.

Lines Protected by Line Hides

The photograph shows a horizontally installed line-hide system at the base of the wall, then extended toward the various areas of the building. These conduits generally protect insulated copper lines, the communication cable, and, depending on the configuration, certain sections of the drain line.

Proper finishing serves several purposes:

• protect the insulation from UV rays and mechanical damage;
• reduce the risk of the lines being pulled or snagged;
• limit exposure to birds and small animals;
• maintain a more uniform appearance on the façade;
• make it easier to identify the route during future service work.

Changes in direction were made using finish fittings rather than leaving the lines exposed. This attention to detail is especially important on multi-unit residential buildings, where several HVAC systems may eventually share the same façade.

An Independent and Accessible Electrical Installation

Electrical boxes are visible near the outdoor units. Their location makes it possible to isolate the power supply to each unit during servicing, in accordance with the applicable installation requirements.

For the Hitachi airHome 800 series, electrical requirements vary according to the selected capacity. The 9,000 and 12,000 BTU models, in particular, use a minimum circuit ampacity of 14 A and maximum overcurrent protection of 25 A, according to the manufacturer’s documentation. The 18,000 and 24,000 BTU models have a minimum circuit ampacity of 20 A and maximum overcurrent protection of 35 A.

These values do not mean that a circuit breaker can be selected approximately. The unit’s nameplate, the exact model specifications, and Code requirements must always be followed.

Why the Hitachi airHome 800 Is Well Suited to Laval Conditions

The Hitachi airHome 800 is a wall-mounted heat pump with an Inverter compressor designed to provide cooling, heating, and several air treatment functions. The line is available in nominal cooling capacities ranging from 9,500 to 22,000 BTU/h, depending on the model.

Its published operating range extends to approximately -30 °C in heating and -20 °C in cooling, which may be useful in certain applications requiring off-season cooling. The documentation also indicates a maximum heating capacity maintained at 100% of rated capacity at -20 °C, depending on the model. Efficiencies reach up to 26.5 SEER2 and up to 9.7 HSPF2 in Climate Zone 5.

A range of capacities for different types of rooms

The series includes four main sizes:

9,000 BTU Hitachi airHome 800

The RAK-XJ09PHAA model, paired with the RAC-XJ09WHAA outdoor unit, provides a rated cooling capacity of 9,500 BTU/h and a rated heating capacity of 12,000 BTU/h.

Its seasonal efficiency can reach 26.5 SEER2. It is generally suitable for smaller spaces when the load calculation confirms that this capacity is appropriate.

12,000 BTU Hitachi airHome 800

The RAK-XJ12PHAA model with the RAC-XJ12WHAA outdoor unit produces 12,500 BTU/h of rated cooling capacity and 13,500 BTU/h of rated heating capacity.

This capacity is often considered for a living room, an open floor, or a medium-sized residential area. However, actual sizing depends on the building envelope.

18,000 BTU Hitachi airHome 800

The RAK-XJ18PHAA and RAC-XJ18WHAA combination offers 18,000 BTU/h of rated cooling capacity and 21,600 BTU/h of rated heating capacity.

The refrigerant connection uses a 1/2-inch gas diameter, compared with 3/8 inch for the more compact models. This detail must be planned before the lines are routed.

24,000 BTU Hitachi airHome 800

The RAK-XJ24PHAA model with the RAC-XJ24WHAA outdoor unit provides 22,000 BTU/h of rated cooling capacity and 25,400 BTU/h of rated heating capacity.

It uses 3/8-inch liquid and 5/8-inch gas connections. Its outdoor unit is also heavier and larger, which affects the choice of brackets, pad, and location.

At the Auteuil site, the nameplates are not readable from the overall view. It would therefore be inaccurate to determine the capacities solely from the photograph. This situation highlights an important rule: two units that look similar on the outside may have different capacities, electrical requirements, and piping dimensions.

Heating performance designed for cold temperatures

In Laval, a heat pump must do more than simply perform efficiently on a cool autumn day. It must also maintain useful capacity when the temperature drops well below freezing.

The HeatForce technology in the airHome 800 series is designed to maintain heating in cold weather. Depending on the capacity, the advertised maximum output at -30 °C ranges from 5,500 to 15,000 BTU/h.

This does not automatically mean that the heat pump completely replaces all heating systems in all buildings. The decision depends on the actual heating load, the installed capacity, and the presence of supplemental heating.

In an older building in Auteuil, Montréal, or Longueuil, infiltration losses can be very different from those of a recent construction. Professional sizing therefore remains essential.

Defrosting technology adapted to periods of freezing rain

The airHome 800 includes an adaptive defrost function. This feature helps the system manage frost formation on the outdoor heat exchanger when the air is cold and humid.

However, installation beneath a metal structure requires additional vigilance. Water draining from a platform, melting snow, and icicles must not be directed toward the top of the unit. When snow protection is necessary, it must be installed without blocking airflow or making maintenance more difficult.

FrostWash 3.0 and Mold Guard 2.0

The airHome 800 series is not limited to heating and cooling. It includes several functions designed to maintain the cleanliness of the indoor unit.

FrostWash 3.0 uses a heating, freezing, and thawing cycle to loosen particles accumulated on the heat exchanger. The manufacturer presents this function as a way to reduce the buildup of contaminants and certain odors.

Mold Guard 2.0 monitors conditions inside the unit, even when it is turned off. When conditions favorable to mold growth are detected, the system can heat the coil to dry it.

These technologies do not replace regular HVAC maintenance. The filters must be inspected, the condensate drain must remain clear, and more thorough cleaning may become necessary depending on the environment, the presence of pets, or the amount of dust.

PM2.5 filtration and stainless-steel prefilter

The indoor unit includes a PM2.5 activated carbon filter and a stainless-steel prefilter. The carbon filter helps trap certain small particles and reduce certain odors and volatile organic compounds.

To maintain this efficiency, the filters must be cleaned or replaced according to the applicable recommendations. A heat pump with clogged filters may produce less airflow, become noisier, and run for longer periods.

Wi-Fi control with airCloud Go

The Wi-Fi interface for the airCloud Go app is included for concealed installation in the indoor unit. The app allows users to change settings remotely, set schedules, and view certain operating information.

Available functions include:

• weekly timer;
• remote temperature control;
• Smart-Fence, based on the user’s arrival or departure;
• estimated energy consumption tracking;
• display of certain error codes;
• activation of self-cleaning functions;
• compatibility with Amazon Alexa and Google Home.

The Smart Eco function also uses a motion sensor to detect when the room is unoccupied. After a set period, the unit can reduce its energy consumption and then resume its original setting when the occupants return.

Quiet indoor operation

The 9,000 and 12,000 BTU indoor units can reach sound levels as low as 30 dB(A) in quiet mode. This figure is particularly relevant for a bedroom, office, or room where ventilation noise is easily noticeable.

Proper installation also affects acoustic comfort. An outdoor unit that is not level, an unstable support, piping in direct contact with the building structure, or an improperly secured line cover can transmit vibrations.

On this site, the units are installed on independent supports rather than directly on the façade. This method can help reduce vibration transmission to the wall, provided that the fasteners and bases are properly installed.

R32 refrigerant and installation considerations

The Hitachi airHome 800 uses the refrigerant R32, which has a lower global warming potential than some older refrigerants.

Its use nevertheless requires installation carried out with the proper tools, procedures, and practices. Connections must be tightened to the recommended torque, the piping must be pressurized to check for leaks, and an adequate vacuum must be pulled before commissioning.

Poor preparation of the lines can cause a slow leak, reduced performance, or premature compressor failure. Installation quality remains just as important as equipment quality.

Mistakes to avoid on a similar installation

This HVAC installation in Auteuil highlights several common mistakes:

1. Install the unit directly in the ground.
   The ground can settle and retain moisture around the unit.
2. Placing the fan in front of a post or fence.
   The discharged warm or cool air may be drawn back into the unit.
3. Neglecting water coming from the upper staircase.
   A structure above can concentrate water, snow, and ice.
4. Choosing a capacity based solely on floor area.
   Two buildings of the same size can have very different heating and cooling loads.
5. Using the same line diameters for all capacities.
   The airHome 800 models do not all use the same refrigerant connections.
6. Forgetting the space required for maintenance.
   An appliance placed too close to a post or wall can become difficult to repair.
7. Concealing the lines without planning for their slope and accessibility.
   A beautiful finish should not compromise drainage or prevent a future inspection.

Warranties and incentive eligibility

Hitachi documentation states a standard seven-year warranty on the compressor and five years on parts. For certain residential installations registered online, extended ten-year coverage on the compressor and parts may be available at no additional cost.

An enhanced option may also provide up to twelve years of coverage on the compressor, ten years on parts, and ten years on labor, depending on the conditions, registration, and selected upgrade.

The brochure also indicates that the airHome 800 series may qualify for several provincial heat pump incentives. Actual eligibility must always be confirmed based on the exact model, the AHRI reference number, the capacity recognized at the required temperature, and the program rules in effect on the installation date.

A representative example of AirGreen’s work in Laval

This project demonstrates our approach to a wall-mounted heat pump installation in Laval: we do not simply look for a space where the equipment can be installed. We analyze the façade, airflow, obstacles, snow, drainage, vibrations, service clearances, and the entire path of the lines.

The rusted staircase, vertical supports, window, landscaped grounds, and the two systems to be integrated required precise planning. The units were separated, elevated, and placed in areas that allow for proper operation and maintenance.

We apply this same level of care to installations completed in Montréal, Laval, Longueuil, the North Shore and the South Shore, whether it involves a single wall-mounted heat pump, several independent systems, or a complete HVAC installation for a multi-unit building.