A compact installation between a deck, a brick wall, and an existing mechanical exhaust outlet
This multizone heat pump installation in Sainte-Catherine presented a challenge we often encounter in established residential areas on Montreal’s South Shore: integrating high-performance outdoor equipment into an already crowded space without compromising access to the yard, movement on the deck, or future system maintenance.
The building had a brick rear facade, an elevated wooden deck, a large mechanical exhaust outlet protected by a metal cover, and a relatively narrow passage between these elements. A HITACHI airHome Multi dual-zone heat pump had to be installed there to power two indoor units while maintaining functional clearance around the unit.
The result visible in the photo is based on several technical decisions made even before the bracket was secured:
- installation of the outdoor unit on an elevated wall bracket;
- positioning between the deck and the existing mechanical exhaust outlet;
- orienting the fan toward an open area;
- vertical routing of the lines inside a line-hide cover;
- installation of an accessible electrical disconnect switch;
- protection for the refrigerant lines where they exit the unit;
- clearance between the unit and the ground, snow, and seasonal debris.
This setup was not improvised. In a confined space, a few inches can determine whether the heat pump will operate efficiently, whether it can be properly serviced, and whether its installation will remain practical for everyday use.
Why choose a dual-zone heat pump for this residence?
A dual-zone multizone heat pump allows two indoor units to be connected to a single outdoor unit. This setup is particularly well suited to homes where two separate areas require independent control, for example:
- a ground floor and an upper floor;
- a living area and a primary bedroom;
- an addition and the original part of the house;
- two dwellings or two different occupancy zones;
- one room that receives a lot of sunlight and another that is cooler.
Each indoor unit can have its own setpoint temperature, fan speed, and settings. One zone can be turned off when no one is using it, while the other continues heating or cooling.
However, the system must remain in a compatible shared mode. In summer, the units can operate in cooling, dehumidification, or ventilation mode. In winter, they can operate in heating or ventilation mode. One indoor unit normally cannot cool while the other heats, since they share the same outdoor circuit.
For this project in Sainte-Catherine, the multi-zone system primarily avoided adding two outdoor units to an already limited yard. A single outdoor unit can serve both areas while reducing visual and mechanical clutter.
An elevated outdoor unit designed to withstand Quebec winters
We mounted the heat pump on a sturdy wall bracket rather than placing it on a ground slab. This choice is particularly relevant in the environment shown in the photo.
The ground beneath the unit is narrow and partially covered with gravel, soil, leaves, and residual snow. A unit installed too low would have been more exposed:
- to snow accumulation;
- to splashes and moisture;
- to fallen leaves;
- to ice from defrost cycles;
- to small debris carried by the wind;
- to reduced access around the deck.
The metal bracket keeps the base of the HITACHI heat pump at a safer height. The support points also include vibration-damping elements, visible beneath the unit’s feet. They help limit the transmission of vibrations to the building structure.
On a brick wall, the quality of the anchoring is essential. We must ensure that the unit’s weight, compressor vibrations, and wind-related stresses are supported by an appropriate structure. Inadequate fastening can cause movement, noise, or premature deterioration of the cladding.
Precise clearance despite very limited space
The unit was placed between the wooden deck on the left and a large existing mechanical outlet on the right. The brick wall is directly behind the unit.
This type of location requires careful verification of several clearances:
In front of the fan
The unit’s fan faces the open space. This orientation allows the discharged air to disperse rather than hit the brick wall directly or circulate beneath the deck.
An obstacle placed too close to the fan can cause air recirculation. In summer, the unit could draw back in the hot air it has just discharged. In winter, it could draw in cold, damp air, increasing operating strain.
Behind and on the sides
The back of the unit must retain the space needed for air intake and access to the components. Even when an appliance appears shallow, the outdoor coil must be able to breathe across its entire surface.
Above the unit
The heat pump is installed below the upper level of the deck, but without being enclosed in a cavity. We must avoid areas where snow, water, or ice could fall directly onto the unit.
Near the mechanical outlet
The large metal cover on the right most likely protects a shaft, outlet, or existing mechanical equipment. We kept space between this structure and the heat pump so as not to block its opening or make future servicing impossible.
This planning is one of the differences between an installation that merely seems to « fit in the space » and a professional HVAC installation designed to last.
The features of the HITACHI airHome Multi and the technical choices behind this installation
The HITACHI airHome Multi range includes multi-zone systems with Inverter technology capable of serving two to five indoor units. The manufacturer's documentation presents outdoor units from 18,000 to 42,000 BTU/h, with various options for wall-mounted units, floor consoles, mini-cassettes, and ducted models.
In the documented range, the outdoor configuration with two connections corresponds to model RAM-G18N2HAA. Its published nominal capacity is 18,000 BTU/h in cooling and 22,000 BTU/h in heating. The actual selection of the two indoor units must comply with the combinations authorized by HITACHI and the heating and cooling requirements of each zone.
Inverter technology for modulating capacity
A traditional fixed-capacity heat pump often alternates between complete shutdown and full power. Inverter technology works differently: it gradually adjusts the compressor speed according to demand.
In a dual-zone installation, this modulation is important. The two rooms do not always require the same amount of heating or cooling. For example, one zone may have reached its temperature while the second continues to demand energy.
The Inverter can then adjust its operation, which promotes:
- more stable temperature;
- less abrupt cycles;
- better management of partial loads;
- quieter operation;
- consumption better aligned with actual demand.
This does not replace a load calculation. An oversized unit or an unsuitable combination of indoor units can still reduce comfort. We therefore assess the dimensions, insulation, windows, solar orientation, and use of each space before finalizing the selection.
Seasonal efficiency of up to a TRÉS2 of 23.0
According to the combinations presented by the manufacturer, the airHome Multi series can achieve a TRÉS2 of 23.0 and a Region 5 CPSC2 of 7.85. These values represent the best results in the range and do not automatically apply to all configurations.
For the ductless dual-zone version, the brochure indicates, among other things:
- a TRÉ2 of up to 12.5;
- a TRÉS2 of up to 23.0;
- a Region 5 CPSC2 of up to 7.85;
- a published COP of 3.3 at 8 °C;
- a maximum heating capacity of 14,300 BTU/h at -15 °C;
- a maximum heating capacity of 9,700 BTU/h at -20 °C.
These data are useful for understanding low-temperature performance. They also show why we never assess a heat pump solely on its rated capacity. In Sainte-Catherine, as elsewhere on the South Shore, the actual capacity available during January cold snaps must be compared with the building’s heat losses.
A heating range down to -20 °C
The airHome Multi system is designed to operate in heating mode down to -20 °C, according to HITACHI documentation. It can therefore make a significant contribution to heating the home during a large part of the winter.
As the outdoor temperature drops, the capacity and efficiency of an air-source heat pump gradually decrease. In many buildings, supplemental heating remains necessary during the coldest periods or when a rapid temperature recovery is required.
We always explain this reality to the customer. The heat pump can significantly reduce the use of electric baseboard heaters or another backup system, but its exact role depends on the home’s heating load and the selected capacity.
R32 refrigerant and the leak sensor
The range uses the refrigerant R32. Compatible indoor units include a leak sensor that can trigger a visual and audible alert, depending on the model and selected accessories.
R32 requires precise installation practices:
- compliant flared connections;
- controlled tightening torque;
- leak test;
- proper evacuation;
- compliance with piping limits;
- complete pipe protection.
In this installation, the two sets of lines are grouped near the base of the outdoor unit before rising into a vertical pipe cover matching the building’s color.
A vertical pipe cover integrated into the brick wall
The pipe cover visible behind the unit serves both an aesthetic and technical purpose. It protects the refrigerant lines, communication cables and, depending on the configuration, condensate drains.
Without protection, pipe insulation can be damaged by:
- ultraviolet rays;
- birds and small animals;
- friction;
- freezing and thawing;
- work carried out near the wall;
- accidental impacts.
The vertical routing reduces detours and maintains a neat appearance on the rear façade. The beige line-set cover also blends in with the brick and existing elements.
At the base of the unit, the lines remain accessible for connections and maintenance. They are bent with a sufficient radius to avoid compressing the copper or placing stress on the service valves.
An accessible, clearly separated electrical circuit
The gray disconnect is installed on the brick wall near the unit. It allows a technician to shut off power to the heat pump before servicing it.
The dual-zone version shown in the brochure operates on a nominal 208-230 V, single-phase, 60 Hz power supply. HITACHI specifies a minimum circuit ampacity of 16 A and maximum overcurrent protection of 25 A for model RAM-G18N2HAA. The nameplate on the installed unit always remains the electrician’s final reference.
The outdoor cable is protected and routed so that it does not rest on the ground or block access to the valves and service panels.
Indoor unit options for two separate zones
The HITACHI airHome Multi series can accommodate several types of indoor units. This flexibility makes it possible to treat two rooms differently according to their layout.
airHome 400 wall-mounted units
They feature a simple design and capacities ranging from 7,000 to 24,000 BTU/h, depending on the model. They include FrostWash technology and filtration suited to residential use.
airHome 650 wall-mounted units
They add features such as a motion detector on certain models, Smart Eco management, and the option to control the unit with the optional airCloud Go interface.
Floor consoles
They can be useful when a wall is occupied by windows, when the ceiling is low, or when air distribution near the floor better suits the layout.
Ducted units and mini-cassettes
They allow for a more discreet installation. Mini-cassettes distribute air in four directions, while ducted units can supply one or more grilles, depending on the duct design.
The presence of two connections does not mean that both indoor units must have the same capacity. However, they must form an approved combination that is appropriate for each room’s load.
FrostWash and Mold Guard: features that do not replace maintenance
The FrostWash technology uses a freezing and thawing process to help clean the indoor unit’s coil. The Mold Guard function circulates air to dry the internal components after cooling or dehumidification.
These features help limit the buildup of contaminants and moisture, but they do not make the unit maintenance-free.
To maintain performance, we particularly recommend:
- cleaning the filters regularly;
- checking that the condensate drains remain clear;
- inspecting the coils;
- keeping the outdoor unit clear;
- removing leaves and debris around the support;
- never covering the unit while it is operating.
In the area visible in the photo, leaves and snow may accumulate beneath the deck. The owner must therefore monitor this area during the fall and winter.
Errors this installation helps avoid
Installing the heat pump directly on the ground
In this narrow passage, a ground slab would have exposed the unit to accumulations while reducing access between the deck and the mechanical outlet.
Directing the fan toward the brick
Such an orientation would have encouraged air recirculation and increased reflected noise toward the building.
Hiding the disconnect switch behind the unit
The disconnect switch must remain accessible. Placing it in an area blocked by the heat pump would complicate every service intervention.
Crushing the lines against the mechanical outlet
The lines must maintain an appropriate bending radius. They must not be pinched between the unit and an existing structure.
Installing a support without vibration control
A heat pump with inadequate mechanical isolation can transmit a hum to the wall, particularly near bedrooms or resting areas.
Neglecting future maintenance
An installer must plan for panel removal, access to the valves, coil cleaning and the possible replacement of components. Equipment that is too tightly confined may function properly at first but be costly to maintain.
A solution suited to compact yards in Sainte-Catherine
This project shows that a HITACHI airHome Multi dual-zone multi-zone heat pump can be installed neatly in a complex backyard when an accurate assessment is conducted before the work begins.
We used the available height, kept the area in front of the fan open, grouped the lines inside a line-hide cover and maintained access to the disconnect switch and existing mechanical components. The outdoor unit serves two zones without occupying two separate spaces.
This type of project is well suited to homes in Sainte-Catherine, Candiac, Delson, Saint-Constant, La Prairie, Brossard and Longueuil, where the distances between buildings, decks, fences and existing equipment often require a very compact installation.
At AirGreen, we perform this same analysis for our heat pump installations in Montreal, Laval, Longueuil, on the North Shore and on the South Shore. Our goal is not simply to make the equipment operate on the day it is commissioned. We aim to create an installation that is stable, accessible, protected and suited to Quebec winters.