Three comfort zones connected by a line route designed around the building’s constraints
At Saint-Laurent, on the island of Montréal, we installed a Hitachi airHome Multi triple-zone multi-zone heat pump designed to heat and cool three separate areas of the property from a single outdoor unit. The main challenge was not limited to connecting the three zones; it primarily involved organizing a complex exterior route on a façade already occupied by several structural and mechanical elements.
The site photograph shows an outdoor unit installed on a raised aluminum structure, itself placed on a concrete slab. A network of exterior line-hide covers can also be seen, featuring several horizontal and vertical sections and precise changes in direction. This route was designed to work around the obstacles on the wall, reach the three indoor units, and protect the refrigerant lines along their entire length.
In a single-zone installation, a single pair of lines can sometimes follow a relatively direct path. With a triple-zone heat pump, three separate refrigerant linesets must be coordinated. Each includes its own liquid line, insulated gas line, and communication wiring. Each indoor unit also has its own condensate drainage system.
The visible result in Saint-Laurent therefore illustrates an essential part of our work: transforming a façade with multiple constraints into an organized, accessible, and durable HVAC route.
Why a triple-zone configuration was appropriate
A single wall-mounted unit can effectively treat a large open area, but it cannot always distribute air to enclosed rooms, a basement, or a remote floor. Walls, doors, and corridors quickly limit air circulation.
A triple-zone configuration brings heating and cooling closer to the areas where comfort is actually needed. It is particularly well suited to properties with:
- multiple floors;
- rooms used daily;
- a separate basement;
- a main area and two enclosed zones;
- an extension with different needs from the original building;
- rooms with different sun exposures.
Each indoor unit can be adjusted separately. This gives occupants better control over the temperature in each zone, fan speed, and operating schedules.
A rarely used zone can be turned off while the other two continue operating. This option reduces unnecessary operating periods while avoiding overcooling or overheating certain parts of the home.
A single outdoor unit to serve three spaces
One of the practical advantages of a multi-zone system is the reduced number of compressors installed around the building. Three single-zone heat pumps would have required three outdoor units, three locations, several supports, and more clearance.
The Hitachi airHome Multi combines the three circuits in a single outdoor unit. This approach helps reduce:
- the space occupied in the yard;
- the visual impact of the equipment;
- the number of exterior electrical circuits;
- maintenance points;
- the obstacles around the property.
This solution must nevertheless be sized correctly. A multi-zone system does not consist of randomly adding three indoor units. The combination must be compatible with the outdoor unit’s capacity and with the actual heating and cooling needs of the rooms.
A complex but structured exterior route
The façade visible in the photo has a textured finish, an old vertical downspout, a gutter, electrical components, and obstacles that made it impossible to follow a single straight line.
We therefore arranged the lines in several sections of light-colored line covers. These sections follow the wall in a geometric pattern and make it possible to work around existing features without leaving the refrigerant lines exposed.
The network includes, in particular:
- several vertical rises;
- two main horizontal sections;
- right-angle bends;
- connections between the sections;
- separate outlets leading to the different zones;
- a connection near the outdoor unit.
This arrangement is particularly important in a three-zone installation. Without line covers, the three sets of lines could quickly make the façade look cluttered.
The exterior protection also serves a technical purpose. It reduces the insulation’s exposure to ultraviolet rays, weather, birds, and mechanical damage.
Why Refrigerant Lines Need to Be Protected
The insulation surrounding the refrigerant line is essential to the proper operation of a heat pump. When it remains directly exposed to sunlight, it can dry out, crack, and gradually lose its properties.
Damaged insulation can lead to:
- condensation;
- heat loss;
- higher energy consumption;
- moisture buildup;
- accelerated deterioration of the pipes;
- a neglected exterior appearance.
Line-set covers also make inspections easier. The covers can be removed when a pipe needs to be checked, while protecting the system the rest of the time.
In this Saint-Laurent project, the amount of line-set covering required directly reflects the complexity of the distribution to the three indoor zones.
Condensate drain management
Each indoor unit produces water when operating in cooling or dehumidification mode. This water must be drained in a controlled manner.
In the photograph, drainage pipes can be seen descending between certain sections of line-set covers. Their positioning must maintain a sufficient slope to allow water to drain naturally when the configuration operates by gravity.
An inadequate drain can cause:
- water backing up into the indoor unit;
- water droplets on the wall;
- ceiling or floor damage;
- odors;
- deposit buildup;
- an avoidable service call.
We check each drainage line separately. In a triple-zone installation, proper operation of one drain does not guarantee that of the other two.
An outdoor unit installed on a raised base
The Hitachi unit rests on an aluminum support installed above a concrete slab. This configuration prevents the appliance from being placed directly on the ground or slab.
The clearance beneath the unit offers several benefits suited to Montreal winters:
- reduced risk of snow blockage;
- improved defrost water drainage;
- protection against leaves and debris;
- easier access beneath the cabinet;
- reduced exposure to stagnant moisture;
- simpler inspection of the supports and connections.
During heating operation, frost may form on the outdoor coil. The heat pump then runs a defrost cycle and releases water beneath the unit. Sufficient clearance must be maintained so this water can drain away without immediately forming a block of ice against the cabinet.
The concrete slab provides a solid base, while the support’s adjustable feet allow the unit to be leveled.
Maintaining airflow despite a compact location
The outdoor unit’s front fan must remain completely unobstructed. It is not enough for the unit to physically fit in the available space: it must also be able to move a large volume of air.
We specifically check:
- the distance in front of the fan;
- the clearance at the back;
- the space around the coil;
- the presence of vegetation;
- obstacles that could retain leaves;
- accessibility for cleaning.
Visible vegetation near the installation must be kept at a reasonable distance from the unit. Plants, leaves, and branches must not reach the coil or obstruct the base.
The Hitachi airHome Multi three-zone system: sizing characteristics and precautions
The RAM-G24N3HAA model for three indoor connections
In the Hitachi airHome Multi range, the model designed for three indoor units is the RAM-G24N3HAA. It offers a rated capacity of 24,000 BTU/h in cooling and 24,000 BTU/h in heating.
In a ductless configuration, cooling capacity can modulate approximately from 7,000 to 28,000 BTU/h. Heating capacity can vary from approximately 9,000 to 26,200 BTU/h, depending on zone demand and outdoor conditions.
Inverter technology allows the compressor to adjust its speed. It is therefore not limited to operating either completely stopped or at full power. This modulation helps maintain a more stable temperature and reduce repeated starts.
The technical data sheet on page 4 of the Hitachi documentation also indicates, for the ductless RAM-G24N3HAA, a maximum TRÉS2 of 22.0, a CPSC2 of 7.8 in Region 5, a power supply of 208 to 230 V, and a heating operating range down to -20 °C.
How capacity is distributed among the three zones
A 24,000 BTU/h three-zone heat pump does not automatically provide 24,000 BTU/h to each of the three indoor units. The available outdoor capacity is distributed according to active demand.
When only one zone is operating, the system can direct a larger portion of its capacity to that room, within the specified limits. When all three units require substantial heating at the same time, the capacity is shared.
Sizing must therefore account for several scenarios:
- operation of a single zone;
- operation of two zones;
- simultaneous demand from the three zones;
- peak cooling load;
- heating demand in cold weather;
- actual room occupancy.
A combination with three high-capacity indoor units may be approved by the manufacturer without meaning that each one will receive its full capacity at the same time.
Seasonal performance and everyday comfort
The TRÉS2 measures the system's seasonal cooling efficiency. A value of up to 22.0 places the ductless configuration of the triple-zone model in an appealing category for homeowners who want to reduce their summer energy consumption.
The CPSC2 indicates seasonal heating efficiency. It is particularly relevant in Montreal, where the heat pump may be used for an extended period between fall and spring.
Actual performance nevertheless depends on:
- building insulation;
- window airtightness;
- the requested temperatures;
- pipe length;
- the combination of indoor units;
- filter maintenance;
- coil cleanliness;
- installation quality.
Excellent technical specifications cannot compensate for improper capacity selection or incomplete commissioning.
Heating down to -20 °C: available capacity in very cold weather
The RAM-G24N3HAA can continue operating in heating mode down to -20 °C. However, its capacity decreases as the outdoor temperature drops.
The documentation indicates a maximum heating capacity of approximately:
- 18,500 BTU/h at -15 °C;
- 13,000 BTU/h at -20 °C.
These values provide a more accurate assessment of winter performance. A heat pump can operate at -20 °C without necessarily covering all of the home's heat losses on its own.
In several Saint-Laurent properties, electric baseboards or another existing system may remain available as supplemental heating during the coldest temperatures.
Three different temperatures, but one shared seasonal mode
Each indoor unit can have its own setpoint. A bedroom can be maintained at 20 °C, the main living area at 22 °C, and a third zone at a different temperature.
However, all three units must operate in compatible modes.
In summer, the zones can use:
- air conditioning;
- dehumidification;
- ventilation.
In winter, they can use:
- heating;
- ventilation.
One unit can be turned off while the others operate. However, one zone normally cannot heat while another requests cooling at the same time.
This feature should be understood before purchase, especially when rooms on different sides of the building have sharply contrasting temperatures in spring or fall.
The pipe sizes for the triple-zone model
The RAM-G24N3HAA outdoor unit has three liquid connections 1/4 po and three gas connections 3/8 po.
Each pair of lines must be connected to the correct indoor unit and the correct communication wiring. Reversing them can cause inconsistent operation or fault codes during commissioning.
We therefore identify the branches before connecting them and verify the matches before activating the system.
The complex routing visible outside makes this identification even more important. Once the lines are installed in several sections of line-hide covers, it would be much more difficult to trace an incorrectly identified branch.
The lengths permitted by Hitachi
For the three-zone model, Hitachi specifies, among other things:
- a maximum total piping length of 200 feet, or approximately 60 meters;
- a maximum length of approximately 82 feet per connection;
- a maximum total height of 66 feet;
- a minimum total length of 16 feet;
- a maximum elevation difference of 16 feet between the indoor units.
These limits offer good flexibility when the three zones are distributed across different floors.
However, you should not systematically aim for the maximum lengths. A shorter, more direct route reduces the amount of materials, potential losses, and the need for exterior protection.
In this project, the building's obstacles required several changes in direction, but the routing was organized in a structured manner rather than scattered across the entire façade.
Leak testing and vacuum evacuation of the three branches
A multi-zone installation has more connections than a single-zone system. Each connection must be prepared correctly.
Our procedure notably includes:
- cleanly cutting the copper tubes;
- deburring;
- making flared connections;
- tightening to the specified torque;
- pressure testing;
- leak detection;
- vacuum evacuation;
- checking vacuum stability;
- opening the service valves;
- individual and simultaneous testing of the three zones.
Vacuum evacuation removes air and moisture from the lines before refrigerant is introduced into the circuit. Residual moisture can affect the compressor oil and reduce the heat pump's durability.
R32 refrigerant
The airHome Multi series uses R32 refrigerant. Its installation requires compatible tools and appropriate procedures.
Compatible indoor units may include a leak sensor. Depending on the model, the alert may be conveyed by an indicator light, an audible alarm, or an optional control accessory.
These features add a layer of monitoring, but they do not replace:
- properly made connections;
- a complete leak test;
- a thorough vacuum evacuation;
- an installation that complies with the manufacturer's requirements.
Several styles of compatible indoor units
The Hitachi airHome Multi series can be combined with different indoor unit formats:
- airHome 400 wall-mounted unit;
- airHome 650 wall-mounted unit;
- floor console;
- mini-cassette;
- ducted unit.
This flexibility makes it possible to adapt the three zones to the building’s architecture. An open area can accommodate a wall-mounted unit, while a room with limited overhead space may be better served by a floor console.
Available capacities generally range from 7,000 to 24,000 BTU/h, depending on the series and format.
Cleaning and comfort management features
Depending on the selected indoor units, the system may offer FrostWash technology, which uses a freeze-and-thaw cycle to help clean the indoor coil.
The Mold Guard function circulates air after certain cooling or dehumidification cycles to dry the internal components for approximately 60 minutes.
Other features may include:
- an activated carbon PM2.5 filter;
- a ViroSense S filter;
- Smart Eco mode;
- a motion detector;
- automatic shutoff;
- the optional airCloud Go interface.
Exact availability depends on the selected indoor model. Do not assume that all features are included on every unit.
Eligibility for financial assistance programs
Hitachi documentation indicates that the airHome Multi range may qualify for several provincial incentives.
Eligibility must nevertheless be confirmed based on the exact combination installed, including:
- the outdoor model;
- the three indoor models;
- the AHRI number;
- the capacity recognized by the program;
- the property type;
- the criteria in effect at the time of the application.
We therefore verify the certified combination before confirming any potential financial assistance. The range name or the presence of an efficiency logo is not enough to guarantee a specific amount.
Mistakes to avoid in an installation like the one in Saint-Laurent
Leaving all three line sets exposed
UV rays damage insulation. Visible line-set covers on the façade protect the lines and provide a neater finish.
Using an unplanned route
Adding sections as you go can create a network that is difficult to maintain. The route must be defined before drilling the wall and cutting the lines.
Mixing up the refrigerant branches
Each line must correspond to the correct indoor unit and its communication cable.
Neglecting drain slope
An improperly sloped condensate drain can cause backflow or runoff down the façade.
Installing the Unit Too Close to the Ground
Snow, leaves, and ice can obstruct the equipment. The raised support visible in this project reduces these risks.
Allowing Vegetation to Reach the Coil
The plants must be maintained to preserve airflow and access to the equipment.
Oversizing the Indoor Units
Three zones do not automatically justify three large units. The capacity of each room and the compressor's total capacity must remain balanced.
An Installation Designed to Remain Accessible
A successful outdoor installation should be attractive, but also serviceable. The line covers must be able to be opened, the outdoor unit must remain accessible, and the drains must be inspectable.
In this Saint-Laurent project, the line routing is visible and logical. The different sections show how the network bypasses obstacles and connects to the compressor.
The unit is elevated, the front fan remains unobstructed, and the pad provides a stable surface for the support.
This approach facilitates future HVAC maintenance, whether cleaning the coil, checking the connections, or inspecting a refrigerant branch line.
Hitachi airHome Multi Warranty and Maintenance
The Hitachi brochure states a standard warranty of seven years on the compressor and five years on parts.
For certain eligible residential installations, online registration may provide a ten-year extended warranty on the compressor and a ten-year warranty on parts. Enhanced warranty coverage may also be available subject to the applicable conditions.
The owner should keep:
- the installation invoice;
- the model numbers;
- the serial numbers;
- the commissioning date;
- the registration confirmation;
- the warranty documents.
Routine maintenance includes cleaning the filters, inspecting the drains, clearing vegetation, and cleaning the outdoor coil as needed.
The line covers should also be checked periodically to ensure that the covers remain securely fastened and that no impact has damaged the lines.
This Hitachi airHome Multi triple-zone heat pump installation in Saint-Laurent stands out for its carefully designed outdoor routing, complete protection of the three refrigerant lines, and layout adapted to the actual constraints of the façade. It demonstrates that a well-executed multi-zone project relies as much on pipe planning as on equipment performance.