Installation of a HITACHI airHome Multi dual-zone, multi-zone heat pump in Ahuntsic-Cartierville, Montreal

Commissioning verified all the way down to the supply-air temperature

In this Ahuntsic-Cartierville residence in Montreal, we installed a HITACHI airHome Multi dual-zone multi-zone heat pump to cool and heat two separate areas of the property using a single outdoor unit. The project did not end when the units were mounted on the wall and the connections were completed. As with each of our installations, we dedicated a full stage to commissioning, operational testing, and verifying actual performance.

The photo taken on site precisely illustrates this phase. A HITACHI indoor unit is operating with its air-distribution louver open, while our technician uses an infrared thermometer to check the temperature near the air outlet. This check is part of a series of tests that allows us to confirm that the heat pump is responding correctly to commands, that air is being distributed throughout the room, and that the refrigeration circuit is operating consistently.

A system may appear to be working simply because the fan is running. However, that is not enough. A true professional HVAC installation must be methodically validated before it is handed over to the owner.

In this Ahuntsic-Cartierville project, we specifically checked:

• the start-up of both indoor units;
• communication between the units and the outdoor unit;
• switching between the permitted modes;
• the operation of the motorized dampers;
• the response to changes in the setpoint temperature;
• the supply-air temperature;
• condensate drainage;
• the absence of vibrations or unusual noises;
• the tightness of the refrigerant connections;
• the individual operation of each zone.

This step makes it possible to immediately identify an issue that might otherwise appear after the team has left: incorrect communication wiring, an improperly sloped drain, an indoor unit connected to the wrong outdoor port, an inadequate amount of refrigerant, or an incorrect control setting.

Why a dual-zone configuration was suitable for this property

A dual-zone heat pump is particularly useful when a single wall-mounted unit cannot distribute air adequately throughout the residence. In many homes and plexes in Ahuntsic-Cartierville, the floor layout, hallways, stairwells, and interior partitions limit the natural movement of air.

A unit installed in the living room may adequately condition the living area without maintaining an even temperature in a distant bedroom or on another floor. Rather than oversizing a single wall-mounted head in the hope of pushing air through several doors, we can create two zones that match the building’s actual needs.

Each indoor unit in the HITACHI system can be controlled separately. Occupants can therefore:

• select a different temperature in each zone;
• adjust fan speeds independently;
• turn off a unit when the room is not in use;
• direct airflow according to the layout;
• schedule operation according to occupancy.

However, the two units share the same outdoor unit. They must therefore operate in compatible modes. In summer, they can be used for cooling, dehumidification, or ventilation. In winter, they operate in heating or ventilation mode. One zone normally cannot heat while the other simultaneously requests cooling.

This detail is important for homeowners comparing a multi-zone heat pump with two independent single-zone systems. A multi-zone system reduces the outdoor footprint and centralizes the installation, but the zones remain linked by the system’s primary mode.

A wall-mounted unit installed to distribute air throughout the room, not merely to occupy an open space

The position of an indoor unit directly affects comfort. We do not choose its location solely based on where it is easiest to drill through the wall.

For this installation, we took several factors into account:

Air throw distance

The unit must blow toward a sufficiently open area. If it faces a nearby partition, cabinet, or obstacle, the treated air quickly returns toward the appliance without mixing properly with the room air.

Installation height

A wall-mounted unit must be high enough to ensure good air distribution while maintaining the clearances specified by HITACHI. The front panel must also be able to open, and the filters must be removable for maintenance.

The occupants’ proximity

An airflow directed continuously toward a bed, sofa, or desk can become uncomfortable, even if the room’s overall temperature is correct. The louver’s orientation and the appliance’s location must therefore be analyzed together.

The routing of the lines and drain

Behind the unit are the refrigerant lines, communication wiring, and condensate drain. Their routing must be feasible without creating a backfall in the drain or unnecessarily adding bends in the copper tubing.

In older buildings in Montréal, we must also work around masonry walls, joists, existing finishes, and renovations carried out over the years. A careful survey helps avoid drilling into a structural element, electrical wiring, or a section that would be difficult to close neatly.

What we check with an infrared thermometer

The thermometer visible in the photo measures a surface temperature in the targeted area. It is useful for making a quick comparison between the return air, the louver, nearby surfaces, and the air outlet.

This measurement does not replace refrigeration diagnostic instruments or a complete temperature analysis. Rather, it is one of the checks performed during commissioning.

We use this information to confirm that:

• the unit responds to the heating or cooling demand;
• the temperature changes after the compressor starts;
• the air outlet louver is receiving the conditioned air properly;
• no abnormal difference appears between the zones;
• operation remains stable after several minutes.

An instantaneous reading must always be interpreted according to the context. The outdoor temperature, the room’s initial temperature, the fan speed, the selected mode, and the operating time all affect the result. That is why we never assess a heat pump based on a single number displayed on a measuring device.

The photo primarily demonstrates an essential practice: we test the installed system instead of assuming it is working properly.

The characteristics of the HITACHI airHome Multi and their importance in an installation in Montréal

The HITACHI airHome Multi series comprises multizone heat pumps with Inverter technology that can power two to five indoor units. According to the manufacturer's documentation, the outdoor capacities in the range extend from 18,000 to 42,000 BTU/h. It allows the combination of wall-mounted units, floor consoles, ducted units, and mini-cassettes according to the architectural needs of the different rooms.

For a dual-zone configuration, the range includes the RAM-G18N2HAA outdoor model, equipped with two indoor connections. Its published rated capacity is 18,000 BTU/h in cooling and 22,000 BTU/h in heating. However, the exact model and the capacities of the installed indoor units must always be confirmed using the nameplates and the combination selected for the project.

Inverter technology suited to two variable demands

In a residence, the two zones do not necessarily reach their set temperatures at the same time. A room exposed to sunlight may continue to require cooling while a shaded bedroom has almost no load.

Inverter technology allows the compressor to adjust its speed rather than operating only at full capacity or being off. This modulation promotes:

• more stable temperatures;
• less abrupt operating cycles;
• a better response when only one zone is active;
• fewer frequent restarts;
• generally quieter operation;
• energy consumption adapted to the actual load.

In a multizone system, this modulation remains constrained by the unit's limits. A single small indoor unit in operation may sometimes receive more minimum capacity than it requires. This is one reason why we carefully select capacities instead of automatically installing the largest outdoor unit available.

High seasonal performance depending on the selected combination

HITACHI documentation indicates that the series can achieve a TRÉS2 of 23.0 and a Region 5 CPSC2 of 7.85. These values correspond to the best configurations in the range and should not be applied indiscriminately to all combinations.

For the ductless dual-zone model, the published data includes, among other things:

• a rated cooling capacity of 18,000 BTU/h;
• a rated heating capacity of 22,000 BTU/h;
• a TRÉ2 of up to 12.5;
• a TRÉS2 of up to 23.0;
• a Region 5 CPSC2 of up to 7.85;
• a maximum heating capacity of 14,300 BTU/h at −15 °C;
• a maximum heating capacity of 9,700 BTU/h at −20 °C.

For an Ahuntsic-Cartierville homeowner, low-temperature capacity is just as important as the nominal BTU rating. A heat pump may be labeled “18,000 BTU” while providing lower capacity when the outdoor temperature drops significantly.

We therefore assess the system based on:

1. of the building’s heat loss;
2. of wall and roof insulation;
3. of window quality;
4. of exposure to wind;
5. of the floor served;
6. of the area of each zone;
7. of the available supplemental heating system.

Heating operation down to -20 °C

HITACHI publishes a heating operating range down to -20 °C for the airHome Multi series. The system can therefore contribute to heating during much of the Montreal winter.

This does not mean that its capacity remains the same at all temperatures. The colder the outdoor air becomes, the harder the heat pump must work to extract heat. Available capacity gradually decreases, and defrost cycles become necessary when frost forms on the outdoor coil.

In a properly sized home, the heat pump can significantly reduce the use of electric baseboard heaters or other supplemental heating. During periods of extreme cold, however, the auxiliary system may still be needed to cover all heat loss.

Indoor units suited to several types of rooms

Page 2 of the HITACHI brochure presents five families of indoor units compatible with airHome Multi. This variety makes it possible to choose a different solution for each zone.

The airHome 400 wall-mounted units

They are available in capacities ranging from 7,000 to 24,000 BTU/h. They are suitable for installations where simple controls, accessible maintenance, and direct air distribution into the room are desired.

The airHome 650 wall-mounted units

They may include additional features, including a motion sensor on certain models, as well as optional compatibility with the airCloud Go app.

The airHome Floor consoles

Installed near the floor, they are an option when the upper part of the walls is occupied by windows, beams, or architectural features.

The ducted units

They are concealed in a ceiling or mechanical space and supply grilles through short ducts. They are suitable when the homeowner wants to reduce the visual presence of the equipment.

The mini cassettes

Their four-way air distribution helps spread air throughout an open space. The documentation indicates a 22 in by 22 in unit format, designed to fit between standard-size joists.

FrostWash and Mold Guard for internal maintenance

Compatible units may incorporate FrostWash technology, which uses a freezing and thawing process to help clean the indoor coil. The cycle is intended to loosen and remove certain contaminants accumulated on the heat exchanger.

The Mold Guard function helps dry the components after cooling or dehumidification operation. According to the documentation, the fan may continue operating for approximately 60 minutes to reduce residual moisture inside the unit.

These functions improve internal humidity management, but they do not replace regular HVAC maintenance. Filters must be washed, drains inspected, and coils checked periodically.

R32 refrigerant and the importance of perfectly airtight connections

The airHome Multi lineup uses R32 refrigerant. Compatible indoor units include a sensor designed to signal a leak with a visual and audible alarm, depending on the appliance and accessories used.

Installing an R32 circuit requires a rigorous method:

• clean cutting of the copper lines;
• uniform flares;
• tightening to the recommended torque;
• leak test;
• deep vacuum evacuation;
• vacuum-hold test;
• proper opening of the service valves;
• adding refrigerant when the length requires it;
• precise identification of the circuits for each zone.

In a dual-zone system, identifying the lines and cables is essential. If an indoor unit’s communication wires are connected to the wrong refrigerant circuit, the system may behave inconsistently. We therefore validate each pairing during commissioning.

Piping limits to observe

For the two-connection version, HITACHI publishes the following limits:

• maximum total piping length: 165 ft;
• maximum length between the outdoor unit and each indoor unit: 82 ft;
• maximum total elevation difference: 66 ft;
• published minimum length: 16 ft;
• external liquid connections: two connections for 1/4 po;
• external gas connections: two connections for 3/8 po.

These limits do not encourage unnecessarily lengthening the lines. A shorter, well-planned route makes installation easier, reduces losses, decreases the number of joints, and simplifies future maintenance.

Mistakes we avoid during a dual-zone installation

Choosing BTUs based solely on floor area

Two rooms of the same size can have very different loads. The floor, windows, orientation, and insulation must all be considered.

Installing a head facing an obstacle

Poor air distribution creates hot or cold spots and can cause conditioned air to return prematurely to the unit’s sensor.

Neglecting the drain slope

A drain without sufficient slope can cause backup, overflow, or drainage noises.

Mixing up circuits A and B

In a multi-zone system, each set of pipes must correspond to the correct communication wiring and the correct indoor unit.

Simply starting the fans

The system must be tested in heating or cooling mode, with enough time to observe the compressor’s response and temperature changes.

Failing to explain the shared mode to the owner

Users should know that the two zones generally cannot operate simultaneously in opposite modes.

Documented commissioning to deliver a fully operational system

At the end of this heat pump installation in Ahuntsic-Cartierville, we checked the airflow, the response of the controls, and the operation of both zones. The measurement visible in the photo represents part of this inspection, not simply a promotional image taken in front of a new appliance.

Our job is to hand the owner a system that is:

• properly sized;
• connected according to the manufacturer’s requirements;
• tested in its various modes;
• ready to drain condensation;
• accessible for maintenance;
• explained to the occupants.

This method applies to our multi-zone heat pump installations in Montreal, as well as in Laval, Longueuil, the North Shore, and the South Shore. Architectural constraints vary from one building to another, but commissioning precision remains the same.

The Ahuntsic-Cartierville project demonstrates that a dual-zone system is not simply a matter of installing two wall-mounted units. Capacity selection, line routing, circuit pairing, drainage, and final testing must form a coherent whole. This coherence enables a HITACHI airHome Multi heat pump to provide stable comfort in two separate spaces, season after season.