Installation of Hitachi airHome 400 wall-mounted heat pumps in Montreal’s Old Port

Two wall-mounted units, a long technical route, and airflow distribution designed for the entire room

This wall-mounted heat pump installation in Montreal's Old Port stands out because of the room's length and the need to distribute comfort across several zones rather than concentrate all the cooling at a single end.

In the photograph, two Hitachi airHome 400 indoor units are visible along the same wall. The first is in the foreground, while the second is installed much farther away in the room. Between them, a white line-hide follows the junction of the wall and ceiling over a considerable distance. The entire setup forms a continuous, orderly route that protects the lines while keeping the lower part of the wall clear.

This configuration addresses a common constraint in Montreal's Old Port buildings: spaces can be long, open, or laid out in structures where points of exit to the outside are limited. Installing a single unit at one end could have created a temperature difference between the two sections of the space. By distributing the indoor units, we can better manage the reach of the airflow and reduce areas that are insufficiently cooled.

The image also reveals several important aspects of the project:

• two Hitachi wall-mounted units installed high up;
• a long line-hide placed near the ceiling;
• several straight connections and changes in direction;
• a technical drop to the second unit;
• a ceiling with recessed lighting;
• an existing wall-mounted fan between the two heat pumps;
• a room whose length requires a real distribution strategy.

It was therefore not simply a matter of placing two units on a wall. The installation had to be designed as a cohesive system, taking into account airflow, drainage, refrigerant piping, maintenance access, and the final appearance.

Why two indoor units were appropriate for this space

A wall-mounted heat pump distributes air throughout the room where it is located, but it cannot effectively bypass every obstacle or automatically maintain the same temperature over a very long distance.

In a long space, a single unit can lead to several problems:

• a very cool area near the unit;
• a higher temperature at the opposite end;
• constantly high fan speed;
• occupants directly exposed to the airflow;
• extended operation to compensate for the distance;
• uneven dehumidification;
• increased use of auxiliary fans.

Rather, the presence of two units makes it possible to distribute the load. Each appliance handles a more logical portion of the room and can modulate its operation according to local demand.

The photograph does not make it possible to confirm whether the two units are connected to a single multi-zone outdoor unit or to two independent single-zone systems. This information must be verified using the outdoor unit models and the installation file. In both cases, the principle remains the same: we created several air-distribution points to achieve more uniform comfort in a long room.

The existing wall-mounted fan and the different role of a heat pump

A wall-mounted fan is visible between the two Hitachi units. It can help circulate the air, but it provides neither cooling nor heating.

Its primary role is to move the air already present. It can reduce the sensation of heat on the skin, but it does not remove humidity or actually lower the air temperature as a wall-mounted heat pump does.

The Hitachi units perform several functions that the fan alone cannot provide:

• remove indoor heat in the summer;
• remove some of the humidity;
• transfer heat indoors during the winter;
• modulate their capacity according to demand;
• maintain a set temperature;
• filter the air passing through the units.

The fan can still be used when needed to promote air mixing, but it becomes supplementary equipment rather than the main source of comfort.

A long pipe cover installed against the ceiling

The visible technical route is one of the most important aspects of this project. Clearly, the lines could not all exit directly behind each appliance. We therefore grouped the connections in a conduit installed near the ceiling.

This position offers several advantages:

1. The wall surface remains usable.
   The cover does not cross the center of the wall and limits conflicts with existing furniture, decorations, or equipment.
2. The route follows a natural architectural line.
   The junction between the wall and ceiling is a more discreet location than a conduit installed at eye level.
3. The lines are protected.
   They are less exposed to impacts, furniture movement, or work carried out in the room.
4. Technical access remains possible.
   The cover sections can be opened if an inspection or repair becomes necessary.
5. The connections are grouped together.
   The finish is cleaner than a set of pipes, cables, and drains installed separately.

In a building in the Old Port, the walls may consist of masonry, older structures, partitions added during renovations, or surfaces that are best not opened along their entire length. The line-set cover then becomes a practical solution for creating a controlled route without undertaking major interior finishing work.

The components running inside the casing

The casing may contain several components depending on the system's precise configuration:

• a liquid refrigerant line;
• a gas refrigerant line;
• the thermal insulation on the lines;
• the communication cable;
• certain electrical conductors;
• a condensate drain;
• fasteners and protective materials.

The copper lines must meet the prescribed diameters for each model. The smaller capacities in the range generally use 1/4 in. fittings for liquid and 3/8 in. fittings for gas. Larger models may require a 1/2 in. or 5/8 in. gas line.

We must also respect the copper bend radius. A bend that is too tight can crush a line, restrict refrigerant flow, and affect system operation.

A clean drop to the second unit

At the far right end of the photograph, the horizontal route drops before reaching the second heat pump. Several finishing pieces make it possible to change direction without leaving the lines exposed.

This part of the work requires precise planning. The drop must:

• reach the correct side of the unit;
• avoid an excessive number of elbows;
• leave sufficient space for the lines;
• not push the casing forward;
• keep access to the front panel;
• allow the drain to pass through when it follows the same route;
• remain firmly attached to the wall.

A misaligned cover immediately draws attention in a long room. We therefore aim to maintain a continuous line and position the joints consistently with the ceiling and the units.

The drain slope over a long distance

Drainage presents a particular challenge when a unit is located far from the discharge point.

In cooling and dehumidification mode, each indoor unit produces condensate. This water must leave the drain pan without backing up.

When a drain operates by gravity, a slight but continuous slope must be maintained. A seemingly horizontal route may therefore be adjusted internally to promote drainage.

The errors to avoid include:

• a rise in the drain line after it exits the unit;
• a crushed section;
• a sag creating a water pocket;
• a bend that is too tight;
• an improperly secured connection;
• an insufficient diameter;
• closing the front cover before the drainage test.

When gravity does not allow for reliable drainage, a condensate pump may be considered. This choice depends on the exact configuration, acceptable noise level, accessibility, and available drainage point.

At AirGreen, we test the drainage during commissioning. An installation that looks successful cannot be considered complete until the water drains properly.

An airflow strategy to prevent the units from interfering with each other

Two units installed in the same large room should be adjusted consistently. If their air jets are directed toward each other, they may create turbulence or distort their temperature readings.

Instead, we aim to assign each unit a logical air-distribution zone.

The unit in the foreground can serve the nearer part of the room, while the one at the back serves the opposite zone. The louvers should be adjusted to extend the airflow through the space without constantly directing air at the occupants.

In heating mode, the air should generally be directed more downward. In cooling mode, a more horizontal orientation promotes gradual distribution of the cool air.

The recessed light fixtures visible in the ceiling do not directly obstruct airflow, but their presence confirms the importance of keeping the units on the wall rather than choosing a suspended solution or a layout that would have passed through the finished ceiling.

The Hitachi airHome 400 in a multi-zone comfort project

A range from 9,000 to 36,000 BTU/h

The Hitachi airHome 400 series is available in several capacities, making it possible to match each unit to the load of the area it serves.

Hitachi documentation presents systems including:

• 9,000 BTU/h;
• 12,000 BTU/h;
• 18,000 BTU/h;
• 24,000 BTU class, with a nominal cooling capacity of 22,000 BTU/h;
• 36,000 BTU class, with a nominal cooling capacity of 33,000 BTU/h.

The exact capacity of the two visible units cannot be confirmed from the photograph. We therefore avoid assigning them a BTU rating without consulting their nameplates.

Sizing must consider:

• the area of each zone;
• ceiling height;
• exterior walls;
• windows and doors;
• solar exposure;
• the number of occupants;
• the lighting and heat-generating equipment;
• the frequency of door openings;
• the insulation level;
• the intended use for heating.

In a space occupied by several people or equipped with numerous electrical appliances, the cooling load may be higher than in a residential room of comparable size.

Units whose dimensions vary with capacity

The 9,000 and 12,000 BTU models use an indoor unit measuring approximately 30.71 in wide, 11.02 in high, and 8.74 in deep.

The 18,000 BTU model is approximately 37.40 in wide. The higher-capacity units reach approximately 41.34 in and 43.3 in.

These dimensions affect:

• the distance from the ceiling;
• the positioning of the line-set cover;
• access to the filters;
• the airflow reach;
• the wall plate mounting;
• the distance from existing equipment.

The first visible unit appears larger because of the perspective of the photograph. This does not allow us to conclude that it has a different capacity from the second.

Vector DC Inverter technology and power modulation

The Hitachi airHome 400 uses Vector DC Inverter technology. The compressor can vary its speed to adapt its capacity to the actual demand.

In this large room, the demand is not constant. The load may vary depending on:

• the time of day;
• the number of people present;
• the use of lighting;
• the outdoor temperature;
• the opening of doors;
• the heat generated by equipment;
• the area actually occupied.

Instead of operating only at full capacity, the unit can slow down after reaching the requested temperature. This modulation helps maintain a more stable climate and limit abrupt cycles.

The product line documentation indicates cooling efficiency of up to 20.0 SEER2, depending on the combination. It also lists different HSPF2 values, a heating range down to approximately -20.5 °C, and the use of R32 refrigerant.

Significant quiet operation in a shared room

The 9,000 and 12,000 BTU models can reach 29 dB(A) in quiet mode, according to the manufacturer. Higher capacities have different sound levels.

In a large room, two units operating at a moderate setting can sometimes be acoustically more comfortable than a single unit forced to operate constantly at high speed.

The quality of the installation nevertheless remains essential. A long pipe cover can transmit noise if the piping is not properly secured.

We check in particular:

• the absence of direct contact between the copper and the duct;
• the securing of the ducts;
• the sealing of the joints;
• the stability of the elbows;
• the anchoring of the units;
• the absence of vibration against the ceiling;
• the operation of the indoor fan;
• the normal movement of the louvers.

FrostWash to help maintain airflow

The FrostWash technology uses a freezing and thawing cycle on the indoor heat exchanger. This process helps capture and remove certain accumulated impurities.

Hitachi presents a comparative test simulating an accumulation of dust and oil. In this test, the unit using FrostWash maintained its airflow performance better than the unit without this function.

In a shared or frequently occupied space, dust can accumulate quickly. FrostWash is therefore a useful function, but it does not replace proper HVAC maintenance.

The filters must always be checked and cleaned. The blower wheel, pan, and heat exchanger should also be inspected when deposits, odors, or reduced airflow appear.

Mold Guard and drying of internal components

The Mold Guard function helps reduce residual moisture in the unit after certain air-conditioning cycles. The system circulates air and may heat the coil for a specified period.

This function is intended to limit conditions that promote odors and mold. However, it does not remove contamination that is already established.

To protect both units in this project, we recommend:

• to clean the filters regularly;
• to monitor unusual odors;
• to check the drains;
• not to spray household products into the units;
• to schedule professional cleaning as needed;
• to keep the upper intake clear.

The brochure also presents removable side covers, a drain configurable on the left or right, a removable collection pan, and simplified access to several components. These features facilitate servicing, particularly when multiple units are installed in the same room.

PM2.5 filtration and activated carbon

The airHome 400 range includes a stainless steel prefilter as well as a PM2.5 activated carbon purification filter.

These components treat the air passing through each unit and may help reduce certain particles and odors. They do not replace mechanical ventilation or central filtration for the entire building.

In a space located in Montreal's Old Port, maintenance frequency may depend on several factors:

• urban traffic;
• traffic in the room;
• frequently opened doors;
• nearby work;
• dust;
• the activities carried out in the room.

Two units also mean two sets of filters to clean. A clear maintenance schedule should therefore be established rather than waiting for a noticeable drop in airflow.

Individual zone control

The presence of two units allows more precise control, particularly if the appliances can be adjusted separately.

Depending on the selected configuration, it may be possible to adjust:

• the temperature;
• the fan speed;
• the airflow direction;
• the operating mode;
• the schedule;
• the sleep function or Eco mode.

An optional Wi-Fi adapter compatible with airCloud Go may also be available for certain models. This platform notably enables control from a phone, weekly scheduling, and certain monitoring functions.

When a multi-zone system is used, the indoor units must generally operate in compatible modes. One unit cannot always request cooling while the other requires heating. This point must be explained to the occupants when the system is handed over.

Vacuum evacuation on an extended refrigeration run

The long visible run requires rigorous commissioning. After the pipes are installed, the circuit must undergo vacuum evacuation to remove air and moisture.

This step protects the system against:

• abnormal pressures;
• oil contamination;
• reduced efficiency;
• acid formation;
• premature compressor wear;
• long-term operating problems.

The total pipe length must also be measured. Depending on the model, the brochure indicates maximum lengths ranging from approximately 82 ft to 165 ft. An additional refrigerant charge may be required beyond the length included by the manufacturer.

Therefore, we must check:

1. the exact models;
2. the pipe diameter;
3. the length of each run;
4. the height difference;
5. load requirements;
6. airtightness;
7. vacuum evacuation;
8. the operation of both units;
9. drainage;
10. supply air temperatures.

Eligibility for subsidies and certification

The brochure presents the airHome 400 combinations as ENERGY STAR certified and potentially eligible for various incentives.

Eligibility must not, however, be determined solely from the name of the product line. It usually depends on:

• of the complete indoor and outdoor model numbers;
• of the AHRI number;
• of the heating capacity at the reference temperature;
• of the system type;
• of the building type;
• of the installation date;
• of the applicable program.

In an installation with two indoor units, the complete combination must also be checked. A multi-zone configuration may be assessed differently from two single-zone systems.

Mistakes to avoid in an installation with multiple units

This Old Port project illustrates several important points:

• do not install the two units too close to each other;
• do not direct their air streams toward each other;
• avoid a misaligned line-set cover;
• do not overlook the drain slope;
• check the total piping length;
• do not compress the copper in the bends;
• preserve access to the filters;
• coordinate the operating modes;
• size each zone separately;
• verify electrical compliance;
• test each unit individually;
• confirm the subsidy with the complete model numbers.

An installation adapted to the room’s actual length

The main advantage of this project is the distribution of comfort.

Rather than requiring a single unit to condition the entire length of the space, we installed two distribution points. The line-set cover visually ties everything together and protects the technical route beneath the ceiling.

This solution keeps the lower wall largely clear, respects the existing light fixtures, and fits around the wall-mounted fan already in place.

Our approach to this HVAC installation in Montréal’s Old Port was based on several objectives:

• effectively treat both ends of the room;
• maintain a clean piping route;
• limit the number of visible drops;
• maintain reliable drainage;
• facilitate future maintenance;
• achieve modulated, quiet operation;
• preserve the use of the wall and ceiling.

We apply this same rigor to our installations in Montréal, Laval, Longueuil, the North Shore and the South Shore. The constraints vary from one project to another, but the principle remains the same: the equipment must be adapted to the building’s actual configuration, rather than simply installed in the quickest location.