A multi-zone installation designed for three spaces without cluttering the building’s façade
On this flat roof in LaSalle, the GREE outdoor unit rests neither on the ground nor against an exterior wall. It is installed on a raised metal support above the roof membrane, in a sufficiently clear space to allow air discharge and maintenance work. The refrigerant lines for the three zones are grouped, insulated, and routed into the building from a single outdoor unit.
This configuration clearly illustrates the benefits of a GREE Free Match R32 3-head heat pump: heating and cooling several spaces with a single outdoor unit while adjusting the temperature of each zone to meet the occupants’ needs.
In an urban Montreal building, choosing the outdoor location is just as important as choosing the capacity. A rooftop installation can free up the yard, preserve the appearance of the façade, keep the equipment away from walkways, and reduce the risk of accidental damage. However, it requires much more thorough preparation than a conventional wall-mounted installation.
What the job-site photograph shows us
The photo was taken during the work. Several characteristic elements of a rooftop HVAC installation are visible:
- The outdoor unit is placed on a raised metal support;
- The fan has open space in front of it;
- The refrigerant lines are protected by black insulation;
- The roof’s white membrane must be protected during movement and work;
- The tools are placed on a work platform to limit direct contact with the membrane;
- Several vents, chimneys, and rooftop equipment surround the installation area.
This last point is particularly important. On a flat roof in LaSalle, Montreal, Laval, or Longueuil, we must work around ventilation outlets, roof drains, parapets, cables, existing ducts, and access areas reserved for other trades. The unit cannot simply be placed in the first available space.
We must maintain adequate clearance for the fan, prevent exhaust-air recirculation, and leave enough space around the service panels. A technician must be able to access the electrical connections, refrigerant valves, and internal components without stepping on the lines or dismantling part of the installation.
Why install the outdoor unit on the roof
The choice of the roof often addresses several constraints simultaneously.
Preserving the façade and outdoor spaces
A multi-zone heat pump can be relatively imposing. On a property with a narrow yard, where side passages are used, or when architectural rules limit visible equipment, the roof becomes a logical option.
In this heat pump installation in LaSalle, the outdoor unit is thus kept away from doors, ground-floor windows, and traffic areas. The three indoor spaces can be served without multiplying outdoor units around the building.
Keeping the equipment above snow and water
A heat pump used for heating produces water during its defrost cycles. On a roof, this water must be able to drain away without creating an accumulation of ice beneath the unit or in front of a service access point.
The elevated support visible in the photo provides clearance beneath the machine. This elevation also helps keep the unit above small snow accumulations and reduce contact with water on the membrane after rain or a thaw.
However, the support height must be selected based on the structure, wind exposure, roof drainage, and the manufacturer's recommendations. A unit that is too low may be blocked by snow. An unnecessarily tall unit may transmit more movement to its base or become more exposed to gusts.
Protecting the roof membrane
A membrane must not be punctured, crushed, or damaged by metal edges. We therefore plan the support method with the roofer or building manager when the situation requires it.
The support points must distribute the weight properly. Paths used during the work must also be protected, particularly when nitrogen cylinders, vacuum pumps, tools, and sections of piping need to be transported to the roof.
Why a three-head GREE Free Match R32
A three-head heat pump can divide the building into three comfort zones. Each indoor unit can be adjusted according to the actual use of the room, rather than treating the entire home as a single space.
A common configuration may include, for example:
- one indoor unit in the main open area;
- one indoor unit in a bedroom or a space located upstairs;
- one indoor unit in an office, a second bedroom, or a room that is more difficult to cool.
However, locations and capacities must never be selected based solely on the total floor area. Window orientation, insulation, number of occupants, ceiling height, heat-generating appliances, and airflow between rooms all change the load of each zone.
The GREE Free Match R32 series is designed to offer multiple combination options. The documentation indicates up to seven types of indoor units, along with features such as self-diagnostics, intelligent defrosting, automatic voltage adaptation, G10 inverter technology, and quiet operation. An A2L leak-detection sensor is also included.
Efficiency suited to Montreal’s climate
The range reaches up to 21 SEER2, 12.5 EER2, and 10 HSPF2. Its stated cooling range goes as low as -30 °C and as high as 48 °C.
For heating, the technical data sheet also specifies outdoor operation from -30 °C to 24 °C.
These values are particularly relevant for an installation in LaSalle. A heat pump must not only be efficient during a mild September day. It must handle Montreal’s humid summer periods, cold nights, and the rapid temperature changes typical of southern Quebec.
The variable-speed compressor modulates its output instead of constantly operating at full capacity. When demand is low, the system can maintain the temperature with reduced power. This modulation promotes a more stable temperature, limits on-off cycling, and improves humidity control in cooling mode.
What outdoor capacity is suitable for a three-head installation
The exact outdoor unit number is not legible in the photograph. We therefore present the models in the range that are compatible with three indoor units rather than arbitrarily assigning a capacity to the project.
| GREE outdoor unit | Number of connectable indoor units | Rated cooling capacity | Rated heating capacity |
|---|---|---|---|
| GWHD(24)ND6MO | 2 to 3 | 24,000 BTU/h | 24,000 BTU/h |
| GWHD(30)ND6MO | 2 to 4 | 28,400 BTU/h | 30,000 BTU/h |
| GWHD(36)ND6MO | 2 to 4 | 36,000 BTU/h | 36,000 BTU/h |
| GWHD(42)ND6MO | 2 to 5 | 42,000 BTU/h | 44,300 BTU/h |
The documentation confirms that the 18,000 BTU/h model accepts only two indoor units, while the 24,000 to 42,000 BTU/h models can be used in various three-head configurations.
The final selection depends on the load calculation and the approved combination of indoor units. Simply adding the capacities listed for the three heads is not sufficient. In a multizone system, the outdoor unit’s capacity is shared among the zones simultaneously calling for heating or cooling.
An oversized system can lead to shorter cycles, less precise humidity control, and unnecessary expense. An undersized system may lack capacity when multiple zones are operating simultaneously.
What to Understand About Multi-Zone Operation
The three indoor units offer individual temperature and fan settings. However, they remain connected to the same outdoor unit.
As with most multi-zone heat pumps of this configuration, the units generally need to operate in the same overall mode. A different temperature can be requested in each room, but one unit normally cannot heat while another is cooling.
This characteristic must be explained before installation, especially in a building where some rooms are exposed to the sun while others remain cool. Proper positioning of the indoor units and consistent use of the settings reduce conflicts between zones.
The Technical Steps in Our HVAC Installation
1. Calculating the Requirements for Each Space
We begin by analyzing the three zones separately. The main room does not necessarily need the same capacity as an enclosed bedroom. A room located beneath the roof may also receive a higher solar load.
We specifically check:
- the dimensions of each room;
- the insulation level;
- the type and area of the windows;
- the building’s orientation;
- ceiling height;
- the available routes for the lines;
- the condensate drainage method.
2. Selecting Indoor Locations
A wall-mounted unit must be able to distribute air without blowing directly onto a bed, sofa, or workstation. It must also remain accessible for filter cleaning and HVAC maintenance.
We pay particular attention to the condensate drain slope. A unit that is well positioned aesthetically can become problematic if its drain requires a long upward run or several changes in direction.
3. Planning the Route to the Roof
A three-unit installation involves three refrigerant circuits or three sets of connections running from the outdoor unit. Communication wiring and condensate drainage must also be provided for each indoor unit.
Penetrations must be sealed, and the lines must be protected from ultraviolet radiation, impacts, birds, and movement caused by temperature changes.
4. Installing the Outdoor Support
The support must be stable, level, and suitable for the weight of the selected model. According to the technical data sheet, compatible outdoor units for three indoor units weigh approximately 112.5 to 174.2 lb, depending on their capacity. Their listed maximum sound pressure level ranges from 58 to 63 dB(A).
These factors influence the choice of location. Even on a roof, we must consider adjacent rooms, vibrations transmitted to the structure, and the proximity of neighboring properties.
5. Connecting the Refrigerant Lines
The GREE specification sheet indicates 1/4 in. liquid lines and 3/8 in. gas lines for the models in this series. It also specifies different length and elevation limits depending on the outdoor unit.
For models compatible with three heads, the indicated maximum total length ranges from 197 to 328 feet, or 60 to 100 meters. The maximum elevation difference ranges from 49 to 82 feet, or 15 to 25 meters.
These limits are important in a rooftop installation. The distance between the heads and the outdoor unit must be measured, not estimated visually. When the pipes exceed the length precharged by the manufacturer, an additional amount of refrigerant must be calculated according to the applicable specifications.
6. Leak test and evacuation
Before releasing the refrigerant into the pipes, we check the fittings for leaks. Proper evacuation removes air and moisture from the circuit.
This step directly affects compressor reliability. An installation that appears to work on the first day may develop problems later if the pipes contain moisture or if a fitting slowly leaks.
7. Electrical supply compliant with the nameplate
All outdoor units in the series presented operate at 208/230 V, but their electrical requirements are not identical.
Depending on the model compatible with three heads, the indicated minimum circuit ampacity ranges from 19.5 to 30 A, while the maximum overcurrent protection ranges from 25 to 45 A.
The circuit breaker must therefore never be selected solely because the system has three heads. We base our selection on the model number, the nameplate, the manufacturer's requirements, and the applicable electrical standards.
8. Commissioning the three zones
Commissioning includes checking the startup of each head, communications, supply-air temperatures, drains, controls, and error codes.
We also check how the system behaves when multiple zones simultaneously request heating or cooling. The client then receives the necessary explanations for adjusting the temperatures without making the three units work unnecessarily against one another.
Mistakes to avoid with a three-head rooftop heat pump
Choosing the capacity solely based on the number of heads
Three heads do not automatically mean 30,000 or 36,000 BTU/h. The capacity must match the actual loads and the combinations authorized by GREE.
Overlooking the elevation difference and total pipe length
A roof can add several meters to the route. Each branch must be measured, and the sum of the lengths must remain within the limit for the selected model.
Install the unit directly on the membrane
The weight, vibrations, and movement of the support can damage the roof. The supports must be suitable, and the membrane must be protected.
Blocking access to the valves and service panels
A compact installation must not become impossible to service. Clearances must be maintained even when available space is limited.
Forgetting to manage defrost water drainage
In heating mode, the outdoor unit produces water. On a flat roof, this water must be directed or allowed to drain into a suitable area without creating a sheet of ice beneath the machine.
Confusing potential eligibility with a guaranteed rebate
The technical sheet lists separate AHRI numbers for ductless, ducted, and mixed installations. It also associates the product line with ENERGY STAR and indicates eligibility for local rebates.
The program, amount, and actual eligibility must nevertheless be confirmed using the AHRI number corresponding to the installed combination, the building address, and the criteria in effect when the application is submitted.
Equipment warranty and registration
The documentation provided indicates a standard ten-year warranty, as well as an additional two-year extension through Wolseley when the product is registered and proof of installation is provided.
The exact conditions must be verified at the time of purchase. A warranty on the compressor and parts should not be confused with a labor warranty. Keeping the invoice, serial number, unit models, and installation certificate makes any future claim easier.
An installation in LaSalle that reflects our work method
This GREE Free Match R32 three-head heat pump installation in LaSalle shows that a multi-zone project involves more than mounting three indoor units and placing an outdoor unit on the roof.
We must coordinate the sizing, equipment combinations, line routing, membrane protection, electrical supply, drainage, and future access to the unit. Each decision affects the installation’s comfort, noise level, efficiency, and lifespan.
In this project, the elevated support keeps the outdoor unit clear of the roof. Its open location promotes airflow, while grouping the lines allows the three zones to be served by a single outdoor unit.
At AirGreen, we carry out this type of HVAC installation in Montreal, LaSalle, Laval, Longueuil, the North Shore, and the South Shore. We assess the building as a whole to ensure that the selected heat pump truly suits the rooms being treated, the roof constraints, and Quebec’s winter conditions.