Two condensers, tailor-made comfort — MultiZone integration designed for Montreal plexes
At AirGreen , we design HVAC systems tailored to the architecture of Greater Montreal. This project in Rosemont–La Petite-Patrie illustrates an optimized MultiZone configuration: two Gree FreeMatch R32 outdoor units installed on a flat roof to supply several indoor units distributed among the floors of a plex. The goal: to ensure efficient heating in extreme cold and uniform cooling while freeing up facades and balconies.
Context and objectives of the project
The owner wanted to modernize a disparate system of wall-mounted air conditioners from different generations. The priorities were clear:
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centralize hot/cold production with a recent MultiZone heat pump ;
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reduce noise from terraces and the alley;
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prepare the building for subsidies related to R-32 appliances efficient in cold weather;
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preserve the roof's watertightness and facilitate long-term maintenance.
After thermal assessment of the housing and recording of the pipe lengths, we recommended a dual FreeMatch R32 configuration (2 to 5 zones per condenser), allowing loads to be balanced: bedrooms and living areas on dedicated circuits, with capacity reserve for a possible additional head.
Technical details of flat roof installation
Supports, interfaces and protections
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Raised chassis : each condenser rests on a galvanized steel support fixed on distribution plates with anti-vibration isolators . This choice limits the transmission of vibrations to the structure and keeps the units away from accumulations of water or snow.
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Membrane protection : under the soles, we installed roof-compatible protective panels (distribution barrier + non-slip underlay) in order to preserve the elastomeric membrane.
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Service clearances : a central corridor between the two units facilitates vacuum gauge, pressure gauge and maintenance operations, while respecting air intake/discharge distances.
Refrigeration and routing
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MultiZone Bundles : the photo shows the grouping of refrigerant connections (several lines) exiting neatly from the roof, continuously insulated and tied every 40–50 cm to prevent wind pumping.
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Waterproof route : the roof penetration is made via a sealed technical penetration (bituminous compatible mastic and flashing), guaranteeing waterproofing. Inside, each copper/communication pair is labeled towards its head.
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Brazing and vacuuming : silver soldering with nitrogen sweeping; deep vacuuming (<500 microns) and nitrogen test to validate integrity before opening the valves.
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Height management : oil traps are integrated into the risers when required by the height between the roof and interior heads, in accordance with Gree recommendations.
Power supply and control
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Disconnect boxes within easy reach behind units, UV-sheathed wiring, verified grounding.
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Shielded communication between condensers and heads, length measured and reported in the commissioning sheet.
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Addressing settings : each zone receives an address and an optimized defrost curve to limit the short cycle during cold nights.
Special conditions of the site
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Evening work to minimize the rental impact and take advantage of the reduced electrical load in the building.
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Safety at height : lifelines, safety perimeter and tool guards. The condensers were mechanically raised to avoid any stress on the roof edge.
Why the Gree FreeMatch R32 for a plex in Rosemont?
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2 to 5 Zone Versatility : Perfect fit for divided Montreal homes, with the ability to add a head in an office or basement without replacing the condenser.
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R-32 refrigerant : reduced GWP footprint vs. R-410A and better thermodynamic performance at equal charge.
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Extreme cold : XLTH modules available, maintaining useful capacity for additional heating down to −25/−30°C depending on the associated heads.
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Quiet and comfortable : reversing compressor, modulating fans; excellent for dense environments in Montreal and Laval .
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Program eligibility : when combined with high-performance heads, the configuration generally meets the criteria of Quebec programs aimed at energy efficiency (to be validated by file).
Result: balanced comfort, clear facades, simplified maintenance
The flat-roof approach frees up floor space and eliminates noise pollution on the balconies. The two condensers are easily accessible for seasonal maintenance: cleaning the coils, checking the supports, monitoring pressures, and updating settings as needed. Tenants experience consistent comfort in each zone, with independent room-by-room control and controlled energy bills thanks to modulation.
Good practices and pitfalls avoided
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Never place directly on the membrane : the absence of soles and protective panels is a source of premature perforation.
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Anti-vibration devices are mandatory : on light roofs, they reduce reverberation and noise perceived inside.
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Tube bend radius : Tight bends increase oil pressure losses; we use suitable springs/flares to preserve the circuit.
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Clear labeling : essential in MultiZone to quickly find the head concerned in the event of maintenance.
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Frost management : poor air circulation between two condensers that are too close causes frequent defrosting; we have respected cross clearances and created a service corridor .
What the customer gets with AirGreen
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Load study by zone and precise selection of heads (wall, consoles, cassettes according to use).
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Grant support : preparation of the file, proof of performance of R-32 equipment and required certificates.
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Installation warranty and planned HVAC maintenance service : annual inspection, tightening of connections, cleaning of evaporators and calibration of smart remote controls.
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Usage tips : winter set point adjustments, shutter management, filter maintenance, and savings recommendations for Montreal, Laval, Longueuil, North Shore, South Shore .
Maintenance tips for MultiZone installations on flat roofs
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Clean the outdoor coils in spring and late summer; check the condition of the snow guards if present.
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Inspection of supports and membrane under soles after freezing/thawing episodes.
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Control of pressures and superheat/subcooling at the start of the heating season.
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Update firmware and defrost settings if recommended by the manufacturer.
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Checking the electrical tightening in the disconnection boxes and compressor terminals.
In summary
This Gree FreeMatch R32 dual-condenser system provides the Rosemont–La Petite-Patrie plex with four-season comfort , energy efficiency , and architectural integrity . It's an ideal solution for Montreal buildings where every square meter counts and reliability in cold weather remains a priority.
Are you planning a MultiZone heat pump on a flat roof in Montreal, Laval, Longueuil, North Shore or South Shore ? Our team will travel, evaluate, advise and install with a constant requirement for AirGreen quality .