Winter work on a snow-covered roof: AirGreen precision in action
In Côte-des-Neiges–Notre-Dame-de-Grâce , in the heart of Montreal, our AirGreen team was called in the middle of February for a Gree MultiZone heat pump installed on the roof of a residential building. The client, a condominium association, contacted us after several indoor units had stopped producing heat , leaving some units without comfort in the depths of winter.
On the roof, our technicians found two Gree outdoor units , partially covered in snow and ice, exposed to the cold winds of the urban plateau. A block of ice had formed on top of the compressor , a clear sign that the defrost system was not functioning normally.
Diagnosis: Gree MultiZone VRF system disrupted by extreme cold
Gree MultiZone heat pumps are renowned for their reliability, even at low temperatures. However, like any sophisticated HVAC system, they require regular maintenance to operate at peak efficiency during Montreal winters.
Our technicians undertook a complete on-site diagnosis :
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Reading error codes via the control module: detection of a defrost fault .
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R-410A refrigerant pressure measurement : slightly below standard, indicating a potential microleak .
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Outdoor coil inspection : partially blocked by ice and compacted snow.
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Analysis of temperature probes : an external probe was sending an erroneous value , preventing the defrost cycle from starting.
The diagnosis made it possible to isolate two major causes:
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A micro-leak of refrigerant , causing pressure too low to properly initiate defrosting.
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A faulty defrost sensor , requiring immediate replacement.
Complete repair and technical adjustments
Once the problem was identified, our technicians proceeded methodically:
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Safe recovery of remaining refrigerant in the system.
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Leak detection using UV tracer and nitrogen test: the leak came from a micro-cracked weld on the condenser collector.
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Silver solder repair followed by a full leak test.
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Replacement of the original Gree defrost probe and calibration of the sensor.
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Recharge the system with R-410A refrigerant according to the manufacturer's exact specifications.
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Complete performance test at different simulated temperatures to verify the correct triggering of the automatic defrost cycle.
Within hours, the Gree MultiZone heat pump was operating optimally again, supplying power to the building's various units without interruption.
Results: restored yield and reassured co-ownership
After the repair, our technicians measured:
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A blown air temperature of 46°C in each indoor unit.
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Automatic defrosting every 50 to 70 minutes , depending on the outside temperature.
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Stabilized electricity consumption , a sign of balanced compression.
The building manager, relieved, told us that before our intervention, two other companies had come but were unable to identify the exact cause of the problem. At AirGreen , our rigorous approach—combining advanced diagnostic tools and field experience —enabled us to resolve the problem in a sustainable manner.
Prevention: our advice for MultiZone roof systems
Rooftop installations , typical of Montreal buildings, present unique challenges: exposure to wind, snow, and ice. Here are our experts' recommendations:
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Check condensation drains to prevent ice buildup under units.
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Clean the coils before winter to ensure even defrosting.
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Install wind deflectors if the roof is very exposed.
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Schedule annual preventative maintenance , especially before the cold season.
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Ensure that refrigeration ducts are well insulated , particularly over long distances between indoor and outdoor units.
These simple actions extend the life of the system and reduce the risk of breakdowns during critical periods.
AirGreen: Trusted HVAC expertise in Montreal and the North Shore
Working on a frozen roof in the middle of winter requires rigor, safety, and expertise . Our teams, trained in the realities of the Quebec climate, work every week in neighborhoods like Outremont, Rosemont, Le Sud-Ouest , and Ville Mont-Royal , always with the same precision.
Whether it's for a MultiZone heat pump repair , preventative maintenance or a complete installation , AirGreen is your trusted HVAC partner in Montreal, Laval, Longueuil, on the North Shore and the South Shore .
We make every effort to ensure that each system regains its original performance , guaranteeing comfort, energy savings and peace of mind.
Conclusion
This intervention in Côte-des-Neiges–Notre-Dame-de-Grâce perfectly illustrates AirGreen's philosophy: diagnose accurately, repair sustainably, and prevent intelligently . Thanks to a replaced sensor, a sealed leak, and perfect calibration, the Gree MultiZone heat pump has regained its full performance—ready to face the harshest Montreal winters.