Emergency service in the middle of winter to restore heating to a Montreal duplex
At AirGreen , our technicians know that every winter HVAC system breakdown requires responsiveness and precision. During this service call in Rosemont–La Petite-Patrie , we were asked about a Windair wall-mounted heat pump installed on a flat roof—typical of duplexes in the neighborhood—that hadn't been heating for several days due to a buildup of snow and ice around the outdoor condenser .
Context of the intervention
The client, an owner-occupant of a two-unit building, contacted us after his tenants reported that the system was blowing only cold air despite the heating mode being activated. The outdoor thermometer read -18°C, and the roof was covered in a thick layer of snow, making it difficult to move around. On site, our team found three outdoor units (Windair, Elios, and Lennox) almost completely buried under the snow.
Diagnosis: airflow blockage and complete icing of the condenser
After securing the perimeter and clearing the snow around the units, our technicians quickly noted that:
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The outdoor fans were no longer turning due to frost accumulating on the blades.
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The coils were completely encased in ice , preventing any heat exchange.
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The pressure sensors had triggered an automatic safety shutdown of the Windair unit.
Using a multimeter and a digital pressure gauge, we checked the supply voltage, the refrigerant pressure, and the control signal from the electronic board. There were no electrical problems: the core of the problem was indeed the lack of defrosting and ventilation .
Steps of repair
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Complete condenser clearance : Using a hot air blower and plastic shovels to avoid mechanical damage, the snow and ice were gently removed.
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Coil and Fan Cleaning : We sprayed a biodegradable coil cleaner to remove residue and restore optimal airflow.
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Defrost temperature sensor inspection : This sensor was slightly displaced, preventing the unit from detecting the presence of frost. It was repositioned and securely fastened.
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Defrost Mode Operation Test : Once restarted, the heat pump initiated its automatic defrost cycle, confirming that the sensor was functioning correctly again.
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Thermal efficiency check : after 20 minutes of operation, the blowing temperature reached 44°C , proof that the Windair heat pump was regaining its full heating capacity.
Result: comfort restored and prevention reinforced
Once the unit was fully operational, the system was able to efficiently heat both floors of the duplex. We also cleaned the area around the roof and installed snow guards under each condenser to prevent future blockages.
The client particularly appreciated our proactive approach: we took the time to explain the crucial role of the defrost mode and the need to keep the condensers clear during winter storms.
AirGreen Technical Analysis and Recommendations
This intervention in Rosemont highlights several essential points for any owner in Montreal:
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Snow buildup on the condenser blocks airflow, causing the system to automatically shut down.
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In winter, defrost cycles are essential to prevent the coils from completely freezing up.
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Temperature sensors should be checked during each seasonal maintenance.
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Installation on a flat roof requires special attention : wind and snow accumulate there more quickly than on open ground.
At AirGreen , we advise our customers to plan preventative winter maintenance , especially for heat pumps installed on duplex or triplex roofs in the Plateau, Rosemont or Southwest.
AirGreen expertise serving Quebec's climate
Our certified technicians operate daily throughout Montreal, Laval, Longueuil, the North Shore and the South Shore , in all weather conditions. Whether you use a Windair, Lennox, Fujitsu, Gree or Midea system, we provide fast and accurate diagnosis, long-lasting repairs and advice tailored to your environment.
Thanks to our interventions, even the harshest winters will no longer hinder your comfort.