A roof intervention carried out with precision
At AirGreen , we regularly work on complex installations located at heights—from commercial rooftops to multi-unit residential buildings. This service call in Rosemère , on Montreal's North Shore , is a perfect example: two Gree MultiZone outdoor units installed on a flat roof had a simultaneous failure.
The context
The client, a rental property owner, contacted us after several tenants reported their indoor wall-mounted units suddenly shutting down. No fans were turning on, and the lights were flashing abnormally. On-site, our technicians quickly identified that the two Gree MultiZone condensers installed on the roof were inactive.
These units, supplying two separate apartments respectively, rested on treated wooden supports, with careful electrical and refrigeration wiring - but exposed to the elements.
Detailed technical diagnosis
After securing the area and turning off the power at the circuit breaker, we undertook a series of methodical analyses:
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Power supply check : Voltage was stable at 240V on each unit. However, no response from the compressor or control module.
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Inspection of protection fuses : internal fuses of the main boards blown on both units.
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Analysis of electronic cards : visible traces of humidity near the power module connectors.
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Compressor resistance measurement : within standards, excluding a motor short circuit.
The diagnosis quickly converged on a simultaneous failure of electronic cards , caused by the infiltration of water and condensation - a common phenomenon on flat roofs when the protective boxes are not perfectly watertight.
Solution implemented
Our certified technicians carried out a complete replacement of the electronic power boards on the two Gree units, accompanied by:
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Adding reinforced gaskets to electrical boxes.
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Repositioning of cable ducts to prevent water stagnation.
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Complete cleaning and drying of internal compartments with compressed air.
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A load start test and synchronization of indoor units to verify MultiZone communication.
Results and performance
After the intervention, both systems restarted normally. Each indoor unit responded immediately to commands from the wall thermostats. The R-410A refrigerant pressure was measured and confirmed to be within the manufacturer's specifications.
The tenants found efficient and quiet air conditioning, while the owner benefited from our preventive maintenance advice:
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Annual inspection of electrical connections .
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Check the watertightness of the boxes after each winter.
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Cleaning the outdoor coils before the summer season.
The importance of a suitable roof installation
On flat roofs, freeze-thaw cycles and water infiltration are silent enemies of HVAC systems. Poor cable management or a lack of waterproofing can quickly cause major electrical outages .
At AirGreen, we always insist on:
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Use waterproof disconnect boxes that comply with CSA standards.
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Install units on raised supports to avoid direct contact with the roof membrane.
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Carefully seal cable entries and refrigeration line exits .
AirGreen: expertise and reliability serving the roofs of Greater Montreal
This repair perfectly illustrates our approach: rigorous, safe, and sustainable. By simultaneously handling two Gree MultiZone units, our team demonstrated its ability to handle complex interventions on multi-zone systems installed at height.
Thanks to our expertise, the customer was able to avoid a prolonged breakdown and higher costs associated with a complete replacement.
AirGreen , your trusted partner in HVAC repair, maintenance and installation in Montreal, Laval, Longueuil, on the North Shore and the South Shore . Our experienced technicians ensure fast interventions that meet the highest standards in the field.