A flat roof intervention in the heart of Montreal
At AirGreen , we regularly work on wall-mounted heat pump installations located on the flat roofs typical of Montreal duplexes and triplexes. This case, carried out in the Rosemont–La Petite-Patrie district, clearly illustrates the specific challenges of this type of installation: direct exposure to the elements, increased vibrations and access constraints for maintenance.
The unit in question was a Compact Air by Monflow Inc. , a wall-mounted heat pump model designed for urban residential spaces. The customer contacted us after noticing that their system was no longer producing heat, despite seemingly normal electrical operation.
Initial diagnosis: telltale clues on the roof
Upon arriving on site, our technician immediately noticed that the outdoor unit was installed on an aging and slightly sagging wooden base. This detail, often trivial, can have major consequences: excessive vibrations , poor condensate drainage , and sometimes even ruptured refrigeration pipes .
Using our digital multimeter and electronic pressure gauges , we started by checking the presence of voltage at the compressor and the refrigerant pressures. We quickly noticed:
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Correct voltage at the compressor input.
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Static pressure too low for a shut-down system (indicating a loss of refrigerant).
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No compressor start when controlling in heating mode.
These elements pointed towards a refrigerant leak accompanied by activated compressor thermal protection .
Step 1: Leak Investigation and Confirmation
We injected a fluorescent tracer into the circuit and then used a UV lamp to locate the leak. It originated from a flare fitting on the liquid line, slightly cracked due to the unit's vibrations. This type of failure is common in rooftop installations, where temperature fluctuations and shaking amplify the mechanical fatigue of the copper.
After isolating the damaged portion, we re-did the flare connection and replaced the gasket.
Step 2: Pressure Test and Vacuum Draw
Once the mechanical repair was completed, we performed a nitrogen leak test at 300 psi for 30 minutes. No pressure drop was observed, confirming the success of the repair.
We then pulled a deep vacuum (down to 250 microns) using a double-stage pump, to remove any moisture from the circuit before recharging the refrigerant.
Step 3: Recharge and restart
The Compact Air heat pump uses R-410A , a high-pressure refrigerant that requires precise handling. We therefore recharged the exact amount recommended by the manufacturer, measured to the nearest gram.
After restart, the operating pressures and discharge temperatures stabilized:
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High pressure: 380 psi
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Low pressure: 120 psi
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Blown air temperature (indoor): 46°C
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Outside temperature: 12°C
The system was working optimally again.
Step 4: Stabilizing the unit and preventing vibrations
To prevent recurrence, we replaced the wooden base with rubber anti-vibration mounts and added insulating pads under the fasteners. This improvement significantly reduces the micro-movements that cause cracks in copper fittings.
We also recommended annual preventative maintenance to the client, which is essential for exposed installations such as those located on Montreal rooftops.
Result: restored performance and reliability
Once the tests were completed, the heat pump operated quietly and stably. The customer could immediately feel the heat being distributed inside his home, confirming that normal operation had returned.
Furthermore, the observed electricity consumption was lower than before the intervention, proving that the machine no longer had to compensate for a loss of refrigerant gas.
AirGreen expertise: technical precision and safety at height
Working on a roof requires not only technical skills, but also rigorous safety management . At AirGreen, all our technicians are trained in working at height protocols and have the necessary equipment to effectively work on flat roofs in Montreal, Laval, and Longueuil.
Our teams frequently encounter situations similar to that of Rosemont–La Petite-Patrie:
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Capacitors blocked by urban dust.
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Copper fittings weakened by vibrations.
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Electrical systems exposed to moisture.
That's why every repair includes a complete safety inspection and energy performance assessment to prevent future breakdowns.
Advice given to the client
We took the time to explain to the customer some simple actions to extend the life of their heat pump:
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Visually check the outdoor unit twice a year.
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Never store heavy or decorative objects on the roof near the heat pump.
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Immediately report any abnormal noise or variation in performance .
These simple habits can prevent up to 70% of service calls related to vibrations and minor leaks.
Summary of the intervention:
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Device type: Compact Air wall-mounted heat pump (R-410A)
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Location: Rosemont–La Petite-Patrie, Montreal
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Problem: Heat loss, inactive compressor, refrigerant leak
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Diagnosis: Flare fitting cracked due to vibration
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Solution: Renovation of the connection, leak test, recharging, anti-vibration stabilization
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Result: Restored heating, quiet operation, optimized efficiency
At AirGreen , we combine technical expertise, rigorous diagnostics and attention to detail to offer sustainable, safe and efficient interventions, throughout Montreal, Laval, Longueuil, on the North Shore and the South Shore .