Work on a flat roof in the heart of the city center
At AirGreen , we recently performed a Midea central heat pump repair on a commercial flat roof in the Ville-Marie district of downtown Montreal. The view from the rooftop offered an iconic panorama: the mountain, the oratory, and the city's heritage rooftops. But behind this backdrop, a service call typical of dense urban environments: a Midea heat pump outdoor unit had completely shut down after a breakdown following an intense heat wave.
Initial diagnosis: total failure of the roof compressor
When we arrived, the Midea EVOX central heat pump was displaying an error code related to the high pressure circuit . By checking the connections and refrigerant pressures, our technician confirmed:
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The condenser fan was running intermittently.
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The compressor was overheating and automatically shutting off.
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An accumulation of gravel debris partially obstructed the condenser fins.
This type of situation is common on gravel-covered flat roofs , where dust and fine particles infiltrate HVAC systems. These contaminants significantly reduce heat exchange and cause a rapid rise in internal pressure.
Steps of repair
1. Securing and complete inspection
We first secured the work area and disconnected power to the unit. An electrical inspection revealed a faulty contactor —responsible for the compressor's unexpected shutdown. This component was replaced immediately.
2. Thorough cleaning of the condenser
Using a biodegradable cleaner designed for urban environments, we carefully cleaned the Midea condenser fins . This cleaning reduced the internal pressure of the system and improved thermal efficiency.
3. Checking refrigerant and operating pressures
We then checked the operating pressures. A slight loss of R410A refrigerant was detected, caused by a micro-leak at a weld in the liquid circuit. After detection, the leak was repaired with solder , and then the system was recharged to the quantity prescribed by the manufacturer.
4. Performance testing and calibration
After restarting, the heat pump returned to normal performance:
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Blown air temperature: 13°C in air conditioning mode
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Balanced and stable pressure
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Noise level in accordance with Midea standard (< 55 dB)
We have also recalibrated the electronic control of the main board , in order to optimize the start-up sequence and avoid short cycles.
Result: performance restored and preventive maintenance recommended
The unit is now operating at full capacity, ensuring optimal building comfort, even on the hottest days. We recommended that the owner perform biannual preventive maintenance , which is particularly important for rooftop units exposed to Montreal's dust and climate variations.
Why choose AirGreen for your flat roof repairs in Montreal?
Interventions on flat roofs require:
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Extensive knowledge of Midea, Lennox, Trane and Goodman central HVAC systems .
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Strict safety protocols , taking into account the height and access conditions.
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Expertise in the diagnosis of complex refrigeration circuits .
At AirGreen, we combine this expertise with a transparent approach: clear explanation of problems, accurate quotes, genuine parts, and a full labor warranty.
Maintenance, repair and replacement of central heat pumps in Montreal, Laval, Longueuil, North Shore and South Shore
Our teams respond quickly throughout Greater Montreal for the repair, maintenance, and replacement of central HVAC systems . Whether your heat pump is installed on a flat roof, in a technical basement, or on an exterior slab, our RBQ and CCQ certified technicians ensure safe and lasting service.