On the flat-roofed duplexes and apartment buildings in the Plateau, outdoor units are often installed on the roof to avoid cluttering backyards, reduce noise near windows, and protect the equipment from snow accumulation on the ground. This week, we serviced a Gree wall-mounted heat pump (mini-split) whose outdoor unit was installed on a raised bracket in the center of a flat roof, with sufficient clearance around the fan.
Context: symptoms reported by the client
The owner contacted us because the comfort level was no longer satisfactory:
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In heating mode, the heat pump blew lukewarm air and then eventually lost efficiency .
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In air conditioning mode, the sensation was the same: insufficient cooling , irregular cycles.
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At times, the unit seemed to be struggling (prolonged operation without reaching the desired temperature).
In a typical condo/plex in the Plateau, these symptoms quickly translate into constant discomfort : rooms that heat poorly in the morning, more humidity, and electricity consumption that climbs because the machine compensates.
The system in place
Based on the configuration and size of the outdoor unit, this is a Gree wall-mounted heat pump (mini-split). Since the exact model isn't visible in the photo, we're describing it as a "new generation" Gree wall-mounted unit (standard residential size), which is very accurate for installations typically found in this area.
Installation details observed on the roof
The installation has some important (and positive) elements:
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The outdoor unit is raised on a metal structure, which promotes drainage, maintenance and air circulation.
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Base placed on pads/soles (and shims), useful for reducing vibration transmitted to the roof membrane.
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Clear space around the coil and fan: essential to avoid air recirculation and loss of performance.
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Urban context: proximity to other buildings, dust, pollen, debris on roof — a classic in Montreal that can accelerate soiling.
Even with a good installation, a rooftop heat pump remains exposed: temperature variations, wind, freeze/thaw cycles, and micro-movements that can, in the long run, weaken certain connections.
AirGreen Diagnostic: our on-site approach
When a Gree heater/cooler malfunctions, avoid guessing. Follow a logical sequence to isolate the cause without wasting time:
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Validation of modes and commands
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Checking the mode (heating/cooling), set temperature, fan speed, and behavior of the indoor unit.
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Complete visual inspection
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Condition of the external coil, presence of dirt, visible damage, traces of oil (frequent indicator of leakage), attachment and stability.
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Electrical controls
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Power supply, voltages, connections, protection, general condition of wiring and terminal blocks.
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Performance metrics
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Air temperatures, defrosting behavior, operational stability.
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Refrigeration check
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Monitoring pressures and parameters that reveal a lack of refrigerant or a restriction.
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Conclusion of the diagnosis
In this case, the measurements and the behavior of the machine pointed to a very common cause in residential settings: an insufficient refrigerant charge , usually linked to a micro-leak (often at the level of a flared fitting / “flare”, or a point of vibration on the lines).
Repair: steps carried out by our team
A heat pump repair, when it involves the refrigeration circuit, must be done properly — otherwise the problem will return.
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Location and confirmation of the leak
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Targeted testing of sensitive fittings and sections.
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Checking for points where vibration or thermal cycles may have created a weakness.
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Repair of the faulty connection
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Reconnection (if necessary), adjustment, and securing.
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Control of the support and contact points to limit mechanical stresses.
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Leak test
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Pressurization (standard procedure) and stability monitoring.
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Vacuuming
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Thorough vacuuming to remove moisture and air from the circuit (essential for the longevity of the compressor).
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Recharging according to best practices
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Load adjustment and validation through operational measurements.
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Final validation
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Complete test in heating and air conditioning, verification of cycles, stability, and return to normal performance.
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Result: comfort restored and machine stabilized
After the repair:
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The Gree heat pump has returned to normal operation.
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The heating has become clear and stable again, without any feeling of “constant warmth”.
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The air conditioning has become efficient again, with better consistency.
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The customer has gained confidence above all: a machine that no longer needs to strain unnecessarily means less wear and tear and healthier fuel consumption.
Why do these breakdowns often occur on flat roofs in Montreal?
Without being dramatic, there are local realities:
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Vibrations + thermal cycles : this can affect certain fittings over the seasons.
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Debris and dust on roofs: an outdoor coil that gets dirty quickly loses heat exchange.
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More difficult access : interviews are sometimes postponed, which allows small problems to become bigger.
Our approach is to correct the cause (not just the symptom), then validate that the machine is stable in both modes.
Need a Gree heat pump repair in Greater Montreal?
At AirGreen, we service Gree wall-mounted heat pumps every week, installed on balconies, backyards, and very often on flat roofs in central areas like the Plateau-Mont-Royal. Our priority: a clear diagnosis, a lasting repair, and a quick return to comfort—no guesswork.