On some condominium buildings in Montreal, the outdoor units are installed on the roof (roof terrace), often in a bank, with grouped refrigerant lines and dedicated electrical boxes. This is precisely the context of this intervention in Ville-Marie , where we were called in for a Sharp heat pump whose efficiency had dropped: uneven cooling, longer cycles, and inconsistent indoor comfort.
Here, the installation is typical of an urban environment: several condensers on rails , mounted on a solid base, with planned clearances, protected wiring, and neatly routed refrigerant lines. On a rooftop, the sun, wind, temperature variations, and vibrations necessitate a more rigorous diagnostic approach—and above all, repairs done "properly" to prevent recurrence.
Type of machine and model selected (consistent with the image)
In this type of configuration (several outdoor units grouped for separate dwellings), wall-mounted heat pumps (mini-splits) or multi-zone systems are very common. Given the layout of the connections and the environment, we are treating this installation as a Sharp wall-mounted heat pump , from the recent residential range — model Sharp ZU1 (a consistent model when the exact identification is not legible in the photo).
Reported symptoms: decreased performance and unstable comfort
The client described:
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a temperature that takes longer to stabilize ,
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a sensation of lukewarm air at times ,
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and a system that seemed to “strain” more (more frequent cycles, more noise).
On a heat pump, these signs can come from several causes: fouling of the outdoor exchanger, disturbed airflow, electrical problem/intermittency, or even refrigerant charge imbalance (often linked to a micro-leak on the connection).
Our on-site diagnosis (AirGreen method)
On a roof, you always start by securing access and checking the immediate environment, because the installation context directly influences the behavior of the machine .
1) Visual inspection of the installation
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Checking the rails , fixings and support points (vibrations, resonance).
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Control of emissions around the condenser (unit breathing, hot air recirculation).
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Observation of grouped refrigeration connections (risk of friction, damaged sheath, bend radius too tight).
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Validation of disconnects and wiring (tightness, signs of overheating, humidity, oxidation).
2) Functional checks
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Pressure and temperature measurements (superheating / subcooling depending on the mode).
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Checking electrical stability (voltage, variations at startup, connections).
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Heat exchange assessment: condition of the external serpentine , presence of deposits, fine dust, urban pollution.
3) Hypothesis confirmed: loss of efficiency due to a weak point on the connection + a clogged heat exchanger
In this type of installation, one of the most common problems is micro-leaks at flare fittings (or fittings that are subject to vibrations and temperature changes). Even a small leak can be enough to:
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decrease capacity,
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lengthen the cycles,
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increase consumption,
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and prematurely wear out the compressor.
In parallel, a partially clogged outdoor heat exchanger on a roof (dust, urban soot, pollen) reduces heat dissipation and can accentuate symptoms.
Repair: targeted and lasting interventions
A simple recharge without addressing the underlying cause is never a solution. Our repair was carried out in several stages:
Step 1 — Resuming the vanishing point (clean method)
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Securing and preparing the line.
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Reworking the fitting in question: correcting the tightening torque, checking the condition of the flare, repositioning if necessary.
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Leak test after intervention (validation that the pressure is maintained, absence of abnormal variation).
Step 2 — Technical cleaning of the outdoor unit
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Cleaning the outer coil to restore optimal heat exchange.
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Check that nothing is obstructing the ventilation (leaves, ingrained dust, residue).
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Vibration control: tightening and minor adjustments to limit mechanical stress on the pipes.
Step 3 — Recommissioning and complete testing
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Rebalancing of operation and validation of parameters.
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Testing under real-world conditions: pressure stability, blowing temperature, start-up and operating behavior.
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Final check: noise, vibration, machine response, and overall performance consistency.
Result: restored comfort, normalized cycles, and improved performance.
After the repair, the Sharp system returned to normal operation:
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more stable temperature
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cleaner and less frequent cycles,
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an immediate feeling of comfort inside,
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and above all, restored confidence : the machine works without unnecessarily straining.
On a rooftop terrace, the key is durability: when the connections are properly repaired and the outdoor unit breathes as intended, performance returns — and the system works less for the same result.
Key takeaways for this type of rooftop installation in Montreal
For heat pumps installed on urban rooftops (Ville-Marie, Plateau, Southwest, etc.), we recommend:
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a periodic inspection of refrigeration connections (friction, ducts, supports),
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maintenance of the exterior serpentine (at least seasonally),
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and special attention to vibrations and support points (rails, silent blocks, fixing).
At AirGreen, our approach is simple: diagnose accurately, correct the cause, then validate the performance with measurements — for a repair that lasts, not just a temporary improvement.