On the rooftops of condo buildings in downtown Montreal, HVAC systems operate in demanding conditions: wind, dust, temperature variations, more complex access, and long refrigerant lines. Here, we intervened in Ville-Marie to recommission a set of Goodman wall-mounted heat pumps (several outdoor units installed on rails, with dedicated electrical boxes and grouped insulated piping).
Context: Inconsistent comfort in several areas of the condo
The client contacted us about a problem typical of multi-unit installations: some zones cooled/heated well , while others remained unstable (fluctuating temperature, long start-up time, reduced performance during heat or cold peaks). In this type of configuration, a single weak point (power supply, communication, drainage, refrigerant charge, obstructed ventilation) can create a cascade of symptoms.
What the image tells us about the installation
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Installation on a gravel roof terrace , with outdoor units on metal supports/rails (good practice to avoid direct contact with the membrane and facilitate drainage).
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Grouping of several Goodman condensers in the same technical area, with lateral clearance to be monitored for the breathing of the exchangers.
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Presence of electrical disconnect boxes — useful for securing the intervention and isolating each system.
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Visible insulated refrigeration lines routed together: practical, but this requires special attention to the condition of the insulation, friction, pinch points and water ingress.
AirGreen diagnosis: methodical, zone by zone
On a roof, you don't "guess"; you check. Our diagnosis was carried out in four steps to precisely identify the cause and avoid replacing parts unnecessarily.
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Electrical verification and control
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Voltage measurement, inspection of connections in the disconnect boxes.
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Checking the protective measures, tightening, and looking for traces of oxidation (common on roofs).
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Validation of control/communication signals (according to the internal configuration).
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Mechanical inspection and air circulation
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Checking the condition of the coils (fine dust, debris, micro-obstructions).
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Control of clearance around units: on a roof, wind and walls (parapet) can create areas of hot air recirculation.
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Refrigeration control (pressure/temperature and behavior)
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Analysis of operation under demand: stability, cycles, blowing temperatures (interior side), performance consistency.
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Search for signs of insufficient load , inadequate indoor airflow , or a heat transfer problem at the exchangers.
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Drainage, insulation and finishing
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Checking sensitive points: damaged pipe insulation, condensation, fasteners, vibration.
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Control of line crossings and mechanical protection (to prevent premature wear).
Repair completed: performance restored, without compromise
Based on on-site observations, our intervention generally involved a combination of corrective actions (roofs often require a "package" of upgrades):
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Technical cleaning of heat exchangers and refurbishment of heat exchange surfaces (without damaging the fins).
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Resumption/optimization of ventilation around the units: slight repositioning, clearing, and checks to limit air recirculation.
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Electrical connection review : tightening, securing, reordering of conductors and validation of the dedicated power supply.
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Correction of installation details (line insulation, fixing, vibration reduction, protection of exposed segments) to stabilize performance and extend service life.
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Complete validation at the end of the work : start-up cycles, stability, temperature control and extended operation test.
Results: restored comfort and renewed confidence
After repair and adjustment:
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The affected areas have regained stable temperatures and a faster response to requests.
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The outdoor units showed more consistent operation, with fewer unnecessary cycles and better efficiency.
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The client has regained consistent comfort , particularly important in an urban condo where sunlight, internal gains and the building's airtightness amplify the differences.
Why this type of intervention requires real expertise (especially for roofs)
On a Goodman rooftop wall-mounted heat pump system, the causes of declining performance are often “silent”: micro-obstructions in the heat exchanger, air recirculation, deteriorated insulation, vibrations, electrical connections that loosen over time, and limited access that delays maintenance. Our approach at AirGreen is to treat the cause , not just the symptom—and to secure the system for seasons to come.