Technical intervention on a roof in downtown Montreal
HVAC systems located on downtown rooftops always present a particular challenge: restricted access, direct sunlight, debris accumulation, and premature wear caused by extreme weather variations. It is in this context that the AirGreen team was called to repair a MultiZone heat pump serving a residential building in the Ville-Marie district of Montreal.
Background to the call
The client, the owner of a triplex converted into a condominium, noticed that two of the three indoor units were no longer responding to the main remote control. Tenants on the second floor were complaining of a lack of cooling, while the ground floor still appeared functional.
On the roof, we found two separate compressors , including a MultiZone model powering several wall-mounted units. The diagnosis was expected to be complex, requiring a methodical assessment of the entire network.
Step 1: Visual inspection and verification of connections
Upon observing the units on the roof, our technician immediately noted:
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Refrigeration line insulation damaged by UV rays;
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Slightly inclined wooden supports , affecting the drainage of condensates;
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And a poorly fixed communication pipe , exposed to the elements.
A closer inspection revealed that one of the cables connecting the communications module to the outdoor unit was damaged by heat and friction against the roof sheathing. This degradation was causing intermittent signal loss between the indoor units and the main compressor.
Step 2: Electrical diagnosis and refrigeration pressures
We then checked:
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Supply voltages : stable at 208V.
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Error codes displayed on the Gree MultiZone panel : code “E7”, indicating loss of communication.
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Refrigerant circuit pressures : normal, which ruled out a leak or a faulty compressor.
The diagnosis was therefore confirmed: the problem was electronic and not mechanical .
Step 3: Repair and secure the installation
To restore the system:
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We replaced the communication cable between the compressor and the MultiZone distribution box.
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We added UV insulation sheathing to all exposed refrigeration lines.
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The wooden supports were readjusted and stabilized using new moisture-resistant composite shims.
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Finally, we performed a full system reboot , followed by a communication test between the three indoor units.
Result: performance and reliability restored
The final test confirmed:
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Stable and constant communication between units;
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Uniform cooling in all areas of the building;
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And a reduction in operating noise thanks to the stabilization of the supports.
The owner was able to immediately notice the difference: the occupants' comfort was restored, and the MultiZone heat pump returned to its optimal performance, without overconsumption.
Advice given to the client
Before leaving the site, our technicians recommended:
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An annual inspection of roof installations to quickly detect wear of cables and insulation.
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Adding a protective cover to extend the life of exposed electronic components.
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Preventative cleaning of roof drains to prevent water backups during summer storms.
AirGreen expertise in urban environments
High-rise installations, often overlooked, require precise technical expertise. At AirGreen , we regularly work on Montreal rooftops—from Plateau-Mont-Royal to Ville-Marie —to maintain, repair, and optimize residential and multi-zone HVAC systems from brands such as Gree, Fujitsu, Midea, Mitsubishi, and Zephyr .
Our interventions combine safety, precision and durability , even in the most demanding conditions.
The result: more comfortable buildings, more reliable systems and fully satisfied customers.