A complex technical intervention on a multi-unit building
At AirGreen , we are often called upon to work on complex HVAC installations, particularly on flat roofs of multi-unit residential buildings .
Recently, our team was called upon in Côte-des-Neiges–Notre-Dame-de-Grâce (Montreal) to diagnose and repair several heat pump and central air conditioning units that were experiencing simultaneous performance problems.
The owner had noticed a noticeable drop in air conditioning in several apartments in the building, accompanied by an abnormal noise coming from the roof.
Inspection and diagnosis of systems
On site, our technicians noted the presence of several mixed brand units , some Goodman and others of the wall-mounted multi-split type, all connected to the same structure of electrical and refrigeration conduits.
The environment — typical of a Montreal flat roof — presented several challenges:
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Direct exposure to sunlight , increasing the operating temperature of the compressors.
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Tangle of refrigeration and electrical conduits , making air circulation and maintenance difficult.
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Accumulation of dust and oxidation on condenser coils.
After a series of measurements using a pressure gauge and an ammeter clamp, our technicians identified several distinct problems:
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A Goodman unit was showing low R410A refrigerant pressure .
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A wall-mounted multi-zone unit had a fan blockage due to debris .
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The wood supports under some units were misaligned, creating excessive vibrations and noise transmitted into the roof structure.
Repair Steps
1. Leak detection and correction
For the Goodman unit, we located a leak at the Schrader seal (service valve). The seal was replaced, and a nitrogen leak test confirmed the repair.
The system was then evacuated under deep vacuum for 50 minutes before being recharged with the exact amount of R410A according to the manufacturer's specifications.
2. Cleaning and restarting the clogged fan
The second unit, a multi-zone type, required partial disassembly of the fan housing . Leaves and dust had accumulated between the blades, blocking the motor.
We cleaned the compartment, lubricated the bearings , and tested the motor rotation before returning it to service.
3. Media stabilization and noise reduction
To reduce excessive vibrations, our technicians replaced worn wooden blocks with high-density rubber anti-vibration mounts . This intervention greatly improved stability and reduced the noise perceptible inside the housing.
Final check and return to service
Once repairs were completed, each unit was independently tested:
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Pressures balanced at 120 psi on the low pressure side.
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Interior blowing temperature at 11°C , guaranteeing optimal performance.
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Stabilized power consumption , a sign of smooth operation.
We have also grouped and labeled the electrical circuits and refrigerant pipes to facilitate future maintenance, a detail often overlooked in this type of shared installation.
Recommended prevention and maintenance
This case perfectly illustrates the need for regular maintenance on flat roof HVAC systems . These equipments are particularly vulnerable to:
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Exposure to sun and bad weather;
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Fouling of the coils;
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Structural vibrations;
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Refrigerant leaks caused by thermal expansion.
We strongly recommend biannual maintenance , ideally before the summer season and before the heating season.
At AirGreen , each interview includes:
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Complete cleaning of the condensers;
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Checking pressures and temperatures;
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Tightening electrical connections;
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Safety testing of relays and compressors;
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And validation of overall energy performance.
AirGreen Expertise in Montreal
Whether in Côte-des-Neiges , Ville-Marie , Rosemont , or elsewhere in Greater Montreal , our team of HVAC experts is equipped to work on all types of systems — from small wall-mounted mini-splits to multi-zone central systems .
Our approach is distinguished by:
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A precise and documented diagnosis ;
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Sustainable interventions focused on reliability;
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And a commitment to optimizing each system to reduce energy consumption while maximizing comfort.
At the end of the intervention, the owner was able to note a complete return to service of the six affected dwellings , restored thermal stability , and above all, a reduction in ambient noise on the roof.
Once again, AirGreen has demonstrated its technical expertise and attention to detail in maintaining HVAC systems in Montreal and its surrounding areas.