A service call on a typical Laval flat roof
At AirGreen , we were recently called to intervene in Sainte-Dorothée , a peaceful residential neighborhood in Laval , for a problem affecting a Mitsubishi wall-mounted heat pump installed on the flat roof of a single-family home. As is often the case in urban areas, this type of installation on a gravel-covered roof aims to free the compressor from snow and noise, while optimizing air circulation. However, Quebec's climatic conditions put this type of equipment to the test, especially during harsh winters and spring thaws.
Diagnosis: loss of efficiency and abnormal noise
The customer contacted us after noticing two worrying symptoms:
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Significant reduction in heating on cold days.
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Intermittent mechanical noises coming from the outdoor condenser.
Our technicians immediately conducted a complete inspection of the Mitsubishi Electric heat pump , an outdoor unit from the Mr. Slim range , commonly used for residential wall-mounted systems. The unit, although robust, was showing signs of premature wear due to prolonged exposure to the elements.
Roof Inspection: Causes Identified
Once on the roof, several observations confirmed the source of the problem:
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Accumulation of debris and dust on the heat exchanger fins, reducing heat exchange capacity.
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Excessive vibrations caused by a sagging wooden support. Although the support was originally correctly sized, repeated freezing and thawing had slightly misaligned the structure.
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Exposed power cable near the base, which may deteriorate over time due to long-term exposure to sunlight.
A pressure test of R-410A refrigerant also revealed a partial charge loss , explaining the drop in performance observed by the customer.
Repair steps performed
Our certified technicians carried out a complete intervention in several stages, while respecting the standards of the manufacturer Mitsubishi Electric and the requirements of the Canadian Building Code:
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Complete cleaning of the condenser using a biodegradable product specific to HVAC surfaces.
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Straightening the fins to restore optimal airflow.
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Readjustment of the support with the addition of high-density composite shims to stabilize the base on the flat roof.
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Restoration of the R-410A refrigerant charge after detection and repair of a micro-leak on the service valve connection.
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Protection of electrical cables using a UV-resistant sheath to ensure the durability of the wiring.
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Complete performance test of the compressor and thermodynamic cycle.
Result: comfort and performance restored
After these interventions, the Mitsubishi wall-mounted heat pump regained its original performance. The customer immediately noticed a difference:
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faster temperature rise,
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quiet operation,
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and constant heating stability, even at low temperatures.
Our final measurements confirmed a COP (coefficient of performance) in line with brand standards, with a stable discharge temperature and a normally operating defrost cycle.
Lessons Learned and AirGreen Tips
This repair perfectly illustrates the importance of preventative maintenance on systems installed on flat roofs in Laval or Montreal. Here are some tips we often share with our clients:
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Visually inspect the condenser at least twice a year.
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Clean the fins in spring and fall to prevent the compressor from overheating.
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Check the stability of the support after each winter, especially when frequent freeze/thaw cycles occur.
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Schedule an annual AirGreen service , including cleaning, refrigerant testing, and electronic calibration.
These simple actions extend the life of the system while guaranteeing substantial energy savings.
Why choose AirGreen in Laval for your HVAC repairs?
At AirGreen , we operate every day in the greater Montreal region, Laval , Longueuil , as well as on the North Shore and the South Shore , to ensure the performance and reliability of heating, ventilation and air conditioning (HVAC) systems.
Our technicians are trained on major brands such as Mitsubishi Electric, Fujitsu, Gree, Sharp, Midea, Goodman and Zephyr , and have the necessary equipment to work on all types of installations: wall-mounted, multi-zone, central or ducted.
Every service call is documented, measured, and verified to ensure your system is working like new after our visit.
Local expertise, guaranteed service
Thanks to our in-depth knowledge of the Montreal climate and the challenges specific to rooftop installations, we offer adapted, sustainable and economical solutions .
Our interventions comply with the strictest electrical and environmental safety standards, and each repair is guaranteed for parts and labor .
For any problem with your Mitsubishi heat pump or any other HVAC system, AirGreen remains your trusted partner in Sainte-Dorothée , Laval and throughout Quebec.