A simple wall-mounted AC can turn into a real headache: authentic stories and concrete lessons from the field in Laval
At AirGreen, we’ve seen every type of HVAC installation over the years—from flawless jobs to the most unpredictable situations. What many people don’t realize is that a poorly installed wall-mounted air conditioner can lead to costly problems, even when the work is done by experienced technicians. In Laval, we were recently called in to fix several recurring mistakes, and these exclusive client testimonials are packed with practical, real-world insights.
The classic mistake: choosing the wrong spot for the indoor unit
During a recent job in Chomedey, a family had a Mitsubishi MSZ-GL 12000 BTU wall-mounted AC installed in their living room. The initial comfort was decent, but certain areas of the room remained strangely warm.
Upon inspection, we found the unit had been mounted too high, only 10 cm (4 inches) from the ceiling, and was pointed directly at an adjacent wall. The result: poor airflow, disrupted circulation, and reduced performance.
Our recommendations:
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Always leave 15 to 20 cm (6 to 8 inches) of clearance above the unit
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Never aim airflow at a nearby obstacle
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Position the unit to allow for central airflow across the room
The duct insulation issue: a case from a condo in Laval-des-Rapides
In a new condo building, a young couple had installed a Gree Lomo 9000 BTU wall-mounted unit. Everything seemed fine until dark moisture stains started appearing on the exterior walls just two weeks after installation.
After investigating, we discovered the refrigerant lines were passing through an uninsulated wall, and the piping sleeves were unprotected from condensation. The result: excessive moisture, water infiltration, and risk of mold.
Solutions we applied:
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Removed and re-routed the ducts
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Added watertight insulated sleeves
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Checked pipe slope to ensure proper drainage
This type of mistake is common, especially in newer condos where exterior walls are thinner. Proper insulation of refrigerant lines is a critical step in any HVAC installation.
A wiring mistake that cost a Vimont homeowner dearly
A general contractor had installed a Tosot Muse 18000 BTU wall-mounted AC himself in a duplex in Vimont. Though the system worked for a few weeks, it failed completely during the first major heatwave. Upon inspection, we found:
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The electrical connections between the indoor and outdoor units were reversed
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The breaker used was incompatible with the required amperage
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The communication cable was too long and not shielded
We redid everything from the electrical panel, installed a certified CSA 20A double breaker, and replaced the wiring with shielded cable to meet code.
Bottom line: even with a quality machine, a wiring error can make the unit unusable and void the manufacturer’s warranty.
Exclusive testimonials: customers share their mistakes (and solutions)
“If I had known how much the orientation of the unit mattered, I would’ve consulted AirGreen from the start. Since the fix, the cool air is even throughout the whole house.” — Sarah L., Laval
“I thought I’d save money by having my electrician friend install the AC. In the end, the repairs cost me twice as much. Luckily, AirGreen made it safe and right.” — Jean-Marc P., Vimont
“I had no idea a poorly insulated pipe could cause that much damage. Thanks to the AirGreen team for their quick and professional work.” — Caroline F., Laval-des-Rapides
What we always recommend in Laval (and beyond)
At AirGreen, we’ve implemented a strict, step-by-step installation procedure, following the highest standards in the HVAC industry:
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Full inspection of the installation site, with placement recommendations
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Thermal load analysis, to properly size the equipment (BTU rating)
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Verification of electrical wiring and breaker compatibility
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Professional insulation of all ducts to prevent condensation
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System startup with full performance testing
Brands installed by AirGreen in Laval
We frequently work with the following brands:
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Fujitsu
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Mitsubishi
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Gree
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Tosot
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Sharp
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Lennox
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Daikin
Each brand has its unique specifications, and our technicians are trained on every model, to ensure peak performance from day one.
Practical tips to avoid installation errors
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Never try to DIY the installation, even if the unit seems easy to mount
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Hire a certified installer with a valid RBQ license
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Make sure the installation site is suitable (structure, space, airflow direction)
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Request a post-installation inspection, especially in newer buildings
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Keep all startup documents, as they’re often required for warranty coverage
Living in Laval and planning to install a wall-mounted AC? Have concerns about an existing setup?
Call AirGreen. We operate throughout Laval, Longueuil, Montreal, the North Shore, and the South Shore, to diagnose, fix, and install systems that meet the highest HVAC industry standards.