When DIY turns dangerous: a look back at disastrous installs and the professional solutions implemented by AirGreen
In our line of work, we’re regularly called in to fix the mistakes of homeowners who tried installing their own wall-mounted air conditioner or wall-mounted heat pump. While many of these DIY efforts are well-intentioned—motivated by saving money or taking on a challenge—the outcome is often catastrophic, especially in Montréal, where climate variations, building codes, and energy efficiency standards are strict. Here are the 5 worst DIY installs we’ve encountered, and how we resolved them.
1. An Air Conditioner Installed... Upside Down in a Plateau-Mont-Royal Condo
One client attempted to install a generic 12,000 BTU wall-mounted air conditioner purchased online, without reading the manual. The result:
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The indoor unit was installed upside down, making drainage impossible
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Water was dripping onto the hardwood floor, causing warping
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No venting was in place for the outdoor unit, which was precariously placed on a weak balcony
AirGreen Solution:
We dismantled the system, repaired the water damage, and installed a FUJITSU KZAH Wall-Mounted Heat Pump | 12,000 BTU | R-32 with custom drainage and a secured outdoor bracket. The unit is now eligible for LogisVert grants.
2. A DIY Electrical Hookup in Rosemont
A self-proclaimed handyman connected an 18,000 BTU wall-mounted air conditioner without consulting an electrician:
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Plugged it into a standard 15A outlet, causing frequent circuit trips
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No dedicated breaker or protected wiring
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Immediate risk of electrocution and fire
AirGreen Solution:
Our team brought in a certified electrician, installed a dedicated 240V line, and replaced the unit with a GREE Extreme Wall-Mounted Heat Pump | 18,000 BTU | R-32. The entire system now complies with the Quebec Electrical Code.
3. A Heat Pump Secured with Garden Hooks in Ahuntsic
Looking to save on materials, one client installed a 24,000 BTU wall-mounted heat pump using plant hanger hooks, mounted on a brick wall:
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The unit lasted three days before crashing to the ground
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Cracks in the wall revealed water infiltration
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The refrigerant line was cut, releasing harmful gas
AirGreen Solution:
We replaced the unit with a MIDEA EVOX G3 Central Heat Pump | 2 Tons, with a professional HVAC installation, reinforced mounting, and complete leak testing.
4. Ventilation-Free Air Conditioning Setup in Saint-Léonard
A family purchased two portable air conditioners and connected them to makeshift ducts punched through their windows—in the middle of August:
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Poor ventilation led to indoor humidity buildup
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Black mold started forming in the room corners
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Excessive electricity use for minimal cooling results
AirGreen Solution:
We replaced the equipment with two Fujitsu Aquila R32 multi-zone systems, with discreet wall-mounted vents and perfectly balanced airflow. The clients now enjoy better comfort, energy efficiency, and qualified for government rebates.
5. An Outdoor Unit Resting on Bricks in Griffintown
To avoid installation costs, a renter placed the outdoor unit on a stack of bricks and wood, with no stabilizing base:
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Constant vibrations caused excessive noise for neighbours
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The compressor degraded due to misalignment
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Manufacturer warranty was voided
AirGreen Solution:
We installed an anti-vibration wall bracket, rebalanced the system, and replaced the unit with a Sharp ZU1 Wall-Mounted Heat Pump | 15,000 BTU | R-32, a quieter and more efficient model.
What We Learned from These Common Mistakes
These five examples show just how serious the risks are with non-professional HVAC installations:
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Structural damage to your home
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Non-compliance with building and safety codes
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Electrical and health hazards
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Disqualification from programs like LogisVert
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Voided warranties and unexpected expenses
Why Choose AirGreen in Montréal for All HVAC Installations?
At AirGreen, we believe a high-performance HVAC system starts with a precise, reliable installation. Our local teams in Montréal, Laval, Longueuil, the South Shore, and the North Shore are ready to respond with solutions that are:
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Custom-tailored to your space layout
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Performed by RBQ-certified technicians and licensed electricians
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Fully supported with grant application assistance
Conclusion: A Poorly Installed AC Will Cost You More Than a Great Installer
The savings promised by DIY quickly disappear in the face of repair costs, lost efficiency, and legal risks. Trust AirGreen’s expertise for an HVAC installation that’s durable, safe, and energy-efficient.
Your comfort starts with flawless installation. Contact us today.