A new system that disappoints? Here's why installation mistakes can cost you big time
At AirGreen, we’re on the ground every day across Montréal, Laval, Longueuil, the North Shore and South Shore, installing or servicing heating, ventilation and air conditioning (HVAC) systems in residential, commercial, and industrial settings. Far too often, we get called in to diagnose issues on brand-new equipment… that shouldn’t be breaking down so soon.
This is not unusual. And in most cases, early breakdowns are not due to the quality of the equipment, but rather the result of poor HVAC installation. Here are the 4 most common mistakes we’ve encountered on real jobs, and the lessons every homeowner or building manager should take seriously.
1. Incorrect sizing of the HVAC system
A miscalculation with costly consequences
An HVAC system that’s oversized or undersized is bound to fail. Many people mistakenly think that a more powerful unit means “better performance,” but that’s not true. An oversized system will run in short cycles, which causes:
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premature wear on components;
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poor humidity control;
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higher energy consumption.
On the other hand, an undersized system will constantly overwork, leading to frequent breakdowns—especially during heatwaves or extreme cold.
What we do at AirGreen
Before every installation, we carry out a complete thermal analysis of the space or building, taking into account:
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insulation,
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window surface and orientation,
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number of occupants,
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sun exposure.
This calculation allows us to recommend the right BTU capacity for your heat pump or wall-mounted air conditioner, ensuring performance, comfort, and durability.
2. Poor placement of indoor and outdoor units
The invisible mistake that leads to failure
The placement of your units is just as important as their power. An indoor unit that’s poorly located can lead to:
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uneven airflow;
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temperature inconsistency;
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increased energy use.
As for the outdoor unit, it must avoid tight or low-ventilation areas, be protected from snow in winter, and have enough clearance to expel heat properly.
Our best practices
We install units:
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at strategic height for optimal performance;
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away from heat sources, humidity, or foot traffic;
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with at least 12 to 24 inches of clearance around the outdoor unit, depending on the manufacturer's recommendations (Fujitsu, Gree, Bosch, Lennox, etc.).
3. Improper or missing drainage
A small detail with major consequences
Poor drainage can cause:
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water leaks in walls or ceilings;
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mold growth;
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system shutdowns for safety reasons.
With a rushed or careless installation, the drainage pipe is often too short, poorly angled, or obstructed. This will eventually shut down your HVAC system or lead to expensive damage.
Our AirGreen method
We always install:
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a properly angled drain line (minimum 1% slope),
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a condensate pump when needed (e.g., in condos or basements),
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overflow protection systems.
These precautions prevent unexpected shutdowns and ensure your system runs smoothly, even in dehumidification mode.
4. Non-compliant electrical or refrigerant connections
Invisible issues… until the system breaks
Even the best wall-mounted heat pumps or central HVAC systems won’t work properly without precise and compliant connections:
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An electrical wire with the wrong gauge can cause overheating;
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Too much or too little refrigerant harms the compressor;
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Poor soldering leads to refrigerant gas leaks.
What we guarantee
At AirGreen, all our technicians:
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are certified to handle R-32, R-410A and R-454B refrigerants;
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comply with CSA and RBQ standards;
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perform a leak and pressure test on every system after installation.
That’s how we prevent breakdowns before they even start.
The AirGreen experience: prevention first
We’re often called in to fix mistakes made by less meticulous contractors. Our priority is to ensure that every HVAC installation is done by the book, right from the start.
Here’s a concrete example: A client in Longueuil had their brand-new central heat pump break down three times in six months. After our diagnosis, we found:
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a damaged compressor due to excess refrigerant;
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an outdoor unit installed too close to a wall, blocking heat expulsion;
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a clogged drain causing the system to auto-shutdown.
We relocated the unit, evacuated and recharged the refrigerant properly, and rebuilt the drain correctly. Since then, no more issues. Performance is stable, energy bills dropped by 22%, and the client even received a $1,704 refund through Hydro-Québec’s LogisVert program.
Practical tips to avoid these traps
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Always request a serious thermal study before installation.
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Make sure the installer is certified and experienced.
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Ask for references and photos of previous installations.
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Never accept a quote without a site visit.
Why choose AirGreen?
At AirGreen, our team serves the entire Greater Montréal area, including:
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Montréal
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Laval
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Longueuil
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North Shore
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South Shore
We install, repair, and maintain all major brands (Fujitsu, Gree, Bosch, Goodman, Lennox, Midea…) while following industry best practices in HVAC. Every client benefits from:
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a customized evaluation;
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a 100% compliant installation;
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maximized rebates;
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fast, human after-sales support.
Need a risk-free installation or a trusted diagnosis?
Call us today. At AirGreen, we turn other contractors’ mistakes into long-lasting solutions—for your comfort and your peace of mind.