A poorly planned installation: the Achilles’ heel of many multi-zone heat pumps
At AirGreen, we know that a multi-zone heat pump can transform your home comfort while significantly reducing your energy costs. But despite their growing popularity in Montréal, Laval, Longueuil, the North Shore and the South Shore, one critical mistake continues to compromise their efficiency: improper system sizing or poor configuration of the indoor zones.
This issue, which we encounter all too often in the field, can lead to a range of problems: uneven temperatures, indoor units running in overdrive, excessive energy consumption, or even a shorter lifespan of the equipment. In this article, we’ll walk you through how to avoid this costly mistake through careful planning, deep technical expertise, and a user-focused approach — the AirGreen method.
Understanding the stakes of system sizing in a multi-zone setup
A multi-zone system, such as those offered by Fujitsu, Gree, Haxxair or Bosch, allows you to connect multiple indoor units (usually wall-mounted) to a single outdoor compressor. Each indoor unit serves a separate area of your home or commercial space, giving you precise room-by-room temperature control.
But here’s what many people don’t realize: choosing the indoor units and the power of the outdoor compressor must be calculated with precision. It’s not just about adding up the BTUs of each unit. Typical errors include:
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Selecting indoor units that are too powerful for small rooms.
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Installing too many units for the compressor’s capacity.
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Creating excessive piping distances between zones.
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Misjudging actual needs based on orientation, insulation, sunlight exposure, etc.
The result? The system becomes unbalanced. Some units fail to heat or cool properly, others freeze or overheat, and the compressor works overtime, consuming more electricity.
Case Study: A project gone wrong in Laval… corrected by AirGreen
A residential client in Chomedey, Laval, contacted us after installing a multi-zone system through an inexperienced contractor. He had chosen a 36,000 BTU compressor, connected to four indoor units (2 x 9,000 BTU and 2 x 12,000 BTU). On paper, the setup looked fine.
But in practice:
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Two units were installed in small, poorly insulated, north-facing bedrooms.
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Another was in a living room full of south-facing windows, exposed to heavy sunlight.
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The living room unit was underpowered, while the bedroom units were oversized.
We re-evaluated everything: thermal load calculations, site configuration analysis, insulation review. In the end, we replaced two units with 7,000 BTU Fujitsu KZAH models, and adjusted the compressor capacity to 30,000 BTU. The result: improved comfort, an 18% drop in electricity usage, and one very satisfied client.
How AirGreen properly sizes your multi-zone heat pump
1. Comprehensive building analysis
We assess each room: air volume, insulation quality, number of windows, orientation, occupancy rate, and heat-generating appliances.
2. Room-by-room thermal load calculations
We use professional-grade tools to calculate exact heating and cooling needs for each zone, year-round.
3. Optimized selection of indoor units
We match size (BTU), type (wall-mounted, cassette, console, ducted), and features (inverter, Wi-Fi, motion detection) to each specific environment.
4. Choosing the right compressor
At AirGreen, we prefer high-efficiency models such as:
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Fujitsu Airstage KX or KZAH R-32
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Bosch BOVA or BIVA IDS Premium R-454B
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Gree Multi-Ultra or MultiSapphire R32
5. Professional installation and system balancing
Our certified technicians install and test each zone, balancing pressure, verifying airflow, and optimizing piping lengths.
The consequences of poor system sizing
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Reduced comfort: Uneven temperatures between rooms.
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Increased noise: Units forced to overwork become noisy.
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High energy bills: Your Hydro-Québec costs go up.
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Frequent maintenance: Overheating, freezing, unexpected shutdowns.
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Loss of eligibility for grants: An inefficient system may not meet the criteria for programs like Hydro-Québec’s LogisVert.
Available grants: beware of the conditions
The LogisVert program offers grants of up to $5,000 for efficient heat pump installations. However, eligibility depends on:
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The system’s energy efficiency (e.g., SEER, HSPF)
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The quality of the installation
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Proper system sizing
A configuration mistake could disqualify you from financial assistance. At AirGreen, we guarantee an installation that meets all program standards.
Practical tips before choosing a multi-zone heat pump
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Avoid quick over-the-phone estimates. A real professional always visits the site.
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Insist on a thermal load calculation. It’s not optional — it’s essential.
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Ask about the installer’s experience with multi-zone systems.
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Request examples of past projects. At AirGreen, we document every installation.
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Verify grant eligibility with the installer.
Why trust AirGreen
In Montréal, Laval, Longueuil, on the North Shore and the South Shore, we’ve installed hundreds of multi-zone systems in homes, multi-unit buildings, commercial spaces, and offices. What sets us apart:
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A team of certified HVAC experts.
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A 100% personalized approach, tailored to your building’s reality.
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Outstanding after-sales service, with preventive maintenance and technical support.
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High-performance, durable equipment, selected to meet your real needs.
In summary: The key to an efficient multi-zone system
The number one mistake to avoid is thinking a multi-zone system is universal and easy to install. It’s quite the opposite. You need to:
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Analyze,
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Calculate,
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Configure,
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Install with precision.
At AirGreen, that’s exactly what we do. And that’s how we ensure optimal comfort, real energy efficiency, and long-term peace of mind for our clients.