A rooftop HVAC installation designed to withstand the realities of Quebec winters
À Rosemère, installing this Samsung Premium FJM dual-zone heat pump required much more than simply placing an outdoor unit. The unit had to be positioned on a flat roof, protected against snow accumulation, kept level, and installed without compromising the integrity of the roof membrane.
In the project photo, the imposing Samsung outdoor unit with two fans immediately stands out, installed on an independent metal support. The structure rests on long crossbars that distribute the weight over a larger surface rather than concentrating the entire load beneath a few small support points. Adjustable feet also allow the unit to be precisely levelled.
This configuration meets a specific goal: ensuring reliable operation of the multi-zone heat pump, while making maintenance easier and protecting the building.
The customer's need: to cool and heat two zones with a single outdoor unit
A dual-zone heat pump allows two indoor units to be connected to a single outdoor condenser. This solution is particularly well suited to homes where two areas have different comfort needs, for example:
- the ground floor and the upper floor;
- the main living space and a bedroom;
- an open-concept area and an office;
- a home addition and the main building;
- two areas that are difficult to serve with an existing central system.
Each indoor unit has its own temperature setting and fan speed. The homeowner can therefore adjust the comfort of each room without having to install two separate outdoor units.
However, it is important to understand an important characteristic of multi-zone systems: the indoor units generally need to operate in the same primary mode. They can maintain different temperatures, but one unit normally cannot cool while the other heats. This information should be explained before installation so that the equipment choice truly matches the occupants’ habits.
Why the Samsung Premium FJM system is suitable for multi-zone applications
The Samsung Free Joint Multi Premium range, often referred to by the abbreviation FJM Premium, is designed to power multiple indoor units from a single outdoor unit. Depending on the selected model, this range is available in nominal capacities of 20,000, 24,000, 30,000 and 36,000 BTU/h, and can support up to four zones. It uses R-32 refrigerant and is designed to maintain high heating capacity in cold weather. Samsung indicates, among other things, full heating capacity at approximately −15 °C, as well as low-temperature operation down to approximately −25 °C, depending on the equipment combination.
In the case of this installation in Rosemère, the system was configured as a dual-zone system. The choice of outdoor capacity depends not only on the sum of the BTUs listed for the two wall-mounted units. We must also take into account:
- the heat loss of each room;
- the floor area and ceiling height;
- sun exposure;
- the quality of the insulation;
- the number and type of windows;
- the distance between the indoor and outdoor units;
- actual heating capacity at low temperatures;
- Samsung-approved combination tables.
An outdoor unit that is too small may operate almost continuously without reaching the desired temperature during cold periods. An oversized unit may, on the other hand, produce more short cycles, reduce dehumidification in summer, and make the temperature less stable.
What the photograph reveals about the quality of the installation
Several visible details show that the positioning of the outdoor unit was carefully planned for the roof.
An independent, adjustable metal support
The Samsung unit is installed on a sturdy metal table rather than directly on the membrane. This structure keeps the unit at a useful height above the roof and provides access beneath the condenser.
Adjustable feet are particularly important on a flat roof. Even when a roof appears horizontal, it normally has a slight slope intended to direct water toward the drains. Without adjustment, the condenser could be tilted, placing unnecessary stress on its frame and potentially impairing the drainage of water produced during defrost cycles.
More uniform weight distribution
The long crossbars visible beneath the support distribute the load over a larger surface area. This method limits concentrated pressure on the membrane and helps stabilize the structure.
Before any rooftop HVAC installation, we must consider the weight of the equipment, the type of roof, the location of load-bearing elements, and the access required for servicing. A heat pump must not be placed on a weak section simply because that location shortens the refrigerant lines.
A height suited to snow and defrosting
In heating mode, an outdoor heat pump extracts heat from the air. When conditions are cold and humid, frost can form on the heat exchanger. The system then initiates a defrost cycle, during which water drains beneath the unit.
On a roof, this water can freeze around the base if the unit is installed too low. The raised support visible on this project provides space for water to move away from the unit and reduces the risk of ice reaching the bottom of the condenser.
This height also helps keep the air intakes clear during snow accumulation. The two large front grilles must remain unobstructed so the fans can move the volume of air specified by the manufacturer.
Clearances that facilitate maintenance
The front of the unit remains completely accessible. A technician can therefore inspect the fans, access the service panels, and clean the heat exchanger without having to dismantle a nearby structure.
Access to the connection side is equally important. The refrigerant lines, communication wiring, and electrical power supply must be accessible for inspection during maintenance or diagnostics.
Care taken when routing the refrigerant lines
In a dual-zone system, two piping circuits connect the outdoor unit to the indoor units. Their installation directly affects system reliability.
Our technicians must check, among other things:
-
Required diameter for each line
Dimensions are determined by the outdoor unit model and by each indoor unit. Pipes should never be selected solely based on the advertised total capacity. -
Actual run length
The manufacturer specifies a maximum total length as well as a limit for each branch. A maximum height difference may also apply. -
Insulation quality
Each line must be properly insulated to limit heat loss and condensation. -
Fitting tightness
Flared fittings must be fabricated cleanly and tightened to the recommended torque. Insufficient tightening can cause a leak; excessive tightening can crack the flare. -
Pressure testing and evacuation
Before commissioning, the system must undergo a leak test and then be evacuated with a vacuum pump. This step removes the air and moisture present in the lines. -
Identifying the two zones
Each pair of lines and each communication cable must correspond to the correct outdoor port. The FJM Premium range includes addressing and verification functions that facilitate matching the indoor units with the refrigerant ports.
A wiring error can create confusing symptoms: one indoor unit receives a command, but the refrigerant flow is directed to the other zone. A methodical commissioning process helps prevent this type of problem.
Comfort, efficiency, and points to check before a multizone installation in Rosemère
Two comfort zones without adding more equipment to the roof
One of the main advantages of this installation is the reduction in the number of outdoor units. Rather than installing two separate condensers, the Samsung system supplies both zones from a single unit.
This solution offers several benefits:
- less roof space occupied;
- a more orderly exterior appearance;
- a single main electrical circuit;
- fewer mechanical supports;
- centralized maintenance access;
- modulation suited to the combined demand of the zones.
The variable-speed compressor adjusts its operation according to actual needs rather than operating only at full capacity or stopping completely. Samsung presents this modulation principle as a way to maintain a more stable temperature and reduce frequent restarts.
An installation suited to the conditions in Rosemère and the North Shore
In Rosemère, as elsewhere on the North Shore, an outdoor unit installed on a roof is exposed to wind, snow, freezing rain, and rapid temperature changes. The location must therefore take winter conditions into account, not just summer operation.
A unit placed too close to a wall or obstacle may draw back in the cold air it has just discharged. This phenomenon reduces its performance and may encourage ice buildup. A unit installed too close to the roof edge may also be more exposed to wind and make service work more difficult.
On this project, the clear space in front of the fans promotes adequate airflow. The support also provides clear separation between the condenser and the roof surface.
The rebates must be validated with the exact AHRI number
A Samsung heat pump does not automatically become eligible for financial assistance simply because it belongs to a recognized product line or because it operates at low temperatures.
Under the Hydro-Québec LogisVert program, the applicable assistance for an eligible heat pump is calculated based on its heating capacity at −8 °C, not simply on its nominal cooling capacity. Hydro-Québec indicates that assistance may correspond to $120 per 1,000 BTU/h at −8 °C for eligible systems, according to the terms in effect.
Validation must be performed using the complete combination:
- exact model of the outdoor unit;
- model of the first indoor unit;
- model of the second indoor unit;
- AHRI certification number;
- certified heating capacity at −8 °C;
- eligibility list in effect on the applicable date.
Since the rating plate is not legible in the photo, we will not publish an AHRI number, a generic SEER2 efficiency rating, or a generic subsidy amount. Two installations using an outdoor unit from the same family may produce different results depending on the connected indoor units.
At AirGreen, we verify the exact combination before confirming financial assistance. This approach prevents presenting the homeowner with an amount based on a combination that does not match the equipment actually installed.
Common mistakes to avoid in a two-zone installation
Choosing the unit based solely on the total floor area
Two homes with the same floor area can have very different heating requirements. The number of windows, insulation, orientation, and room layout strongly influence the load.
Automatically adding up the capacities of the indoor units
A configuration consisting of two 12,000 BTU/h wall-mounted units does not necessarily mean that the outdoor unit must provide exactly 24,000 BTU/h under all conditions. Combination tables and the diversity of zone usage must be studied.
Installing the condenser directly on the roof
This practice can concentrate the load, make defrost drainage difficult, trap snow around the unit, and complicate repairs.
Neglecting vibrations
Even a quiet heat pump produces slight vibrations. On a roof, these can be transmitted to the building structure. The supports, mounting system, and positioning must therefore be selected accordingly.
Install the unit without planning for future servicing
A compact installation must not become inaccessible. The panels, fittings, disconnect switch, and electrical components must remain accessible.
Assuming that both zones can heat and cool simultaneously
The owner should understand how a multi-zone system works before purchasing it. A good explanation prevents misunderstandings when the seasons change.
Commissioning: the step that confirms the quality of the work
After the mechanical and refrigeration installation, we carry out a series of checks:
- confirming that the outdoor unit is level;
- checking clearances;
- inspecting the connections and insulation;
- checking the electrical power supply;
- communications test;
- addressing the two indoor units;
- cooling test;
- heating test;
- checking supply-air temperatures;
- confirming condensate drainage;
- explaining the remote controls and settings to the owner.
For a unit installed on a roof, we also examine the structure’s behavior at startup. No excessive movement or abnormal vibration should be transferred to the crossmembers or the roof.
Recommended maintenance to preserve performance
The owner can help extend the system’s lifespan by regularly cleaning the indoor unit filters and avoiding blocking the air inlets or outlets.
The outdoor rooftop unit should also be inspected periodically. Maintenance includes, among other things:
- cleaning the heat exchanger;
- inspecting the grilles and fans;
- checking the support;
- checking the feet and fasteners;
- examining the insulation on the lines;
- looking for traces of oil that could indicate a leak;
- checking the space beneath the unit;
- removing debris that could block water drainage.
After a particularly snowy winter, it is wise to confirm that snow and ice have not accumulated around the condenser.
An AirGreen installation designed as a complete system
This Samsung Premium FJM dual-zone heat pump installation in Rosemère illustrates our approach: we never consider the equipment independently of its building.
The choice of support, weight distribution, height above the roof, clearances, routing of the lines, and access for maintenance all affect long-term operation.
We carry out projects comparable to Rosemère, Laval, Montreal, Longueuil, on the North Shore, and on the South Shore. Whether it involves a house, a multi-unit building, or a commercial space, our objective remains the same: to install an HVAC system that is properly sized, documented, and adapted to the building’s actual constraints.