A high-altitude installation designed to withstand wind, protect the roof, and provide comfort to two zones
In Terrebonne, we installed a Samsung Premium FJM two-zone heat pump in a configuration that required preparation very different from a conventional ground-level installation. The outdoor unit had to be installed on a flat roof above neighboring buildings, in an environment highly exposed to wind and the winter conditions of the North Shore.
The photograph of this project shows a vertical Samsung unit with two stacked ventilation sections. Its size allows it to power several indoor units while limiting the number of appliances installed outdoors. In this project, a single outdoor unit serves two distinct zones of the building.
The main challenge was not limited to connecting the refrigerant lines. We also had to create a stable base, distribute the weight across the membrane, raise the unit to support winter operation, and reinforce the assembly against the lateral forces exerted by gusts.
This HVAC installation in Terrebonne therefore relies on several complementary elements:
- a raised metal structure;
- long wooden crosspieces used to distribute the loads;
- protection between the base and the roof membrane;
- diagonal braces secured on both sides of the unit;
- positioning that allows access to the service panels;
- an organized piping route to the indoor zones.
Every component addresses a real job-site constraint. On a flat roof, a heat pump should never be treated as equipment that can simply be placed in the first available spot.
Why choose a two-zone Samsung Premium FJM heat pump?
The Samsung Premium FJM series is designed for multi-zone installations. In a two-zone configuration, a shared outdoor unit powers two indoor units installed in different areas.
This configuration is particularly well suited to properties where needs are not uniform. A large living area may receive more sunlight than a bedroom. An upstairs office may overheat more quickly than a ground-floor space. Two indoor units then make it possible to distribute the air more effectively and adjust temperature setpoints separately.
Compared with installing two completely independent systems, a dual-zone heat pump offers several practical advantages:
- a single outdoor condenser;
- a smaller roof footprint;
- fewer visible pieces of equipment;
- powering two separate spaces;
- modulation adapted to the combined demand of the zones;
- a more centralized outdoor installation.
For this project in Terrebonne, the vertical format of the Samsung unit was particularly appealing. It concentrates the system’s capacity within a relatively limited footprint, helping preserve circulation and maintenance areas on the roof.
However, this compact design must be paired with an adequate structure. A tall, narrow unit presents a significant surface area to the wind. The higher the installation, the more critical lateral stability becomes.
Two independent zones, but coordinated operation
Each indoor unit in a Samsung FJM system can generally have its own temperature setpoint. Occupants can therefore adjust comfort according to how each room is used.
However, it is important to understand how a multizone heat pump works. The two indoor units share the same outdoor unit. They must normally operate in a compatible mode. One zone generally cannot request heating while the other simultaneously requests cooling.
The available capacity is also distributed among the active zones. When both indoor units place a heavy demand on the system at the same time, the condenser adjusts its output and distributes its capacity according to the detected needs.
This factor must be taken into account during sizing. A dual-zone system should not be selected solely by approximately adding up the floor area of the rooms. We assess, among other things:
- the building’s heat loss;
- wall and roof insulation;
- the amount of glazing;
- solar exposure;
- ceiling height;
- air infiltration;
- how the rooms are used;
- the distance between the units;
- available capacity at low temperatures;
- the combination limits established by the manufacturer.
An undersized unit may run continuously on the coldest days. An unnecessarily oversized unit may lose some of its modulation capacity and cause less regular cycles during milder periods.
A large-format outdoor unit installed above the roof
The unit visible in the photo has two large, stacked ventilation sections. This format is frequently found on multizone units with greater capacity than small, simple wall-mounted systems.
The equipment’s height improves use of the space, but it also increases the leverage exerted on the base. On an exposed roof, wind pushes against the entire front and side surfaces of the cabinet. A solid base must therefore withstand not only the vertical weight but also tipping forces and repeated movement.
For this reason, we used a metal support resting on a structure much wider than the unit itself. The wooden crossbars extend the base in several directions to distribute the loads over a larger area.
This arrangement helps prevent the weight from being concentrated beneath four metal feet. On a flat roof, excessive pressure on small contact points can damage the membrane or compress the layers beneath it.
Protective separation between the structure and the membrane
A membrane or separation layer is visible beneath the crossbars. This protection prevents the wood and support components from rubbing directly against the roof.
Materials installed on a roof move slightly due to:
- temperature variations;
- moisture;
- mechanical vibrations;
- snow loads;
- freeze-thaw cycles;
- the expansion of metal components.
Even minimal movement, repeated over several years, can wear down a membrane. The protective layer limits this risk and helps distribute the load.
We must also preserve water drainage. A poorly oriented structure can create a dam, retain water, or trap debris. The installation must therefore follow the roof’s slope and keep the drainage areas functional.
A necessary elevation for winter conditions in Terrebonne
A heat pump operating in heating mode periodically performs defrost cycles. During these cycles, ice accumulated on the outdoor coil melts and produces water.
If the unit is installed too close to the roof, this water can freeze beneath the chassis and form a mass of ice around the base. Significant accumulation can hinder drainage, reduce the clearance beneath the equipment, and affect the unit’s operation.
The metal structure used for this installation keeps the heat pump sufficiently above the surface. This elevation provides several advantages:
- it leaves room for defrost water drainage;
- it reduces the risk of being buried by snow;
- it facilitates inspection beneath the unit;
- it protects the lower components against certain accumulations;
- it improves accessibility during maintenance.
In Terrebonne, as elsewhere on the North Shore, snow does not always fall vertically. Winds can create localized accumulations against walls, parapets, and mechanical equipment. The location of an outdoor unit must therefore be assessed according to the possible movement of snow on the roof, not only according to the average height observed at ground level.
Diagonal braces designed to counter lateral movement
The two long, inclined metal pieces are among the most important elements of this installation. They act as diagonal braces between the upper part of the heat pump and the enlarged base.
Without diagonal braces, a rectangular structure can undergo greater lateral deformation. Adding a triangulated brace significantly improves its rigidity. The forces exerted by the wind are transferred to a much wider base, reducing movement of the unit.
This solution was particularly well suited to the format of the Samsung unit. The enclosure is tall and has two large ventilation surfaces. On an unobstructed roof, gusts can come from several directions and change intensity quickly.
The braces were positioned so as not to block:
- the fan air outlet;
- the coil air intakes;
- access panels;
- refrigerant connections;
- cleaning operations;
- the eventual replacement of a component.
A perfectly stabilized heat pump that cannot be serviced is not a successful installation. The structure must protect the equipment while preserving its accessibility.
The importance of clearance around both fans
Air must be able to circulate freely through the outdoor coil and be discharged without significant obstruction. Poor airflow can cause air recirculation, reduce available capacity, and increase operating time.
In this installation, the heat pump is positioned in a clear area of the roof. No nearby wall directly obstructs either of the two ventilation sections. The location also allows technicians to move around the unit.
The exact clearances must always be verified in the technical documentation for the installed model. They may vary depending on:
- the unit's capacity;
- the direction of the air discharge;
- the presence of a parapet;
- the proximity of another condenser;
- the possibility of installing several units in a row;
- the manufacturer's maintenance requirements.
Equipment installed too close to a parapet may operate properly under certain conditions, then lose efficiency when the wind redirects hot or cold air toward the heat exchanger.
The route of the refrigeration lines across the roof
Behind the unit, we can see the lines and wiring grouped together before their route into the building. A dual-zone installation has two distinct refrigeration assemblies connected to the indoor units.
Each zone generally requires:
- a liquid line;
- a refrigerant gas line;
- suitable insulation;
- an interconnection cable;
- a condensate drainage system on the indoor side.
Outdoor lines must be arranged to avoid overly tight bends, friction, and movement caused by wind. An excessively bent copper line can become flattened or develop permanent stress. The insulation can also tear when left against an edge or abrasive material.
On a roof, protection from ultraviolet rays is particularly important. Deteriorated insulation gradually exposes the copper and reduces the thermal efficiency of the lines. It can also promote condensation on cold sections in cooling mode.
We therefore plan a layout that facilitates both:
- mechanical protection;
- drainage;
- circuit identification;
- access to the connections;
- future roof repairs;
- heat pump maintenance.
Separate commissioning for each of the two zones
The physical installation represents only part of the work. A Samsung FJM heat pump must then be commissioned methodically.
We check each refrigeration circuit before opening the valves. The steps include, among other things, a leak test, evacuation, and confirmation that the connections have no leaks.
The two zones are then tested individually and simultaneously. We check:
- the response of each indoor unit;
- the correct pairing between the units and their ports;
- fan operation;
- discharge air temperatures;
- communication codes;
- condensate drainage;
- how the system responds when both zones call for heating or cooling;
- the noise level and vibrations of the outdoor unit.
This step also makes it possible to explain to occupants how to use the system without creating conflicting commands between the zones.
Technical decisions that extend the service life of a rooftop HVAC installation
Common mistakes we avoid on a flat roof
An installation may look clean at startup while still having weaknesses that appear after several seasons. Among the most common mistakes, we find:
- install the unit directly on the membrane;
- use supports that are too small;
- overlook the effect of wind on a vertical unit;
- place the heat pump too close to a parapet;
- block a service panel with a brace;
- allow the lines to rub against the roof;
- underestimate the water produced during defrosting;
- install the support in a drainage area;
- forget about the roofer’s future access;
- choose the capacity based on area alone.
In this Terrebonne project, the wider base, load-distribution crossbars, raised installation, and diagonal braces were designed to reduce several of these risks.
Vibration must be considered from the design stage
A modern heat pump uses a variable-speed compressor, which generally helps reduce abrupt starts. Despite this, the unit produces vibrations that can be transmitted to the building structure.
On a roof, this transmission can become noticeable in rooms located directly beneath the unit. An unstable base can also amplify certain movements.
We therefore pay attention to:
- the rigidity of the support;
- the balance of the unit;
- tightening the fasteners;
- the presence of suitable supports;
- the distance from sensitive areas;
- the absence of unnecessary rigid contact with the building.
A wider structure helps distribute loads, but it must remain properly aligned. The feet must bear evenly, without twisting the frame.
Coordination with the roofer and electrician
Rooftop installations often require more extensive coordination between trades. The roofer must be able to inspect the materials beneath the structure and confirm that drainage remains functional.
The electrician must size the circuit according to the nameplate data for the exact model. The nominal BTU capacity alone is not sufficient to select a circuit breaker or conductor size.
The electrical elements to be confirmed include, in particular:
- minimum circuit ampacity;
- maximum permitted protection;
- supply voltage;
- disconnect type;
- cable routing;
- mechanical protection for the outdoor wiring;
- grounding.
At AirGreen, we coordinate these aspects to prevent a properly sized heat pump from being compromised by inadequate electrical power or a location incompatible with the roof.
Rebates and certification must be verified using the exact models
A Samsung Premium FJM heat pump may be available in different capacities and different combinations of indoor units. Eligibility for a rebate therefore cannot be determined solely from the series name.
To verify an applicable financial incentive, we need the complete information:
- outdoor unit model;
- models of both indoor units;
- certified combination;
- AHRI number;
- heating capacity at the required temperature;
- purchase and installation date;
- program criteria at the time of application;
- building type and existing heating system.
This verification prevents unpleasant surprises. Two units with similar commercial names may have different performance levels, low-temperature capacities, or certifications.
We always recommend confirming eligibility before signing the contract when the rebate represents a significant part of the budget.
Maintaining a Samsung heat pump installed on a roof
A rooftop outdoor unit is less accessible than a unit installed at ground level. This reality should not lead to neglecting its maintenance.
A periodic inspection should include:
- cleaning the heat exchanger;
- checking airflow;
- inspecting both fans;
- checking the diagonal braces;
- tightening the fasteners;
- the condition of the crossbars and roof protection;
- checking the insulated lines;
- checking for traces of oil near the connections;
- inspecting the wiring;
- confirming defrost drainage;
- cleaning the filters of both indoor units;
- checking the condensate drains.
Windblown debris can accumulate in the heat exchanger or near the base. Leaves, roofing dust, or fragments of materials can reduce airflow or trap moisture.
Preventive HVAC maintenance also helps detect a loose attachment or damaged insulation before the problem affects the system’s operation.
An installation adapted to buildings in Terrebonne and Greater Montreal
This project illustrates our approach to more complex projects in Terrebonne. We do not simply aim to make the equipment work on the day of installation. We prepare the system for the conditions it will face over several years: wind, snow, defrosting, vibrations, maintenance, and work on the roof.
The Samsung Premium FJM dual-zone heat pump was installed on a base designed specifically for its vertical format. The diagonal braces contribute to its stability, while the enlarged structure distributes its weight across the roof.
This method can be adapted to different types of buildings:
- flat-roof residences;
- condominiums;
- small multi-unit buildings;
- commercial properties;
- mixed-use buildings;
- properties with limited ground space.
We install multi-zone heat pumps in Terrebonne, as well as in Montreal, Laval, Longueuil, on the North Shore and the South Shore. Each project is assessed according to its architecture, exposure, and the occupants’ actual needs.
What this project demonstrates in practical terms
The quality of a dual-zone heat pump installation depends as much on the choice of equipment as on how it is integrated into the building.
On this project, the most important elements are clearly visible:
- a Samsung unit installed in a clear area;
- a metal support providing adequate elevation;
- an enlarged wooden base to distribute the loads;
- a protective membrane beneath the structure;
- two diagonal braces against lateral movement;
- access maintained around the panels and fans;
- lines grouped toward the building.
These details are not decorative. They directly affect stability, maintenance, roof protection, and the system’s lifespan.
At AirGreen, we adapt each project to the building’s conditions rather than applying the same method everywhere. A heat pump installed on the ground in Laval, on a wall in Longueuil, or on a roof in Terrebonne faces different constraints. Our job is to identify these differences and design an HVAC solution that is consistent down to the less visible elements.