Installation of a GREE FreeMatch R32 2-head heat pump (GWHD(36)ND6MO) in Pointe-Claire

A condenser on a flat roof, with no baseboards behind it, and a green grille over the coil

This Pointe-Claire project is the first in our series where there is no electric baseboard behind the heat pump. In the approximately fifty installations we have documented, supplemental heating was always present and remained in service. Here, the unit is the heating system. This changes the sizing, the model selected, and what must be written into the contract.

The usual debate over choosing between the two smallest units in the range has been covered elsewhere, and we will not revisit it here: the third port for a Beaconsfield project, reading the “min. – max.” line for a Dorval project, the rooftop run length for a Dollard-des-Ormeaux project, and the extra margin purchased for an aggressive environment for a Montreal East project. What follows concerns two subjects not covered on those pages: what shares the roof with the condenser, and the protective grille installed over its coil.

The context: a city where 82% of the property tax base is non-residential

Pointe-Claire has approximately 36,255 residents across 34.7 km², or nearly 1,050 inhabitants per square kilometre. The city is part of the Montreal agglomeration and the Montreal Metropolitan Community, and was reconstituted on January 1, 2006.

The figure that explains this project is found elsewhere, in the property assessment roll: 82.3% of Pointe-Claire's property tax base is non-residential, compared with 17.7% residential. This is a profile of a business and light-industrial city as much as a suburb, and it shows in the types of requests we receive there—many professional premises, retail spaces, and upper floors occupied by offices rather than dwellings.

Alongside this, Pointe-Claire preserves a heritage site of approximately 2.7 hectares around Saint-Joachim Church, the rectory, and the sexton's house, with the windmill at the point — an area where the constraints on outdoor-unit placement are of an entirely different nature. We published an analysis of decibel levels and municipal placement regulations for a project in Huntingdon, and our site maintains a section of regulations by city and borough for Montreal, Laval, Longueuil, the North Shore, and the South Shore.

Two 18,000 BTU/h heads, with no baseboard heaters to take over

The space occupies the floor of a mixed-use building with a flat roof: two work areas, each equipped with an 18,000 BTU/h head, for 36,000 BTU/h of installed indoor capacity on a 36,000 BTU/h nominal GWHD(36)ND6MO — exactly 100%, with two identical heads.

Why this model, and not a smaller one. In all our other two-head installations, the electric baseboard heaters remained in service, set 2 to 3 °C below the head setpoints, and served as backup on the coldest days. A unit that was slightly undersized in January was therefore not a continuity problem: it simply meant a somewhat higher bill for a few days.

There are no baseboard heaters here. The space has no supplemental heating, and the heat pump is the only heat source. The consequence is direct: sizing is based on the peak heating load, not the peak cooling load. This is the opposite of the usual residential approach, and it is what led us to select the GWHD(36)ND6MO rather than stop at the models that would have been sufficient in summer.

Two points we put in writing before signing:

• The balance point is calculated and provided to the customer, along with the outdoor temperature at which the available capacity no longer covers the building's load. The method was published for a project in Franklin, with an observation that applies here more than elsewhere: an operating range advertised down to -30 °C indicates that the unit will operate, not what it will deliver.
• A cold-weather plan is provided, because there is nothing behind it. Without supplemental heat, the issue is no longer the comfort of a morning; it is the continuity of operations in a workplace. The matter is settled before installation—either a supplemental-heating circuit is planned or the risk is documented and accepted—never at the first extreme-cold warning.

Finally, two identical heads, for three reasons we apply systematically: a single filter reference for the entire premises, identical behavior that occupants learn once, and no zone oversized relative to the other. The system's modulation floor, 8 870 BTU/h, remains well below the capacity of either head: neither zone short-cycles, which was not the case with several small-head configurations we documented elsewhere.

The roof is a shared mechanical platform, and the condenser has neighbors there

The outdoor unit rests on a four-legged metal stand, placed on treated timbers that themselves rest on protective membranes—the roof is not penetrated anywhere. That subject—the membrane, ballast, load distribution, parapet crossing, and roofer's certification—was covered in detail for a job in Dollard-des-Ormeaux, and we will not revisit it.

What nobody talks about is what is already on the roof.

A plumbing vent, an exhaust hood, a chimney, and guy wires

In this jobsite photo, within a few meters of the condenser: a white PVC plumbing vent, a metal gooseneck exhaust hood, a brick chimney, and a guyed antenna whose cables cross the roof diagonally. This is the ordinary configuration of a flat roof on a mixed-use building, and each of these elements imposes constraints.

What the neighbors discharge, the condenser draws in

An outdoor unit draws air in from the rear and sides. It makes no distinction between ambient air and air discharged by the neighboring appliance.

• An exhaust hood—in a bathroom, kitchen, dryer, or mechanical ventilation system—releases warm, humid air, sometimes carrying lint or grease. In cooling mode, this warm air raises condensing pressure and reduces available capacity. In heating mode, it's worse: the moisture settles on a coil colder than the surrounding air and directly contributes to icing, thereby multiplying defrost cycles.
• A plumbing vent must never be obstructed or cluttered, and its position relative to air intakes and outlets is the plumber's and the Code's responsibility, not the HVAC installer's. We verify this before securing a support, never afterward.
• A chimney or combustion vent introduces a similar constraint, along with the additional issue of combustion products.
• Antenna guy wires do not emit anything, but they cross the path of the technician who will come to perform maintenance in July, and they provide a route for ice runoff.

We published our own outdoor placement standards — including three metres from a dryer vent, the distance most often ignored — for a project in Montréal-Est. They apply in full on the roof. What changes on a roof is that there is no hedge or wall to make these nearby obstacles obvious: everything is flat, everything seems far away, and nothing really is.

The roof will change after we leave, and that is predictable

Here is the point we consider most useful in this section, because it concerns the next ten years rather than the day of installation.

A flat roof on a mixed-use building is where things get added. A new exhaust fan when a space changes use. A hood when a business moves into the ground floor. An antenna, panels, an air intake. None of these additions will be coordinated with us, and none of the people installing them will know that a condenser needs clearance on the intake side.

Three measures we take as a result:

1. Document the layout in the file, with a plan and photo, including the clearances selected and the reasons for them — a document the owner can give to the next contractor.
2. Choose the location based on the roof's remaining available space, not just the shortest distance to the heads. A condenser placed in the middle of the only open area will be bypassed; a condenser placed at the edge of the open area will be surrounded.
3. Tell the building manager: the clearance around the unit is not wasted space; it is part of the installation.

The disconnect switch mounted on the support, for lack of a wall

A detail visible in the photo and specific to the rooftop: the disconnect box is attached to the support structure rather than to a wall—because there is no wall. This remains consistent with the approach we published for a Côte Saint-Luc project—the disconnect is visible and accessible from the unit, never behind it, with the height chosen for snow—with two additions specific to the support:

• The support must be designed to bear this load and accommodate these penetrations. An equipment support is not a universal rack.
• Continuity of the metal assemblies between the unit, the support, and the circuit is the responsibility of the licensed electrician. We provide the manufacturer's data—MCA 30 A, maximum protection 45 A—and the electrician ensures compliance.

The green grid on the coil: what it protects and what it costs

The photo shows an element rarely seen and absent from every technical sheet: a green protective screen stretched across the entire face of the coil, held in place by a metal grid.

What a front screen actually prevents

An outdoor coil is a tightly packed sheet of aluminum fins, and anything that gets into it stays there. On an urban rooftop, three things happen regularly:

• Poplar seeds and willow fluff, in June, which form a gray felt on the fins within a few days. This is the most difficult debris to remove without bending the fins, and it is precisely what this type of screen is sold to protect against.
• Leaves and windblown debris, which move freely across a flat roof surrounded by parapets and eventually accumulate against the first vertical obstacle—the unit.
• Gravel and roofing-work debris, thrown up during a roof replacement or cleaning.

A properly tensioned screen intercepts all of this upstream of the coil, where it can be cleaned with a soft brush from the outside, rather than in the coil, where cleaning requires a technician, time, and considerable care. We published the method for cleaning an outdoor coil for a Pierrefonds-Roxboro project, and the attack on the metal itself for a Montréal-Est project: a screen replaces neither, but it extends the interval between cleanings.

What it costs, and why it must be explained

A screen is not aerodynamically free, and a contractor who installs one without explaining this is setting the customer up for disappointment.

• Any obstacle in front of an intake face adds pressure loss. A clean screen adds little. A loaded screen adds a lot.
• A clogged screen is more insidious than a clogged coil because it is uniform and cannot be seen from a distance: from the other end of the roof, it looks exactly the same whether it is clean or blocked. You have to go look at it closely, against the light.
• It does not eliminate any clearance requirements. The values in the installation manual for the equipment actually delivered continue to govern, and a screen must not be installed flush against the fins.
• It must be removable without special tools; otherwise, it becomes the reason no one cleans the coil.

What we include in the HVAC maintenance contract when a screen is installed: screen inspection at every visit, removal and rinsing in the spring, before the cooling season and after the seeding period—and a written reminder to the customer that a screen is a filter, meaning something that must be cleaned, not a piece of equipment that is installed and forgotten.

The service loop on the refrigerant lines

The last visible element, and one that is rarely explained: the two insulated refrigerant lines do not run straight to their destination. They descend, form a loop, then join the protected route that crosses the roof.

This loop is not excess piping that was cut poorly. It serves three purposes:

1. Move the equipment without cutting the copper. A condenser that needs to be shifted twenty centimeters for a membrane replacement or to access a service panel can be shifted without refrigeration work if there is spare length available.
2. Absorb movement. A roof responds to temperature, and so does copper. A line stretched between two fixed points transmits these movements to the fittings—that is, the exact place where a slow leak begins.
3. Dampen the compressor's vibrations before they reach the fixed route.

The price to pay is the developed length, which is included in the piping budget and, beyond the 40 m precharge, translates into refrigerant weighed out at 20 g/m. It is a deliberate trade-off, not an oversight.

Mistakes to avoid when installing equipment on a roof

• Install the equipment without considering what neighboring equipment exhausts. A hood two meters away costs more than a longer piping route.
• Treat the roof as a surface rather than as a collection of systems belonging to multiple trades.
• Piercing the membrane. Never without the roofer, never without certification.
• Installing a protective screen without adding it to the maintenance schedule.
• Stretching refrigerant lines from one fixed point to another without a service loop.
• Removing backup heating from premises that do not already have it, or rather: not planning for an extreme-cold-weather strategy when the heat pump is the only heat source.

Rebates, warranty, and maintenance

For commercial or professional premises, residential programs—LogisVert, Rénoclimat—are not the applicable ones; business projects fall under energy-efficiency programs intended for companies. The criteria and funding amounts change, and we validate eligibility when opening the file rather than announcing an amount in the quotation. The declared AHRI code must correspond to the combination actually installed.

The warranty is 10 years, extended to 12 years upon product registration with proof of installation submitted to the distributor; we complete the registration at the end of the project.

In terms of maintenance, this system requires two filters to be rinsed every 4 to 8 weeks under intensive use, two pans and two drains to be checked, an annual rinse of the outdoor coil, and, here, inspection of the screen at every visit. Roof access must be organized and planned: there is no improvised maintenance on a flat roof in February.

AirGreen in Pointe-Claire and Greater Montreal

At AirGreen, we design, install, and maintain multi-zone wall-mounted heat pump systems in Montreal, Laval, Longueuil, on the North Shore, and on the South Shore, for both residential properties and commercial and professional premises. In Pointe-Claire, where most of the land base is non-residential, a significant portion of our projects take place on flat roofs, in mixed-use buildings, for premises without backup heating that cannot afford to wait.

A successful HVAC installation in this context can be recognized by three things: the unit can breathe, the roof has not been pierced, and the next contractor who goes up there will know why this clearance exists.