Installation of a GREE FreeMatch R32 2-head wall-mounted heat pump (GWHD(18)ND6MO) in Côte Saint-Luc, Montreal agglomeration

The photo was taken at the only moment when the installation is truly at stake.

Nearly all job-site photos published by HVAC contractors show a finished, clean unit on a clean wall. This one shows something else: the outdoor unit is installed, the tools are still on top of the chassis, and a digital gauge is connected to the service valves. The Côte Saint-Luc installation is not finished in this image—it is exactly at the stage that determines whether the unit will last fifteen years or four.

The discussion about choosing the two-zone model was covered elsewhere: the complete overview of the GWHD(18)ND6MO in our Ahuntsic-Cartierville article, the question of the heating ceiling in the Baie-D'Urfé one, and the reverse reasoning—why a larger unit can be the right choice for two heads—in the Beaconsfield one. This page focuses on what no one shows: the connection work.

What we installed in Côte Saint-Luc

The unit is installed, and nothing has been done yet

A customer returning home in the late afternoon sees an outdoor unit in place and concludes that the work is finished. What remains to be done at that point represents half the time and nearly all the risk:

1. Form and tighten the flared connections on the four fittings of the outdoor unit and on those of the two heads.
2. Pressurize the circuit with nitrogen and check for leaks.
3. Recover the nitrogen, then evacuate the circuit to a deep vacuum.
4. Perform the rise test with the pump isolated.
5. Weigh in the additional refrigerant corresponding to the actual developed length.
6. Open the service valves, switch on the power, and only then perform the functional tests, one head at a time.

Between step 5 and step 6 lies a point of no return: once the valves are opened, the outdoor unit's 900 g of R32 is throughout the entire circuit, and correcting an error requires recovering the charge. Everything that needs to be checked must be checked beforehand.

The flare: the most common leak point on a wall-mounted heat pump

A multi-zone wall-mounted heat pump almost never leaks through the piping. It leaks at the connections, and on this type of unit the connections are flare fittings—a cone formed in the copper, pressed against the fitting seat and held in place by a nut. There is no solder and no sealing gasket: it is metal against metal, and the quality of the flare is the only thing separating a leak-tight installation from a slow leak.

What a proper flare requires

• Make a straight cut, then deburr carefully, directing the shavings downward so no particles fall into the tube. A simple burr left in place creates a radial scratch on the flare, and that scratch becomes a leak path.
• Thread the nut on before flaring. The number of connections remade because the nut was forgotten is considerable, and cutting the copper back several times shortens an already measured line.
• A smooth flare, without cracks or eccentricity, inspected visually every time. A drop of refrigerant oil on the mating surface helps with tightening and sealing.
• Tighten to the specified torque with a torque wrench, using a backup wrench on the valve body. Too little torque causes leaks; too much torque splits the flare, and a split flare cannot be seen once the nut is tightened.
• Never reuse a flare. If a connection is loosened for any reason, remake the flare.

The stakes are proportionally higher on this unit than on the larger models in the range. A leak that would lose 150 g of refrigerant represents about 5% of the charge in a GWHD(42)ND6MO and nearly 17% of the charge in a GWHD(18)ND6MO. On a small system, a small leak is a big leak.

The nitrogen pressure test, before evacuation

Evacuation does not detect leaks: it detects the presence of a significant leak without ever indicating where it is, and it may stabilize despite a defect. That is why the circuit is first placed under dry nitrogen pressure and left under observation. A pressure drop signals a leak, which can then be located using nitrogen and foaming solution, with the circuit open and accessible—that is, at the point when correcting it costs only a few minutes.

Two rules we apply without exception: we never pressurize a circuit with refrigerant to look for a leak, and the nitrogen used is dry nitrogen, free of moisture, introduced through a regulator set to the manufacturer's test pressure.

Vacuum is not read on a needle gauge

The instrument connected to the service valves in the photo is a digital pressure gauge, and that detail sets professional jobs apart. The needle on an analog manifold bottoms out well before the vacuum is truly deep: it indicates “vacuum” even though there is still more than enough moisture in the circuit to cause a problem. Only a micron gauge measures the final stage of evacuation.

Three method points rarely explained to a client:

• The gauge is connected far from the pump, on the opposite side of the circuit. Connected next to the pump, it measures the pump's vacuum, not the system's.
• The rise test is performed with the pump isolated. We close the valve, stop the pump, and observe. A vacuum that holds is a successful vacuum.
• The rise tells the story. A rise that stabilizes at a plateau indicates residual moisture that is still evaporating: we extend the evacuation. A rise that never stops indicates a leak: we return to nitrogen. These two diagnoses do not resemble each other, yet they are constantly confused.

The threshold we maintain—less than 500 microns, stable—and the deeper reason residual moisture is a compressor's enemy are explained in our Saint-Louis-de-Gonzague article, devoted to what fails in a heat pump after fifteen years.

What we check before opening the valves

• Port matching. Each pair of copper lines and its interconnection cable must terminate at the same numbered port. The symptoms of a crossover look like a faulty unit; the details are in our Hinchinbrooke article.
• Insulation continuity along both lines, all the way to the fittings, with no compression or bare copper.
• The condensate drain slope of each head, checked with water before anything is closed up.
• The actual developed length, measured and recorded, which determines the amount to be weighed in.
• The electrical circuit, its rating, disconnect switch, and connection.

Tools on top of the unit

A word about what the photo also shows, and what we do not defend as good practice: the top of an outdoor unit serves as a work surface on just about every jobsite in Quebec, including ours. The chassis can support it, but two things do not survive there—a tool that slips against the coil fins, which bend without ever generating an error code and permanently reduce capacity, and a mark left on the sheet metal of a new unit that the client will see every time they walk past it. A workbench mat, a toolbox on the ground, and cleaning the top before leaving resolve the issue.

The bottom of the range is a floor that cannot be crossed

Both rooms served are small, and both can be closed off: two 6,000 BTU/h indoor units, or 12,000 BTU/h installed on an 18,000 BTU/h unit—67%, the lowest ratio we have published. This figure deserves an explanation because it looks like an error, but it is not.

A house that needs only 12,000 BTU/h distributed across two rooms has no smaller unit to buy: the GWHD(18)ND6MO is the first model in the FreeMatch range, it requires exactly two indoor units, and nothing smaller exists. The compressor was therefore not chosen because it would be fully utilized, but because it is the bottom of the catalog. This is the opposite of what we described in Très-Saint-Rédempteur, where a fifth room forced the purchase of the largest compressor in the range: here, two small rooms force the purchase of the smallest one, and it is still larger than the load.

Two consequences were explained to the client. The first is favorable: at 67%, the unit’s two modulated maximum capacities are well above the installed capacity, so neither indoor unit is ever deprived, even when both call for heat at the same time. The second is honest: the system’s modulation floor, approximately 7,300 BTU/h, exceeds the capacity of a single 6,000 BTU/h indoor unit, so each zone operates better accompanied than alone—the mechanism is explained in our Saint-Chrysostome article, and the workaround, which consists of running both zones together at a moderate setpoint rather than running one at full capacity, in the one about Saint-Urbain-Premier. The electric baseboard heaters remain in service throughout the house, set below the indoor units’ setpoints.

A wall already occupied: a window, a disconnect switch, a mast, and a fence forty centimeters away

On a suburban property, we choose the location of the outdoor unit. In Côte Saint-Luc, we negotiate it with what is already there. Before we arrived, the wall on this job had a window, a disconnect, a galvanized electrical mast with its watertight junction box, a string of lights, and a cedar fence less than one metre away.

The outdoor unit beside a window

This is the most common constraint in dense areas and the least discussed in the quote.

Glass is the weakest element of the wall

An insulated wall attenuates noise well; a window much less so. An outdoor unit placed in front of a solid section of wall and the same unit placed in front of a window produce completely different results inside the room at the same distance. This appliance's 54 dB(A) is the lowest level in the FreeMatch range, which factored into the model choice, but the proper interpretation of decibels and their attenuation with distance are covered in our Huntingdon article.

And the reasoning is reversed in summer: the air-conditioning season is exactly when windows are opened. An open window no longer attenuates anything; it lets everything through. So before fixing the location, we ask the customer: what room is this, and does this window open at night?

The window must still be able to open

A casement window opens outward, and its sash sweeps through an arc. An outdoor unit installed too close effectively eliminates that arc: the customer ends up with a window that opens only halfway, or with a sash that rubs against the unit. The check is performed with the window fully open, not on a plan, and includes the crank, the screen, and seasonal window cleaning. Two additional points apply in urban settings: a window is sometimes an emergency exit in a bedroom, and a unit installed below a window receives snow sliding off the sill.

The disconnect, the mast, and the boxes already in place

The outdoor electrical connection is the part of the job that ages worst when it is done carelessly.

• The disconnect remains visible and accessible from the unit. It is not placed behind the unit, behind the fence, or somewhere that can only be reached by moving something. A technician servicing it eight years from now must be able to shut off the power without searching.
• Its height accounts for snow, as do the junction box and the flexible conduit that descends toward the unit.
• Every penetration through the cladding is sealed, with a drip loop if the orientation requires it. Water that gets behind cladding cannot be seen, and still cannot be seen three years later.
• The existing electrical mast is not a support. Not for piping, a junction box, or a convenience cable clamp. Anything attached to it will eventually move with it.
• Existing cables should be located before drilling. A string of lights, alarm wire, or camera cable will not trip a circuit breaker when cut: it will simply stop working, and no one will connect the two events.

One useful detail in a quote: the notes “electrical to be confirmed” or “electrical by others” are the main source of discrepancies between three quotes that seemed comparable. Our Saint-Chrysostome article offers a ten-point comparison checklist that resolves this kind of uncertainty before signing.

The fence at forty centimeters

The cedar fence visible on the right is close, as is the case on half the city’s job sites. The clearance in front of a unit is what gets trimmed because it seems unnecessary; yet it is what determines whether the discharged air returns to the coil. The full mechanism and its consequences—rising condensing pressure in cooling mode, increasingly frequent defrost cycles in heating mode, and no error message in either case—are detailed in our Ahuntsic-Cartierville article. The manual supplied with the unit is authoritative, the measurement is taken before anything is secured, and removing a fence slat costs infinitely less than having a unit that “lacks capacity” for ten years.

Côte Saint-Luc: a dense city where the neighbor’s window is just a few meters away

Côte Saint-Luc is a city in the Montreal agglomeration, reconstituted on January 1, 2006, after a referendum held in 2004. It covers approximately 7 km² and has around 34,500 residents, or nearly 4,900 inhabitants per square kilometer—about eight times the density of Baie-D'Urfé, where we documented another two-head installation the same day. Enclosed within the island and bordered by Hampstead, Montreal West, Mount Royal, Côte-des-Neiges–Notre-Dame-de-Grâce, and Lachine, it has two small exclaves and a housing stock where 1960s apartment towers stand alongside postwar single-family homes. Its name refers to the officer Luc de La Corne Saint-Luc.

For a heat pump installation in this context, density calls for three reflexes:

1. Account for the neighbor’s window as well as the customer’s. A unit positioned perfectly from the served home’s perspective may blow toward a neighboring bedroom five meters away. This check is performed on-site, before the quote.
2. Check the municipal bylaws before choosing the location — setbacks from property lines, restrictions in front yards, noise limits at the property line, sometimes lower at night. The municipal bylaws section of our website lists this information for cities in Greater Montreal, and our office can also answer these questions by phone. The complete method appears in our Huntingdon article.
3. Planning for access. In a narrow side yard bordered by a fence, this unit’s 35.5 kg weight and 352 mm depth are what make the project feasible; handling is done by two people, without machinery.

Mistakes to avoid

• Judging an installation by its final appearance. A spotless unit whose vacuum has never been measured with a micron gauge is a delayed failure.
• Accepting a refrigerant leak test instead of a nitrogen test.
• Tightening the flare fittings “by feel” instead of to the specified torque.
• Placing the disconnect switch behind the unit or behind the fence.
• Reducing the clearance in front because the air exits on that side and “is no longer needed.”
• Forgetting to check that the window opens fully before securing the base.
• Neglecting to register the warranty, which extends coverage from 10 to 12 years with proof of installation. We do this with the customer at the end of the job.

Commissioning, maintenance and financial assistance

Commissioning includes a leak test, a deep vacuum with a rise test, weighing the additional refrigerant charge, a functional test of one indoor unit at a time in both modes with physical verification of the room served, and recording the serial numbers associated with each component. The readings are documented and provided to you: this document serves as a reference if a question arises five years from now.

Routine maintenance involves two tasks: rinsing the filters every 4 to 8 weeks during the intensive season and having the outdoor coil cleaned once a year.

As for financial assistance, a residential installation may qualify for LogisVert and be part of a Rénoclimat process; the Chauffez vert program does not apply to a home already heated with electricity. The criteria change, and we verify them when the file is opened.

For a wall-mounted heat pump installation in Côte Saint-Luc, Montreal, Laval, Longueuil, the North Shore or the South Shore, we document every job as it unfolds, not just once it looks finished. That is also what we recommend asking any contractor for: not just the final photo, but the readings taken along the way.