Installation of a GREE FreeMatch R32 2-head heat pump (GWHD(18)ND6MO) in Ahuntsic-Cartierville, Montreal

Two zones, 900 grams of R32, and a 20 A breaker: the smallest FreeMatch in a red-brick semi-detached house

After more than thirty documented HVAC installations on the GREE FreeMatch R32 range, this Ahuntsic-Cartierville project is the first we are publishing with a two-head configuration. This is not an editorial detail: it is the only case in which the GWHD(18)ND6MO is usable, because it accepts exactly two indoor units—no more. The entire range is reorganized around this constraint, and the resulting figures are the ones no commercial specification sheet highlights.

The context: a 1950s semi-detached house and a three-foot side yard

The Ahuntsic-Cartierville borough has approximately 135,000 residents across 24 km², or nearly 5,600 people per square kilometre. This density is not an abstract statistic when it comes time to install a wall-mounted heat pump: it describes exactly the setting where our teams work. The area's housing stock includes a large proportion of red-brick semi-detached houses built in the 1950s and 1960s, set on narrow lots, with a shared side driveway or barely a one-metre strip of land between the house wall and the neighbour's property line.

This property fits the profile: two stories, entirely electric heating with baseboards, no ventilation ductwork, a ground floor where the living room and dining room form one open space, and a primary bedroom upstairs that became unbearable in July. The owners did not want to air-condition the entire house. They wanted two comfortable rooms and a lower electricity bill in October and April.

Why the GWHD(18)ND6MO rather than the GWHD(24)ND6MO

For a two-head system, two units in the range are eligible. The choice does not come down to capacity—the two units more than cover the need—but to one question: might you want a third port someday?

Across five lines in this table, the smaller unit clearly wins: it weighs fifteen and a half kilograms less, is the quietest in the entire FreeMatch range at 54 dB(A), posts the family’s best EER2 of 12.5—tied only with the 30,000 BTU/h model—and is protected by a 20 A breaker instead of 25 A. It loses on only one point, but that point is permanent: there will never be a third port. If the basement needs air conditioning in five years, it will require a second complete system, not an additional head. We state this plainly in the quote, exactly as we do for five-head configurations, where the fifth port also closes that door.

The homeowners made an informed decision: their basement is finished, occupied one hour a week, and already tempered by the ground’s thermal inertia. The 18,000 BTU/h model was selected.

The 10-meter precharge trap

Here is the figure we had never had to address in this series, because no other model in the range exposes the customer to it so much: the GWHD(18)ND6MO is precharged for only 10 meters of piping. The 24,000 covers 30, the 30,000 and 36,000 cover 40, and the 42,000 covers 50.

Ten meters, on a two-story house with the outdoor unit in a side yard, is almost always exceeded. On this job, the two lines measure 5 m and 11 m, for a total of 16 developed meters. Six meters beyond the factory charge, at 20 g of R32 per meter, means 120 g of refrigerant to be added and weighed.

On a unit charged at 2,700 g, 120 g represents less than 5%. On this one, charged at 900 g, it is more than 13% additional charge. Proportionally, this is the largest charge adjustment in the entire range, and it is exactly where a rushed installer “estimates” instead of weighing.

The added charge increases the minimum room area

The consequence is more serious than a mere methodological issue. R32 is an A2L refrigerant, slightly flammable, and the indoor unit's nameplate specifies a minimum room area—we published the values recorded from a nameplate in this product line in our Dundee article, with the appropriate caveat. That minimum area, however, depends on the system's total charge; it is not a constant of the model.

In other words, the smallest room is not checked at the quotation stage; it is checked again once the actual line lengths are known and the added charge has been weighed. In an upstairs bedroom in a Montreal semi-detached house—often 9 or 10 m² beneath the eaves—this check is not a formality. We repeated it here after the lines were routed, before commissioning, and recorded the value in the file. The same reasoning had served us on a five-head installation in Sainte-Martine, where 440 g had to be added; the principle is identical, but the relative effect is much greater with 900 g.

12,000 + 6,000: with two zones, diversity is no longer a statistical matter

The two selected heads total 18,000 BTU/h on an 18,000 BTU/h compressor, exactly 100%.

We have long explained, notably in our Saint-Denis-sur-Richelieu article, why having a total head capacity greater than the compressor's capacity is normal: not all rooms call for cooling at the same time. This argument relies on the law of large numbers. With two zones, that law no longer applies. A living room and a bedroom in a two-person home are two occupied spaces in the evening, at the same time, almost every day. Betting on two rooms not coinciding is not statistics; it is a coin toss.

That is why we refuse to oversize a two-head configuration the way we are willing to do with four or five heads. The open-plan ground floor received 12,000 BTU/h, the primary bedroom 6,000 BTU/h, and no one is being promised that the entire house will be air-conditioned.

Modulation floor: 7,300 BTU/h

The honest counterpoint, which we publish systematically: the system's minimum modulation is 2,140 W, or approximately 7,300 BTU/h, and this is a property of the entire system, not of each head. The 6,000 BTU/h bedroom head, operating alone on a September night, requires less than that floor. The compressor will therefore operate in short cycles rather than continuously.

Two nuances, both favorable to the smaller unit this time. First, 7,300 BTU/h is the lowest floor in the entire FreeMatch lineup—the 42,000 model's is 8,870 BTU/h. The smaller system is structurally the one that performs best at low load, which is the opposite of what intuition might suggest. Second, the setting selected during commissioning makes both zones operate together at moderate setpoints rather than having one zone run hard, an adjustment we had already applied to five-head configurations. The mechanism behind the modulation floor is explained in our Saint-Chrysostome article.

The electrical panel of a 1955 house

Many homes in this part of Ahuntsic-Cartierville still have a modest electrical service with baseboard heaters, a water heater, stove, and dryer already in place. The 14.5 A MCA and 20 A maximum protection of the GWHD(18)ND6MO are decisive here: it has the lowest electrical demand in the lineup, and is often the difference between adding a circuit breaker and upgrading the service. The load calculation under the Code is the electrician's responsibility; our contribution is the manufacturer's data. We covered this reasoning in depth for a Saint-Édouard project and will not revisit it here.

The outdoor unit on wall mounts: what the photo really shows

The second half of this project does not take place indoors. It takes place in a one-meter-wide side passage between the brick-and-vinyl-sided wall of the semi-detached house and a perpendicular concrete wall.

Why there is no ground-level base

In our South Shore and North Shore articles, the outdoor unit almost always rests on a raised base of drainage stone. In Montréal, in a neighborhood built in the 1950s, that option often rules itself out: the side yard is paved, serves as a pedestrian passage to the backyard, is sometimes subject to a right-of-way easement, and there simply is no soil available. The wall mount is therefore not a refinement; it is the only possible installation.

We had discussed this choice among three basic options in our article about Rigaud, on a sloping, rocky property. The Montreal case is different and deserves its own treatment.

35.5 kg and 352 mm: the dimensions make the support possible

This is where the choice of GWHD(18)ND6MO stops being a capacity calculation and becomes a structural calculation. The unit weighs 35.5 kg and is 352 mm deep. The 42,000 BTU/h model in the same range weighs 79 kg and measures 427 mm. Mounting 35 kg on a foundation wall, while maintaining the required rear clearances in a one-metre-wide passage, is routine; mounting 79 kg of vibrating equipment in the same location is not, and many Montreal side yards that “cannot accommodate a heat pump” can in fact accommodate this one.

What the support anchors into — never the siding

This is the point we most often correct in other people’s work. Vinyl siding is not a structural support, and brick veneer is not one either: it is a cladding held in place by ties, designed to support itself. The support’s anchors must reach a real structure — a concrete foundation wall, solid blocks, or framing behind the siding — and the cladding penetration must be sealed with a drip flashing; otherwise, water will run behind the vinyl for ten years without anyone seeing it.

On this job, the concrete wall provided a solid anchor point. The rule that applies everywhere: anchor into the load-bearing material, never into the mortar joint, and never into anything that is there only for appearance.

The vibration travels through the wall, not through the air

A ground-mounted unit transmits its vibrations to the ground. A wall-mounted unit transmits them to the house. The anti-vibration pads between the unit’s feet and the support arms — visible in the photo — are not a decorative accessory: they are the reason no one hears the compressor in the bedroom behind this wall. We systematically add a flexible pipe support at the wall penetration so that the unit’s movement is not transmitted to the copper tubing.

The 54 dB(A) sound level, the lowest in the range, helps considerably in an area where the neighbor is three meters away. We published a complete reading of decibel levels and municipal installation regulations in our Huntingdon article, and the borough and municipal regulations section of our website covers Greater Montreal, the North Shore, and the South Shore. In Montreal, the location is checked by borough before choosing the installation site, not afterward.

The space beneath the unit is not storage space

The photo from this job shows more than the installation: it shows what the space beneath a wall-mounted unit becomes six months later. A coiled garden hose, a plastic container, a PVC pipe, a plastic bag, a terracotta pot, a tray. Nothing harmful, nothing intentional—and that is precisely the problem. A unit mounted on the wall gives the impression that it has freed up the ground. It has not.

Defrost water falls from a greater height

In winter, the outdoor unit defrosts. The water leaves the pan and falls. From a wall bracket, it falls from a greater height and onto a more concentrated area. If a flat object is underneath—a tray, a lid, a tarp—the water collects there, freezes, and the column of ice rises toward the chassis. By the third February thaw, the ice touches the underside of the unit and defrosting can no longer drain anything. No error code appears. The customer only notices that “it hasn’t been heating as well since Christmas.”

The rule we put in writing at the end of the job fits on one line: nothing under the unit, across the entire surface, in every season—and a bed of draining stone underneath rather than a slab or grass.

The plastic bag, the hose, and the tarp

An outdoor unit draws air in from the rear and sides and exhausts it from the front. A plastic bag left in a windy side passage eventually gets pressed against the intake side. The unit does not stop or issue any warning; it simply loses capacity as long as the bag remains there.

As for the garden hose, there is a useful irony worth pointing out: it is exactly the tool needed in August to rinse the outdoor coil, and the worst place to store it is beneath the unit, where it occupies the drainage area and freezes trapped in the January ice. We suggest a wall hook two metres away.

Finally, the winter cover. A heat pump operates in winter: it should not be covered. A full cover prevents defrost water from drying and traps moisture against the sheet metal. If protection from falling ice from the roof is necessary, use a clear awning, never a cover—an issue we discussed in detail in our article about Les Cèdres.

Front clearance, or why a corner costs capacity

The last visible element in the photo: the unit is installed in a corner, with the house wall behind it and a concrete wall to the right. This is common in Ahuntsic-Cartierville and is acceptable—with one condition.

The rear clearance feeds the coil. The front clearance, however, is the one everyone cuts back because it appears to serve “no purpose.” In fact, it prevents air recirculation: if discharged air encounters a nearby obstacle, it returns toward the intake face. In cooling mode, the unit draws in its own hot air again, condensing pressure rises, and capacity drops. In heating mode, it draws in its own cold air again and multiplies defrost cycles. In both cases, there is no alarm or error code—just a unit that “lacks power” even though it is properly sized.

Clearance values are specified in the installation manual for the actual unit delivered, and that manual governs. Our method for narrow passages: measure before securing the brackets, direct the discharge toward the passage's open axis rather than toward a wall, and if the clearances do not work, change the location or the model—never squeeze it in.

Mistakes to avoid with a two-head configuration

• Choose the 18,000 without explaining that the third port does not exist. This is the unit's only real drawback, and it must be disclosed before signing.
• Do not weigh the top-up charge. With 900 g of original charge, estimating by eye compromises performance and distorts the verification of the room's minimum area.
• Redo the A2L verification only at submission. It is redone after the line layout has been drawn.
• Anchor the bracket into the vinyl or brick veneer.
• Remove the electric baseboards. They remain in place, set 2 to 3°C below the heads' setpoints; they provide peak-load backup and freeze protection.
• Store anything underneath the outdoor unit.

Rebates, warranty, and maintenance

The system qualifies for applicable residential energy-efficiency programs in Quebec—notably Hydro-Québec's LogisVert and Rénoclimat programs. The Chauffez vert program does not apply here because the home is already heated with electricity. Criteria and amounts change, so we verify eligibility when opening the file rather than announcing a figure in the quote. The declared AHRI number must match the combination actually installed—this is a common administrative reason for refusals.

The warranty is 10 years, extended to 12 years when the product is registered with proof of installation through the distributor. We complete the registration at the end of the project rather than leaving it to the customer.

When it comes to HVAC maintenance, a two-head configuration is the easiest in the range to maintain: two filters to rinse every 4 to 8 weeks during the intensive season, two drain pans, two drains, and an outdoor coil to rinse once a year. In a side passage where street dust, pollen, and debris accumulate, this annual rinse is not a sales option; it is essential for maintaining performance.

AirGreen in Ahuntsic-Cartierville and Greater Montreal

At AirGreen, we design, install, and maintain multi-zone wall-mounted heat pump systems in Montreal, Laval, Longueuil, the North Shore, and the South Shore. Projects in Ahuntsic-Cartierville—Bordeaux, Cartierville, Sault-au-Récollet, Saraguay, the area around Gouin Boulevard, and its fifteen kilometres of shoreline along the Rivière des Prairies—present constraints that suburban properties do not: narrow side passages, neighbouring homes in close proximity, shared walls, original electrical services, and brick façades that leave no room for a poorly executed penetration.

This is exactly the kind of project where the smallest unit in the range is the right choice, and where saying so honestly is better than selling a larger one.