Installation of a GREE FreeMatch R32 2-head heat pump (GWHD(24)ND6MO) in Côte-des-Neiges–Notre-Dame-de-Grâce, Montreal

A single room eliminated the smallest unit in the line, and a hot tub dictated everything else

This Côte-des-Neiges–Notre-Dame-de-Grâce project is the fourth we have published involving a two-head configuration from the GREE FreeMatch R32 line, and it is the first where the outdoor unit is not located against the house. It is at the back of the yard, against the fence, one metre from a hot tub, beneath a Virginia creeper, on a stone-paver patio. Each of these four elements changed something about the project.

The context: a backyard in the island's densest borough

Côte-des-Neiges–Notre-Dame-de-Grâce has approximately 185,000 residents across 21.4 km², or nearly 8,700 residents per square kilometre—the highest density among the boroughs where we regularly work, almost twice that of Ahuntsic-Cartierville. The borough includes Monkland Village, the Loyola neighbourhood, Benny Farm, the university district, Côte-des-Neiges Road, and the Victoria neighbourhood, with 47 parks and green spaces, four universities, and five hospitals within its territory.

One figure matters more than the others for a heat pump project: 73% of households are renters. The owner-occupants who call us are often duplex or row-house owners, and their backyard is not a yard—it is an extra room. Paver patio, cedar fence, string lights, hot tub, flower beds: the space is landscaped and already completely occupied. Installing an outdoor unit in there is not a clearance exercise; it is an exercise in trade-offs.

18,000 + 9,000: when a single room determines the model

The layout was simple: an open ground floor—living room, dining room, and kitchen in one space, with large south-facing windows—and the primary bedroom upstairs. Two zones, 18,000 BTU/h and 9,000 BTU/h, for a total of 27,000 BTU/h of installed indoor capacity.

It was this 18,000 BTU/h head that determined the model choice, and it did so through arithmetic rather than preference. The GWHD(18)ND6MO modulates in cooling between 7,300 and 19,800 BTU/h, and in heating between 7,300 and 18,100 BTU/h. A single 18,000 BTU/h head would therefore use nearly its entire range, leaving nothing for the second zone as soon as both call at the same time. The smaller unit was not ruled out because it is small: it was ruled out because one of the two rooms is large.

The selected GWHD(24)ND6MO lists SEER2 21, HSPF2 10, EER2 12, EER 3.80 W/W, and COP 3.9, with a 1,887 W compressor (RLA 12 A) and a factory charge of 1,700 g of R32. We have already explained elsewhere, for a Beaconsfield project, why we sometimes choose the larger unit on a two-head project to preserve a third port and heating reserve; here the logic is the opposite and is worth distinguishing: the third port is not the argument, it is a bonus. The argument is that no other unit in the range can properly power an 18,000 BTU/h head in a two-zone setup.

Two-thirds of the system in one room

At 18,000 versus 9,000, one zone represents two-thirds of the installed indoor capacity—the most unbalanced distribution we have published for a two-head system. This has two consequences that we document at commissioning.

When the large head operates alone on a July afternoon, the system works near the top of its range and everything is fine. When the small bedroom head operates alone on a September night, it calls for 9,000 BTU/h against a modulation floor of 7,500 BTU/h—just above it, so acceptable, but with little margin. The selected setting raises this zone's minimum fan speed by one step and maintains a stable setpoint rather than three-degree jumps. The modulation-floor mechanism, which is a system property rather than a property of each head, is detailed in our Saint-Chrysostome article.

The 113% ratio is justified here by a real, rather than statistical, lack of coincidence: the ground floor calls for heat during the day, while the bedroom calls for it at night. We explained in our Ahuntsic-Cartierville article why, with two zones, the law of large numbers no longer applies and why we refuse to oversize by reflex.

The panel, the breaker, and the baseboard heaters

19.5 A MCA, 25 A maximum protection, a single circuit for the entire system since the indoor units are powered by the outdoor unit. In an area where many homes have retained their original service entrance, this 5 A difference from the smaller model is not insignificant, and the load calculation under the Code belongs to the electrician. The full reasoning was published for a project in Saint-Édouard.

The electric baseboard heaters remain in service, set 2 to 3 °C below the setpoints of the indoor units. They are the peak backup for the coldest days, not a relic to remove on installation day.

The hot tub, the vine, and the deck: what a Côte-des-Neiges backyard requires of an outdoor unit

This is where this project becomes different from all those we have documented. The outdoor unit is not against a wall of the house: it is at the back of the courtyard, against the shared property fence, on a raised-leg base installed on the slab deck.

Why the unit is at the back of the property, and what it costs

No wall of the house was available. The front façade faces the street, one side is occupied by the access path, and the other by the neighboring home's bedroom windows — at 8,700 inhabitants per square kilometer, this constraint is the rule rather than the exception. The back of the courtyard was the only acceptable location.

The price to pay is in piping. The two lines are approximately 16 m and 21 m, or 37 m in total — more than the GWHD(24)ND6MO's 30 m precharge, hence 7 m over at 20 g/m, or 140 g of R32 weighed out and added to the factory charge of 1,700 g. We remain well below the maximum total length of 60 m and the maximum elevation difference of 15 m. The piping budget as a selection criterion was covered in detail for a project in Varennes, and we will not revisit it here.

What is specific to this project is the route. Crossing a landscaped courtyard with two refrigerant lines, a drain, and an interconnection cable requires three decisions to be made before digging:

• The route never crosses an unprotected trafficable surface. Under a deck, the line runs through a sleeve in a trench opened while the slabs are already lifted — it is a unique opportunity that will not come again.
• The insulation on both lines remains continuous along the entire run, including in the trench. A poorly insulated suction line condenses in cooling mode, and beneath a deck this water never evaporates. The same principle, applied to a wall cavity and an indoor line set cover, was published for projects in Saint-Étienne-de-Beauharnois and Saint-Louis-de-Gonzague.
• The electrical disconnect must be installed near the unit, not near the panel. A technician who needs to shut off the power in February should not have to cross the yard to do so.

The spa one metre from the outdoor unit

A four-season spa placed next to a condenser is a first in our publications, and it is the most useful point from this project.

Water chemistry does not stay in the water

A spa cover is not airtight, and it is opened several times a week. Each opening releases a plume of hot steam laden with bromine or chlorine. This plume does not disperse in a yard enclosed by a solid fence and a hedge: it rises, lingers, and some of it is drawn into the unit.

The outdoor coil is made of aluminum fins crimped onto copper tubes. This is precisely the combination of metals most readily attacked by treated-water chemistry, and the attack produces no error code: it causes a gradual loss of efficiency, fins that turn white and then become pitted, and eventually a risk to the seals. Environment-related corrosion is normally treated as an exposure and maintenance issue, not as a manufacturing defect—this should be verified in the warranty terms rather than assumed.

What we did here, in order: maximize the available distance between the spa and the unit, direct the discharge toward the side opposite the pool, and specify in the contract rinsing the coil with clean water twice a year instead of once. What we recommend from the design stage, when the spa has not yet been installed: do not place both units on the same side of the yard.

In winter, the plume goes directly into the coil

The point no one anticipates. A spa operates year-round in Quebec, and its plume is most visible in January—and therefore contains the most water. At the same time, the heat pump is in heating mode: its outdoor coil is colder than the surrounding air, and it normally frosts over.

Adding a local source of saturated steam to this air amounts to feeding the icing. The defrost cycles multiply, each one costs efficiency, and the meltwater is more abundant than elsewhere. The customer only notices that the unit “produces steam and starts up again nonstop” on evenings when the spa is being used. The mechanism is normal; it is the frequency that is abnormal, and it is caused by the proximity.

Electrical requirements, clearances, and service access

A spa has its own dedicated circuit, ground-fault protection, and disconnect switch. The heat pump does too. The required distances between a pool, its equipment, and any other electrical apparatus are governed by the Code and must be verified by the licensed electrician before installation, never afterward. We provide the manufacturer's data — MCA, maximum overcurrent protection, disconnect location — and the electrician provides compliance.

Two practical points should be added. The spa skirt must remain removable: its motor, pump, and heater are serviced through it, and a condenser planted in front of the access panel turns a one-hour repair into a half-day dismantling job. And the spa must not be drained toward the base of the unit — several hundred litres, once or twice a year: the drain hose must be directed, not simply allowed to drop.

Virginia creeper on the fence

The photo was taken in autumn, and the vine is beautiful. It is also thirty centimetres from the top of the unit.

We have already covered the outdoor unit under trees for a project in Rigaud — samaras, resin, falling branches. A climbing plant is a different, faster problem. It does not drop debris: it grows into the unit. Virginia creeper gains several metres per season, its tendrils adhere to smooth surfaces, and its stems reach the fan grille and coil face within a single year. It also holds moisture against the sheet metal and the fence, and in autumn its leaves fall directly onto the top and into the grille.

The solution is not pruning, but an maintenance rule recorded in the file: maintain clear space around the unit, check it at every annual visit, and prune the vine in spring and late summer rather than carry out emergency work in August when the air conditioning weakens.

A solid fence behind the unit is on the air-intake side

We published an article for a project in Ahuntsic-Cartierville about the cost of insufficient front clearance. Here, the opposite is at issue.

The unit draws air in from the rear and sides. Behind it is a solid wooden fence, and a dense vine grows on that fence. The rear clearance is therefore not merely reduced: it is seasonal, smaller in August than in April. Equipment that was breathing properly when commissioned can find itself suffocated two summers later without anything having been moved.

Clearance values are given in the installation manual for the unit actually delivered, and that manual is the governing document. Our method for a vegetated fence: measure the rear clearance taking growth into account, never just the foliage present on the day of installation.

The four-legged base installed on slabs

The unit rests on a four-legged metal support, with anti-vibration pads between the unit's feet and the support's crossbar. This is neither the drainage-stone base we use on the North Shore and South Shore, nor the wall-mounted supports we used in a side yard in Ahuntsic-Cartierville. It is the third family of solutions, and it has its own logic.

Its advantage over a wall-mounted support is clear: no vibration is transmitted to the home's structure, since the unit does not touch the house. Its disadvantage is equally clear: a slab deck is not a foundation. Irregular slabs laid on a sand bed shift, and four legs concentrate the load at four points. A slab that tilts by one centimetre puts the unit out of level, and a unit that is out of level drains its defrost water poorly.

On this project, a concrete footing was poured beneath the support's footprint before it was installed, solving the problem at its source. The slope is adjusted through the footing, never with shims under the feet. The full reasoning regarding bases and frost heave was published for a project in Rigaud.

Defrost water and the surface where people walk

Here is the detail that distinguishes a landscaped backyard from all the other locations we have documented: the deck is the pathway. It is how people get to the spa, wearing a bathrobe, in November.

A heat pump in heating mode releases defrost water all winter. On a lawn, no one notices. On smooth stone slabs with slight depressions at the joints, this water freezes and forms a sheet of ice exactly where people walk, reforming after every cycle. This is the most concrete risk in the entire project, and it has nothing to do with the unit's efficiency.

The selected corrections: a base high enough to clear both snow and ice buildup, the unit positioned outside the main route to the spa, and the water directed toward the adjacent flower bed rather than the centre of the deck. We had already noted, for a project in Les Cèdres, that a drain or water outlet discharging onto a pedestrian path in September becomes ice in October.

Mistakes to avoid in a landscaped backyard

• Choose the location based on aesthetics alone. The most discreet spot is often the least well ventilated.
• Measure clearances based on foliage. A hedge and a vine are shorter in April than in August.
• Install the unit in front of the hot tub access panel or any other equipment requiring maintenance.
• Place a legged base directly on slabs without a stable foundation underneath.
• Direct the hot tub drain or gutter toward the unit's base.
• Cover the unit for the winter. A heat pump operates in January; a full cover traps moisture and prevents defrost water from drying.
• Remove the electric baseboards after a first winter deemed successful.

Subsidies, Warranty, and Maintenance

The system qualifies for applicable residential energy-efficiency programs in Quebec, including Hydro-Québec's LogisVert and Rénoclimat. Chauffez vert does not apply because the home is already heated with electricity. Eligibility criteria change, and we confirm eligibility when the file is opened rather than stating an amount in the quote. The declared AHRI code must match the combination actually installed, otherwise a subsidy application may be rejected for a purely administrative reason.

The warranty is 10 years, extended to 12 years when the product is registered with proof of installation through the distributor. We register it at the end of the project.

For HVAC maintenance, this system requires two filters to be rinsed every 4 to 8 weeks during the intensive season, two drain pans and two drains to be checked, and—in this particular yard—two annual rinses of the outdoor coil instead of one, along with a check of vegetation clearance at every visit. This is not a commercial option; it is what ensures the unit will deliver in ten years what it delivers today.

AirGreen in Côte-des-Neiges–Notre-Dame-de-Grâce 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. In Côte-des-Neiges–Notre-Dame-de-Grâce, from Monkland Village to the Loyola neighbourhood, including Benny Farm and the university area, backyards are small, landscaped, shared, and often occupied by a hot tub, deck, or vegetable garden. These constraints, more than the load calculation, determine where the unit can go and how long it will last.

A successful HVAC installation in this type of space begins with a technical site visit to assess the hot tub, fence, vine, and path to the back door—before looking at the catalog.