Eighty-five kilograms suspended in a one-metre corridor: how we installed a central heat pump where there was no room on the ground
There are job sites where half the work takes place before a box is even opened. This was one of them.
The Saint-Nazaire-d'Acton home had only one acceptable location for an outdoor unit: a narrow corridor between the brick wall and the property line, barely one metre wide, occupied by a downspout, a well-established cedar hedge, and a flowerbed strip that the owner wanted to preserve. In front, the driveway and façade. Behind, the terrace. Installing a ground-level pad in this corridor would have blocked the passage and buried the unit under snow for four months of the year.
We therefore installed the GREE FLEXX R32 ULTRA central heat pump on a wall mount anchored to the foundation. Here is why, and above all, how.
The context: rural Montérégie without a natural-gas network
Saint-Nazaire-d'Acton, in the Acton RCM, is neither Montreal nor the suburbs. It is an agricultural municipality where natural gas simply is not distributed. Homes there are heated with electricity, oil, propane, wood, or a combination of these sources. Winds sweep across the fields unobstructed, winter outages sometimes last longer than in the city, and the nearest neighbour is rarely three metres from the wall—except, precisely, in village centres like this one.
This context has two direct consequences for the choice of a central heat pump:
- Natural-gas dual-fuel operation is not an option. The backup system will be electric, oil-fired, or propane-powered.
- The actual heating load must be calculated using a more severe design wind than for a protected home in a densely populated urban area.
Why the outdoor unit is suspended rather than placed on the ground
The wall mount is not an aesthetic compromise. In this specific case, it was the best technical solution—and it had to be executed properly, otherwise it would become the worst one.
The actual weight of the unit
The outdoor unit GUD36W2/NhE-D(U) weighs 187.5 lb net (85 kg), and measures 990 x 960 x 370 mm. This is not a 9,000 BTU, 30-kilogram wall-mounted unit. A quality bracket rated for this weight with a safety margin, along with anchoring hardware suited to the material, is not optional.
Facing brick is not a load-bearing wall
This is the most serious mistake we see with this type of installation, and it is common.
A facing brick is a finish material. It is separated from the structure by an air cavity, held in place by ties, and is not designed to support a suspended load—much less a load that vibrates 3,000 hours per year. An 85 kg machine bolted into mortar will eventually crack the joints, pull out the ties, and, in extreme cases, destabilize a section of facing.
On this project, the bracket was anchored into the parged concrete foundation, below the brick line, using mechanical anchors installed in solid concrete rather than in the mortar joint. The cost difference is a few dozen dollars. The difference in consequences is several thousand.
Vibration is transmitted to the structure
A ground-mounted unit dissipates its vibrations into the gravel. A suspended unit sends them directly into the wall, and the wall redistributes them throughout the house. A bedroom located behind that wall can become uninhabitable at night.
The treatment is done at three levels: anti-vibration pads between the unit’s feet and the bracket, torque tightening without crushing the pads, and decoupling of the refrigerant piping—never rigidly fasten the line to both the unit and the wall over a short distance, or it will become a transmission bridge.
The secondary advantage: snow and defrost water
In rural Montérégie, a ground-mounted unit regularly ends up buried in 60 to 90 cm of snow, with defrost water also freezing and forming a block of ice beneath the heat exchanger. The wall bracket solves the problem at the outset: the base is above the accumulated snow level, air circulates beneath the unit, and defrost water falls into the flower bed instead of accumulating.
The narrow corridor: two problems few contractors anticipate
Air recirculation
A corridor between two walls behaves like a channel. Air discharged by the unit, cooled in heating mode, can be drawn back in through the intake side if clearances are insufficient. The result: the unit “thinks” it is colder than it actually is, performance drops, and defrost cycles multiply.
We oriented the unit so that the air discharge was unobstructed toward the corridor opening, and maintained the manufacturer's clearances at the rear and sides. The cedar hedge was trimmed accordingly, and the homeowner was advised in writing that she would need to maintain this clearance every year—a cedar grows 20 to 30 cm per season and does not ask anyone's permission.
Acoustics between two walls
The unit is rated at 60 dB(A) at maximum sound pressure level. In an open field, that is unobtrusive. Between two rigid parallel surfaces, reflections can add several perceived decibels, and the sound travels toward the neighboring property rather than dissipating.
We systematically check the applicable municipal regulations—minimum distances from property lines and permitted nighttime sound levels—before determining the location, not afterward. Moving a heat pump after a neighbor's complaint costs as much as a complete second installation.
The outdoor line set cover
The house had no usable interior chase between the outdoor connection point and the indoor section. We therefore installed the refrigerant line set outside, in a rigid UV-resistant line set cover visible along the entire height of the wall.
Done properly, this is a durable, clean solution. Done halfway, it is a source of trouble. The points to follow are:
- The insulation does not stop at the line set cover. The cover provides mechanical protection, not thermal insulation. The gas line must remain insulated along its entire length, including inside the cover. A bare line inside a cover will condense; the water runs down, and the cover becomes a reservoir.
- The wall penetration must slope downward toward the exterior and be sealed with the appropriate caulking, using a sleeve. A horizontal penetration sealed with expanding foam lets water and insects in.
- Fasteners must go into the appropriate joints for the substrate, using stainless-steel screws. A line set cover attached with ordinary hardware will leave rust stains running down the brick within two winters.
- The condensate line and control wiring must not be run haphazardly through the same conduit.
The horizontal-airflow indoor section
The FLEXX is designed with horizontal (side-discharge) airflow, making it a good candidate for homes where the mechanical space is not a dedicated basement room. We selected the GUD24AH2/G-D(U) indoor section, which measures 460 x 1105 x 540 mm, weighs 135.6 lb (61.5 kg), and delivers up to 3,176 ft³/min.
The connection to the existing ductwork was preceded, as always, by a static pressure measurement. With this type of conversion, we refuse to rely on the apparent diameter of the ducts: a system designed for a high-temperature warm-air furnace does not necessarily provide the airflow required by a heat pump, which operates with a smaller temperature differential and therefore has to move more air to deliver the same amount of heat.
Specifications of the installed combination
| Data | GUD36W2/NhE-D(U) + GUD24AH2/G-D(U) |
|---|---|
| Rated cooling capacity | 24,000 BTU/h (modulation 12,000–30,000) |
| Rated heating capacity | 23,000 BTU/h (modulation 12,000–30,000) |
| SEER2 | 18 |
| HSPF2 | 10 |
| EER2 | 12,5 |
| COP | 3,6 |
| AHRI number | 217120759 |
| ENERGY STAR | Yes |
| Heating range | -30 °C to 24 °C |
| Cooling range | -15 °C to 54 °C |
| Power supply | 208-230 V — MCA 27.7 A / MOCP 30 A (outdoor) |
| Refrigerant | R32 (A2L), leak detection sensor included |
| Piping | 3/8 in. liquid, 3/4 in. gas — max. 98.4 ft (30 m), max. elevation difference 49.2 ft (15 m) |
| Wi-Fi | Included, factory-installed |
| Warranty | 10 years + 2 years on the compressor and parts with registration |
The 3.6 COP of this combination is the highest in the FLEXX ULTRA range, ahead of the 34,000, 48,000 and 54,000 BTU configurations. For a home whose actual load is two tons, oversizing offers no benefit: the larger unit modulates less precisely, cycles more often, dehumidifies less effectively in summer and costs more to purchase and install.
It's a principle we apply everywhere, from Montreal to Laval, from Longueuil to the North Shore and throughout Montérégie: the right capacity, not the largest one.
Dual energy, Dual Fuel and subsidies: what the absence of natural gas changes in rural areas
The FLEXX is Dual Fuel compatible—and that matters even more outside major urban centres
The FLEXX ULTRA range is advertised as compatible with Dettson's Ultra Heat and Dual Fuel systems and works with a conventional 24 VAC thermostat. In a village without a gas network, this compatibility opens a door that many homeowners overlook: a home still equipped with an oil- or propane-fired furnace can keep that unit as backup and have it controlled automatically based on the outdoor temperature, rather than paying for its immediate removal.
The heat pump covers the vast majority of the season's heating hours. Fuel is needed only during the coldest fraction of those hours. This is often the most cost-effective path for a two-step transition, and it provides access to Hydro-Québec's dual-energy rates, which a heat pump + electric heating combination does not.
LogisVert: heating oil and propane change the equation
Hydro-Québec's LogisVert program calculates the assistance for an air-source heat pump based on its heating capacity at -8 °C, according to a rate of approximately $120 per 1,000 BTU/h, with a maximum of around $6,700. The enhanced amounts specifically target the replacement of an oil- or propane-fired heating system—exactly the situation in many homes in the Acton RCM.
The requirements to meet:
- Be a residential property owner and a Hydro-Québec customer.
- Have the work carried out by a contractor holding an RBQ licence.
- Install a certified, ENERGY STAR-certified appliance bearing an AHRI number corresponding to the combination actually installed.
The combination selected here, AHRI 217120759, meets these requirements, as does the product line's Cold Climate certification. Since the scales are revised periodically, we verify the amount applicable to the file before including it in a quote rather than announcing an appealing figure that may not materialize.
A check we systematically perform in the region
In rural areas, the electrical service is often the real limiting factor. A rural home supplied by a 100 A panel, with an electric furnace, water heater, well pump, and sometimes a sump pump, may not have enough available capacity to add an outdoor unit requiring MCA 27.7 A / MOCP 30 A.
We perform this load calculation before ordering the equipment. Discovering on installation day that there is not enough space in the electrical panel turns a one-day job into a three-week project, with an electrician to find and an application to Hydro-Québec.
Our presence in Montérégie
At AirGreen, we install central heat pumps, wall-mounted heat pumps, and central air conditioning systems in Greater Montreal and throughout Montérégie: Longueuil, Boucherville, Châteauguay, Saint-Constant, Delson, the Saint-Hyacinthe area, and the Acton RCM. We also serve Montreal, Laval, the North Shore, and the South Shore for both installation and HVAC maintenance.
If you own a home without an obvious location for an outdoor unit—narrow corridor, sloped terrain, right-of-way, snow accumulation, immediate neighbor—that is precisely the kind of constraint we handle regularly. We visit the property, take measurements, check the electrical capacity and ductwork, and provide a quote with every line item clearly explained.