Installation of a GREE UNIX R32 central heat pump on a high wall-mounted bracket in Sainte-Hélène-de-Bagot, Les Maskoutains RCM

A central heat pump mounted at balcony height: how the vertical position changes noise, maintenance and water

Most discussions about the location of an outdoor unit focus on the horizontal plane: which side of the house, how far from the property line, and away from which window. The vertical dimension is treated as a detail — the appliance is mounted “high enough for the snow” and everyone moves on.

The de Sainte-Hélène-de-Bagot project shows why this dimension deserves a proper calculation. The outdoor unit of the GREE UNIX R32 is installed at ground-floor level, beside a balcony, in a side clearance of approximately one metre between two built volumes. Each of these three constraints has an acoustic consequence, and they combine.

Sainte-Hélène-de-Bagot: a large lot, a narrow passage

Sainte-Hélène-de-Bagot, in the Maskoutains RCM, is an agricultural municipality along the Highway 20 corridor, between Saint-Hyacinthe and Drummondville. Lots there are generally generous in size, which usually leaves a choice of location.

This property was an exception. The front and rear were occupied — an entrance on one side, a terrace and landscaping on the other — and the only available passage ran along the side wall for approximately one metre, between the house and the adjacent structure. Above this passage was a raised balcony with its wooden structure. Below it was a basement window.

In other words: a narrow passage, enclosed on three sides, with openings immediately nearby. This is the worst acoustic scenario one can encounter in a residential setting, and it was the only possible location.

Why the appliance was mounted so high

Three reasons, in this order:

1. The passage had to remain usable. A ground-level appliance in a one-metre-wide corridor makes it unusable.
2. The basement window and its window well had to remain clear. An appliance placed in front of them blocks light, access and, in an emergency, an exit.
3. The snow. In a narrow passage between two buildings, snow accumulates and does not melt — it is a shaded area for much of the winter.

Mounting it high up, on a galvanized steel wall bracket with a diagonal brace, solved all three at once. It created a fourth issue that had to be addressed: noise.

Noise: what the specification sheet says, and what it does not say

60 dB(A)—but at what distance?

The UNIX R32 specification sheet states a sound pressure level of 60 dB(A) for the outdoor unit in this combination, and 50 dB(A) for the indoor section. In both cases, these are the lowest values in the range.

One point to understand before comparing two units: a sound pressure level only has meaning when accompanied by a measurement distance. The specification sheet does not state it—the industry standard is generally one meter in free field. Two manufacturers that publish “60 dB(A)” and “57 dB(A)” at different distances simply cannot be compared.

This is the first question we ask a representative when a customer is hesitating between two brands based on noise.

What one wall does, and what two walls do

In free field, sound levels drop by approximately 6 dB every time the distance doubles. At three meters from a unit measured at 60 dB(A) at one meter, the level is around 50 dB(A). At six meters, around 44 dB(A).

This rule no longer applies when there are reflective surfaces:

• A wall behind the unit reflects some of the energy and can add up to approximately 3 dB.
• An angle formed by two surfaces can add up to 6 dB.
• Two closely spaced parallel walls, as in this passage, create multiple reflections: the sound no longer dissipates; it is channeled and emerges at the ends of the passage.

To put this into perspective: an increase of 3 dB is barely perceptible, but 10 dB corresponds to a doubling of perceived loudness. Unfavorable geometry alone can therefore turn a quiet unit into one the neighbor can hear.

The balcony acts like a lid

This is the element most often overlooked. A horizontal structure above an outdoor unit—balcony, overhang, platform—closes off the space from above. Sound that would normally travel toward the sky is reflected back toward the ground and nearby openings.

It also has an aerodynamic effect: it promotes recirculation of the discharged air, which rises along the front rather than dissipating. In heating mode, the unit re-aspirates its own cooled air, its performance drops, and its defrost cycles become more frequent.

Low frequencies do not behave like the fan’s whoosh.

An outdoor appliance produces two categories of noise:

• The fan’s whoosh, which is relatively high-pitched and highly directional, is easy to reduce with a screen or distance.
• The compressor’s rumble, which is relatively low-pitched and non-directional, goes around obstacles and passes through walls much more easily.

A-weighting — the “(A)” in dB(A) — reproduces the sensitivity of the human ear and deliberately underestimates low frequencies. An appliance can therefore display an excellent dB(A) rating and still be noticeable in a bedroom behind the wall, because what is heard there is not the whoosh, but the low-frequency rumble.

That is why two appliances with the same dB(A) rating are not necessarily equivalent once installed.

What we did on this project

• Orienting the discharge face toward the opening of the passageway, so that the air and sound can escape instead of being trapped.
• Positioning it as far as possible beneath the balcony rather than directly underneath it, to reduce the lid effect.
• Manufacturer clearances respected at the rear and on the sides, which is precisely what mounting on a support makes possible in a narrow passageway — a floor-mounted appliance would inevitably be too close to at least one surface.
• Choosing the quietest combination in the range, at 60 dB(A) outdoors and 50 dB(A) indoors.
• Complete mechanical decoupling, which brings us to the next point.

Structure-borne noise

An appliance suspended from a wall does not transmit noise only through the air: it also transmits it through the structure. The compressor vibrates the casing, the casing vibrates the support, the support vibrates the wall, and the wall radiates into the rooms alongside it.

This is a particularly effective transmission method at low frequencies, and a particularly troublesome one because it does not diminish with distance in the same way as airborne sound.

The treatment is carried out on three levels, all visible in the photo:

1. Anti-vibration mounts between the appliance’s feet and the support arms, compressed without being crushed — a mount tightened all the way can no longer do its job.
2. A rigid support with a diagonal brace, anchored in the foundation’s concrete. A flexible support resonates; a rigid, properly triangulated support does not move.
3. Decoupled piping, with a flexible loop, never rigidly fastened to both the unit and the wall over a short distance. A line pulled taut between the two becomes an acoustic bridge—this is the defect we correct most often in existing installations.

Water falling from higher up

A unit in heating mode produces defrost water. Mounted one and a half meters above the ground rather than thirty centimeters, this water falls from higher up, splatters more, and spreads over a larger surface.

In a narrow passageway with a basement window below, this is not a minor detail: water splashed onto the masonry freezes, and the window well can fill with ice.

We address this during the layout stage by offsetting the unit's vertical alignment from the window well and checking that the receiving surface drains properly toward the outside of the passageway rather than toward the foundation.

Maintenance access: the point we forget in June

A unit mounted high is pleasant to install and difficult to maintain if no one has thought about it.

The questions we ask ourselves before setting the final height:

• Can a technician reach the service panels from a stable ladder? In a one-meter-wide passageway, setting up a ladder requires space—and ground that is not sloped.
• Can the heat exchanger be rinsed? Annual cleaning with clean water requires reaching the face of the heat exchanger, not merely seeing it.
• Is access still possible in winter? A narrow, shaded passageway accumulates snow and ice. An intervention in January should not require twenty minutes of snow removal before work can begin.

On this project, the selected height is the compromise between the clearance needed above the snow and the point beyond which maintenance becomes acrobatic.

Service valves and terminals accessible from the rear

The UNIX R32 places its service valves and electrical terminals outside the casing, on a rear panel. In the photo, you can make out the connection and the flexible conduit leading to it.

In a one-meter-wide passageway, with a unit mounted high, this feature stops being a mere installation convenience: it determines whether maintenance is feasible. Taking pressure readings without having to remove a side panel jammed against masonry is the difference between a forty-minute maintenance visit and a two-hour visit.

The installed combination

The 3.60 COP of this combination is the highest among the four configurations in the range, and it has the lowest sound level. In an acoustically challenging location, these two characteristics work in the same direction: less power drawn, less noise produced, provided the home actually has a load of this magnitude—which we validate through a calculation, not a square-footage rule.

Regulations, rebates, and the right step to take before deciding on a location

Municipal noise bylaws

Most municipalities in Quebec regulate mechanical equipment noise, generally in two ways: a minimum distance from property lines and a maximum level measured at the property line, often stricter at night.

These rules vary from one municipality to another, including between immediate neighbors in the same RCM. We check the applicable bylaw before determining the location, not afterward.

The financial calculation is simple: moving an outdoor unit after a complaint means a second complete installation—new support, new piping, new drilling, refrigerant recovery and recharge. A ten-minute check protects several thousand dollars.

LogisVert

Hydro-Québec's LogisVert program calculates the incentive for an air-source heat pump based on its heating capacity at -8 °C, using a scale of approximately $120 per 1,000 BTU/h, with a maximum of around $6,700, and provides enhanced amounts when the installation replaces oil or propane heating—a common situation in municipalities along the Highway 20 corridor that are not served by natural gas.

Conditions: you must own a residential property and be an Hydro-Québec customer, have the work carried out by a contractor holding an RBQ licence, and install an approved system that is ENERGY STAR certified and bears an AHRI number corresponding exactly to the installed combination. Since the scales are updated periodically, we verify the applicable amount for the project before including it in a quote.

Three questions to ask before signing when space is limited

1. At what distance was the stated sound level measured? Without that information, the figure cannot be used for comparison.
2. How will vibration be isolated from the wall? If the answer is “there are rubber feet in the box,” that is not a method.
3. How will a technician access the unit five years from now, in February? A location that cannot be serviced is a location that will not be serviced.

Our service area

At AirGreen, we install and maintain central heat pumps, wall-mounted heat pumps, and central air conditioning systems in Sainte-Hélène-de-Bagot, Saint-Hyacinthe, Acton Vale, and throughout the Maskoutains RCM, as well as in Longueuil, Boucherville, Châteauguay, and the Sorel-Tracy area. We also serve Montréal, Laval, the North Shore, and the South Shore.

If the only available space at your property is a narrow passage, a shared wall, or an area near a bedroom, that is exactly the kind of constraint that calls for an on-site visit rather than a quote over the phone. We take measurements, assess the site's acoustic geometry, and tell you honestly whether the proposed location is the right one.