Installation of a 5-ton GREE UNIX R32 central heat pump in Sainte-Madeleine, Les Maskoutains RCM

Installing a 110 kg central heat pump on a surface we are not allowed to drill into

Most outdoor units we install sit on the ground or on a bracket bolted to a wall. This one sat on an elevated slab, with one simple, non-negotiable constraint: no penetrations through the slab. Not a bolt, screw, or anchor.

This constraint is not unusual. It arises whenever a central heat pump must be installed on a roof, patio, concrete balcony, or slab protected by a membrane. It changes everything: how the load is distributed, how defrost water is managed, how vibrations are transmitted, and even how the refrigerant line is secured.

Here is the project in Sainte-Madeleine, in the Maskoutains RCM in Montérégie, where we installed a five-ton GREE UNIX R32: a GUD60W2/NhE-D(U) condenser and a GUD60AH2/G-D(U) air handler.

Sainte-Madeleine: a village between Route 116 and the railway corridor

Sainte-Madeleine occupies a unique position in the Maskoutains RCM: a dense village core crossed by Route 116 and the railway corridor, halfway between Saint-Hyacinthe and the Richelieu Valley.

This setting creates a mixed urban fabric we know well: tightly packed village houses, a few brick apartment buildings, shallow lots, and outdoor spaces divided among parking, access routes, and utilities. As a result, the ideal location for an outdoor unit is not always at ground level—and a flat elevated surface becomes the best available option.

We encounter exactly the same pattern in the Montreal plexes, the buildings of Longueuil, and the older areas of Laval: when the ground is taken, we build upward.

Installed pairing

The constraint that dictated everything

Distribute the load: sleepers, protective sheet, base

The outdoor unit weighs 241.4 lb when empty. Resting on four feet, this mass is concentrated on four points of a few square centimeters each. On a bare concrete slab, this is acceptable. On a surface protected by a membrane, it is a guarantee of perforation over the medium term, worsened by freeze-thaw cycles.

The assembly shown here, visible in the photo, consists of layers:

1. A protective sheet laid directly on the surface, preventing direct contact between the wood and the coating.
2. Two treated-wood sleepers laid flat and oriented perpendicular to the direction of the supporting structure, transforming four load points into two continuous support lines.
3. An aluminum base screwed to the sleepers, which raises the unit and provides it with a rigid, level mounting plane.
4. Anti-vibration pads between the unit's feet and the base.

Each layer serves a purpose. Remove the sleepers, and you concentrate the load. Remove the protective sheet, and the treated wood works against the coating with every change in humidity. Remove the base, and the unit ends up flush with the surface, in the water.

Why we never drill

A through-anchor on a watertight surface is a permanent perforation. Even when properly sealed on the day of installation, it ages differently from the rest of the surface, undergoes the same thermal cycles, and sooner or later becomes the starting point for water infiltration.

Our rule is absolute: the support is freestanding and ballasted by the weight of the unit, never fastened through the surface. If wind stability requires it, we add ballast—never anchors.

Wind uplift

An outdoor unit 900 mm wide and 1,260 mm high, elevated in an open area along a road and rail corridor, presents considerable wind exposure. Its weight of 241 lb is an asset, but it does not eliminate the need to verify the stability of the assembly.

What we control: the base must be securely attached to the sleepers, the sleepers must not be able to slide, and the unit must be fastened to the base using its designated anchor points. A unit simply placed on a base is not an installation; it is an object set down.

Vibration: a slab transmits what the ground absorbs

This is the least understood difference between a ground installation and an installation on a structure. Ground absorbs vibration. A slab, joist, or load-bearing wall transmits it.

A variable-speed compressor produces low-frequency vibrations. In a multi-unit residential building, these vibrations travel through the structure and sometimes appear two floors away, in a room with no apparent connection to the unit. The phenomenon often occurs only at certain operating frequencies, making diagnosis difficult afterward.

Our preventive measures:

• antivibration mounts as standard, selected according to the actual weight rather than picked at random from the truck;
• decoupling of the refrigerant line at the unit outlet, with a flexible loop that absorbs movement instead of a rigid connection that transmits it;
• no direct contact between the support and any sensitive structural element;
• listening while operating, at several operating levels, before leaving the site.

In a multi-unit residential building, this step is not a refinement. It is the difference between a system nobody notices and repeated tenant complaints.

Defrost water on a raised surface

In winter, each defrost cycle releases water from the bottom of the unit. On the ground, it seeps in. On a raised flat surface, it does something else: it spreads out, freezes, and creates a sheet of ice where someone will eventually walk.

What we check before fixing the location:

• the actual slope of the surface and the direction of drainage;
• the position of the drains or outlets, and the distance to them;
• the risk of refreezing at the drainage point, which turns a drain into an ice blockage;
• pedestrian traffic on the surface, in winter and summer.

The elevation provided by the sleepers and base plays a direct role here: it keeps the unit from sitting in its own defrost water and allows that water to spread out and drain freely.

The refrigerant line lying flat, and why it is secured this way

In the photo, the refrigerant line runs flat across the surface, sheathed in white and secured with fasteners at regular intervals before reaching the drop point.

Three reasons for this treatment:

• Mechanical and solar protection. A continuous sleeve protects the insulation from ultraviolet rays, which crack it within a few seasons, and from impacts—shovel, patio chair, cart.
• Restraint. A loose line on a flat surface moves with the wind, thermal expansion, and snow removal. Every movement strains the connections at both ends.
• Identification. A visible, clearly marked line is one a roofer will not accidentally cut ten years from now. We explicitly flag this to the client when the surface in question is likely to be redone.

The piping uses 3/4 in. on the suction side and 3/8 in. on the liquid side, with a standard length of 7.5 m (24.6 ft), a maximum length of 30 m (98.4 ft), and a maximum elevation difference of 15 m (49.2 ft) between the two units. A high-elevation connection quickly consumes the available elevation difference: we measure before ordering, not afterward.

1,500 CFM at 125 Pa: the real constraint on the indoor side

The GUD60AH2/G-D(U) air handler is the largest in the UNIX R32 series. It delivers 1,500 CFM at a nominal external static pressure of 125 Pa (0.5 in. w.c.).

This figure determines the success of a project of this size, and it is almost always overlooked. A duct system designed for an old furnace, with a single undersized return, cannot deliver 1,500 CFM at 0.5 in. w.c. This is not an opinion: it can be measured with a differential manometer in about fifteen minutes.

Our sequence for this type of project:

1. Building load calculation, room by room.
2. Measurement of the existing system's external static pressure while operating.
3. Comparison with the rating of the proposed unit.
4. Decision: either the duct system passes, or we correct it—additional return air, modified ductwork, redesigned filter—or we adjust the unit size.

Putting a five-ton unit on a duct system that can only handle three tons results in a noisy system that frosts in summer, blows lukewarm air in winter, and whose actual performance has nothing to do with the CPSC2 of 10.5 listed on the data sheet.

Electrical, handling, and R32

The condenser requires a MCA of 39.9 A and maximum overcurrent protection of 45 A on a dedicated circuit; the air handler requires its own circuit (MCA 7.7 A, MOP 15 A). If an electric auxiliary heater is added to the air handler, these values must be recalculated—the manufacturer's data sheet states this explicitly.

Handling deserves a sentence because it is rarely anticipated: getting 241 lb onto an elevated surface requires a plan, access, and sometimes lifting equipment. We account for this when preparing the quote, and we systematically ask the following question: how will this unit come back down in twelve years? A location where you can get it up but not back down is not a location.

The system contains 4.6 kg of R32, an A2L-classified refrigerant that is mildly flammable and has a significantly lower global warming potential than R-410A. The warning label is visible at the bottom of the cabinet. The refrigerant leak detection sensor is factory-installed on the indoor unit of all GREE Canada equipment and must remain powered at all times.

What This Sainte-Madeleine Project Reminds Us

Mistakes to Avoid

• Anchoring a support through a watertight surface. No sealant can compensate for a perforation that deteriorates over time.
• Placing the unit directly on its four feet on a membrane or protected slab.
• Putting treated wood in direct contact with the cladding, without a protective sheet.
• Ignoring vibration transmission through the structure. What the ground absorbs, a building conducts.
• Failing to consider where defrost water will go on a surface where people walk.
• Leaving the refrigerant line unsecured on a flat surface. Wind and thermal expansion eventually take their toll.
• Ordering a five-ton unit before measuring the system's static pressure.
• Failing to plan how the unit will be removed at the end of its service life.

Rebates and Eligibility

The installed configuration carries AHRI code 217120762. This code, specific to the exact pairing of the condenser and air handler cabinet, is what government programs and local rebates verify — not the series' commercial name. The criteria, performance thresholds, and amounts change from year to year and depend on the heating source being replaced. We confirm eligibility with the client before signing and provide the AHRI code in writing.

Our Coverage

We carry out these HVAC installations in Montréal, Laval, Longueuil, the North Shore, the South Shore, and throughout Montérégie, including Sainte-Madeleine, Sainte-Marie-Madeleine, Saint-Hyacinthe, Saint-Damase, and Mont-Saint-Hilaire. Every project begins with a technical visit: load calculation, static pressure measurement, electrical inspection, and a complete assessment of the outdoor location — including the surface's capacity to support the unit and the route for bringing it there.

If your only available location is a roof, terrace, or elevated slab, the project is still entirely feasible. It simply needs to be designed by someone who understands why you don't drill. Our team travels to the site for an assessment.