A shingle roof, two zones to cool, and a compressor that had to withstand the Richelieu winter
This Saint-Roch-de-Richelieu project did not resemble typical residential installations on the South Shore. The client, who owned a low-slope-roof home adjoining a section with vinyl siding, had no viable ground location for the outdoor unit: a side easement that was too narrow on one side, mature landscaping on the other, and a bedroom window less than two metres from the only remaining clearance. At AirGreen, we proposed a solution that few contractors are willing to take on: installing the compressor on the roof, on an elevated aluminum structure resting on treated-wood sleepers, itself supported by a protective membrane.
The result is visible in the project photos: a GREE FreeMatch R32 wall-mounted heat pump, with two heads, powered by a GWHD(24)ND6MO compressor, evacuated and tested on-site before startup.
Why FreeMatch R32 for this home
The system choice was anything but arbitrary. Two zones to condition, a need for heating down to -30°C, and severe outdoor space constraints: the specifications pointed directly to a multi-zone system with a single compressor.
Technical data for the GWHD(24)ND6MO
| Parameter | Value |
|---|---|
| Rated cooling capacity | 24,000 BTU/h (7,030 W) |
| Cooling modulation range | 7,500–31,400 BTU/h |
| Rated heating capacity | 24,000 BTU/h |
| Heating modulation range | 7,500–31,400 BTU/h |
| SEER2 | 21 |
| HSPF2 | 10 |
| EER2 | 12 |
| COP | 3,9 |
| Connectable indoor units | 2 to 3 |
| Power supply | 208/230 V |
| MCA / MOCP | 19.5 A / 25 A |
| Refrigerant | R32, 60 oz (1,700 g) precharge |
| Precharged piping length | 98 ft (30 m) |
| Maximum total length | 197 ft (60 m) |
| Maximum height difference | 49 ft (15 m) |
| Heating range | -30°C to 24°C |
| Cooling range | -30°C to 48°C |
| Sound level (high speed) | 58 dB(A) |
| Net weight | 112.5 lb (51 kg) |
| Certifications | ENERGY STAR, AHRI, ENERGY STAR Cold Climate |
| Warranty | 10-year compressor and parts warranty (+2 years with registration) |
The decisive factor here is the modulation range: 7,500 to 31,400 BTU/h. A fixed-speed 24,000 BTU system would have cycled continuously during the shoulder seasons in a house of this size. The FreeMatch’s G10 inverter technology allows the compressor to operate below one-third of its rated capacity and maintain the temperature without the fluctuations that undermine comfort—and the compressor’s service life.
Second point: the allowable 15 m height difference. On a rooftop installation with indoor units located one floor below, this allowance is not a theoretical luxury; it determines oil return to the compressor. We verified the calculation before even ordering the equipment.
The actual course of the installation
Day 1 — Assessment and load calculation
We never size a heat pump by square footage. A simplified Manual J–style assessment was carried out: facade orientation, window area and type, wall insulation level, estimated air infiltration, and above all the actual use of the rooms. This step ruled out both an 18,000 BTU system (insufficient for the main open-plan area) and a 36,000 BTU system (oversized, and therefore poor at summer dehumidification).
Day 2 — Structure and outdoor-unit positioning
A rooftop installation imposes requirements that a ground-level installation does not:
- Load distribution: the 51 kg compressor cannot rest on two points. We used treated-wood sleepers placed on a protective membrane, distributing the load across several rafters rather than a single one.
- Elevated aluminum stand: the frame raises the unit above the roof surface. This clearance is essential for draining defrost water in winter and preventing accumulated snow from obstructing the coil.
- Anti-vibration strapping: the unit is secured to the wall structure with straps, a detail visible in the photo. On a roof, transmitting vibrations through the framing is the main source of customer complaints. We systematically anticipate it.
- Condensate recovery pan: visible on the ground in the image before installation. In heating mode, defrosting produces water. Without a pan or a directed drain, this water freezes on the shingle and destroys the membrane within three winters.
Day 3 — Refrigerant lines, brazing, and evacuation
The 1/4 in. (liquid) and 3/8 in. (gas) lines were insulated and routed along the siding, with a downward path toward the indoor heads. Two points on which we do not compromise:
- Nitrogen brazing. Any soldering performed without a nitrogen purge leaves copper oxides inside the line. These particles migrate, clog the expansion valve, and kill the compressor—often after the competitor’s labor warranty has ended.
- Evacuation to 500 microns with a standing vacuum test. In the photo, the manifold gauge set is connected to the service ports. Evacuation is not a three-minute formality: we pull down to the target, isolate the system, and observe the rise. A rapid rise indicates residual moisture or a leak. With R32, whose operating pressures are higher than those of R410A, this rigor is non-negotiable.
The compressor’s third port (identified as GAS C on the chassis) was left capped and sealed. This is a tangible benefit for the customer: adding a third head in the basement remains possible without replacing the compressor.
Day 4 — Electrical connection and commissioning
Dedicated 208/230 V power supply, 25 A protection in accordance with the technical data sheet’s MOCP, an accessible outdoor disconnect, and verified grounding. Commissioning includes checking superheat and subcooling, verifying the integrated self-diagnostic system, and providing the customer with a complete demonstration—controls, night mode, and filter cleaning.
The mistakes we see most often on multi-zone installations
We regularly take over improperly installed systems in Montreal, Laval, Longueuil, and along the North Shore. The defects recur with striking consistency:
- Unadjusted refrigerant charge. The GWHD(24) is precharged for 30 m of piping. Beyond that, you must add 0.2 oz/ft (20 g/m). An installer who skips this step on a 40 m run delivers an undercharged system that will never achieve its advertised SEER2.
- Oversized indoor units for the rooms. On a multi-zone system, the combined capacities of the indoor units can exceed that of the compressor—this is normal and expected. What is not normal is a 12,000 BTU indoor unit in a 100 sq. ft. bedroom. It will short-cycle, circulate cold, un dehumidified air, and the client will sleep poorly.
- Indoor condensate drain running uphill. The gravity drain must have a continuous slope. A 5 mm low spot is enough to create a biological blockage and a leak through the wall in the middle of a heat wave.
- No protection for the outdoor coil. On an exposed installation like this one, the coil is protected by a mesh guard against debris and hail.
Eligibility for financial assistance
The GWHD(24)ND6MO is ENERGY STAR certified and bears the ENERGY STAR Cold Climate designation, with an HSPF2 of 10 and a SEER2 of 21. These specifications place the unit in the categories generally covered by energy-efficiency programs available in Quebec, including Hydro-Quebec's LogisVert program. The criteria, amounts, and eligibility conditions change from year to year: we systematically verify the application with the client before signing, and we provide the required technical documentation and proof of installation. We never promise an amount without verifying it beforehand—that is a frequent source of disappointment in our industry.
What this project illustrates about our approach
A rooftop installation is not a fallback solution. It is a technical choice that requires a structural assessment, serious management of winter condensate, vibration control, and safe access for future HVAC maintenance. We recommended it in Saint-Roch-de-Richelieu because it gave the client a unit away from their bedroom window, protected from snow removal, and fully accessible for servicing.
AirGreen serves Montreal, Laval, Longueuil, the North Shore, and the South Shore, including the Richelieu Valley. We perform load calculations, supply, complete HVAC installation, electrical connection, documented commissioning, and annual maintenance of your wall-mounted heat pump.
For an evaluation of your project or a detailed quote, contact our team.