Raised on supports, vacuum-pumped, weighed to the gram: the anatomy of an outdoor commissioning in Montérégie
In Saint-Théodore-d'Acton, houses are not built right next to one another. You might think this makes installing a central heat pump easier. The opposite is true. In rural areas, the outdoor unit must withstand blowing snow sweeping across the fields, snow sliding off the roof, defrost water freezing in place, and sometimes three feet of accumulation on the ground between snowblower passes. The cabinet is the same as in Montreal. The setting is not.
This project involved a complete central system: a 4-ton GREE FLEXX R32, with the GUD60W2/NhE-D(U) outdoor unit paired with the GUD48AH2/G-D(U) air handler. The FLEXX R32 series is distributed in Quebec by Dettson, a manufacturer based in Sherbrooke, which simplifies access to parts and technical support in the region.
This jobsite photo was taken at the most critical moment of the day: gauges connected, vacuum pump running, and yellow and blue hoses connected to the service valves. This is where the system's service life is determined, much more than by the choice of brand.
The selected pairing and why this capacity
The installed system specifications, based on the manufacturer's data:
- Outdoor unit: GUD60W2/NhE-D(U) — two fans, 2 × 1/6 HP motors
- Air handler: GUD48AH2/G-D(U)
- Rated capacity: 48,000 BTU for both cooling and heating
- Cooling modulation: 34,000 to 50,000 BTU — Heating: 34,000 to 52,000 BTU
- SEER2: 19 — the best seasonal efficiency in the FLEXX lineup
- HSPF2: 10 — EER2: 12 — COP: 3.4
- AHRI number: 217120761, ENERGY STAR certified
- R32 refrigerant, factory charge of 4.6 lb (162.3 oz)
- Guaranteed heating down to -30 °C, cooling from -15 °C to 54 °C
- 208–230 V power supply: outdoor MCA 39.9 A / MOCP 45 A, indoor MCA 7.1 A / MOCP 15 A
- Outdoor cabinet: 35 1/2 x 49 3/5 x 13 1/3 in., 241.4 lb (109.5 kg)
- Factory-installed Wi-Fi, A2L leak detection sensor included
The choice of 4 tons did not come from a rule of thumb based on square footage. The house has a large ground floor, a partially finished upper floor, and a heated basement, with the typical solar gains of an unobstructed rural setting. The load calculation produced a peak demand that fit comfortably within the modulation range of the GUD48AH2/G-D(U).
This range — 34,000 to 50,000 BTU — matters most. A unit that never drops below 34,000 BTU in a house requiring only 20,000 BTU in March would operate in short cycles. Here, the actual load overlaps the modulation range for most of the season, resulting in long cycles, proper dehumidification in July, and a stable temperature from room to room.
The two-fan cabinet: how it changes placement
The 4- and 5-ton outdoor unit is a slim vertical cabinet — only 13 1/3 in. deep — with two stacked fans and a front discharge. This format fits along a wall where a conventional square unit would not. It does, however, require precise planning:
- The rear clearance must remain unobstructed. The coil draws air in from the rear and sides. A cabinet placed flush against a concrete block wall draws in its own discharged air, causing heating capacity to drop exactly when it is needed.
- The front discharge must not point toward a hedge, shed, or solid fence. The discharged air must be able to move away without returning.
- The two fans work together. A partial obstruction at the top or bottom unbalances airflow across the coil and distorts pressure readings during commissioning.
On this job, the unit is positioned against the foundation wall with the required clearance behind the coil and a clear discharge path toward the yard.
The raised stand: the most cost-effective decision of the day
The unit does not rest on a slab at ground level. It is mounted on a galvanized steel stand with adjustable feet, placing it well above ground level. Three reasons, all verifiable the following winter:
- Snow accumulation. In Saint-Théodore-d'Acton, snow on the ground does not melt between December and March. A unit installed too low eventually becomes buried, its battery clogged, and its defrosting ineffective.
- Defrost water. In heating mode, the heat pump reverses its cycle several times a day to defrost its coil. This water must leave the base pan and drain away. If it accumulates beneath the unit, it freezes, rises, and eventually traps the lower fan in a block of ice.
- Maintenance. A raised unit can be cleaned, inspected, and repaired standing up, not on your knees in the mud.
We systematically add a bed of clean stone beneath the stand so defrost water percolates away instead of stagnating. This small detail distinguishes an installation that lasts ten winters from one that requires a visit every February.
Evacuation: the step the customer never sees and that determines everything
In the photo, the vacuum pump is running at the unit's base, connected to the gauges by the yellow hose. This is the step most often neglected in the industry, and the only one a homeowner absolutely cannot verify afterward.
Here is what we do, in order:
- Dry nitrogen pressure test on the complete refrigerant line before any evacuation, with timed pressure holding and readings. Find a leak with nitrogen, not refrigerant.
- Nitrogen sweeping to drive residual moisture out of new connections.
- Deep evacuation with a micron gauge connected at the end opposite the pump, never directly to the pump.
- Decay test: the pump is isolated and the reading must remain stable. A rapid rise indicates moisture or a leak. A slow rise that stabilizes indicates residual moisture.
- Opening the service valves only once the vacuum has been validated and documented.
With the R32, this rigor is not optional. Residual moisture in an R32 circuit reacts with POE oil and forms acids that attack the compressor windings. The system works perfectly for two years, then dies without warning. No one connects it to the fifteen minutes saved on installation day.
Refrigerant charge: weigh it, record it, label it
The GUD60W2/NhE-D(U) leaves the factory with 4.6 lb of R32, a charge intended for a line length of 24.6 ft (7.5 m). Beyond that, add 0.22 oz per linear foot (20 g/m).
The manufacturer's limits define the scope of the work:
- Liquid line: 3/8 in. — Gas line: 3/4 in.
- Maximum length between units: 98.4 ft (30 m)
- Maximum elevation difference: 49.2 ft (15 m)
We measure the actual length, calculate the required addition, weigh it on an electronic scale, and record the value on a label affixed inside the electrical compartment. A system charged “by ear” or “by pressures” on an inverter-compressor unit is a system whose efficiency drift can never be diagnosed, because there is no baseline reference.
The flare fittings are tightened to the specified torque with a torque wrench and then checked with an electronic detector. The R32 belongs to the class A2L, mildly flammable: the orange labels visible on the unit's lower panel are not decorative. A slow leak at a loose fitting is not merely a loss of efficiency.
Electrical connection and disconnect
With an MCA of 39.9 A and an MOCP of 45 A, the outdoor unit is not something you plug into an existing circuit and hope for the best. The dedicated circuit, conductor size, nearby disconnect, and routing of the low-voltage interconnection cable are checked even before the equipment is ordered.
The indoor unit, for its part, requires only 7.1 A MCA with an MOCP of 15 A. The difference often surprises homeowners: it is the outdoor compressor that consumes power, not the indoor fan.
Noise, neighbors, and placement in the countryside
The cabinet is rated at up to 63 dB(A) sound pressure at high speed. In practice, an inverter compressor spends most of its life at reduced speed, and therefore well below that level. But placement still matters:
- Avoid placing the unit beneath a bedroom window, even in the countryside.
- Avoid inside corners between two walls, which reflect sound instead of allowing it to disperse.
- Install vibration-isolating pads between the cabinet and its support, especially when the support is anchored to a structure.
A concrete block wall like the one at this job site reflects sound. The clearance left behind the unit therefore serves two purposes at once: airflow and acoustics.
Certified matching: why the AHRI number matters more than tonnage
A central heat pump is not a single unit; it is a pairing. The advertised performance—here 19 TRÉS2—exists only for the exact combination GUD60W2/NhE-D(U) + GUD48AH2/G-D(U), registered under AHRI number 217120761.
Replacing the indoor unit with a model of a different capacity, or reusing an existing coil because it “looks like the right size,” destroys three things at once: actual performance, ENERGY STAR certification, and eligibility for financial assistance programs. We offer only certified pairings and provide the AHRI number for the file.
Grants: what to verify before purchasing
A central ENERGY STAR-certified system with a valid AHRI number qualifies for Quebec heat pump installation assistance programs. Hydro-Québec's LogisVert program generally determines the assistance based on the unit's certified capacity at -8 °C, which explains why two systems with the same tonnage may not qualify for the same amount. Rénoclimat may be added when other energy-efficiency work accompanies the installation, while Chauffez vert targets the replacement of an oil- or propane-fired system—a common case in the Acton RCM.
Two conditions cause many applications to fail:
- The contractor must be enrolled in the program and hold a valid RBQ licence. Enrollment is not automatic.
- The exact installed pairing must appear on the list of eligible equipment, and the AHRI number must match what is actually installed.
Amounts and rules change from year to year. At AirGreen, we verify eligibility before the order, not after the invoice.
The mistakes that recur most often in an outdoor installation
- Install the unit too low. The most common mistake in Quebec, and the costliest in terms of winter service calls.
- Skip the evacuation procedure. Invisible on the same day, but potentially fatal in the medium term for an R32 circuit.
- Do not document the added charge. Any future diagnosis then starts blindly.
- Push the cabinet against the wall. Air recirculation comes at the cost of heating capacity at -20 °C.
- Insulate only the suction line. In heating mode, both lines are active; the insulation must be continuous, sealed where it passes through walls, and protected from ultraviolet radiation.
- Don't forget to seal the wall penetration. An improperly sealed refrigerant-line opening lets in cold air, moisture, and sometimes small animals.
What Saint-Théodore-d'Acton reminds us about central heat pumps in rural areas
The equipment is available everywhere. What varies from one job to another is site preparation and the rigor of commissioning. A 4-ton FLEXX R32 mounted on a solid stand, at the proper height, with a deep vacuum verified to the micron and a weighed and documented charge, will provide ten or fifteen years of high-efficiency heating. The same machine installed directly on the ground, evacuated for fifteen minutes, and charged by estimate will deliver three mediocre winters and a compressor bill.
That is the only real difference between two quotes that look similar on paper.
Our service area, from Acton to downtown
At AirGreen, we design, install, and maintain central heat pumps, ductless heat pumps, air conditioners, VRF systems, and air exchangers in Montreal, Laval, Longueuil, on the North Shore, on the South Shore, and in the MRCs of Montérégie, including Saint-Théodore-d'Acton, Acton Vale, Roxton Falls, Upton, and Saint-Hyacinthe.
Our teams work on rural homes with existing ductwork networks as well as on Plateau triplexes and apartment buildings on the North Shore. The constraints vary, but the method remains the same: a load calculation before the quote, an AHRI-certified matched system, documented commissioning, and a report provided to the customer with the recorded values.
Get a serious assessment
If you are considering a central heat pump to replace an aging forced-air system or to add air conditioning to an existing ductwork network, ask anyone providing a quote for three things: the load calculation, the AHRI number for the proposed matched system, and the commissioning method.
Contact AirGreen for a home assessment, a detailed quote on a GREE FLEXX R32 system, and full validation of your eligibility for rebates. We measure before making recommendations, document what we install, and respond quickly when you call back.