A 26-inch mechanical closet, a −30 °C winter, and the only configuration that held up
The project came to us at the beginning of spring, from a residential property in the Bassin area of Chambly: an end-of-life central electric furnace, a duct system in good condition, and a mechanical closet so narrow that a technician could not stand facing it. The owner wanted two things: to retain the safety of full electric heating during extreme weather and stop paying to heat at 100% with electric resistance from November to April. We installed a GREE UNIX R32 central system—an indoor air handler cabinet paired with an electric heat kit and an outdoor inverter condenser. Here is the full project breakdown, including what did not work the first time.
The starting point: what we found on site
The preliminary inspection revealed a situation common in homes built on the South Shore between the late 1990s and mid-2000s:
- A vertical upflow electric furnace, powered by two dedicated circuits, with no modulation. On-off heating.
- A rectangular galvanized sheet-metal supply plenum in very good condition, extended by a 30 cm round duct identified as “30G.”
- A duct system cleaned a few years earlier: the access panel still bore the cleaning contractor’s sticker, dated August 2019. A good sign, but one we still verified with a camera.
- A Honeywell bypass humidifier mounted on the plenum, with its copper water supply line, drain, and black bypass duct.
- No central air conditioning. Two window air conditioners in summer, and a winter electricity bill the owner described as “the most predictable and unpleasant budget line of the year.”
The physical constraint was the real issue. The mechanical closet, set against a partition wall and closed by a standard interior door, provided 26 inches of usable width. Any solution that required demolishing a partition would have sent the budget soaring for plastering, painting, and flooring.
Why the UNIX R32 air handler stood out
The GREE UNIX R32 is a central heat pump system designed for the Canadian climate. Its distinguishing feature, in a replacement project for an electric furnace, is that the indoor air-handler cabinet accepts an integrated electric heating kit. The result: a single appliance in the closet that performs both roles. The heat pump handles the vast majority of the season's heating hours, and the electric elements take over only when demand exceeds the available capacity.
We selected the 36,000 configuration:
- Indoor unit: GUD36AH2/G-D(U) — 540 mm wide (21-17/64 in.), 1,224 mm high, 540 mm deep, 74 kg net.
- Outdoor unit: GUD36W2/NhE-D(U) — 990 × 960 × 370 mm, 85 kg, 61 dB(A).
- Nominal cooling capacity: 34,000 BTU/h, modulating from 18,000 to 37,000 BTU/h.
- Nominal heating capacity: 34,000 BTU/h, modulating from 18,000 to 38,000 BTU/h.
- SEER 2 of 18.0, EER 2 of 12.0, HSPF 2 of 10.0, COP of 3.20 at 8 °C.
- Nominal airflow of 1,000 CFM at an external static pressure of 125 Pa (0.5 in. w.c.).
- Heating range down to −30 °C, while maintaining 100% heating capacity at −20 °C.
- Refrigerant R32, 2.9 kg charge, two-stage, two-cylinder compressor, and DC Inverter technology.
The cabinet's 540 mm width left us with less than two inches of actual clearance on each side in the closet. It's tight, but workable—and that's exactly why we measure three times before ordering.
The electric heating kit: the insurance policy, not the main engine
The cabinet was equipped with a 15 kW electric heating kit (approximately 51,200 BTU/h), distributed across three breakers integrated into the unit's panel, visible in the upper-left corner. This point deserves an explanation because it is often misunderstood.
Without the kit, the indoor unit's minimum circuit ampacity (MCA) is 5.3 A, with a maximum protection of 15 A. With the 15 kW kit, everything changes: it requires a properly sized dedicated power supply and an inspection of the main electrical panel. For this client, the 200 A panel had the necessary space, but we had to reroute the conductors from the basement. This is the step that low bids systematically fail to include in their pricing.
In practice, with a heat pump that delivers its full capacity down to −20 °C, the electric kit operates rarely: during morning recovery after a temperature setback, during defrost cycles, and on the few winter nights when Chambly drops below −22 °C. The rest of the time, it sits idle.
R32 and the A2L label: what changes in a closed closet
The R32 is a low-global-warming-potential refrigerant classified as A2L, meaning it is mildly flammable. This classification imposes rules that we apply systematically and that the general public often overlooks:
- A minimum room volume based on the refrigerant charge. The label affixed to the cabinet provides the table: for a 2.9 kg charge, a minimum floor area is required for the installation or storage room. We validate this calculation before even proposing a model.
- A factory-integrated refrigerant leak detector on all GREE Canada cabinets. It shuts down the system and activates ventilation if a leak is detected.
- No ignition sources in the air circuit. This rules out certain auxiliary devices in the duct.
- Dedicated tools: gauges, a vacuum pump and A2L-compatible detectors, along with compliant recovery of the old refrigerant.
In a closed 26-inch closet adjoining a living area, these checks are not an administrative formality. They determine whether the installation is legal.
The worksite process, step by step
Day 1 — dismantling, refrigerant line, and outdoor base
Removal of the existing electric furnace and recovery of the metal components. Cutting and adapting the plenum: the old unit had different dimensions, so we fabricated the sheet-metal transitions on site instead of using generic flexible fittings, to prevent air leaks and pressure losses.
Drilling through the exterior wall and routing the refrigerant line: 3/4-inch suction and 3/8-inch liquid lines, insulated along their entire length, including the indoor section visible in the closet. We see the suction line left bare indoors far too often—it is a guaranteed source of condensation and water damage to the basement ceiling.
Installation of the condenser pad and vibration-damping supports, with sufficient clearance for defrosting and meltwater drainage. In Chambly, raising the unit above the snow level is not a theoretical concern: we mount outdoor units on supports to prevent accumulated snow from blocking the heat exchanger.
Day 2 — evacuation, connections, and commissioning
Evacuation of the circuit to a stabilized deep vacuum, with a hold test before opening the service valves. The UNIX R32 series has external service valves and electrical terminals, which genuinely simplifies this step in the field.
Connecting the condensate drain in PVC with a trap and continuous slope, plus a secondary overflow line. Connecting the 24 V thermostat—the system is compatible with most wired 24 V thermostats on the market and also supports RS485 communication.
Reconnecting the existing Honeywell humidifier: bypass duct, copper water supply, drain, and control. We replaced the evaporative pad and checked the flow before closing everything up.
The issue that required correction: static pressure
At initial commissioning, the measured total external static pressure exceeded the nominal value of 0.5 in. w.c. specified in the catalog. The culprit was not the new system but the air return: a single central return, undersized for 1,000 CFM, inherited from an electric furnace that tolerated restriction better because it was not designed to modulate.
We returned to add a return section and replace the grille with a model offering a larger free area. Static pressure dropped back into the specified range, the noise level decreased noticeably, and the compressor’s low modulation range became genuinely usable. An inverter system installed on an overly restrictive duct network will never deliver its advertised efficiency—this is the number-one cause of disappointment with central heat pumps.
The mistakes we correct most often in Chambly, Carignan, and Saint-Basile-le-Grand
Oversizing “to be safe”
The temptation is strong to choose the 48,000 or 60,000 BTU/h model. An oversized system short-cycles, dehumidifies poorly in summer, and wears out its compressor. Load calculation according to the CSA F280 method remains the only sound basis. For this customer, the home’s cooling requirement came in well below 36,000 BTU/h: the 36,000 model, with its modulation range of 18,000 to 37,000 BTU/h, was an exact fit.
Setting the balance point at random
If the thermostat is configured to call for auxiliary heat as soon as the temperature reaches −5 °C, the homeowner pays the bill for a conventional electric furnace while having invested in a heat pump. We set the balance point based on the actual load calculation and the unit’s capacity curve, then revalidate it after the first cold snap.
Reusing ducts without evaluating them
Reusing an existing duct network is often the right economic decision—provided it is properly measured. Joint airtightness, insulation of sections in unheated spaces, return sizing, and outlet balancing. Without this step, the initial savings are paid for through fifteen years of discomfort.
Ignoring A2L requirements
The transition to R32 changes the installation, storage, and servicing requirements. A contractor who treats an A2L cabinet like an older R410A appliance exposes you to a potential insurance coverage denial and a compliance issue.
What you need to know about rebates
Hydro-Québec’s LogisVert heat pump component is intended for replacing an existing heating system in an already constructed residential building connected to the grid. Conditions to verify before purchase, not afterward, include the exact model being on the list of eligible equipment, ENERGY STAR certification for installations completed after November 26, 2025, and the contractor being enrolled in the program in addition to holding an RBQ licence. The Rénoclimat program may be added, with an energy assessment before and after the work. The Chauffez vert program, meanwhile, targets the replacement of an oil- or propane-fired system: it does not apply to an already fully electric home like this one.
The amounts and criteria for these programs change periodically. At AirGreen, we verify eligibility on file before finalizing a quote rather than promising a figure that never materializes.
The result, four months later
The system went into service in the spring and operated in cooling mode throughout the summer. The owner reported two specific observations: a much more stable temperature upstairs, a direct result of continuous modulation rather than on-off cycles, and an appliance quiet enough that he forgot it was there behind the closet door—the cabinet is rated at 51 dB(A). The real validation will come in January, and we have scheduled a follow-up visit to adjust the settings after the first sustained cold spell.
AirGreen on the South Shore
We carry out HVAC installation and HVAC maintenance projects in Chambly, Carignan, Saint-Basile-le-Grand, Beloeil, Saint-Bruno, Longueuil, as well as in Montréal, Laval, and on the North Shore. Electric furnace replacements, central heat pumps, wall-mounted air conditioners, multi-zone systems: every project begins with a load calculation and an assessment of the duct network, never with a preselected model.
For a central system replacement project in Chambly or elsewhere in Montérégie, contact us for an on-site assessment.