Installation of a GREE UNIX R32 central system with an integrated electric auxiliary furnace in McMasterville, in the La Vallée-du-Richelieu RCM

A basement storage room, a label that almost nobody reads, and 8.6 m² that determined the entire installation

McMasterville is one of the smallest municipalities in Montérégie by area, and one of the few to have been founded by a single employer: the village was established in 1917 to house workers of Canadian Explosives Limited, along the Richelieu River, opposite Mont-Saint-Hilaire and Otterburn Park. A century later, the residential landscape combines the original workers’ homes, postwar bungalows, and split-level houses from the 1960s through the 1980s. What most of them have in common is all-electric heating, with baseboards and an electric furnace installed in the basement. The basement itself was never designed as a mechanical room. It is the family’s storage space. Boxes pile up, metal shelves are added, and the heating equipment eventually ends up surrounded by notebooks, spare light bulbs, and sewing machines.

That is exactly the situation we found on this job. And it is also why this installation was not decided by tonnage, price, or brand: it was decided by a number printed on a label affixed at eye level to the GREE UNIX R32 air handler cabinet. That number is 8.6 m². The minimum floor area required for this unit’s refrigerant charge. Below, we explain why it governed every decision made that day.

Why the customer called it an “electric furnace,” and why that is no longer quite the right term

The customer called us to “replace the electric furnace.” That is the language used in the field, and it is perfectly legitimate: what had occupied this corner of the basement for decades really was an electric furnace—that is, a cabinet filled with resistance heating elements and a fan that pushes warm air through the ducts. Efficiency: one kilowatt consumed, one kilowatt delivered. Nothing more, ever.

What we installed does the same job, takes up the same space, connects to the same ducts, but operates according to a different logic. The UNIX R32 air handler cabinet is first and foremost the indoor unit of a central heat pump. It contains the coil, fan, control board, and leak detector. The electric element, meanwhile, is optional and provides backup heat. It operates only in three situations:

• when the heating demand exceeds what the heat pump can provide in very cold weather;
• during defrost cycles, to temper the supply air and prevent cold drafts in the house;
• in emergency mode, if the heat pump section is out of service.

For the rest of the winter, the compressor provides the heat. That is why we refer to it as an integrated electric backup furnace rather than simply an electric furnace: the distinction is worth several hundred dollars per season on a Hydro-Québec bill, and it completely changes the electrical panel load calculation.

What we installed in McMasterville

The configuration selected 36 000 (36/36) for the UNIX R32 series, with a nominal capacity of three tons.

The system figures

• Indoor unit (air handler cabinet): GUD36AH2/G-D(U)
• Outdoor unit (condenser): GUD36W2/NhE-D(U)
• AHRI reference code : 217120760
• Cooling capacity: 34,000 BTU/h, modulating from 18,000 to 37,000 BTU/h
• Heating capacity: 34,000 BTU/h, modulating from 18,000 to 38,000 BTU/h
• SEER 2 : 18,0 — EER 2 : 12,0 — HSPF 2 : 10,0 — COP at 8°C : 3,20
• Airflow: 1,700 m³/h, or 1,000 CFM, at a nominal external static pressure of 125 Pa (0.5 in. w.g.)
• Indoor sound level: 51 dB(A) — outdoor: 61 dB(A)
• Cabinet dimensions: 540 mm wide × 1,224 mm high × 540 mm deep (21-17/64 × 48-3/16 × 21-17/64 in)
• Net cabinet weight: 74 kg (163.1 lb) — condenser: 85 kg (187.4 lb)
• Refrigerant : R32, 2.9 kg charge (102.3 oz)
• Lines: suction ø 3/4 in, liquid ø 3/8 in — standard length 7.5 m, maximum 30 m, maximum elevation difference 15 m
• Power supply: 208–230 V / 60 Hz / 1 phase — MCA 5.3 A and MOP 15 A indoors (without backup heat), MCA 27.7 A and MOP 30 A outdoors

What these figures mean in a Vallée-du-Richelieu home

Two figures matter more than SEER 2 in our climate. First, the heating operating range extends down to -30 °C, with the Ultra Heat function maintaining 100% heating capacity at -20 °C. In an area where January nights near the river regularly flirt with -25 °C, this means the electric element remains a supplemental heat source rather than the disguised primary heating system.

The second: modulation from 18,000 to 38,000 BTU/h. A two-stage, two-cylinder compressor controlled by a DC Inverter spends most of the winter at the lower end of its range. That is where comfort is achieved—stable temperatures, no short cycling, no blasts of airflow—and it is also why we refused to oversize the system. A four-ton unit in this house would have spent the fall and spring starting and stopping, with poor dehumidification in summer.

We also point out, in all honesty, that the COP of 3.20 for this configuration is the lowest in the UNIX R32 range: the two-ton model reaches 3.60, and the four- and five-ton models reach 3.40. The three-ton model was not chosen for its specifications, but because the home's load calculation required it. That is the right order of priorities.

The minimum-area label: the A2L calculation done properly

Here is the heart of this project, and the subject that is rarely discussed in Quebec even though it now affects every new central installation.

R32 is not R410A, and the rule has changed

The R32 is gradually replacing R410A for a good reason: its global warming potential is approximately 675, compared with nearly 2,088 for R410A. That is a reduction of about two-thirds, with equal or better performance. In return, R32 is classified as A2L, meaning it is mildly flammable and has low toxicity. It does not ignite easily, but it is no longer considered completely nonflammable, as R410A was.

Two practical consequences in a basement:

1. R32 is denser than air. In the event of a leak, it does not rise: it descends and accumulates at the lowest point. A basement is, by definition, the lowest point in the house.
2. The permitted refrigerant charge depends directly on the room's volume and floor area where the appliance is installed, as well as the appliance's installation height.

The label affixed to the unit

On the UNIX R32 cabinet, GREE prints a “NOTICE” that gives the minimum floor area of the room based on the refrigerant charge, for a low-height installation—the case for all floor-standing vertical cabinets:

Our unit contains 2.9 kg. It therefore required a room of at least 8.6 m², or approximately 93 sq. ft. A 9 ft × 11 ft basement storage room passes the test. A small enclosed 4 ft × 6 ft mechanical closet does not, and no workaround will make it pass.

This detail also explains why, when replacing a unit, the refrigerant charge becomes a selection criterion rather than merely a service specification. In the UNIX R32 range, the two- and three-ton models share the same 2.9 kg charge, while the four- and five-ton models increase to 4.6 kg. Moving from a three-ton to a four-ton unit does not merely raise the price: it moves the minimum room-area requirement up by a full tier. In a tight space, the higher capacity can sometimes become simply impossible.

The leak detector must remain powered twelve months a year

All GREE Canada indoor units are equipped with a refrigerant leak detection sensor. The safety label is explicit: the unit must remain powered at all times, except during servicing. This is not a comfort recommendation; it is a safety requirement, because the sensor and mitigation logic—which forces the fan to circulate the air in the room and ducts when a leak is detected—exist only when the control board is powered.

We draw three instructions from this and leave them in writing with every customer:

• Never turn off the cabinet's circuit breaker for the summer, even if you are not using the air conditioning.
• Never power the unit through a wall switch shared with a basement light. We have already found some inherited from old furnaces. They must be removed.
• The sensor has a precise position inside the cabinet, indicated by a warning label on the panel. It must not be moved or bypassed during servicing.

What may no longer enter the ducts of an R32 system

The second warning printed on the cabinet is even less well known, and it is the one we most often see violated out of ignorance, despite the best intentions.

The rule governing ignition sources in the duct system

The label is clear: auxiliary devices that could constitute an ignition source must not be installed in the ducts, unless they are specifically approved for use with this appliance. In practical terms, this includes:

• germicidal UV lamps installed in the plenum;
• electronic air cleaners with charged cells that are not approved for an A2L application;
• ozone generators or cold-plasma devices sold as accessories;
• electric heating coils that are not those specified by the manufacturer for this cabinet.

The logic is simple: if a leak occurs inside the cabinet, refrigerant circulates through the ducts. You do not place an electrical arc or a high-voltage lamp along that path. On renovations, this raises a real question because many homes on the South Shore had an electronic air cleaner installed in the 2000s, and the instinct is to keep it. On this job, every accessory present in the system was evaluated before being put back into service, and the selected electric auxiliary heat is the one approved by the manufacturer for this cabinet.

The 125 Pa budget that determines everything else

The other figure to watch on a retrofit is the nominal external static pressure of 125 Pa (0.5 in. w.c.). This is the total budget the blower has to push 1,000 CFM through everything you put in front of it: the supply plenum, the original ductwork, flexible connections, grilles, the return, and especially the filter.

In a house built around an electric furnace, the existing system was sized for supply air at 50 °C and above. A heat pump delivers air between 32 and 43 °C: more airflow is needed to deliver the same perceived heat. We therefore measured static pressure before choosing the filter, rather than the other way around. A 1-inch MERV 13 filter on an already marginal system is the fastest way to turn an 18 SEER 2 unit into an ordinary one and lower the heat pump’s balance point by several degrees.

The existing ducts were retained, which is one of this series' selling points: GREE explicitly provides for retrofit installation, with external service valves and electrical terminals, simplifying field connections. But retaining a duct system is not the same as ignoring it. Every reused connection was sealed, and the sections of flexible duct were stretched and supported, because a sagging flex duct costs more in static pressure than ten feet of rigid duct.

Living beside the machine: clearances, shelving, and cardboard

This is where the installation differs from a simple equipment replacement.

The twelve-month test

When we leave a job site, the unit is clear. The real question is what the room will look like a year from now. In a storage room, the default answer is: boxes stacked against the cabinet, a shelf moved a few inches closer, and an inaccessible service panel.

We therefore treat clearance as part of the installation, not as a courtesy:

• the service panel side and the side with the detection sensor must remain clear, and we explain this to the customer on site with the unit open;
• the filter must be accessible without moving anything, otherwise the filter will never be changed;
• nothing combustible should lean against the cabinet, including cardboard boxes, bags, and clothing;
• the return air must not be obstructed by any stored objects, or the airflow will be choked and performance will drop without triggering any alarm.

Condensate above the boxes

An air-handling cabinet produces water in cooling mode. In a room where the floor is occupied by cardboard boxes, a condensate overflow is not noticed on the floor—it is noticed when the contents of the boxes are ruined. Our installation always includes:

• a properly sized condensate trap for a negative-pressure coil, with accessible cleaning plugs;
• a continuous slope toward the discharge point, checked with a level rather than by eye;
• choosing the appropriate drainage port according to the orientation of the multiposition cabinet, following the installation manual;
• a high-level safety switch that shuts off the cooling call before the drain pan overflows.

The mistakes we see most often with this type of replacement

1. Installing an R32 appliance in a room that is too small without ever reading the minimum-area table affixed to the unit.
2. Turning off the breaker during the off-season, which leaves the leak-detection sensor out of service for months.
3. Keeping a UV lamp or electronic air cleaner in the plenum without verifying its certification for an A2L application.
4. Reusing the ductwork without measuring static pressure, then blaming the heat pump for insufficient airflow.
5. Oversizing because “it can't hurt,” even though an oversized modulating unit loses exactly what makes it efficient.
6. Sizing the backup heating element without recalculating the electrical panel load. The manufacturer's note is explicit: the MCA and MOP values must be recalculated whenever an electrical element is added. In an all-electric home in McMasterville, with baseboard heaters, a water heater, and an EV charger, this calculation is not a formality.
7. Neglecting condensate protection in a room that also serves as storage.

Rebates and Eligibility

A central system in this category is generally covered by the energy-efficiency programs offered in Quebec, including those administered by Hydro-Québec for converting from fully electric heating to a high-efficiency heat pump. Eligibility is always verified the same way: using the AHRI reference code for the exact installed combination—here, 217120760—not by the brand or model alone. An indoor unit paired with a condenser other than the certified one has a different code, different ratings, and sometimes no eligibility at all. At AirGreen, we provide this code on the quotation and assist our clients with preparing their applications. We always encourage you to verify the current amounts and conditions before signing, since they are reviewed periodically.

Two Documentation Inaccuracies We Are Publishing Openly

We read technical data sheets line by line, and this one contains two points on which a rushed installer could make a mistake.

First, the ratings displayed prominently on the first page—SEER 2 of 18.0, EER 2 of 12.5, HSPF 2 of 10.0, and COP of 3.60—do not correspond to a single unit in the product line. The EER 2 of 12.5 and COP of 3.60 are those of the two-ton model. Our three-ton model shows 12.0 and 3.20. You have to read the table, not the cover page.

Next, the version of this product line distributed under another commercial label lists the refrigerant charge in pounds even though it is actually in kilograms. The check is immediate: 2.9 kg does correspond to the stated 102.3 oz, or approximately 6.4 lb. A technician who weighed 2.9 lb into the cylinder would install less than half the required charge. We prefer to point out this kind of detail rather than let it circulate.

Our work in the Richelieu Valley and on the South Shore

McMasterville joins a series of projects carried out in the Montérégie region, several of them along the Richelieu River: Saint-Mathias-sur-Richelieu, Saint-Roch-de-Richelieu, Saint-Sébastien, as well as Saint-Liboire, Sainte-Madeleine, and La Présentation near Saint-Hyacinthe. Every home presents a different challenge— a 42-inch crawl space, an attached garage ceiling, a raised slab that cannot be drilled, or a cluttered storage room—and that is precisely what makes a HVAC installation interesting to do properly.

At AirGreen, we design, install, and maintain central heat pumps, wall-mounted air conditioners, multizone systems, and commercial solutions in Montreal, Laval, Longueuil, on the North Shore, and on the South Shore. We hold RBQ licence 5645-9605-01, including the ventilation, refrigeration, and electrical subcategories, and support our clients from needs assessment through the subsidy application.

If your basement still houses an original electric furnace, the first step is not choosing a model: it is measuring the room, the ductwork, and the electrical panel. We come to your home to do this and provide you with the figures, including those that may not work in our favor.