Installation of a GREE FLEXX R32 electric furnace in Mont-Saint-Grégoire

Building a mechanical room where there was none: the electrical-conversion project at the foot of Mount Saint-Grégoire

There was no mechanical room. That was the first thing our estimator noted upon arriving in this fully finished basement of Mont-Saint-Grégoire, with wall-to-wall carpeting, bookshelves, framed pictures on the walls, and a furnished workspace. The old electric furnace occupied an open recess in one corner of the room, with no door or partition, and a supply plenum passing through the finished ceiling.

Replacing the equipment was the simple part. The real mandate was elsewhere: deliver a modern central system in an occupied room, without turning the basement into a demolition site and without allowing the new equipment to become a permanent source of noise three metres from a reading chair.

We therefore treated this as two projects carried out in parallel: a HVAC installation and carpentry work. Here is the complete process, including the decisions that are not visible in a finished photo.

The starting point: equipment that was no longer in the right place

The owner, a retired couple who had lived in the area for about fifteen years, contacted us for two specific reasons:

• An electricity bill that rose every winter even though consumption itself was not increasing.
• No central air conditioning in a house where the upper floor becomes barely habitable in July.

The inspection revealed a third issue, the one that would dictate everything else: the existing ductwork was usable, but the equipment location no longer met the recommended service clearances, and the open recess allowed fan noise to spread freely into a room that had become a living space.

What we measured before proposing anything

• Room-by-room load calculation, taking into account the actual insulation, orientation, and glazed areas.
• Dimensions of the existing recess and the available clearance at the front for access to the service panels.
• Main return-air opening and the condition of the transitions.
• Remaining electrical panel capacity, including the amperage actually available for auxiliary components.
• Possible route for the refrigerant line to the side wall, where the outdoor unit was to be installed.

The load calculation produced an answer that surprised the client: 2 tons were sufficient. The old electric furnace delivered much more. That's normal—an electric furnace is sized for the absolute cold-weather peak and does not modulate, whereas an inverter-compressor central heat pump continuously adjusts its output and relies on supplemental heating elements only when outdoor temperatures require it.

The choice: GREE FLEXX R32, indoor unit GUD24AH2/G-D(U)

The GREE FLEXX R32, distributed in Quebec by Dettson, is a horizontal-airflow central system available from 2 to 5 tons. We selected the 2-ton format for this project.

The data behind the decision

The 12,000 to 30,000 BTU/h modulation range is the most useful specification for a homeowner to understand. It means the unit can run at less than half its rated capacity on an October day at 8 °C, instead of starting and stopping in bursts. Fewer short cycles, less noise, better heat distribution between floors, and more effective dehumidification in summer.

Three other elements are worth mentioning: the unit works with a conventional 24 VAC thermostat, includes factory-installed Wi-Fi, and comes with an A2L leak-detection sensor, mandatory with R32 refrigerant. The standard warranty is 10 years, extended to 12 years when the unit is registered with proof of installation.

Building the enclosure: the part of the job no one talks about

This is where this project differs from most replacements we carry out in Montréal, Laval, or on the North Shore, where the unit simply goes back into an existing mechanical room.

Step 1 — Protecting a finished room

Before touching the old unit, we installed a protective membrane over the carpet, a polyethylene containment curtain between the work area and the rest of the basement, and moved the lightweight furniture. Dismantling an electric furnace generates metal dust and duct insulation debris. In an unfinished room, you sweep it up. On a light-colored carpet, you don't get a second chance.

Step 2 — Wood framing and service clearances

We built a wood-stud frame enclosing a genuine enclosed mechanical room around the unit, while meeting two non-negotiable requirements:

• Sufficient front clearance to remove the access panels, take out the blower, and change the filter without disassembling anything.
• Side clearance for the electrical connection and access to the junction boxes.

A common mistake is to frame the unit as tightly as possible to reclaim a few inches of floor space. The technician who comes to service it three years from now would then have to work blind, or worse, cut into the wall. We would rather give up six inches during construction.

Step 3 — The most frequently overlooked code requirement: return air

An enclosed mechanical room must not serve as a return-air plenum. In other words, you do not simply install a grille in the wall and let the unit draw in the closet's ambient air.

We therefore connected the return air through a dedicated duct, with a sheet-metal transition and an accessible filter rack on the outside of the enclosure. The owner can change the filter without opening the mechanical room. This is a design requirement, not a luxury: an unducted return inside an enclosed room unbalances the room's pressure, draws in construction dust, and deprives the unit of the airflow it needs.

Step 4 — Acoustic treatment

The unit is located in a living space. Three measures reduced the perceived noise level:

• Raised base with vibration-isolation insulation beneath the cabinet, to prevent vibration transmission to the slab and carpet.
• Acoustic insulation in the framing cavities before the wall was closed.
• Section of insulated flexible duct on the supply outlet, acting as a break between the cabinet and the rigid sheet-metal ductwork.

This last point requires some technical clarification. The insulated flexible duct visible in the jobsite photo is not a shortcut: it is installed taut, without compression, over a short length and with a generous bend radius. A sagging or crushed flexible duct multiplies pressure loss and eliminates the unit's efficiency gains. This is one of the installation defects we correct most frequently when taking over another contractor's work.

Condensate drainage, with no floor drain

The basement had no accessible drain nearby. We assembled a PVC network comprising:

1. A P-trap appropriate for the blower type, installed at the outlet of the condensate pan.
2. Cleanout plugs allowing the line to be flushed annually.
3. A continuous slope toward the discharge point, checked with a level before final gluing.
4. A secondary drain pan beneath the unit, in a finished room where an undetected leak could ruin a carpet overnight.

The sections of PVC visible on the ground in the photo are part of the dry-fit assembly, completed before gluing. We systematically dry-fit the piping to verify the slope and clearances before applying the glue.

The outdoor unit and refrigerant line

The outdoor unit was installed on a raised base, elevated from the ground to prevent snow accumulation and allow defrost water to drain. Its MCA is 27.7 A and its MOCP is 30 A, which allowed for a dedicated circuit without upgrading the electrical panel.

The refrigerant piping uses the specified diameters, 3/8 in. for the liquid line and 3/4 in. for the gas line, insulated along its entire length, including the indoor sections. The FLEXX R32 accepts up to 98.4 ft (30 m) of piping length and 49.2 ft (15 m) of elevation difference, with a factory charge covering 24.6 ft (7.5 m). Our run stayed below this threshold, so no refrigerant was added.

The vacuum was pulled below 500 microns with a standing vacuum test, an essential procedure for an R32 system.

What to know before replacing an electric furnace

Four decisions that determine the outcome

1. Perform a load calculation, not a kilowatt conversion. Converting a 20 kW electric furnace into equivalent tonnage almost always leads to oversizing. An oversized unit costs more, short-cycles, and dehumidifies poorly.
2. Check the return-air system before choosing the equipment. An undersized return-air system, invisible with an electric furnace, becomes the limiting factor as soon as a central heat pump is installed.
3. Require a staging strategy for supplemental heat elements. If the electric elements activate alongside the compressor without a time delay or switchover point, the promised savings will never materialize. This is the most common source of dissatisfaction after installation.
4. Verify the AHRI number for the exact matched system. An indoor unit and an outdoor unit may operate together without being certified as a match. Without a corresponding AHRI number, no rebate is awarded.

Eligibility for rebate programs

In 2026, a conversion of this type may qualify for the LogisVert program from Hydro-Québec, whose incentive for central air-to-air systems is calculated in increments of 1,000 BTU/h, as well as the Rénoclimat program for the energy assessment component.

Conditions to verify before signing the contract:

• Existing residence in Québec served by Hydro-Québec.
• ENERGY STAR-certified equipment, as the FLEXX R32 is across the entire product line.
• Valid AHRI number corresponding exactly to the installed pairing.
• Installation by a contractor holding an RBQ licence and registered with the program.
• Submit the application within the prescribed period following the invoice date.

Please note: a home already heated with electricity is not eligible for the Chauffez vert program, which targets the replacement of oil- and propane-fired systems. Since amounts and terms are revised periodically, we verify each application’s eligibility when preparing the quote rather than after the work is completed.

Maintaining a unit installed in an enclosed space

• Filter: check every three months and replace based on actual dirt accumulation. Exterior access to the filter rack makes this possible without tools.
• Condensate pan and drain: annual flushing through the cleaning ports.
• A2L sensor: functional check at every visit.
• Outdoor coil: annual cleaning and snow clearance in winter.
• Pressures, overheating, and undercooling: annual inspection by a qualified technician.

Our work in Haut-Richelieu and Montérégie

Mont-Saint-Grégoire is the kind of area we know well: single-family homes on large lots, fully electric heating, finished basements, and unforgiving winter conditions at the foot of the Montérégie hills. We have completed comparable conversions there, as well as in Saint-Jean-sur-Richelieu, Marieville, Sainte-Angèle-de-Monnoir, Saint-Césaire, and Chambly.

At AirGreen, we design, install, and maintain HVAC systems in Montréal, Laval, Longueuil, the North Shore, the South Shore, and throughout Montérégie. Every electric furnace replacement begins with a visit, a load calculation, and an assessment of the existing ductwork — because a properly selected unit that is poorly integrated produces disappointing results, while a well-designed network built around a correctly sized unit produces a system the homeowner completely forgets about, which is exactly the point.