The figure written in pencil on a stud that sums up the entire project
On this Saint-Blaise-sur-Richelieu job, there is a pencil inscription on a wooden stud, right in front of the unit: 1531 CFM.
This is not an incidental job-site note. It is the airflow actually measured through the system once everything is connected, and it is the most important figure in the entire installation. It determines the cooling capacity, the safety of the electric furnace, the temperature of the air delivered to each room, the lifespan of the heating elements, and the customer's electricity bill.
At AirGreen, we measure this airflow on every central system we install, in Saint-Blaise-sur-Richelieu as well as in Montréal, Laval, Longueuil, on the North Shore and the South Shore. And we write it down on-site, where the next technician will read it.
The context: a home in Haut-Richelieu, a low basement, and a horizontally mounted unit
The house is located in the Richelieu corridor, between Saint-Jean-sur-Richelieu and the border. Like many homes in this area, it has limited clearance beneath the joists and no dedicated mechanical room. A 1.32 m-high vertical cabinet simply could not fit upright.
The GREE FLEXX R32 addresses this constraint through its design: it is designed for a horizontal (side) airflow. The unit is laid on its side, air enters through one side and exits through the other, and the entire system fits into the available space beneath the floor rather than requiring height that simply does not exist.
This is not an improvised setup. It is the installation method specified by the manufacturer, and that is precisely what makes this product line interesting for renovations in single-story homes and bungalows in Montérégie.
The installed equipment and its certified data
The selected configuration is a 5-ton GREE FLEXX R32:
- Indoor unit (air-handler cabinet): GUD60AH2/G-D(U)
- Outdoor unit: GUD60W2/NhE-D(U)
- AHRI number : 217120762
- Cooling capacity: 53,000 BTU/h nominal, modulating from 35,000 to 55,000 BTU/h
- Heating capacity: 54,000 BTU/h nominal, modulating from 35,000 to 60,000 BTU/h
- HSPF2: 10.5, the best seasonal heating value in the FLEXX lineup
- SEER2 : 18,5 — EER2 : 11,7 — COP : 3,4
- Nominal airflow: 1,500 CFM at an external static pressure of 125 Pa (0.5 in. w.c.)
- Refrigerant: R32, factory charge of 4.6 kg
- Heating range: -30 °C to 24 °C — Cooling range: -15 °C to 54 °C
- Power supply: 208–230 V, MCA of 7.7 A and MOCP of 15 A for the indoor cabinet alone
- Outdoor unit : MCA of 39.9 A and MOCP of 45 A
- Indoor unit weight: 90.5 kg
- ENERGY STAR certification, A2L leak-detection sensor included, factory-installed Wi-Fi, control via a conventional 24 VAC thermostat
The measured airflow of 1,531 CFM is therefore just above the nominal airflow of 1,500 CFM. In other words, this home’s ductwork does not restrict the appliance. That is the result we are looking for, and it is not guaranteed in advance.
The open control panel: what is actually inside the box
The photo shows the appliance with its electrical panel open, which the customer never sees. This box contains three distinct systems that must never be mixed.
The power section: the electric furnace’s circuit breakers
At the top of the panel, the black two-pole circuit breakers with their red conductors power the components of the electric heating kit integrated into the cabinet. This is where this home’s “electric furnace” is physically located: not in a separate appliance, but in a heating section inserted into the same cabinet as the blower and coil.
Each circuit breaker protects one heating stage. The fact that they are staged, rather than all powered at once, is what allows the control system to call for only the power needed when it is needed, rather than switching 15 kW onto the home's electrical system all at once.
The control section: the electronic board and the Class 2 circuit
At the bottom of the panel is the control board with its terminal blocks and Class 2 labeling. This is the 24 VAC circuit: the thermostat, the A2L leak-detection sensor, and the communication signals to the outdoor unit.
The brown cable running down along the panel is the thermostat wire. The distinction is fundamental: a Class 2 conductor cannot run in the same cable pathway as a power conductor without separation. An installer who groups them together for convenience creates interference on the control signal, and the symptom appears months later as erratic starts that no one can diagnose.
The power supply and cable entry
On the right, the flexible armored cable enters the unit through a dedicated connector, with its black, red, and green conductors. Three requirements apply to this detail, and they are systematically met on our job sites:
- An approved connector at every point where the cable penetrates the sheet metal—never a cable passed through a raw hole. The edge of cut sheet metal can shear through a jacket within a few years of vibration.
- A cable clamp to bear the mechanical load, so that no tension reaches the terminals.
- A drip loop before the entry point, so that condensation forming on the cable in a cold basement drips onto the floor rather than into the enclosure.
1,531 CFM: why this number governs everything else
This is where the difference lies between an installation that works and one that works well.
The electric heating kit requires a minimum airflow
Resistive elements placed in an airflow are cooled by that air. If the airflow drops, heat is no longer carried away quickly enough, the temperature rises inside the cabinet, and the thermal limiter trips. The customer calls in January because their house is cold, and the technician finds a unit locked out for safety.
A dirty filter, a damper closed by an occupant, and a return grille blocked by furniture: these are the three most common causes we encounter. The airflow measured during commissioning is the reference that makes it possible to determine, three years later, that the system is delivering only half as much as it did initially.
Temperature rise is calculated, not estimated
The relationship between electrical power, airflow, and temperature rise is simple and can be verified on site:
Temperature rise (°F) = (kW × 3 412) ÷ (1.08 × CFM)
For example, a 15 kW kit at this airflow of 1,531 CFM produces a temperature rise of about 31 °F, or approximately 17 °C between return air and supply air. This value must fall within the range shown on the unit's nameplate. A technician checks it with two thermometers, one in the return and one in the supply, in less than five minutes.
If the measured temperature rise exceeds the range, there is too much heating capacity or not enough airflow. If it is well below the range, a heating stage is probably not being powered.
In heat pump mode, the supply air is cooler, and that is normal
This is the comment we hear most often after a conversion. With an electric furnace alone, air came out of the grilles at around 45 to 50 °C. With the heat pump operating, it comes out at around 32 to 38 °C.
The explanation lies in the same equation: the heat pump delivers its heat continuously across a large volume of air rather than in bursts through a small one. The house is heated more evenly, with less variation between rooms, but a hand placed in front of a grille no longer feels a scorching blast. We systematically explain this to the customer before leaving the job site, because poorly explained comfort is perceived as a failure.
Static pressure: the other half of the equation
A flow rate of 1,531 CFM is meaningful only if it is achieved at a reasonable static pressure. The cabinet is designed to deliver its rated airflow at 125 Pa. A fan that reaches the correct airflow while working against 200 Pa consumes more energy, makes more noise, and wears out faster.
We therefore record both values together, never one without the other.
Horizontal installation: four points to watch
Laying a 90.5 kg appliance beneath joists requires precautions that are not necessary for vertical installation.
- The support. The unit rests on a wood frame sized for the load, supported by load-bearing members. A cabinet placed on two boards spanning floor joists transmits every blower vibration to the entire floor structure above.
- The level and slope of the condensate pan. In a horizontal position, the pan drains through only one end. A unit installed slightly out of level retains water inside, and that is how stains appear on the basement ceiling.
- The secondary safety pan. Whenever a unit is installed above a finished space, a secondary pan with a drain or safety switch is required. It is a modest expense compared with the cost of replacing a drywall ceiling.
- The orientation of the access panels. The electrical panel and the blower panel must remain accessible once the unit is in place. On this job, the control panel faces the passageway, allowing service without dismantling anything. It is a ten-second decision when installing the unit, and it determines the cost of every service call for fifteen years.
The complete electrical scope: what to check before ordering
A 5-ton central system with built-in electric heating represents a substantial load for a residential panel. The calculation must add three items:
- The air handler cabinet: MCA of 7.7 A, MOCP of 15 A.
- The electric heating kit, whose capacity is determined by the building load calculation and which has its own protection.
- The outdoor unit: MCA of 39.9 A, MOCP of 45 A.
In a house in Saint-Blaise-sur-Richelieu that is already heated electrically, the old furnace circuit can generally be reused for the kit. The circuit that must be added is for the outdoor unit, and that is where you need to check the available space in the panel before signing anything.
Mistakes to avoid
- Do not measure the airflow. Without this value, no one can confirm that the system is delivering its capacity, and no future diagnosis has a point of comparison.
- Install an oversized heating kit compared with the available airflow. The temperature rise falls outside the range, and limit switch trips begin.
- Install the unit horizontally without checking that it is level. The condensate pan will not forgive you.
- Route the thermostat wire together with the power conductors.
- Position the access panels toward a wall. The unit then becomes impossible to service properly.
- Omit the secondary pan above a finished space.
- Do not explain the supply-air temperature in heat pump mode to the customer. A perfectly installed system may be perceived as inadequate for lack of a two-minute explanation.
Eligibility for rebates
The GREE FLEXX R32 is ENERGY STAR certified, and each indoor-outdoor match has its own AHRI number. For the configuration installed here, it is 217120762.
This is the number that government programs and distributors require to validate eligibility for applicable rebates, not the product line's commercial name. Criteria and amounts vary by program and period; we verify the exact pair's eligibility before the contract is signed and provide the corresponding AHRI certificate with the invoice.
What this Saint-Blaise-sur-Richelieu project demonstrates
The quality of a HVAC installation is not visible on the unit's exterior. It can be seen in the control panel, in the separation of the circuits, in the level of the condensate pan, and in a figure written in pencil on a wood stud because someone took the time to measure it.
At AirGreen, we perform HVAC installation and HVAC maintenance for central systems in Saint-Blaise-sur-Richelieu, throughout the Haut-Richelieu RCM and Montérégie, as well as in Montreal, Laval, Longueuil, on the North Shore, and on the South Shore. Our technicians measure airflow and static pressure, check the temperature rise of the electric furnace, weigh the refrigerant charge, and provide written commissioning readings.
For an assessment of your home and a detailed quote for a GREE FLEXX R32 central system, contact our team. We measure before making recommendations, and we explain every figure.