Installation of a GREE FLEXX R32 electric furnace in Saint-Valentin

A “25 x 28” written in marker on the filter housing: why maintenance is decided on the day of installation

In the photo from this Saint-Valentin project, one detail catches the eye before the unit itself: two notes written in black marker on the filter housing. “Air filter 25 x 28” and “Change every 2 months”. This is not aesthetic neglect. It is a practice we apply to every HVAC installation, and it alone addresses the most common service issue we encounter.

A homeowner who does not know the exact size of their filter ends up buying the closest size at the store, forcing it into the rack as best they can and allowing air to bypass the media around the sides. The result is not just less effective filtration: the coil gets dirty, airflow drops, and the electric heating section trips its thermal limiters at the first severe cold snap.

The context of this project

Saint-Valentin is one of the smallest municipalities in Haut-Richelieu. Scattered homes, farmland, and service times that are nothing like those in a central neighborhood of Montreal or Longueuil. This context guided two technical decisions that we detail below: choosing equipment whose routine maintenance can be performed without a service visit, and ensuring clear service access.

The customer was replacing an aging heating system and wanted to add central air conditioning to a fairly large single-story home with an open-concept area that was difficult to cool in the summer.

The system we installed

A GREE GUD60AH2/G-D(U) air handler with an integrated electric heating section, connected to an outdoor GUD60W2/NhE-D(U) unit using R32 refrigerant.

The 10.5 CPSC2 is the most relevant figure for a home in Saint-Valentin. It is a seasonal heating-efficiency rating: it accounts for mild fall periods, January thaws, and cold snaps. A system that posts the best value in its range for this rating is precisely the one suited to a home where the heating runs seven months a year.

The filter: a chosen size, not one imposed on us

Why 25 x 28 instead of a standard size

A 25 x 28 in filter provides approximately 700 in² of face area, or just under 5 sq. ft. This size was not dictated by the cabinet: we custom-built the cabinet to obtain this area.

The reason is face velocity, meaning the speed at which air passes through the filter media. Above approximately 350 ft/min, three things happen:

• pressure drop increases and the blower consumes more power;
• fine particles pass through the media instead of being captured, negating the benefit of a high-efficiency pleated filter;
• the whistling becomes audible at the return grilles.

By enlarging the cabinet, we bring the face velocity into the useful range, allowing a MERV 11 to 13 pleated filter to be installed without choking the system. A high-performance filter installed in a cabinet that is too small does more harm than good.

The “4,000 CFM” trap in the specifications

The FLEXX data sheet indicates an airflow of 4,000 CFM for this cabinet. That is the unit’s maximum capacity, not its operating point. A system with this capacity actually operates well below it, and most of the time at reduced output thanks to the inverter compressor.

We regularly see installers—and sometimes well-intentioned homeowners doing their own calculations—size a filter cabinet based on this maximum figure. They end up with unrealistic filter areas or give up on a good filter, thinking the system will not support it. Sizing should be based on the actual airflow measured during commissioning, not the catalog figure.

The two-month interval

The note “every 2 months” is not a universal rule. It is the interval we chose for this house, taking into account the agricultural environment, the presence of animals, and the fan's near-continuous operation. In a condo in Laval without animals, we would instead write “every 4 months.” The interval is customized; what matters is that it is written where the homeowner will read it.

The transparent condensate trap, with valve

The condensate drain on this job was installed in PVC with a transparent trap and a ball valve on a branch, plus two capped cleanout tees.

Three concrete advantages:

1. The transparent trap allows the homeowner to check for themselves, in three seconds, that the water seal is present. A trap that dries out in winter allows the unit to draw air through the drain.
2. The valve makes it possible to flush the line with lukewarm water once a year without taking anything apart.
3. Cleanout tees provide access to both sides of the trap in the event of an algae blockage, which is common at the end of summer.

The installation takes longer than a simple PVC elbow. It does, however, prevent a service call 40 minutes away on a sweltering Sunday when the pan overflows because the line is clogged.

Horizontal suspended installation

The unit is installed horizontally and suspended. This configuration has requirements that vertical installation does not:

• The cabinet's slope must be checked both along its length and across its width; otherwise, the condensate pan retains water instead of draining it. We check it with a digital level, not by eye.
• The supports must bear the unit's 199.5 lb when fully loaded, with vibration isolators between the cabinet and the structure.
• The front service clearance must allow the access panels to be removed completely. On this job, the ladder visible in the photo shows that the unit is elevated: without sufficient clearance, every maintenance visit becomes a major project.
• The ceiling penetration was insulated and sealed to prevent condensation around the refrigeration lines in summer.

The A2L detection sensor and its location

R32 is an A2L refrigerant, which is mildly flammable. The appliance comes factory-equipped with a leak-detection sensor, and the cabinet bears a warning label stating that this sensor must be located in a position determined by the manufacturer.

This point is more important than it may seem with a high-mounted horizontal installation: the sensor's position is calculated based on the behavior of refrigerant vapors, which are heavier than air. An appliance reoriented without following the manufacturer's instructions could end up with a sensor positioned where it would detect nothing. We verify this location at every installation and test activation during commissioning.

The cabinet also displays the regulatory table for the minimum room area based on the charge. With 4.6 kg of R32, the room had to be at least 13.7 m² (147.5 sq. ft.), a requirement verified with a tape measure before the equipment was ordered.

How distance changes things when you live in a village in Montérégie

Choose a system whose routine maintenance does not depend on anyone

In Saint-Valentin, as in several municipalities on the South Shore far from major routes, response times are not the same as in the city. Our response is not to sell more maintenance, but to make routine maintenance self-sufficient:

• a filter housing accessible without tools, with the dimensions marked on it;
• a trap that can be inspected visually and rinsed under the tap;
• a conventional 24 VAC thermostat, replaceable with any model on the market rather than a proprietary part;
• a factory-installed Wi-Fi module that enables an initial remote diagnosis before dispatching a technician.

Subsidies: our position

• The central heat pump, certified ENERGY STAR and identified by a valid AHRI number — in this case, 217120762 — is the component that provides access to the energy-efficiency programs currently in effect.
• The electric furnace on its own is not eligible: it is a supplemental heating component.
• Conversion programs are intended for homes that are moving away from fossil fuels. Eligibility must be verified on a house-by-house basis.
• We confirm eligibility for the application using the exact AHRI number, rather than relying on a program from last year.

Three mistakes we regularly correct for other contractors

1. A filter cabinet sized to the unit cabinet. It is almost always too small for a high-efficiency pleated filter. It is a modest sheet-metal addition at the time of installation, but an expensive retrofit later.
2. A drain without a proper trap. An appliance under negative pressure draws air through a trap that is too short and pushes water back into the pan.
3. The changeover point left at the factory settings. The heat pump heats down to -30 °C. A setting that starts the electric elements at -5 °C means paying for a high-performance system and then heating as though you had baseboard heaters.

Our maintenance schedule for this type of installation

• 25 x 28 filter: replace every 2 months, according to the labeling on the cabinet.
• Trap: visually check the water seal every time the filter is changed; rinse annually with tap water.
• Coil and drain pan: clean annually before the cooling season.
• Brackets and isolators: check the tightness annually on a suspended installation.
• Electrical section connections: check the torque once a year.
• Outdoor unit: maintain winter clearance; clean the condenser in the spring.

Our approach at AirGreen

At AirGreen, we believe that a successful HVAC installation should be judged over ten years, not on the day it is installed. The oversized filter cabinet, transparent trap, and marker labeling cost a few dozen dollars and an extra hour of work. Yet they determine most of what the homeowner will experience over the following decade.

We apply the same approach to our heat pump, ductless mini-split air conditioner, electric furnace, and HVAC maintenance projects in Montreal, Laval, Longueuil, across the North Shore, and throughout the South Shore, from densely populated neighborhoods to the agricultural villages of Haut-Richelieu.