Central Heat Pump ARCOAIRE N4H5S Performance | 3.5 Tons - 42,000 BTU (Air Handler FJMA4X) - R410A

The whole house heated and cooled through its ducts, with a size chosen for it

In a home that already has ductwork, a central heat pump cools every room and handles most of the heating, with a single thermostat and no equipment visible in the rooms. The Central Heat Pump ARCOAIRE N4H5S Performance | 3.5 Tons - 42,000 BTU (Air Handler FJMA4X) - R410A pairs the N4H5S42AKAAA outdoor unit with the FJMA4X42L0BB indoor unit, an air handler that pushes warm or cool air through the existing duct system.

At 3.5 tons, this system sits between the common 3-ton and 4-ton sizes. That is exactly what makes it useful: in many homes in the Montreal area, the load calculation lands between the two, and an in-between size avoids having to choose between a unit that is a little short and one that is too big.

Homes that suit the 3.5-ton size

This size typically suits medium to large homes that already have a complete duct system: a bungalow with a finished basement, a two-level cottage, an enlarged semi-detached house or a split-level home whose electric furnace is reaching the end of its life. It also shows up in homes where an old central air conditioner and a furnace are replaced at the same time, which lets you start over with two units designed to work together.

Floor area alone is never enough to choose. Two homes of the same size can have very different needs depending on wall and attic insulation, the age and orientation of the windows, the airtightness of the envelope and ceiling height. A seventies home that was never renovated may need more; a recent, well-sealed home may need less. We run a room-by-room load calculation before recommending a size, and that calculation decides.

Why the right size heats and cools better

The habit of going "a little bigger, just to be sure" hurts comfort with a central heat pump. An oversized unit reaches the setpoint too quickly, shuts off, then starts again. These short cycles wear out components, leave temperature gaps between the basement and the bedrooms and, in summer, stop the cooling before the coil has had time to remove the moisture. The house is cool, but clammy.

On the other hand, an undersized unit runs nonstop on heat-wave days and calls on the backup heat more often in winter. The right size runs long, steady cycles, moves air through the whole duct system and keeps temperatures even from one level to the next. The 3.5-ton size exists for homes that fall between two standard sizes, and it is often the one that delivers that steady operation.

Two units working together

The N4H5S42AKAAA outdoor unit houses the compressor, the outdoor coil and the fan that exchanges heat with the outside air. The FJMA4X42L0BB indoor unit holds the indoor coil, the blower that pushes air into the ducts and the filter location. The two are connected by an insulated copper refrigerant line set, control wiring and, on the indoor side, a condensate drain.

The system runs on R-410A, a refrigerant that refrigeration technicians know well and for which parts and service tools are widely available. The pairing of the two units is not a detail: they are chosen to work together, and it is the ratings of the complete pairing that count, not those of a single unit.

How a heat pump works

A heat pump does not create heat, it moves it. In winter, the refrigerant captures the heat contained in the outdoor air, even cold air; the compressor concentrates it and sends it to the indoor unit's coil, and the blower distributes it through the ducts. In summer, a reversing valve flips the cycle: heat is captured inside the house and released outdoors.

Because it moves heat instead of producing it with electric resistance, a heat pump delivers more energy than it consumes for most of the year. That is what makes it the heart of a modern heating and cooling system in a home that already has its ducts.

Quebec winters and backup heat

This pairing is a conventional central heat pump; it is not listed as a cold-climate heat pump. Its heating capacity decreases as the outdoor temperature drops, as with any heat pump of this type. During periods of deep cold, the backup heat takes over: electric elements in the air handler, or the existing furnace in an installation that keeps it.

This is normal and planned from the outset. The thermostat runs the heat pump first and only calls on the backup when the house needs it. We size that backup according to the load calculation and list it in the quote, so the coldest January nights hold no surprises. During defrost cycles, the backup may also come on briefly to avoid blowing lukewarm air into the rooms.

Cooling and humidity in summer

In summer, the system cools the whole house through the same ducts, from the upstairs bedrooms down to the finished basement. The indoor coil also removes moisture from the air: the condensed water drains away through the condensate drain. A properly sized system runs cycles long enough to dry the air well, which keeps the house comfortable at a reasonable setpoint.

In a two-level home, the upper floor tends to stay warmer. A balanced duct system, well-placed return air grilles and the right blower setting correct most of that gap. We check these points during the visit rather than relying on a bigger unit.

System ratings

The pairing of the N4H5S42AKAAA outdoor unit and the FJMA4X42L0BB indoor unit is not listed with SEER2 ratings in the AHRI certification directory. We therefore publish no efficiency rating for this pairing on this page. We confirm the ratings of the complete system before the quote; they also determine grant eligibility.

If certified ratings are decisive for your project, we will show you during the visit the pairings of the same size that are listed in the directory, so you can compare on a clear basis.

LogisVert

This pairing does not carry an amount on Hydro-Québec's LogisVert list of October 19, 2026. If the grant matters for your project, we will point you to an eligible pairing of comparable size. We take it into account from the assessment onward, before you have to choose.

Installation in a ducted home

The indoor unit takes the place of the old furnace or air handler and connects to the existing duct system. Before the quote, we check duct sizes and the air return, because a central heat pump only delivers its full efficiency if the airflow keeps up.

From the visit to commissioning

• Visit and load calculation: we assess the insulation, the windows and each room, then confirm the size.
• Ducts and air return: we inspect the duct system, spot undersized sections and insufficient returns, and list the corrections in the quote.
• Outdoor unit: it goes on a stand, above the snow line, away from snow sliding off the roof and from dryer vents.
• Line set and drain: the line set is installed, insulated, evacuated and checked before the refrigerant is released; the condensate drain is connected to a compliant discharge point.
• Electrical: the heat pump is fed by a dedicated circuit, and we check that the panel has the capacity needed for the heat pump and for the backup heat.
• Commissioning: we check the charge, temperatures, airflow and thermostat, then explain the settings.

Maintenance

Replace the system filter according to its format, keep the outdoor unit clear of snow and leaves, and plan annual HVAC maintenance of the coil, condensate drain and electrical connections. In winter, white vapour during defrost is normal. After a heavy snowfall, clear the top and sides of the outdoor unit by hand, without sharp tools, so the fins are not damaged.

AirGreen, for the life of the installation

A family business active for more than fifteen years in Montreal, Laval, Longueuil, the North Shore and the South Shore, we hold RBQ licences for ventilation, refrigeration and electrical work and carry $5,000,000 in liability insurance. The in-home assessment is free, the quote is in writing, and our financing options let you choose the right unit rather than the cheapest one.

Request your free estimate for the Central Heat Pump ARCOAIRE N4H5S Performance | 3.5 Tons - 42,000 BTU (Air Handler FJMA4X) - R410A. We assess the home room by room and confirm the right size and your grant eligibility before signing.

Warranty: 10 years on the compressor, 10 years on parts and 6 years on labor.