Central Heat Pump ARCOAIRE H4H5S ION | 3.5 Tons - 42,000 BTU (Air Handler FJMA4X) - R410A
Even temperatures from the basement to the bedrooms, thanks to well-distributed air
A central heat pump heats and cools the whole house from a single unit, using the duct system to bring air to each room. The Central Heat Pump ARCOAIRE H4H5S ION | 3.5 Tons - 42,000 BTU (Air Handler FJMA4X) - R410A pairs the H4H5S42AKAAA outdoor unit with the FJMA4X42L0BB indoor unit, an air handler that pushes air through the existing duct system.
On this page, we focus on a point that is often overlooked: the quality of the air distribution. It decides whether the upstairs bedrooms are as comfortable as the living room, and whether the 3.5-ton system delivers what you expect from it.
Comfort is decided in the ducts
The heat pump produces the heat or the cooling; the ducts deliver it. An excellent unit connected to a poorly suited duct system gives an uneven house: a cool basement, an acceptable main floor and bedrooms that are too hot in summer. Conversely, a well-sized, well-balanced duct system lets each room get its share, with a single thermostat.
A heat pump is more demanding than a furnace on this point. It blows air that is less hot, but for longer and in greater volume. If the duct system chokes the airflow, the coil works poorly, efficiency drops and the blower strains. That is why we examine the duct system before talking about equipment.
What we examine before the quote
- Supply ducts: their size, their route and the number of registers per room.
- Air return: the number and size of return grilles, and their position in the house.
- Leaks and insulation: open joints and ducts that run through a garage, a crawl space or an unheated attic.
- Static pressure: a measurement that shows whether the duct system lets air through easily or holds it back.
What we find is written into the quote: what can stay as is, what benefits from being corrected, and what is essential for the system to work properly.
Homes that have been transformed over the years deserve special attention. A finished basement with no air return, an extension served by a single register or a bedroom added above the garage are common cases. These rooms are often the ones people complain about, and replacing the unit is the right time to correct them.
Balancing the duct system and taking care of the air return
Balancing means distributing air between the rooms using the dampers and registers. In summer, more air is sent upstairs, where heat rises; in winter, more goes back to the main floor and basement. We make an initial adjustment during commissioning and show you how to adjust it from one season to the next.
The air return is often the weak link. A house with only one large return grille in the basement struggles to renew the air in closed bedrooms. Depending on the case, a return grille upstairs, transfer grilles or a gap under the doors clearly improve comfort. This work is modest compared with the gain.
The 3.5-ton size and the airflow it requires
The bigger the system, the more air it must move. The 3.5-ton size typically suits a medium to large home: a cottage with four bedrooms upstairs, a bungalow with a finished basement and a large open area, or an enlarged semi-detached home. It requires a duct system able to carry the corresponding airflow.
The room-by-room load calculation confirms the size based on the insulation, windows and airtightness of the house. When an existing duct system is too small for the size needed, we say so and propose corrections, rather than installing a unit that will not be able to deliver its efficiency.
The air handler at the centre of the duct system
The FJMA4X42L0BB indoor unit takes the place of the old furnace or air handler. It houses the indoor coil, the blower that feeds the whole duct system and the filter. In winter, the R-410A refrigerant releases there the heat captured outdoors by the H4H5S42AKAAA outdoor unit; in summer, a reversing valve flips the cycle and the coil captures heat from the house to send it outdoors.
The blower can also run continuously, depending on the thermostat setting. This mode mixes the air between levels, reduces temperature differences and passes the air through the filter more often.
In deep cold, the backup heat takes over
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. During deep cold, the air handler's backup heat takes over, or the existing furnace in an installation that keeps it.
The air still travels through the same ducts: the balancing done for the heat pump also benefits the backup heat. We size it according to the load calculation and list it in the quote.
Humidity, summer and winter
In summer, the indoor coil removes moisture from the air at the same time as it cools it; the water drains through the condensate drain. Well-adjusted airflow and long enough cycles give a dry, comfortable house, even in muggy weather.
In winter, cold outdoor air holds little moisture, and the air in the house becomes dry, whatever the heating method. If that is the case in your home, a humidifier connected to the duct system can complement the system; we discuss it during the visit.
System ratings
The pairing of the H4H5S42AKAAA 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. We confirm the ratings of the complete system before the quote; they also determine grant eligibility.
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.
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. The outdoor unit goes on a stand, above the snow line, on a dedicated circuit.
How the job unfolds
- Removal of the old unit and installation of the air handler on the plenum and return.
- Duct corrections listed in the quote: returns, registers, joints, insulation.
- Outdoor unit set on its stand, line set insulated, evacuated and checked.
- Condensate drain, dedicated circuit and backup heat connected.
- Commissioning: charge, temperatures, airflow, initial balancing and thermostat.
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. Keep registers and return grilles clear of furniture and rugs: one blocked return is enough to unbalance the whole house.
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 H4H5S ION | 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.