Central Heat Pump ADD-ON ARCOAIRE H4H7T ION 2 stages | 3 Tons - 36,000 BTU (Coil EVD4X 17.5 in.) - R410A
A two-stage heat pump that works with the furnace you already have
The ADD-ON system adds a heat pump to an existing electric furnace: a coil is installed on the furnace and the outdoor unit heats and cools through the same ducts. The furnace is only used as backup, through its electric elements. The Central Heat Pump ADD-ON ARCOAIRE H4H7T ION 2 stages | 3 Tons - 36,000 BTU (Coil EVD4X 17.5 in.) - R410A pairs the H4H7T36AKAAA outdoor unit with the EVD4X36M17A coil.
This pairing is for homeowners who have an electric furnace in good condition and a duct system that already serves the whole house. Instead of replacing everything, you keep what works and hand most of the heating season, along with all of the summer cooling, to a central heat pump.
The 3-ton size: which home it suits
A 3-ton system is often found in a mid-size two-storey house, a bungalow with a finished basement or a semi-detached home on two levels in Laval or on the South Shore. These examples are only a guide. Wall and attic insulation, the age of the windows, the orientation of the house and the airtightness of the envelope change the result considerably: two homes that look alike can need different sizes.
In an ADD-ON installation, we size the heat pump first on the cooling load. The furnace's electric elements remain in place for the coldest days, so there is no need to oversize the outdoor unit so that it covers the whole winter on its own. An oversized unit cools in short cycles, removes less humidity and wears out faster. A room-by-room load calculation settles the question before the quote.
A two-stage compressor
The H4H7T36AKAAA outdoor unit belongs to Arcoaire's ION 2 stages series and uses a two-stage compressor: a reduced stage for the hours when the house asks for little, and a full stage for the hours when it needs all of the capacity. The reduced stage lengthens cycles in mild weather, which keeps the temperature more even from one room to the next.
In an ADD-ON, this flexibility adds to that of the furnace. In spring and fall, the compressor runs mostly on its reduced stage; when the first cold spells arrive, it moves to the full stage; and when the heat pump is no longer enough, the furnace's electric elements come in as backup. Three levels of response, from a single installation.
Ratings that depend on your furnace
The AHRI certification directory lists the pairing of the H4H7T36AKAAA outdoor unit and the EVD4X36M17A coil only with specific furnaces: the SEER2 and HSPF2 ratings depend on the blower of the furnace in place. We confirm them with your furnace model before the quote.
That is why this page shows no efficiency rating: a rating published with a furnace other than yours would not describe your installation. During the visit, we record the brand, model and serial number of the furnace, then give you the confirmed ratings in writing, with the quote.
The furnace blower, the key part of the system
In an ADD-ON, neither the outdoor unit nor the coil moves the air in the house: the furnace blower pushes the air through the coil, then into the ducts. Well-adjusted airflow gives the coil what it needs. Airflow that is too low reduces capacity and can freeze the coil in cooling mode; airflow that is too high hurts dehumidification.
We check the type of motor, the speeds available and the general condition of the blower, then set the cooling and heat pump heating speeds at commissioning. If the blower is near the end of its life, we tell you before the quote rather than after the installation.
The thermostat: when electric auxiliary heat comes in
Every ADD-ON relies on auxiliary-heat logic. A compatible thermostat, often connected to an outdoor sensor, decides at each call for heat whether the heat pump is enough or whether the furnace's electric elements should come in as auxiliary heat. In cool weather, the heat pump heats alone and the elements stay off. When the cold deepens and it can no longer hold the set point, the elements top up the heat.
The moment auxiliary heat comes in takes into account the heat loss of the house, the furnace in place and your priorities: some people want the heat pump to work as long as possible, to keep the elements off, others prefer warmer air as soon as the temperature drops. We set it at commissioning and show you how to change it.
One detail sometimes surprises people: the air delivered by the heat pump feels warm rather than hot, and the cycles are longer than with the furnace alone. The house stays at a more even temperature; this is normal operation. During the outdoor unit's defrost, the furnace's elements may also heat briefly so that cool air does not circulate in the rooms.
Summer cooling and dehumidification
In summer, the same coil cools the air and removes humidity, which flows through a condensate drain to the floor drain or to a condensate pump. The whole house is cooled through the existing ducts, with no units in the windows. The compressor's reduced stage suits hot, humid days well, when the house mostly needs to be dried out.
If the upper floor stays warmer than the main floor, the cause is often in the duct system: poorly balanced registers or not enough return air upstairs. We look at this during the visit and suggest corrections when needed.
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 on the existing furnace
The coil sits on the furnace's air outlet, and a compatible thermostat decides when the heat pump heats alone and when the furnace's elements take over. We check the condition of the furnace, the airflow of its blower and the duct sizes before the quote. The outdoor unit goes on a stand, above the snow line, on a dedicated circuit.
Project steps
- Home visit: survey of the electric furnace, the ducts, the electrical panel, which already carries the furnace's elements, and the planned location of the outdoor unit.
- Room-by-room load calculation, to confirm that the 3-ton size suits the house.
- Written quote, with the ratings confirmed for your furnace.
- Installation of the 17.5 in. coil on the furnace, with a sheet-metal transition if the cabinet width differs, and connection of the condensate drain.
- Outdoor unit on a stand, away from roof drip, then routing of the insulated refrigerant line set to the coil.
- Electrical: dedicated circuit, outdoor disconnect and control wiring between the thermostat, the furnace and the outdoor unit.
- Commissioning: nitrogen pressure test, vacuum, adjustment of the R-410A charge, the airflow and the moment the thermostat brings in electric auxiliary heat.
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.
The electric furnace also deserves a check of its elements and its blower. Its elements run fewer hours than before, but they must stay ready for the days when the heat pump hands over to them.
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.
The refrigeration and electrical licences cover both sides of an ADD-ON: the refrigerant circuit between the outdoor unit and the coil, and the electrical connection of the outdoor unit and the thermostat.
Request your free estimate for the Central Heat Pump ADD-ON ARCOAIRE H4H7T ION 2 stages | 3 Tons - 36,000 BTU (Coil EVD4X 17.5 in.) - R410A. We assess the home room by room and confirm the right size and your grant eligibility before signing.
Available while supplies last.
Warranty: 10 years on the compressor, 10 years on parts and 6 years on labor.