Central Heat Pump ADD-ON ARCOAIRE N4H5S Performance | 1.5 Tons - 18,000 BTU (Coil EVD4X 14.5 in.) - R410A
A small home, an electric furnace and a thermostat that puts the heat pump to work first
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's elements are only used as backup. The Central Heat Pump ADD-ON ARCOAIRE N4H5S Performance | 1.5 Tons - 18,000 BTU (Coil EVD4X 14.5 in.) - R410A pairs the N4H5S18AKAAA outdoor unit with the EVD4X18M14A coil.
In this type of installation, the equipment matters, but the logic that runs it matters just as much. Two heat sources share the same blower and the same ducts, and the thermostat decides, hour by hour, whether the heat pump is enough or whether the furnace's electric elements need to back it up. This page explains how that sharing works in a compact home, then what the installation includes.
Heat pump and electric backup, plainly
Both sources run on electricity, but not in the same way. The furnace's heating elements produce heat directly: they give back as heat the electricity they use, and no more. The heat pump, for its part, moves heat from the outdoor air into the house. For most of the year, it heats alone. When the cold becomes too sharp for it, the furnace's elements join in as backup. In summer, the heat pump cools the whole house through the same grilles.
The coil sits on the furnace's air outlet, and the furnace blower serves both sources. The thermostat brings in the elements as auxiliary heat when the heat pump can no longer hold the set point, then takes them out as soon as it is enough again. That is the basic rule of an ADD-ON system on an electric furnace.
Your home's balance point
The colder it gets outside, the more heat the house loses, and the less the heat pump can capture. At a certain moment, the two curves cross: that is the balance point. Above it, the heat pump is enough; below it, the furnace's elements must supplement the heat. This point is not printed on the unit; it depends on your house: its insulation, its windows, its airtightness and its size.
In a compact, well-insulated home, a 1.5-ton size pushes that point fairly deep into winter. In a house that loses a lot of heat, it arrives sooner. That is one of the reasons we do a load calculation, room by room, before confirming the size.
Keeping the elements at rest as long as possible
The second setting determines when the electric backup comes in. With an electric furnace, the logic is simple: the heat pump keeps control as long as it is enough, and the elements only come in once it no longer is. Every hour the heat pump heats alone is an hour when the elements, which only give back the electricity they use, stay off.
Backup that comes in too early runs the elements when the heat pump would be enough; backup that comes in too late can leave the house cool on the morning of a cold snap. We set these parameters with you at commissioning, and they remain adjustable.
What the thermostat needs to do
A furnace-only thermostat cannot control a heat pump. The thermostat we install controls the reversing valve, the furnace's blower and elements, and the outdoor unit, and it takes the outdoor temperature into account, through a sensor or weather data depending on the model. It also manages defrost: during those few minutes, the furnace's elements can come on so that the air coming out of the grilles stays warm.
Where needed, we add the wiring missing between the furnace and the outdoor unit, and at commissioning we explain how to read the screen: which source is heating, when the furnace's elements join in, and how to adjust the setpoint without upsetting the sharing.
Which homes this size suits
The 1.5-ton size is aimed at compact homes that already have a forced-air electric furnace: a small bungalow, a townhouse, a semi-detached house or a plex unit served by its own furnace and its own duct network. With an ADD-ON system, the heat pump is chosen first according to cooling needs, since the furnace's elements cover the deep cold. A unit larger than needed would cool in fits and starts and remove humidity poorly.
Floor area alone does not settle it. A house from the seventies whose attic was never re-insulated does not compare with a recent, well-sealed townhouse, even if both have the same living area. The load calculation accounts for the walls, the windows, the orientation and air leakage, and it is what confirms whether 1.5 tons is enough or whether the next size up is needed.
Summer: cooling and drier air
In cooling mode, the house air passes through the cold coil, which removes both heat and humidity. The condensed water flows through a drain to a floor drain or a pump. A properly sized unit runs long enough on each cycle to dry the air well, which you feel most in the bedrooms and the basement.
We also check the return air: a house heated by an electric furnace alone does not always have enough returns for cooling, and a closed bedroom without a return stays warmer than the rest of the house.
System ratings
The pairing of the N4H5S18AKAAA outdoor unit and the EVD4X18M14A coil is not listed with SEER2 ratings in the AHRI certification directory. We confirm the ratings of the complete system before the quote; they also determine grant eligibility. We therefore publish no rating figure here for this pairing.
Once these ratings are confirmed, here is how to read them: SEER2 reflects cooling efficiency over a season, EER2 the efficiency on a heat-wave day, and HSPF2 heating efficiency over a season. In an ADD-ON installation, HSPF2 tells only part of the story, since the furnace's elements supplement the heat during the coldest hours.
LogisVert grant
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. The program's conditions are summarized on our page on the grant for efficient heat pumps.
The installation, from the furnace to the thermostat
The visit before the quote
We check the condition of the electric furnace and its elements, the airflow of its blower and the duct sizes before the quote. The blower must be able to move the air the coil needs, and the ducts must deliver it to the grilles without whistling. We also measure the furnace outlet and the clearance above it: the 14.5 in. coil must line up with it, or a sealed transition is planned. If the furnace shows signs of advanced wear, we tell you before you sign.
The job
- Coil: set on the furnace's air outlet, connected to the plenum and to its condensate drain.
- Outdoor unit: on a bracket, above the snow line, away from roof drips and dryer vents.
- Refrigerant line: insulated copper, brazing, pressure test and vacuum before the valves are opened.
- Electrical: dedicated circuit and outdoor disconnect.
- Commissioning: refrigerant charge, airflow, defrost and setting of the electric backup.
Maintenance
The furnace filter now works summer and winter: check it every month and replace it according to its format. Keep the outdoor unit clear of snow and leaves. Plan annual HVAC maintenance of the coil, the condensate drain and the electrical connections, in addition to a check of the electric furnace and its elements. In winter, white vapour during defrost is normal.
Warranty: 10 years on the compressor, 10 years on parts and 6 years on labor.
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 ADD-ON ARCOAIRE N4H5S Performance | 1.5 Tons - 18,000 BTU (Coil EVD4X 14.5 in.) - R410A. We assess the home room by room and confirm the right size and your grant eligibility before signing.
Available while supplies last.