Central Heat Pump ADD-ON ARCOAIRE R4H5S Economy | 1.5 Tons - 18,000 BTU (Coil EVD4X 14.5 in.) - R410A
Add air conditioning and shoulder-season heating to your electric furnace without replacing it
In many small homes across Greater Montreal, the electric furnace still works very well, but it heats alone from fall to spring and the house has no central air conditioning. The ADD-ON system meets both needs at once: a coil is installed on the existing furnace and an outdoor unit heats and cools through the same ducts. The furnace stays in place and its elements are only used as backup. The Central Heat Pump ADD-ON ARCOAIRE R4H5S Economy | 1.5 Tons - 18,000 BTU (Coil EVD4X 14.5 in.) - R410A pairs the R4H5S18AKAAA outdoor unit with the EVD4X18M14A coil.
The R4H5S series is the entry level of this Arcoaire family, and the 1.5-ton size is aimed at compact homes. It is a measured way to hand a good share of the heating over to the heat pump rather than the furnace's elements, and add summer comfort, without dismantling a system that works.
Which homes this size suits
A 1.5-ton ADD-ON central heat pump is meant for smaller homes that already have a forced-air electric furnace and a duct network: a small, well-insulated bungalow, a townhouse, a compact semi-detached house or a duplex unit with its own furnace. What matters is that this electric furnace is in good condition and that its blower can move the air the coil needs.
Floor area alone does not settle the question. Attic and wall insulation, window age, orientation and the airtightness of the envelope change the needs from one house to the next. An older home that was never renovated may call for the next size up, while a recent, well-sealed house is often fine with this one. We do the load calculation, room by room, before proposing a size.
What the heat pump does, what the furnace keeps
A heat pump does not produce its heat with heating elements, the way the electric furnace does: it moves it. In winter, the refrigerant picks up heat from the outdoor air, the compressor concentrates it and sends it to the coil sitting on the furnace. The furnace blower pushes the house air through that coil, then into the ducts. In summer, a reversing valve flips the cycle and the heat from the house is rejected outdoors.
The furnace, for its part, stays ready to heat. Its blower now serves both appliances, and its electric elements only come on when the thermostat calls for backup heat. The refrigeration circuit runs on R-410A, a refrigerant that refrigeration technicians know well.
A size chosen first for cooling
With an ADD-ON system, the electric furnace's elements already cover the coldest days. The heat pump therefore does not need to be sized for the worst of winter: it is chosen according to the home's cooling needs, while checking that it carries a good share of the heating the rest of the year. That is why a small house is often better served by 1.5 tons than by a larger size.
An oversized unit cools too fast, shuts off, then starts again. These short cycles leave humidity in the air, create temperature differences between rooms and wear out components. A properly sized unit runs longer on each cycle, which gives drier air in summer and steadier heat in the shoulder seasons.
Summer: the whole house cooled through the ducts
Once installed, the heat pump cools every room served by the ducts, with no unit visible on the wall. Cool air comes out of the existing grilles and returns through the furnace's return air. The coil also removes humidity: the condensed water flows through a drain to a floor drain or a pump, and a basement served by the ducts benefits from this drier air.
In a small house, the bedrooms are often the rooms that get the hottest in July. We check that each one has its supply register and that air can return to the furnace, even with the door closed. A bedroom without a return path stays warmer than the rest of the house, whatever the equipment.
Winter: the heat pump first, the electric backup next
In fall, in spring and through a good part of winter, the heat pump heats alone. As the cold deepens, the heat it can capture decreases while the home's needs increase. The thermostat then brings in the furnace's elements, which supplement the heat on the coldest nights. This pairing does not carry the cold-climate designation: the furnace's electric backup is precisely what serves as the safety net.
The thermostat adds the electric 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. During defrost cycles, the elements may also come on for a few minutes so that cool air does not come out of the grilles.
System ratings
The pairing of the R4H5S18AKAAA 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. This page therefore publishes no rating figure for this pairing.
To read these ratings when the time comes: SEER2 measures seasonal cooling efficiency, EER2 the efficiency on a hot day at full demand, and HSPF2 seasonal heating efficiency. They apply to a specific combination, outdoor unit and coil, and that is the combination we write into the quote.
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. Our page on the grant for efficient heat pumps summarizes the program's conditions.
What installation on your furnace includes
The 14.5 in. EVD4X coil
The coil sits on the furnace's air outlet, in the supply plenum. Before the quote, we check the condition of the electric furnace, the airflow of its blower and the duct sizes, then we measure the furnace outlet and the free space above it. The 14.5 in. coil must line up with the furnace; if it does not, we fabricate a sealed transition. In a basement with a low ceiling, this measurement sometimes decides how the plenum is rebuilt.
The coil has its own pan and condensate drain. We connect it to a floor drain or a pump with a steady slope, and if a humidifier already drains to the same spot, we arrange the two drains so that both flow without backing up.
Outdoor unit, refrigerant line and electrical
The outdoor unit goes on a bracket or a pad, above the snow line, away from roof drips, dryer vents and bedroom windows. Defrost water must be able to drain without freezing on a driveway or a walkway. The insulated copper line connects the unit to the coil; we braze it, pressure test it and pull a vacuum before opening the valves.
On the electrical side, the outdoor unit requires a dedicated circuit and a nearby disconnect. In a house heated by an electric furnace, the panel is often already heavily loaded: we check its capacity and free space during the visit rather than on installation day.
Thermostat and commissioning
A compatible thermostat decides when the heat pump heats alone and when the electric furnace's elements add backup heat. A furnace-only thermostat cannot control a heat pump; we replace it and add, where needed, the wiring missing between the furnace and the outdoor unit.
At commissioning, we check the refrigerant charge, the airflow in heat pump mode, defrost and how the electric backup comes in. We then set with you the point at which the furnace's elements should step in, and show you how to read the thermostat.
Maintenance and warranty
The furnace filter now works all year: check it every month and replace it according to its format. Keep the outdoor unit clear of snow and leaves, without covering it in winter since it heats. Plan annual HVAC maintenance of the coil, the condensate drain and the electrical connections; the electric furnace and its elements are checked during the same visit. 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.
For an ADD-ON system, these three licences cover the three parts of the job: the connection to the ducts, the refrigeration circuit and the electrical supply to the outdoor unit.
Request your free estimate for the Central Heat Pump ADD-ON ARCOAIRE R4H5S Economy | 1.5 Tons - 18,000 BTU (Coil EVD4X 14.5 in.) - R410A. We examine your furnace and ducts and confirm the right size and your grant eligibility before signing.
Available while supplies last.