Central Heat Pump ADD-ON ARCOAIRE HSH6 Premium | 1.5 Tons - 18,000 BTU (Coil EVD4X 14.5 in.) - R410A
Replace the old central air conditioner with a heat pump that also heats
Many homes already have a central air conditioner added to the electric furnace: a condenser in the yard and a coil above the furnace. When that air conditioner reaches the end of its life, replacing it with an ADD-ON system changes things: the new outdoor unit still cools in summer, but it also heats the house for a good part of the year, through the same ducts. The furnace stays in place and its elements are only used as backup.
The Central Heat Pump ADD-ON ARCOAIRE HSH6 Premium | 1.5 Tons - 18,000 BTU (Coil EVD4X 14.5 in.) - R410A pairs the HSH618GKA outdoor unit with the EVD4X18M14A coil. The HSH6 series is presented as the premium tier of this Arcoaire family, and the 1.5-ton size is aimed at small houses and compact homes.
From air conditioner to heat pump: what changes
An air conditioner does only one thing: it rejects the heat of the house outdoors. A heat pump does the same job in summer, then reverses the cycle in winter thanks to a reversing valve: it captures heat from the outdoor air and delivers it to the coil, which the furnace blower then distributes through the ducts. The circuit runs on R-410A.
For you, the difference shows mostly at the thermostat. It now controls two heat sources: the heat pump heats first, and the furnace's electric elements join in as backup when the cold becomes too sharp. The original thermostat, designed for a furnace and an air conditioner, cannot manage this sharing; we replace it with a compatible model.
Why the old coil does not stay
The coil in place was chosen for an air conditioner. In heating mode, a heat pump's coil becomes the hot side of the circuit, and an air conditioner coil is not always designed for this double role. It may also have been intended for another refrigerant. Above all, a system's ratings are established for a specific combination, outdoor unit and coil: that is why we install the EVD4X18M14A coil with the HSH618GKA unit, rather than connecting a new unit to a coil from another generation.
The existing refrigerant line
The copper line connecting the old condenser to the coil often runs through a finished wall or a basement ceiling. Keeping it would simplify the work, but only if its diameter suits the new unit, if it is in good condition and if it can be properly cleaned. R-410A works at higher pressures than older-generation refrigerants, and a doubtful line eventually calls for a service visit. We assess it during the visit; when in doubt, we replace it.
The right size is not necessarily the old air conditioner's
The size of the old unit gives a hint, not an answer. Many air conditioners were chosen "a little bigger, to be sure," and the house may have changed since: new windows, a re-insulated attic, a finished basement. With an ADD-ON system, the heat pump is sized first according to cooling needs, since the furnace's elements cover the deep cold.
The 1.5-ton size usually suits a small, well-insulated bungalow, a townhouse or a duplex unit with its own electric furnace. A larger house, or one that loses a lot of heat, will call for the next size up. The room-by-room load calculation settles it before the quote.
The ducts of an older home
The ducts of a bungalow built for an electric furnace alone were designed for warm air. Air conditioning and a heat pump generally require more airflow than the furnace does in heating, and the return air is often what limits the system. We check the condition of the furnace, the airflow of its blower and the duct sizes before the quote, as well as the number of returns and where they are.
Another change sometimes surprises people: the air a heat pump delivers in winter is milder than the air the electric furnace's elements used to blow. The house is no less warm for it, but the system runs longer and more gently. Tight ducts and unobstructed grilles make a real difference to that comfort.
If part of the ductwork runs through a garage, a crawl space or an attic, it must be insulated: in summer, a cold duct in a warm space becomes covered with condensation. We locate these sections during the visit and note them in the quote when they require work.
Winter, with the furnace's electric backup
In fall, in spring and through a good part of winter, the heat pump heats alone. When the cold deepens, the heat it captures decreases while the home's needs increase, and the furnace's elements join in as backup. This pairing does not carry the cold-climate designation; in an ADD-ON system, the furnace's electric backup is there precisely for the coldest nights. The thermostat brings the elements in when the heat pump can no longer hold the set point, then takes them out as soon as it is enough again.
The moment the elements come in is set at the thermostat, according to your house and your comfort preferences. During defrost cycles, the furnace's elements may also heat for a few minutes so that the air from the grilles stays warm. We set these parameters with you at commissioning.
System ratings
The pairing of the HSH618GKA 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. No rating figure is therefore published on this page.
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 its conditions.
The replacement, step by step
From removing the old unit to commissioning
- Visit and load calculation: electric furnace and its elements, ducts, return air, electrical panel and location of the outdoor unit.
- Removal of the old air conditioner: the refrigerant is recovered before disconnection, then the old coil is removed from the plenum.
- New coil: the 14.5 in. coil is set on the furnace's air outlet; if the widths do not match, we fabricate a sealed transition. The condensate drain goes to a floor drain or a pump.
- Outdoor unit: on a bracket or a pad, above the snow line, where defrost water can drain without freezing on a walkway.
- Refrigerant line: new, or reused after verification, brazed, pressure tested and put under vacuum.
- Electrical and thermostat: dedicated circuit, outdoor disconnect, new thermostat and control wiring.
- Commissioning: refrigerant charge, airflow, defrost, setting of the electric backup, then an explanation of how it all works.
Maintenance
The furnace filter now works all year: check it every month and replace it according to its format. Unlike the old air conditioner, the outdoor unit is not covered in winter, since it heats; keep it clear of snow and leaves. Annual HVAC maintenance of the coil, the condensate drain and the electrical connections also includes a check of the electric furnace and its elements. In winter, white vapour during defrost is normal.
Warranty
Warranty: 10 years on the compressor, 10 years on parts and 6 years on labor.
Keep the invoice and the commissioning report, with the serial numbers of both units: they serve as the reference for any service request.
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 HSH6 Premium | 1.5 Tons - 18,000 BTU (Coil EVD4X 14.5 in.) - R410A. We examine your current air conditioner, your furnace and your ducts, then confirm the right size and your grant eligibility before signing.
Available while supplies last.