Central Heat Pump ADD-ON ARCOAIRE N4H5S Performance | 3.5 Tons - 42,000 BTU (Coil EVD4X 17.5 in.) - R410A
Replace the central air conditioner with a unit that also heats
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 N4H5S Performance | 3.5 Tons - 42,000 BTU (Coil EVD4X 17.5 in.) - R410A pairs the N4H5S42AKAAA outdoor unit with the EVD4X42M17A coil.
Many homes heated by an electric furnace already have a central air conditioner: an outdoor unit that only runs in summer and a coil sitting on the furnace. When that air conditioner reaches the end of its life, replacing it with a central heat pump takes little more work, and the equipment starts working in winter too.
From air conditioner to heat pump: what changes
An air conditioner and a heat pump look very much alike. Both have an outdoor unit, an indoor coil and a refrigerant line set between them. The difference lies mainly in a reversing valve: in a heat pump, it reverses the refrigeration cycle in winter to capture heat from the outdoor air and deliver it to the coil, instead of rejecting the home's heat outside.
In practice, the replacement involves four items. The outdoor unit is changed. The existing coil makes way for the EVD4X42M17A coil, designed to work in both directions. The thermostat is replaced with a model that can control both the heat pump and the furnace's electric elements. Finally, the location of the outdoor unit is reviewed, because equipment that works in winter is not installed like an air conditioner that sleeps under the snow.
The 3.5-ton size
The 3.5-ton size sits between the common 3-ton and 4-ton sizes. It often suits a large house on two levels, a two-storey home with a finished basement and large south-facing windows, or a house whose old air conditioner struggled to keep the upper floor comfortable. These examples are only a guide: insulation, orientation, airtightness and sun exposure change the actual load.
Replacing an air conditioner is the right time to redo the calculation. Many older units were chosen by eye, often oversized. A heat pump sized on the cooling load runs longer on each cycle, removes humidity better and leaves the coldest days to the furnace's elements. The load calculation is done room by room, before the quote.
The Performance series and the 17.5 in. coil
The name Performance refers to the place of the N4H5S42AKAAA unit in the Arcoaire lineup. For this size, we offer the same EVD4X42M17A coil with several series of outdoor units; what sets them apart is the outdoor unit. The series name does not replace the ratings of the pairing, which we confirm before the quote.
The coil is a 17.5 in. format, a dimension that has to match the width of the furnace cabinet. When they match, the coil sits directly on the air outlet; when they differ, we fabricate a sheet-metal transition so that all of the air passes through the coil, with no leakage around the sides.
System ratings
The pairing of the N4H5S42AKAAA outdoor unit and the EVD4X42M17A 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.
That is why no efficiency rating appears on this page. You receive the confirmed ratings in writing, with the quote, before you make your decision.
Winter: the heat pump first, the furnace's elements second
The old air conditioner shut down in the fall. The heat pump keeps going: in cool weather, it heats on its own, and the thermostat brings in the furnace's electric elements as auxiliary heat when the heat pump can no longer hold the temperature. The moment auxiliary heat comes in is set at commissioning, based on the heat loss of the house and your comfort. Every hour the heat pump is enough is an hour those elements stay off.
In winter, the outdoor unit sometimes gets covered in frost. It melts it with short defrost cycles, during which a plume of vapour comes off the unit. Depending on the setting, the furnace's elements heat during that time so the air blown into the house stays warm.
The air delivered by the heat pump is cooler to the touch than the air from the furnace's elements, and the cycles are longer. Heat is spread more evenly through the house; this is normal operation.
Summer: the same comfort, better adjusted
In cooling mode, little changes for you: cool air flows through the same ducts and the same registers. The new coil removes humidity from the air; the water drains through the condensate line, which we check and connect to the floor drain or to a condensate pump. A new coil and properly adjusted airflow often make a clear difference compared with a worn-out unit.
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.
The line set and R-410A
The system runs on R-410A. If the old air conditioner used the same refrigerant, the existing line set can sometimes be kept, provided its diameter suits the new pairing, it is in good condition and it passes a pressure test. If the old unit ran on an older refrigerant, or if the line set is damaged or poorly insulated, we replace it. We decide during the visit, and the quote spells it out.
The refrigerant in the old unit is recovered before it is taken apart, as regulations require. Commissioning then always follows the same sequence: nitrogen pressure test, vacuum, then charge adjustment according to the manufacturer's instructions.
The outdoor unit, in the right place
The old air conditioner often sat on a ground-level slab, sometimes behind a hedge or under a porch. That location does not always suit a heat pump, which works all winter. We install it on a stand, above the snow line, so that air flows freely and defrost water drains away without forming ice under the unit. We avoid roof drip, dryer vents and bedroom windows, and we check your municipality's rules on the location of outdoor equipment.
The electrical connection includes a dedicated circuit, an outdoor disconnect within sight of the unit and control wiring to the furnace and thermostat. We also check that the electrical panel, which already feeds the furnace's elements, has the required capacity.
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.
Because the heat pump now runs in winter as well as summer, the filter gets dirty faster than in the days of the air conditioner alone. Check it every month for the first few seasons, until you know its pace. The electric furnace, for its part, still deserves a check of its elements and its blower.
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 | 3.5 Tons - 42,000 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.