Central Heat Pump ADD-ON ARCOAIRE N4H5S Performance | 3 Tons - 36,000 BTU (Coil EVD4X 17.5 in.) - R410A

Three tons to cool a large home and take on most of its heating

In a large house heated by a forced-air electric furnace, the duct network serves several living areas, bedrooms and often a finished basement. The ADD-ON system builds on that network: a coil is installed on the existing furnace and an outdoor unit heats and cools the whole house through the same ducts. The furnace stays in place and is only used as backup, through its electric elements.

The Central Heat Pump ADD-ON ARCOAIRE N4H5S Performance | 3 Tons - 36,000 BTU (Coil EVD4X 17.5 in.) - R410A pairs the N4H5S36AKAAA outdoor unit with the EVD4X36M17A coil. At this size, success depends less on the equipment than on the way air reaches each room.

Which homes this size suits

The 3-ton size is aimed at roomy homes: a spacious cottage, a bungalow with a large finished basement, an open-plan house with lots of windows, as seen in the newer neighbourhoods of Laval, the North Shore or the South Shore. With an ADD-ON system, the heat pump is sized first on cooling needs, since the furnace's elements cover the deep cold.

It is also a size that is easy to choose too large. A recent, well-insulated house, even a large one, is often fine with the next size down. An oversized unit reaches the setpoint too fast, runs in short cycles and leaves humidity in the air. The room-by-room load calculation takes into account the insulation, windows, orientation and airtightness of the house; it is what confirms whether 3 tons is the right choice.

A large open area, a single duct network

An open area brings together the kitchen, the dining room and the living room, often in front of large windows. In summer, it is the zone that builds up the most heat: sun, cooking, appliances. The supply grilles there must be numerous enough and well placed to cover the whole space, not just one corner. We look at their position relative to the windows and the island, and we check that the return air lets warm air come back to the furnace.

Air distribution in a large home

In a large house, the rooms farthest from the furnace are the first to suffer from a poorly suited network: the bedroom at the end of the hallway, the room above the garage, the basement office. Air conditioning and a heat pump generally require more airflow than the furnace does in heating, and a main duct that is too narrow or too few returns limit the whole system.

We check the condition of the furnace, the airflow of its blower and the duct sizes before the quote. We count the supplies and returns room by room, and we state in the quote the adjustments needed: an additional return, a larger grille, a duct to insulate if it runs through an unheated space. At commissioning, we balance the dampers so that each room gets its share.

What the furnace must provide

In an ADD-ON system, the furnace blower is what pushes the air through the coil. A 3-ton coil requires substantial airflow, and a furnace sized primarily for heating cannot always provide it. It is one of the first things we confirm.

The 17.5 in. coil is set on the furnace's air outlet; if it does not line up with it, we fabricate a sealed transition. We also measure the clearance above the furnace, often limited in a finished basement, and identify any humidifier mounted on the plenum, whose location will need to be reviewed.

How the heat pump works

A heat pump moves heat instead of producing it. In winter, its refrigerant, R-410A, captures heat from the outdoor air; the compressor concentrates it and sends it to the coil, which the furnace blower sweeps before pushing the air into the ducts. In summer, a reversing valve flips the cycle and rejects the heat of the house outdoors.

Winter, with the furnace's elements taking over

The thermostat decides when the heat pump heats alone and when the furnace's electric elements come in as auxiliary heat. In fall, in spring and through a good part of winter, the heat pump heats alone. When the cold becomes too sharp for it, the elements top up the heat. This pairing does not carry the cold-climate designation; in an ADD-ON system, the furnace's elements are precisely what covers the coldest nights.

In a large electrically heated house, those elements represent a significant load all winter. With the heat pump, they stay off as long as it is enough, and during defrost they may heat for a few minutes so that the air from the grilles stays warm. The moment auxiliary heat comes in is set according to your house, its heat loss and your comfort.

Summer: heat and humidity

In cooling mode, the cold coil removes heat and humidity from the air; the condensed water flows through a drain to a floor drain or a pump. In a large house, a right-sized unit runs long enough on each cycle to dry the air in every room, not just near the thermostat. A large finished basement benefits especially from this drier air.

System ratings

The pairing of the N4H5S36AKAAA outdoor unit and the EVD4X36M17A 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.

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.

Installation in a large home

Outdoor unit, refrigerant line and electrical

The outdoor unit is installed on a bracket or a pad, above the snow line, away from roof drips, dryer vents and bedroom windows. In a large house, the mechanical room is sometimes far from the most practical exterior wall; we choose the location that keeps the copper line as short and direct as possible, while letting defrost water drain without freezing on a walkway. The insulated line is brazed, pressure tested and put under vacuum before the valves are opened.

The unit gets a dedicated circuit and a nearby disconnect; we check the panel's space and capacity during the visit, since it must carry the heat pump in addition to the furnace's elements. The thermostat is replaced with a model that manages the heat pump and electric auxiliary heat, wired to the furnace and the outdoor unit. At commissioning, we check the refrigerant charge, airflow, defrost and the furnace's elements coming in, then we balance the dampers.

Maintenance and warranty

The furnace filter now works all year; with a system this size, a clogged filter is quickly felt in the far rooms. 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 | 3 Tons - 36,000 BTU (Coil EVD4X 17.5 in.) - R410A. We assess the home room by room, check the air distribution and confirm the right size and your grant eligibility before signing.

Available while supplies last.