Central Heat Pump ADD-ON ARCOAIRE HSH4 Premium | 4 Tons - 48,000 BTU (Coil EVD4X 24.5 in.) - R410A

A 24.5 in. coil that fits properly in the furnace room

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 electric elements are only used as backup. The Central Heat Pump ADD-ON ARCOAIRE HSH4 Premium | 4 Tons - 48,000 BTU (Coil EVD4X 24.5 in.) - R410A pairs the HSH448GKA outdoor unit with the EVD4X48M24A coil.

In an ADD-ON, a good part of the work happens around the furnace, in a space that is often tight: a mechanical room in the basement, sometimes a furnace squeezed between a water heater and a finished wall. That is where the coil has to find its place, with its drain, its connections and the access needed for maintenance. This page details what we check in that room.

The 24.5 in. coil and the furnace

The EVD4X48M24A coil sits on the furnace's air outlet. Its 24.5 in. format matches the wide cabinets often found on high-capacity furnaces. When the widths match, the coil sits directly on the furnace; when they differ, we fabricate a sealed sheet-metal transition so that all of the air passes through the coil, not around it.

Most basement furnaces blow upward, but some blow horizontally or downward. We check the orientation of yours and how the coil must connect to it before giving you the quote.

Available height and the plenum

The coil fits between the furnace and the supply plenum, the sheet-metal box from which the main ducts branch out. Clearance is therefore needed above the furnace. In a basement with a low ceiling, or when the plenum is enclosed in a finished ceiling, this height has to be worked out carefully: sometimes the plenum must be rebuilt, a duct takeoff moved or part of the ceiling opened. We note it during the visit and the quote spells it out, rather than finding out on installation day.

Condensate: drain, trap and pump

In summer, the coil cools the air in the house and removes its humidity. At this size, the amount of water collected on a hot, humid day is significant. It flows through a condensate drain fitted with a trap, on a steady slope to the floor drain. When no drain is within reach, a condensate pump lifts the water to a discharge point.

If the coil sits above a finished space or a floor that is sensitive to water, we add overflow protection, such as an auxiliary pan or a safety switch that stops cooling if the water no longer drains.

The filter and furnace accessories

The filter stays at the furnace inlet, upstream of the blower and the coil: it now protects both. Accessories already connected to the plenums, such as a humidifier or an air exchanger connection, stay in place in most cases. We do check their position, though, since the coil takes up part of the supply plenum and some accessories have to be moved to fit.

The 4-ton size and the HSH4 series

The 4-ton size often serves a large two-level house, an extended two-storey home or a house with a finished basement and lots of windows, in Longueuil or on the North Shore. These examples are only a guide. A room-by-room load calculation establishes the cooling load; because the furnace's electric elements cover the deep cold, that load guides the choice of size. An oversized unit cools in short cycles and removes humidity poorly.

The HSH448GKA unit belongs to the HSH4 series, one of Arcoaire's Premium series. The coil is the same for the other series of this size; the outdoor unit makes the difference.

Equipment of this size also needs a furnace blower that can keep up. We check that the existing blower can deliver the airflow the coil requires at full capacity; if it cannot, the quote says so clearly, before any decision.

System ratings

The pairing of the HSH448GKA outdoor unit and the EVD4X48M24A 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.

The confirmed ratings are given to you in writing with the quote; this page shows none.

Two heat sources, one thermostat

The heat pump thermostat replaces the furnace thermostat. In cool weather, it hands heating to the heat pump; when the cold deepens and the heat pump is no longer enough, it brings in the furnace's electric elements as auxiliary heat. The auxiliary heat threshold is set at commissioning, according to the heat loss of the house and your preferences.

During the outdoor unit's defrost, the furnace's elements may come on briefly so that the air at the registers stays warm, and a plume of vapour comes out of the unit. The heat pump's air is less hot than the air from the electric elements; its cycles are longer and the house stays at a more even temperature.

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 electric furnace takes 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.

Outside: the unit, the line set and the electrical work

The HSH448GKA outdoor unit goes on a sturdy stand above the snow line, out of roof drip and away from bedroom windows, in compliance with municipal rules. The insulated refrigerant line set passes through the wall via a sealed opening and runs to the coil; its joints are brazed under nitrogen, then it undergoes a pressure test and a vacuum before the R-410A charge. The electrical work includes a dedicated circuit, an outdoor disconnect and control wiring between the thermostat, the furnace and the unit.

At commissioning, we adjust the charge, the blower airflow and the thermostat's auxiliary heat threshold, then check the condensate drain flow and, where applicable, that the pump starts.

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.

Keep access to the coil and drain clear in the mechanical room: the annual maintenance depends on it. If a condensate pump is installed, check from time to time during the summer that it starts and that its tubing is neither kinked nor clogged. The electric furnace keeps its usual maintenance, centred on the blower, the heating elements and their connections.

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 HSH4 Premium | 4 Tons - 48,000 BTU (Coil EVD4X 24.5 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.