Wall-Mounted Heat Pump CONFORTO MHWAL | 24,000 BTU - R410A

A large high-ceilinged space, heated down low and cooled all the way up

A converted loft, a living room under a cathedral ceiling, a double-height room with a mezzanine: these spaces are spectacular, and they are also the hardest to keep comfortable. In winter, heat builds up under the ceiling while your feet are cold; in summer, the mezzanine becomes stifling. The Wall-Mounted Heat Pump CONFORTO MHWAL | 24,000 BTU - R410A brings the capacity and air mixing these large volumes need.

Its certified ratings are 21.5 SEER2, 13.0 EER2 and 11.4 HSPF2. The system is ENERGY STAR certified with the cold-climate designation under ENERGY STAR ID 4480245. It qualifies for a $2,544 LogisVert grant.

Large volumes, a case of their own

Most sizing rules start from a room's floor area. In a loft or under a cathedral ceiling, that shortcut does not work: the volume of air is much larger, the exterior walls and windows rise higher, and the roof is often right above. It is these surfaces, more than the floor area, that determine the capacity needed.

A nominal capacity of 24,000 BTU/h typically suits a large high-ceilinged living space, an open loft or an open area with a mezzanine, in a well-insulated building. The load calculation done during the visit takes the height, the windows and the roof into account.

A single head works when the volume is truly open, from the living zone up to the mezzanine. If the mezzanine is closed off by partitions or a bedroom with a door is set up there, it becomes a separate room: a dedicated small-capacity head will be more effective there than a single large head on the lower level.

Stratification, explained

Warm air rises and cool air falls. In an ordinary room, the difference stays modest; in a double-height volume, it becomes noticeable. In winter, a baseboard under the window heats the air, which shoots up to the ceiling and stays there: the mezzanine is warm, the floor is cold. In summer, it is the reverse: cool air from an air conditioner stays down low, and the mezzanine overheats.

A wall-mounted heat pump mixes the air continuously, at low airflow, thanks to its indoor fan. In heating, louvres aimed downward send warm air back toward the occupied zone; in cooling, aimed upward, they let cool air settle naturally through the whole volume. A ceiling fan, if one is already installed, complements this mixing well.

Winter, certified figures

The certificate lists 21,200 BTU/h at -8 °C (17 °F), about 88% of nominal capacity, with a COP of 2.88, and 25,000 BTU/h at -15 °C (5 °F), about 104%, with a COP of 2.21. The two points are measured separately; we report each one as published, even though the -15 °C value is higher than the -8 °C value.

For a large volume, this is reassuring: the variable-speed compressor delivers its full nominal capacity, and even a little more, in January cold. The heat pump can therefore carry the main heating of the space for most of the winter, with the baseboards as backup for cold peaks. The ENERGY STAR cold-climate designation confirms that the pairing was evaluated for this climate.

Summer, all the way up to the mezzanine

In cooling mode, the nominal capacity is 24,000 BTU/h. The 13.0 EER2 rating measures efficiency on a hot day, when the sun heats the roof and the large windows; the SEER2 rating of 21.5 sums up the full season. At low speed, the indoor coil condenses moisture from the air, which drains away: continuous dehumidification avoids the heavy air that often builds up high in lofts. Blinds on high windows and skylights also make a big difference, since that is where the sun strikes the longest.

Electrical: planning the capacity

A heat pump of this capacity needs a dedicated circuit of a higher rating than a small unit. In lofts set up in older buildings and in some condos, the panel is sometimes limited. We check the capacity of the panel and the electrical service during the visit, before proposing a configuration.

Inverter and R-410A refrigerant

The heat pump moves heat: in winter, it draws it from the outdoor air; in summer, it rejects the loft's heat outside. Inverter technology varies the compressor's speed instead of running all-or-nothing, which lets a large capacity stay gentle in the shoulder seasons. The circuit uses R-410A refrigerant, proven and well known to refrigeration technicians. In cold, humid weather, short defrost cycles pause heating for a few minutes; the white vapour rising from the outdoor unit is normal.

The ratings, explained

• SEER2 of 21.5: cooling efficiency over the whole summer.
• EER2 of 13.0: cooling efficiency at the hottest moment.
• HSPF2 of 11.4: heating efficiency over the whole season, the most decisive in Quebec.
• COP of 2.88 at -8 °C and 2.21 at -15 °C: heat delivered per unit of electricity, where an electric baseboard delivers one.

These figures come from certificate AHRI 210605805, published by NEEP.

The $2,544 LogisVert grant

The system is listed in Hydro-Québec's LogisVert program, with $2,544 for the owner of an existing home, according to the list in effect on the installation date. We confirm eligibility before signing and prepare the detailed invoice, model numbers and proof of payment. Our page on the efficient heat pump grant summarizes the program's conditions.

Installation, step by step

How high to mount the head

In a double-height volume, the temptation is to mount the head very high. That is rarely the best idea: installed near the ceiling, it mostly heats air that is already there and reads a temperature that is not that of the occupied zone. Instead, we mount it at a height that lets the airflow reach the floor in heating and sweep the volume in cooling, often on a solid wall under the mezzanine or facing the large window. The chosen height must also allow easy access to the filters. The head is secured to the framing with a drainage slope for condensate.

Outdoor unit, lines, commissioning and maintenance

The outdoor unit, bulkier on a heat pump this size, sits on a sturdy ground stand or a wall stand designed for its load, above the snow line, away from bedroom windows, including the neighbours'. The refrigerant lines, the cable and the drain go through a single sealed opening. At commissioning, the circuit is evacuated and checked for tightness, then we test both modes and the drain. After that, rinse the indoor filters every two weeks in season, keep the outdoor unit clear of snow and leaves, and plan annual HVAC maintenance of the coils, drain and electrical connections. In winter, white vapour during defrost and a short pause in heating are normal. Our cleaning service takes over when you prefer to hand off the annual visit.

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 Wall-Mounted Heat Pump CONFORTO MHWAL | 24,000 BTU - R410A. We assess your large space and confirm the right size and your grant eligibility before signing.